linux/arch/arm64/kernel/entry.S

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/*
* Low-level exception handling code
*
* Copyright (C) 2012 ARM Ltd.
* Authors: Catalin Marinas <catalin.marinas@arm.com>
* Will Deacon <will.deacon@arm.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <linux/init.h>
#include <linux/linkage.h>
#include <asm/alternative.h>
#include <asm/assembler.h>
#include <asm/asm-offsets.h>
#include <asm/cpufeature.h>
#include <asm/errno.h>
#include <asm/esr.h>
#include <asm/irq.h>
#include <asm/memory.h>
#include <asm/thread_info.h>
#include <asm/unistd.h>
/*
* Context tracking subsystem. Used to instrument transitions
* between user and kernel mode.
*/
.macro ct_user_exit, syscall = 0
#ifdef CONFIG_CONTEXT_TRACKING
bl context_tracking_user_exit
.if \syscall == 1
/*
* Save/restore needed during syscalls. Restore syscall arguments from
* the values already saved on stack during kernel_entry.
*/
ldp x0, x1, [sp]
ldp x2, x3, [sp, #S_X2]
ldp x4, x5, [sp, #S_X4]
ldp x6, x7, [sp, #S_X6]
.endif
#endif
.endm
.macro ct_user_enter
#ifdef CONFIG_CONTEXT_TRACKING
bl context_tracking_user_enter
#endif
.endm
/*
* Bad Abort numbers
*-----------------
*/
#define BAD_SYNC 0
#define BAD_IRQ 1
#define BAD_FIQ 2
#define BAD_ERROR 3
.macro kernel_entry, el, regsize = 64
sub sp, sp, #S_FRAME_SIZE
.if \regsize == 32
mov w0, w0 // zero upper 32 bits of x0
.endif
stp x0, x1, [sp, #16 * 0]
stp x2, x3, [sp, #16 * 1]
stp x4, x5, [sp, #16 * 2]
stp x6, x7, [sp, #16 * 3]
stp x8, x9, [sp, #16 * 4]
stp x10, x11, [sp, #16 * 5]
stp x12, x13, [sp, #16 * 6]
stp x14, x15, [sp, #16 * 7]
stp x16, x17, [sp, #16 * 8]
stp x18, x19, [sp, #16 * 9]
stp x20, x21, [sp, #16 * 10]
stp x22, x23, [sp, #16 * 11]
stp x24, x25, [sp, #16 * 12]
stp x26, x27, [sp, #16 * 13]
stp x28, x29, [sp, #16 * 14]
.if \el == 0
mrs x21, sp_el0
mov tsk, sp
and tsk, tsk, #~(THREAD_SIZE - 1) // Ensure MDSCR_EL1.SS is clear,
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
ldr x19, [tsk, #TI_FLAGS] // since we can unmask debug
disable_step_tsk x19, x20 // exceptions when scheduling.
mov x29, xzr // fp pointed to user-space
.else
add x21, sp, #S_FRAME_SIZE
get_thread_info tsk
/* Save the task's original addr_limit and set USER_DS (TASK_SIZE_64) */
ldr x20, [tsk, #TI_ADDR_LIMIT]
str x20, [sp, #S_ORIG_ADDR_LIMIT]
mov x20, #TASK_SIZE_64
str x20, [tsk, #TI_ADDR_LIMIT]
/* No need to reset PSTATE.UAO, hardware's already set it to 0 for us */
.endif /* \el == 0 */
mrs x22, elr_el1
mrs x23, spsr_el1
stp lr, x21, [sp, #S_LR]
stp x22, x23, [sp, #S_PC]
/*
* Set syscallno to -1 by default (overridden later if real syscall).
*/
.if \el == 0
mvn x21, xzr
str x21, [sp, #S_SYSCALLNO]
.endif
/*
* Set sp_el0 to current thread_info.
