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arm64: simplify ptrauth initialization

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Currently __cpu_setup conditionally initializes the address
authentication keys and enables them in SCTLR_EL1, doing so differently
for the primary CPU and secondary CPUs, and skipping this work for CPUs
returning from an idle state. For the latter case, cpu_do_resume
restores the keys and SCTLR_EL1 value after the MMU has been enabled.

This flow is rather difficult to follow, so instead let's move the
primary and secondary CPU initialization into their respective boot
paths. By following the example of cpu_do_resume and doing so once the
MMU is enabled, we can always initialize the keys from the values in
thread_struct, and avoid the machinery necessary to pass the keys in
secondary_data or open-coding initialization for the boot CPU.

This means we perform an additional RMW of SCTLR_EL1, but we already do
this in the cpu_do_resume path, and for other features in cpufeature.c,
so this isn't a major concern in a bringup path. Note that even while
the enable bits are clear, the key registers are accessible.

As this now renders the argument to __cpu_setup redundant, let's also
remove that entirely. Future extensions can follow a similar approach to
initialize values that differ for primary/secondary CPUs.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Reviewed-by: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Amit Daniel Kachhap <amit.kachhap@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20200423101606.37601-3-mark.rutland@arm.com
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Mark Rutland 2020-04-23 11:16:06 +01:00 committed by Will Deacon
parent d0055da526
commit 62a679cb28
7 changed files with 32 additions and 69 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
arch/arm64/include/asm/asm_pointer_auth.h
View File

@ -60,6 +60,28 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
alternative_else_nop_endif
.endm
.macro __ptrauth_keys_init_cpu tsk, tmp1, tmp2, tmp3
mrs \tmp1, id_aa64isar1_el1
ubfx \tmp1, \tmp1, #ID_AA64ISAR1_APA_SHIFT, #8
cbz \tmp1, .Lno_addr_auth\@
mov_q \tmp1, (SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \
SCTLR_ELx_ENDA | SCTLR_ELx_ENDB)
mrs \tmp2, sctlr_el1
orr \tmp2, \tmp2, \tmp1
msr sctlr_el1, \tmp2
__ptrauth_keys_install_kernel_nosync \tsk, \tmp1, \tmp2, \tmp3
isb
.Lno_addr_auth\@:
.endm
.macro ptrauth_keys_init_cpu tsk, tmp1, tmp2, tmp3
alternative_if_not ARM64_HAS_ADDRESS_AUTH
b .Lno_addr_auth\@
alternative_else_nop_endif
__ptrauth_keys_init_cpu \tsk, \tmp1, \tmp2, \tmp3
.Lno_addr_auth\@:
.endm
#else /* CONFIG_ARM64_PTR_AUTH */
.macro ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3

11
arch/arm64/include/asm/smp.h
View File

@ -23,14 +23,6 @@
#define CPU_STUCK_REASON_52_BIT_VA (UL(1) << CPU_STUCK_REASON_SHIFT)
#define CPU_STUCK_REASON_NO_GRAN (UL(2) << CPU_STUCK_REASON_SHIFT)
/* Possible options for __cpu_setup */
/* Option to setup primary cpu */
#define ARM64_CPU_BOOT_PRIMARY (1)
/* Option to setup secondary cpus */
#define ARM64_CPU_BOOT_SECONDARY (2)
/* Option to setup cpus for different cpu run time services */
#define ARM64_CPU_RUNTIME (3)
#ifndef __ASSEMBLY__
#include <asm/percpu.h>
@ -96,9 +88,6 @@ asmlinkage void secondary_start_kernel(void);
struct secondary_data {
void *stack;
struct task_struct *task;
#ifdef CONFIG_ARM64_PTR_AUTH
struct ptrauth_keys_kernel ptrauth_key;
#endif
long status;
};

3
arch/arm64/kernel/asm-offsets.c
View File

@ -92,9 +92,6 @@ int main(void)
BLANK();
DEFINE(CPU_BOOT_STACK, offsetof(struct secondary_data, stack));
DEFINE(CPU_BOOT_TASK, offsetof(struct secondary_data, task));
#ifdef CONFIG_ARM64_PTR_AUTH
DEFINE(CPU_BOOT_PTRAUTH_KEY, offsetof(struct secondary_data, ptrauth_key));
#endif
BLANK();
#ifdef CONFIG_KVM_ARM_HOST
DEFINE(VCPU_CONTEXT, offsetof(struct kvm_vcpu, arch.ctxt));