*/
.if \el == 0
msr sp_el0, tsk
.endif
/*
* Registers that may be useful after this macro is invoked:
*
* x21 - aborted SP
* x22 - aborted PC
* x23 - aborted PSTATE
*/
.endm
.macro kernel_exit, el
.if \el != 0
/* Restore the task's original addr_limit. */
ldr x20, [sp, #S_ORIG_ADDR_LIMIT]
str x20, [tsk, #TI_ADDR_LIMIT]
/* No need to restore UAO, it will be restored from SPSR_EL1 */
.endif
ldp x21, x22, [sp, #S_PC] // load ELR, SPSR
.if \el == 0
ct_user_enter
ldr x23, [sp, #S_SP] // load return stack pointer
msr sp_el0, x23
#ifdef CONFIG_ARM64_ERRATUM_845719
alternative_if ARM64_WORKAROUND_845719
tbz x22, #4, 1f
#ifdef CONFIG_PID_IN_CONTEXTIDR
mrs x29, contextidr_el1
msr contextidr_el1, x29
#else
msr contextidr_el1, xzr
#endif
1:
alternative_else_nop_endif
#endif
.endif
msr elr_el1, x21 // set up the return data
msr spsr_el1, x22
ldp x0, x1, [sp, #16 * 0]
ldp x2, x3, [sp, #16 * 1]
ldp x4, x5, [sp, #16 * 2]
ldp x6, x7, [sp, #16 * 3]
ldp x8, x9, [sp, #16 * 4]
ldp x10, x11, [sp, #16 * 5]
ldp x12, x13, [sp, #16 * 6]
ldp x14, x15, [sp, #16 * 7]
ldp x16, x17, [sp, #16 * 8]
ldp x18, x19, [sp, #16 * 9]
ldp x20, x21, [sp, #16 * 10]
ldp x22, x23, [sp, #16 * 11]
ldp x24, x25, [sp, #16 * 12]
ldp x26, x27, [sp, #16 * 13]
ldp x28, x29, [sp, #16 * 14]
ldr lr, [sp, #S_LR]
add sp, sp, #S_FRAME_SIZE // restore sp
eret // return to kernel
.endm
.macro get_thread_info, rd
mrs \rd, sp_el0
.endm
.macro irq_stack_entry
mov x19, sp // preserve the original sp
/*
* Compare sp with the current thread_info, if the top
* ~(THREAD_SIZE - 1) bits match, we are on a task stack, and
* should switch to the irq stack.
*/
and x25, x19, #~(THREAD_SIZE - 1)
cmp x25, tsk
b.ne 9998f
adr_this_cpu x25, irq_stack, x26
mov x26, #IRQ_STACK_START_SP
add x26, x25, x26
/* switch to the irq stack */
mov sp, x26
/*
* Add a dummy stack frame, this non-standard format is fixed up
* by unwind_frame()
*/
stp x29, x19, [sp, #-16]!
mov x29, sp
9998:
.endm
/*
* x19 should be preserved between irq_stack_entry and
* irq_stack_exit.
*/
.macro irq_stack_exit
mov sp, x19
.endm
/*
* These are the registers used in the syscall handler, and allow us to
* have in theory up to 7 arguments to a function - x0 to x6.
*
* x7 is reserved for the system call number in 32-bit mode.
*/
sc_nr .req x25 // number of system calls
scno .req x26 // syscall number
stbl .req x27 // syscall table pointer
tsk .req x28 // current thread_info
/*
* Interrupt handling.
*/
.macro irq_handler
ldr_l x1, handle_arch_irq
mov x0, sp
irq_stack_entry
blr x1
irq_stack_exit
.endm
.text
/*
* Exception vectors.
*/
.pushsection ".entry.text", "ax"
.align 11
ENTRY(vectors)
ventry el1_sync_invalid // Synchronous EL1t
ventry el1_irq_invalid // IRQ EL1t
ventry el1_fiq_invalid // FIQ EL1t
ventry el1_error_invalid // Error EL1t
ventry el1_sync // Synchronous EL1h
ventry el1_irq // IRQ EL1h
ventry el1_fiq_invalid // FIQ EL1h
ventry el1_error_invalid // Error EL1h
ventry el0_sync // Synchronous 64-bit EL0
ventry el0_irq // IRQ 64-bit EL0
ventry el0_fiq_invalid // FIQ 64-bit EL0
ventry el0_error_invalid // Error 64-bit EL0
#ifdef CONFIG_COMPAT
ventry el0_sync_compat // Synchronous 32-bit EL0
ventry el0_irq_compat // IRQ 32-bit EL0
ventry el0_fiq_invalid_compat // FIQ 32-bit EL0
ventry el0_error_invalid_compat // Error 32-bit EL0
#else
ventry el0_sync_invalid // Synchronous 32-bit EL0
ventry el0_irq_invalid // IRQ 32-bit EL0
ventry el0_fiq_invalid // FIQ 32-bit EL0
ventry el0_error_invalid // Error 32-bit EL0
#endif
END(vectors)
/*
* Invalid mode handlers
*/
.macro inv_entry, el, reason, regsize = 64
kernel_entry \el, \regsize
mov x0, sp
mov x1, #\reason
mrs x2, esr_el1
b bad_mode
.endm
el0_sync_invalid:
inv_entry 0, BAD_SYNC
ENDPROC(el0_sync_invalid)
el0_irq_invalid:
inv_entry 0, BAD_IRQ
ENDPROC(el0_irq_invalid)
el0_fiq_invalid:
inv_entry 0, BAD_FIQ
ENDPROC(el0_fiq_invalid)
el0_error_invalid:
inv_entry 0, BAD_ERROR
ENDPROC(el0_error_invalid)
#ifdef CONFIG_COMPAT
el0_fiq_invalid_compat:
inv_entry 0, BAD_FIQ, 32
ENDPROC(el0_fiq_invalid_compat)
el0_error_invalid_compat:
inv_entry 0, BAD_ERROR, 32
ENDPROC(el0_error_invalid_compat)
#endif
el1_sync_invalid:
inv_entry 1, BAD_SYNC
ENDPROC(el1_sync_invalid)
el1_irq_invalid:
inv_entry 1, BAD_IRQ
ENDPROC(el1_irq_invalid)
el1_fiq_invalid:
inv_entry 1, BAD_FIQ
ENDPROC(el1_fiq_invalid)
el1_error_invalid:
inv_entry 1, BAD_ERROR
ENDPROC(el1_error_invalid)
/*
* EL1 mode handlers.
*/
.align 6
el1_sync:
kernel_entry 1
mrs x1, esr_el1 // read the syndrome register
lsr x24, x1, #ESR_ELx_EC_SHIFT // exception class
cmp x24, #ESR_ELx_EC_DABT_CUR // data abort in EL1
b.eq el1_da
arm64: Handle el1 synchronous instruction aborts cleanly Executing from a non-executable area gives an ugly message: lkdtm: Performing direct entry EXEC_RODATA lkdtm: attempting ok execution at ffff0000084c0e08 lkdtm: attempting bad execution at ffff000008880700 Bad mode in Synchronous Abort handler detected on CPU2, code 0x8400000e -- IABT (current EL) CPU: 2 PID: 998 Comm: sh Not tainted 4.7.0-rc2+ #13 Hardware name: linux,dummy-virt (DT) task: ffff800077e35780 ti: ffff800077970000 task.ti: ffff800077970000 PC is at lkdtm_rodata_do_nothing+0x0/0x8 LR is at execute_location+0x74/0x88 The 'IABT (current EL)' indicates the error but it's a bit cryptic without knowledge of the ARM ARM. There is also no indication of the specific address which triggered the fault. The increase in kernel page permissions makes hitting this case more likely as well. Handling the case in the vectors gives a much more familiar looking error message: lkdtm: Performing direct entry EXEC_RODATA lkdtm: attempting ok execution at ffff0000084c0840 lkdtm: attempting bad execution at ffff000008880680 Unable to handle kernel paging request at virtual address ffff000008880680 pgd = ffff8000089b2000 [ffff000008880680] *pgd=00000000489b4003, *pud=0000000048904003, *pmd=0000000000000000 Internal error: Oops: 8400000e [#1] PREEMPT SMP Modules linked in: CPU: 1 PID: 997 Comm: sh Not tainted 4.7.0-rc1+ #24 Hardware name: linux,dummy-virt (DT) task: ffff800077f9f080 ti: ffff800008a1c000 task.ti: ffff800008a1c000 PC is at lkdtm_rodata_do_nothing+0x0/0x8 LR is at execute_location+0x74/0x88 Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Laura Abbott <labbott@redhat.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2016-08-10 01:25:26 +00:00
cmp x24, #ESR_ELx_EC_IABT_CUR // instruction abort in EL1
b.eq el1_ia
cmp x24, #ESR_ELx_EC_SYS64 // configurable trap
b.eq el1_undef
cmp x24, #ESR_ELx_EC_SP_ALIGN // stack alignment exception
b.eq el1_sp_pc
cmp x24, #ESR_ELx_EC_PC_ALIGN // pc alignment exception
b.eq el1_sp_pc
cmp x24, #ESR_ELx_EC_UNKNOWN // unknown exception in EL1
b.eq el1_undef
cmp x24, #ESR_ELx_EC_BREAKPT_CUR // debug exception in EL1
b.ge el1_dbg
b el1_inv
arm64: Handle el1 synchronous instruction aborts cleanly Executing from a non-executable area gives an ugly message: lkdtm: Performing direct entry EXEC_RODATA lkdtm: attempting ok execution at ffff0000084c0e08 lkdtm: attempting bad execution at ffff000008880700 Bad mode in Synchronous Abort handler detected on CPU2, code 0x8400000e -- IABT (current EL) CPU: 2 PID: 998 Comm: sh Not tainted 4.7.0-rc2+ #13 Hardware name: linux,dummy-virt (DT) task: ffff800077e35780 ti: ffff800077970000 task.ti: ffff800077970000 PC is at lkdtm_rodata_do_nothing+0x0/0x8 LR is at execute_location+0x74/0x88 The 'IABT (current EL)' indicates the error but it's a bit cryptic without knowledge of the ARM ARM. There is also no indication of the specific address which triggered the fault. The increase in kernel page permissions makes hitting this case more likely as well. Handling the case in the vectors gives a much more familiar looking error message: lkdtm: Performing direct entry EXEC_RODATA lkdtm: attempting ok execution at ffff0000084c0840 lkdtm: attempting bad execution at ffff000008880680 Unable to handle kernel paging request