12
arch/arm64/kernel/head.S
View File

@ -13,6 +13,7 @@
#include <linux/init.h>
#include <linux/irqchip/arm-gic-v3.h>
#include <asm/asm_pointer_auth.h>
#include <asm/assembler.h>
#include <asm/boot.h>
#include <asm/ptrace.h>
@ -118,7 +119,6 @@ SYM_CODE_START(stext)
* On return, the CPU will be ready for the MMU to be turned on and
* the TCR will have been set.
*/
mov x0, #ARM64_CPU_BOOT_PRIMARY
bl __cpu_setup // initialise processor
b __primary_switch
SYM_CODE_END(stext)
@ -417,6 +417,10 @@ SYM_FUNC_START_LOCAL(__primary_switched)
adr_l x5, init_task
msr sp_el0, x5 // Save thread_info
#ifdef CONFIG_ARM64_PTR_AUTH
__ptrauth_keys_init_cpu x5, x6, x7, x8
#endif
adr_l x8, vectors // load VBAR_EL1 with virtual
msr vbar_el1, x8 // vector table address
isb
@ -717,7 +721,6 @@ SYM_FUNC_START_LOCAL(secondary_startup)
* Common entry point for secondary CPUs.
*/
bl __cpu_secondary_check52bitva
mov x0, #ARM64_CPU_BOOT_SECONDARY
bl __cpu_setup // initialise processor
adrp x1, swapper_pg_dir
bl __enable_mmu
@ -739,6 +742,11 @@ SYM_FUNC_START_LOCAL(__secondary_switched)
msr sp_el0, x2
mov x29, #0
mov x30, #0
#ifdef CONFIG_ARM64_PTR_AUTH
ptrauth_keys_init_cpu x2, x3, x4, x5
#endif
b secondary_start_kernel
SYM_FUNC_END(__secondary_switched)

1
arch/arm64/kernel/sleep.S
View File

@ -100,7 +100,6 @@ ENDPROC(__cpu_suspend_enter)
.pushsection ".idmap.text", "awx"
ENTRY(cpu_resume)
bl el2_setup // if in EL2 drop to EL1 cleanly
mov x0, #ARM64_CPU_RUNTIME
bl __cpu_setup
/* enable the MMU early - so we can access sleep_save_stash by va */
adrp x1, swapper_pg_dir

8
arch/arm64/kernel/smp.c
View File

@ -114,10 +114,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
*/
secondary_data.task = idle;
secondary_data.stack = task_stack_page(idle) + THREAD_SIZE;
#if defined(CONFIG_ARM64_PTR_AUTH)
secondary_data.ptrauth_key.apia.lo = idle->thread.keys_kernel.apia.lo;
secondary_data.ptrauth_key.apia.hi = idle->thread.keys_kernel.apia.hi;
#endif
update_cpu_boot_status(CPU_MMU_OFF);
__flush_dcache_area(&secondary_data, sizeof(secondary_data));
@ -140,10 +136,6 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
pr_crit("CPU%u: failed to come online\n", cpu);
secondary_data.task = NULL;
secondary_data.stack = NULL;
#if defined(CONFIG_ARM64_PTR_AUTH)
secondary_data.ptrauth_key.apia.lo = 0;
secondary_data.ptrauth_key.apia.hi = 0;
#endif
__flush_dcache_area(&secondary_data, sizeof(secondary_data));
status = READ_ONCE(secondary_data.status);
if (status == CPU_MMU_OFF)

44
arch/arm64/mm/proc.S
View File

@ -386,8 +386,6 @@ SYM_FUNC_END(idmap_kpti_install_ng_mappings)
*
* Initialise the processor for turning the MMU on.
*
* Input:
* x0 with a flag ARM64_CPU_BOOT_PRIMARY/ARM64_CPU_BOOT_SECONDARY/ARM64_CPU_RUNTIME.
* Output:
* Return in x0 the value of the SCTLR_EL1 register.
*/
@ -446,51 +444,9 @@ SYM_FUNC_START(__cpu_setup)
1:
#endif /* CONFIG_ARM64_HW_AFDBM */
msr tcr_el1, x10
mov x1, x0
/*
* Prepare SCTLR
*/
mov_q x0, SCTLR_EL1_SET
#ifdef CONFIG_ARM64_PTR_AUTH
/* No ptrauth setup for run time cpus */
cmp x1, #ARM64_CPU_RUNTIME
b.eq 3f
/* Check if the CPU supports ptrauth */
mrs x2, id_aa64isar1_el1
ubfx x2, x2, #ID_AA64ISAR1_APA_SHIFT, #8
cbz x2, 3f
/*
* The primary cpu keys are reset here and can be
* re-initialised with some proper values later.
*/
msr_s SYS_APIAKEYLO_EL1, xzr
msr_s SYS_APIAKEYHI_EL1, xzr
/* Just enable ptrauth for primary cpu */
cmp x1, #ARM64_CPU_BOOT_PRIMARY
b.eq 2f
/* if !system_supports_address_auth() then skip enable */
alternative_if_not ARM64_HAS_ADDRESS_AUTH
b 3f
alternative_else_nop_endif
/* Install ptrauth key for secondary cpus */
adr_l x2, secondary_data
ldr x3, [x2, #CPU_BOOT_TASK] // get secondary_data.task
cbz x3, 2f // check for slow booting cpus
ldp x3, x4, [x2, #CPU_BOOT_PTRAUTH_KEY]
msr_s SYS_APIAKEYLO_EL1, x3
msr_s SYS_APIAKEYHI_EL1, x4
2: /* Enable ptrauth instructions */
ldr x2, =SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \
SCTLR_ELx_ENDA | SCTLR_ELx_ENDB
orr x0, x0, x2
3:
#endif
ret // return to head.S
SYM_FUNC_END(__cpu_setup)