at virtual address ffff000008880680 pgd = ffff8000089b2000 [ffff000008880680] *pgd=00000000489b4003, *pud=0000000048904003, *pmd=0000000000000000 Internal error: Oops: 8400000e [#1] PREEMPT SMP Modules linked in: CPU: 1 PID: 997 Comm: sh Not tainted 4.7.0-rc1+ #24 Hardware name: linux,dummy-virt (DT) task: ffff800077f9f080 ti: ffff800008a1c000 task.ti: ffff800008a1c000 PC is at lkdtm_rodata_do_nothing+0x0/0x8 LR is at execute_location+0x74/0x88 Acked-by: Mark Rutland <mark.rutland@arm.com> Signed-off-by: Laura Abbott <labbott@redhat.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2016-08-10 01:25:26 +00:00
el1_ia:
/*
* Fall through to the Data abort case
*/
el1_da:
/*
* Data abort handling
*/
mrs x0, far_el1
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg
// re-enable interrupts if they were enabled in the aborted context
tbnz x23, #7, 1f // PSR_I_BIT
enable_irq
1:
mov x2, sp // struct pt_regs
bl do_mem_abort
// disable interrupts before pulling preserved data off the stack
disable_irq
kernel_exit 1
el1_sp_pc:
/*
* Stack or PC alignment exception handling
*/
mrs x0, far_el1
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg
mov x2, sp
b do_sp_pc_abort
el1_undef:
/*
* Undefined instruction
*/
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg
mov x0, sp
b do_undefinstr
el1_dbg:
/*
* Debug exception handling
*/
cmp x24, #ESR_ELx_EC_BRK64 // if BRK64
cinc x24, x24, eq // set bit '0'
tbz x24, #0, el1_inv // EL1 only
mrs x0, far_el1
mov x2, sp // struct pt_regs
bl do_debug_exception
kernel_exit 1
el1_inv:
// TODO: add support for undefined instructions in kernel mode
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg
mov x0, sp
mov x2, x1
mov x1, #BAD_SYNC
b bad_mode
ENDPROC(el1_sync)
.align 6
el1_irq:
kernel_entry 1
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
#endif
irq_handler
#ifdef CONFIG_PREEMPT
ldr w24, [tsk, #TI_PREEMPT] // get preempt count
cbnz w24, 1f // preempt count != 0
ldr x0, [tsk, #TI_FLAGS] // get flags
tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling?
bl el1_preempt
1:
#endif
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on
#endif
kernel_exit 1
ENDPROC(el1_irq)
#ifdef CONFIG_PREEMPT
el1_preempt:
mov x24, lr
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
1: bl preempt_schedule_irq // irq en/disable is done inside
ldr x0, [tsk, #TI_FLAGS] // get new tasks TI_FLAGS
tbnz x0, #TIF_NEED_RESCHED, 1b // needs rescheduling?
ret x24
#endif
/*
* EL0 mode handlers.
*/
.align 6
el0_sync:
kernel_entry 0
mrs x25, esr_el1 // read the syndrome register
lsr x24, x25, #ESR_ELx_EC_SHIFT // exception class
cmp x24, #ESR_ELx_EC_SVC64 // SVC in 64-bit state
b.eq el0_svc
cmp x24, #ESR_ELx_EC_DABT_LOW // data abort in EL0
b.eq el0_da
cmp x24, #ESR_ELx_EC_IABT_LOW // instruction abort in EL0
b.eq el0_ia
cmp x24, #ESR_ELx_EC_FP_ASIMD // FP/ASIMD access
b.eq el0_fpsimd_acc
cmp x24, #ESR_ELx_EC_FP_EXC64 // FP/ASIMD exception
b.eq el0_fpsimd_exc
cmp x24, #ESR_ELx_EC_SYS64 // configurable trap
b.eq el0_sys
cmp x24, #ESR_ELx_EC_SP_ALIGN // stack alignment exception
b.eq el0_sp_pc
cmp x24, #ESR_ELx_EC_PC_ALIGN // pc alignment exception
b.eq el0_sp_pc
cmp x24, #ESR_ELx_EC_UNKNOWN // unknown exception in EL0
b.eq el0_undef
cmp x24, #ESR_ELx_EC_BREAKPT_LOW // debug exception in EL0
b.ge el0_dbg
b el0_inv
#ifdef CONFIG_COMPAT
.align 6
el0_sync_compat:
kernel_entry 0, 32
mrs x25, esr_el1 // read the syndrome register
lsr x24, x25, #ESR_ELx_EC_SHIFT // exception class
cmp x24, #ESR_ELx_EC_SVC32 // SVC in 32-bit state
b.eq el0_svc_compat
cmp x24, #ESR_ELx_EC_DABT_LOW // data abort in EL0
b.eq el0_da
cmp x24, #ESR_ELx_EC_IABT_LOW // instruction abort in EL0
b.eq el0_ia
cmp x24, #ESR_ELx_EC_FP_ASIMD // FP/ASIMD access
b.eq el0_fpsimd_acc
cmp x24, #ESR_ELx_EC_FP_EXC32 // FP/ASIMD exception
b.eq el0_fpsimd_exc
cmp x24, #ESR_ELx_EC_PC_ALIGN // pc alignment exception
b.eq el0_sp_pc
cmp x24, #ESR_ELx_EC_UNKNOWN // unknown exception in EL0
b.eq el0_undef
cmp x24, #ESR_ELx_EC_CP15_32 // CP15 MRC/MCR trap
b.eq el0_undef
cmp x24, #ESR_ELx_EC_CP15_64 // CP15 MRRC/MCRR trap
b.eq el0_undef
cmp x24, #ESR_ELx_EC_CP14_MR // CP14 MRC/MCR trap
b.eq el0_undef
cmp x24, #ESR_ELx_EC_CP14_LS // CP14 LDC/STC trap
b.eq el0_undef
cmp x24, #ESR_ELx_EC_CP14_64 // CP14 MRRC/MCRR trap
b.eq el0_undef
cmp x24, #ESR_ELx_EC_BREAKPT_LOW // debug exception in EL0
b.ge el0_dbg
b el0_inv
el0_svc_compat:
/*
* AArch32 syscall handling
*/
adrp stbl, compat_sys_call_table // load compat syscall table pointer
uxtw scno, w7 // syscall number in w7 (r7)
mov sc_nr, #__NR_compat_syscalls
b el0_svc_naked
.align 6
el0_irq_compat:
kernel_entry 0, 32
b el0_irq_naked
#endif
el0_da:
/*
* Data abort handling
*/
mrs x26, far_el1
// enable interrupts before calling the main handler
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg_and_irq
ct_user_exit
bic x0, x26, #(0xff << 56)
mov x1, x25
mov x2, sp
bl do_mem_abort
b ret_to_user
el0_ia:
/*
* Instruction abort handling
*/
mrs x26, far_el1
// enable interrupts before calling the main handler
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg_and_irq
ct_user_exit
mov x0, x26
mov x1, x25
mov x2, sp
bl do_mem_abort
b ret_to_user
el0_fpsimd_acc:
/*
* Floating Point or Advanced SIMD access
*/
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg
ct_user_exit
mov x0, x25
mov x1, sp
bl do_fpsimd_acc
b ret_to_user
el0_fpsimd_exc:
/*
* Floating Point or Advanced SIMD exception
*/
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg
ct_user_exit
mov x0, x25
mov x1, sp
bl do_fpsimd_exc
b ret_to_user
el0_sp_pc:
/*
* Stack or PC alignment exception handling
*/
mrs x26, far_el1
// enable interrupts before calling the main handler
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg_and_irq
arm64: entry: fix context tracking for el0_sp_pc Commit 6c81fe7925cc4c42 ("arm64: enable context tracking") did not update el0_sp_pc to use ct_user_exit, but this appears to have been unintentional. In commit 6ab6463aeb5fbc75 ("arm64: adjust el0_sync so that a function can be called") we made x0 available, and in the return to userspace we call ct_user_enter in the kernel_exit macro. Due to this, we currently don't correctly inform RCU of the user->kernel transition, and may erroneously account for time spent in the kernel as if we were in an extended quiescent state when CONFIG_CONTEXT_TRACKING is enabled. As we do record the kernel->user transition, a userspace application making accesses from an unaligned stack pointer can demonstrate the imbalance, provoking the following warning: ------------[ cut here ]------------ WARNING: CPU: 2 PID: 3660 at kernel/context_tracking.c:75 context_tracking_enter+0xd8/0xe4() Modules linked in: CPU: 2 PID: 3660 Comm: a.out Not tainted 4.1.0-rc7+ #8 Hardware name: ARM Juno development board (r0) (DT) Call trace: [<ffffffc000089914>] dump_backtrace+0x0/0x124 [<ffffffc000089a48>] show_stack+0x10/0x1c [<ffffffc0005b3cbc>] dump_stack+0x84/0xc8 [<ffffffc0000b3214>] warn_slowpath_common+0x98/0xd0 [<ffffffc0000b330c>] warn_slowpath_null+0x14/0x20 [<ffffffc00013ada4>] context_tracking_enter+0xd4/0xe4 [<ffffffc0005b534c>] preempt_schedule_irq+0xd4/0x114 [<ffffffc00008561c>] el1_preempt+0x4/0x28 [<ffffffc0001b8040>] exit_files+0x38/0x4c [<ffffffc0000b5b94>] do_exit+0x430/0x978 [<ffffffc0000b614c>] do_group_exit+0x40/0xd4 [<ffffffc0000c0208>] get_signal+0x23c/0x4f4 [<ffffffc0000890b4>] do_signal+0x1ac/0x518 [<ffffffc000089650>] do_notify_resume+0x5c/0x68 ---[ end trace 963c192600337066 ]--- This patch adds the missing ct_user_exit to the el0_sp_pc entry path, correcting the context tracking for this case. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Acked-by: Will Deacon <will.deacon@arm.com> Fixes: 6c81fe7925cc ("arm64: enable context tracking") Cc: <stable@vger.kernel.org> # v3.17+ Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2015-06-15 15:40:27 +00:00
ct_user_exit
mov x0, x26
mov x1, x25
mov x2, sp
bl do_sp_pc_abort
b ret_to_user
el0_undef:
/*
* Undefined instruction
*/
// enable interrupts before calling the main handler
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg_and_irq
ct_user_exit
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
mov x0, sp
bl do_undefinstr
b ret_to_user
el0_sys:
/*
* System instructions, for trapped cache maintenance instructions
*/
enable_dbg_and_irq
ct_user_exit
mov x0, x25
mov x1, sp
bl do_sysinstr
b ret_to_user
el0_dbg:
/*
* Debug exception handling
*/
tbnz x24, #0, el0_inv // EL0 only
mrs x0, far_el1
mov x1, x25
mov x2, sp
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
bl do_debug_exception
enable_dbg
ct_user_exit
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
b ret_to_user
el0_inv:
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg
ct_user_exit
mov x0, sp
mov x1, #BAD_SYNC
mov x2, x25
bl bad_mode
b ret_to_user
ENDPROC(el0_sync)
.align 6
el0_irq:
kernel_entry 0
el0_irq_naked:
enable_dbg
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_off
#endif
ct_user_exit
irq_handler
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on
#endif
b ret_to_user
ENDPROC(el0_irq)
/*
* Register switch for AArch64. The callee-saved registers need to be saved
* and restored. On entry:
* x0 = previous task_struct (must be preserved across the switch)
* x1 = next task_struct
* Previous and next are guaranteed not to be the same.
*
*/
ENTRY(cpu_switch_to)
mov x10, #THREAD_CPU_CONTEXT
add x8, x0, x10
mov x9, sp
stp x19, x20, [x8], #16 // store callee-saved registers
stp x21, x22, [x8], #16
stp x23, x24, [x8], #16
stp x25, x26, [x8], #16
stp x27, x28, [x8], #16
stp x29, x9, [x8], #16
str lr, [x8]
add x8, x1, x10
ldp x19, x20, [x8], #16 // restore callee-saved registers
ldp x21, x22, [x8], #16
ldp x23, x24, [x8], #16
ldp x25, x26, [x8], #16
ldp x27, x28, [x8], #16
ldp x29, x9, [x8], #16
ldr lr, [x8]
mov sp, x9
and x9, x9, #~(THREAD_SIZE - 1)
msr sp_el0, x9
ret
ENDPROC(cpu_switch_to)
/*
* This is the fast syscall return path. We do as little as possible here,
* and this includes saving x0 back into the kernel stack.
*/
ret_fast_syscall:
disable_irq // disable interrupts
str x0, [sp, #S_X0] // returned x0
ldr x1, [tsk, #TI_FLAGS] // re-check for syscall tracing
and x2, x1, #_TIF_SYSCALL_WORK
cbnz x2, ret_fast_syscall_trace
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_step_tsk x1, x2
kernel_exit 0
ret_fast_syscall_trace:
enable_irq // enable interrupts
b __sys_trace_return_skipped // we already saved x0
/*
* Ok, we need to do extra processing, enter the slow path.
*/
work_pending:
mov x0, sp // 'regs'
bl do_notify_resume
arm64: Add trace_hardirqs_off annotation in ret_to_user When a kernel is built with CONFIG_TRACE_IRQFLAGS the following warning is produced when entering userspace for the first time: WARNING: at /work/Linux/linux-2.6-aarch64/kernel/locking/lockdep.c:3519 Modules linked in: CPU: 1 PID: 1 Comm: systemd Not tainted 4.4.0-rc3+ #639 Hardware name: Juno (DT) task: ffffffc9768a0000 ti: ffffffc9768a8000 task.ti: ffffffc9768a8000 PC is at check_flags.part.22+0x19c/0x1a8 LR is at check_flags.part.22+0x19c/0x1a8 pc : [<ffffffc0000fba6c>] lr : [<ffffffc0000fba6c>] pstate: 600001c5 sp : ffffffc9768abe10 x29: ffffffc9768abe10 x28: ffffffc9768a8000 x27: 0000000000000000 x26: 0000000000000001 x25: 00000000000000a6 x24: ffffffc00064be6c x23: ffffffc0009f249e x22: ffffffc9768a0000 x21: ffffffc97fea5480 x20: 00000000000001c0 x19: ffffffc00169a000 x18: 0000005558cc7b58 x17: 0000007fb78e3180 x16: 0000005558d2e238 x15: ffffffffffffffff x14: 0ffffffffffffffd x13: 0000000000000008 x12: 0101010101010101 x11: 7f7f7f7f7f7f7f7f x10: fefefefefefeff63 x9 : 7f7f7f7f7f7f7f7f x8 : 6e655f7371726964 x7 : 0000000000000001 x6 : ffffffc0001079c4 x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffffffc001698438 x2 : 0000000000000000 x1 : ffffffc9768a0000 x0 : 000000000000002e Call trace: [<ffffffc0000fba6c>] check_flags.part.22+0x19c/0x1a8 [<ffffffc0000fc440>] lock_is_held+0x80/0x98 [<ffffffc00064bafc>] __schedule+0x404/0x730 [<ffffffc00064be6c>] schedule+0x44/0xb8 [<ffffffc000085bb0>] ret_to_user+0x0/0x24 possible reason: unannotated irqs-off. irq event stamp: 502169 hardirqs last enabled at (502169): [<ffffffc000085a98>] el0_irq_naked+0x1c/0x24 hardirqs last disabled at (502167): [<ffffffc0000bb3bc>] __do_softirq+0x17c/0x298 softirqs last enabled at (502168): [<ffffffc0000bb43c>] __do_softirq+0x1fc/0x298 softirqs last disabled at (502143): [<ffffffc0000bb830>] irq_exit+0xa0/0xf0 This happens because we disable interrupts in ret_to_user before calling schedule() in work_resched. This patch adds the necessary trace_hardirqs_off annotation. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Reported-by: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
2015-12-04 12:42:29 +00:00
#ifdef CONFIG_TRACE_IRQFLAGS
bl trace_hardirqs_on // enabled while in userspace
arm64: Add trace_hardirqs_off annotation in ret_to_user When a kernel is built with CONFIG_TRACE_IRQFLAGS the following warning is produced when entering userspace for the first time: WARNING: at /work/Linux/linux-2.6-aarch64/kernel/locking/lockdep.c:3519 Modules linked in: CPU: 1 PID: 1 Comm: systemd Not tainted 4.4.0-rc3+ #639 Hardware name: Juno (DT) task: ffffffc9768a0000 ti: ffffffc9768a8000 task.ti: ffffffc9768a8000 PC is at check_flags.part.22+0x19c/0x1a8 LR is at check_flags.part.22+0x19c/0x1a8 pc : [<ffffffc0000fba6c>] lr : [<ffffffc0000fba6c>] pstate: 600001c5 sp : ffffffc9768abe10 x29: ffffffc9768abe10 x28: ffffffc9768a8000 x27: 0000000000000000 x26: 0000000000000001 x25: 00000000000000a6 x24: ffffffc00064be6c x23: ffffffc0009f249e x22: ffffffc9768a0000 x21: ffffffc97fea5480 x20: 00000000000001c0 x19: ffffffc00169a000 x18: 0000005558cc7b58 x17: 0000007fb78e3180 x16: 0000005558d2e238 x15: ffffffffffffffff x14: 0ffffffffffffffd x13: 0000000000000008 x12: 0101010101010101 x11: 7f7f7f7f7f7f7f7f x10: fefefefefefeff63 x9 : 7f7f7f7f7f7f7f7f x8 : 6e655f7371726964 x7 : 0000000000000001 x6 : ffffffc0001079c4 x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffffffc001698438 x2 : 0000000000000000 x1 : ffffffc9768a0000 x0 : 000000000000002e Call trace: [<ffffffc0000fba6c>] check_flags.part.22+0x19c/0x1a8 [<ffffffc0000fc440>] lock_is_held+0x80/0x98 [<ffffffc00064bafc>] __schedule+0x404/0x730 [<ffffffc00064be6c>] schedule+0x44/0xb8 [<ffffffc000085bb0>] ret_to_user+0x0/0x24 possible reason: unannotated irqs-off. irq event stamp: 502169 hardirqs last enabled at (502169): [<ffffffc000085a98>] el0_irq_naked+0x1c/0x24 hardirqs last disabled at (502167): [<ffffffc0000bb3bc>] __do_softirq+0x17c/0x298 softirqs last enabled at (502168): [<ffffffc0000bb43c>] __do_softirq+0x1fc/0x298 softirqs last disabled at (502143): [<ffffffc0000bb830>] irq_exit+0xa0/0xf0 This happens because we disable interrupts in ret_to_user before calling schedule() in work_resched. This patch adds the necessary trace_hardirqs_off annotation. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Reported-by: Mark Rutland <mark.rutland@arm.com> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com>
2015-12-04 12:42:29 +00:00
#endif
ldr x1, [tsk, #TI_FLAGS] // re-check for single-step
b finish_ret_to_user
/*
* "slow" syscall return path.
*/
ret_to_user:
disable_irq // disable interrupts
ldr x1, [tsk, #TI_FLAGS]
and x2, x1, #_TIF_WORK_MASK
cbnz x2, work_pending
finish_ret_to_user:
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_step_tsk x1, x2
kernel_exit 0
ENDPROC(ret_to_user)
/*
* This is how we return from a fork.
*/
ENTRY(ret_from_fork)
bl schedule_tail
cbz x19, 1f // not a kernel thread
mov x0, x20
blr x19
1: get_thread_info tsk
b ret_to_user
ENDPROC(ret_from_fork)
/*
* SVC handler.
*/
.align 6
el0_svc:
adrp stbl, sys_call_table // load syscall table pointer
uxtw scno, w8 // syscall number in w8
mov sc_nr, #__NR_syscalls
el0_svc_naked: // compat entry point
stp x0, scno, [sp, #S_ORIG_X0] // save the original x0 and syscall number
arm64: debug: avoid accessing mdscr_el1 on fault paths where possible Since mdscr_el1 is part of the debug register group, it is highly likely to be trapped by a hypervisor to prevent virtual machines from debugging (buggering?) each other. Unfortunately, this absolutely destroys our performance, since we access the register on many of our low-level fault handling paths to keep track of the various debug state machines. This patch removes our dependency on mdscr_el1 in the case that debugging is not being used. More specifically we: - Use TIF_SINGLESTEP to indicate that a task is stepping at EL0 and avoid disabling step in the MDSCR when we don't need to. MDSCR_EL1.SS handling is moved to kernel_entry, when trapping from userspace. - Ensure debug exceptions are re-enabled on *all* exception entry paths, even the debug exception handling path (where we re-enable exceptions after invoking the handler). Since we can now rely on MDSCR_EL1.SS being cleared by the entry code, exception handlers can usually enable debug immediately before enabling interrupts. - Remove all debug exception unmasking from ret_to_user and el1_preempt, since we will never get here with debug exceptions masked. This results in a slight change to kernel debug behaviour, where we now step into interrupt handlers and data aborts from EL1 when debugging the kernel, which is actually a useful thing to do. A side-effect of this is that it *does* potentially prevent stepping off {break,watch}points when there is a high-frequency interrupt source (e.g. a timer), so a debugger would need to use either breakpoints or manually disable interrupts to get around this issue. With this patch applied, guest performance is restored under KVM when debug register accesses are trapped (and we get a measurable performance increase on the host on Cortex-A57 too). Cc: Ian Campbell <ian.campbell@citrix.com> Tested-by: Marc Zyngier <marc.zyngier@arm.com> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
2014-04-29 18:04:06 +00:00
enable_dbg_and_irq
ct_user_exit 1
ldr x16, [tsk, #TI_FLAGS] // check for syscall hooks
tst x16, #_TIF_SYSCALL_WORK
b.ne __sys_trace
cmp scno, sc_nr // check upper syscall limit
b.hs ni_sys
ldr x16, [stbl, scno, lsl #3] // address in the syscall table
blr x16 // call sys_* routine
b ret_fast_syscall
ni_sys:
mov x0, sp
bl do_ni_syscall
b ret_fast_syscall
ENDPROC(el0_svc)
/*
* This is the really slow path. We're going to be doing context
* switches, and waiting for our parent to respond.
*/
__sys_trace:
mov w0, #-1 // set default errno for
cmp scno, x0 // user-issued syscall(-1)
b.ne 1f
mov x0, #-ENOSYS
str x0, [sp, #S_X0]
1: mov x0, sp
bl syscall_trace_enter
cmp w0, #-1 // skip the syscall?
b.eq __sys_trace_return_skipped
uxtw scno, w0 // syscall number (possibly new)
mov x1, sp // pointer to regs
cmp scno, sc_nr // check upper syscall limit
b.hs __ni_sys_trace
ldp x0, x1, [sp] // restore the syscall args
ldp x2, x3, [sp, #S_X2]
ldp x4, x5, [sp, #S_X4]
ldp x6, x7, [sp, #S_X6]
ldr x16, [stbl, scno, lsl #3] // address in the syscall table
blr x16 // call sys_* routine
__sys_trace_return:
str x0, [sp, #S_X0] // save returned x0
__sys_trace_return_skipped:
mov x0, sp
bl syscall_trace_exit
b ret_to_user
__ni_sys_trace:
mov x0, sp
bl do_ni_syscall
b __sys_trace_return
.popsection // .entry.text
/*
* Special system call wrappers.
*/
ENTRY(sys_rt_sigreturn_wrapper)
mov x0, sp
b sys_rt_sigreturn
ENDPROC(sys_rt_sigreturn_wrapper)