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e0969e0c9b
linux/arch/sh/kernel/entry-common.S
Stuart Menefy e0969e0c9b sh: Fix syscall tracing ordering. 
The implementation of system call tracing in the kernel has a
couple of ordering problems:

 - the validity of the system call number is checked before
   calling out to system call tracing code, and should be
   done after

 - the system call number used when tracing is the one the
   system call was invoked with, while the system call tracing
   code can legitimatly change the call number (for example
   strace permutes fork into clone)

This patch fixes both of these problems, and also reoders the
code slightly to make the direct path through the code the
common case.

Signed-off-by: Stuart Menefy <stuart.menefy@st.com>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>
2006-12-06 10:45:38 +09:00

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/* $Id: entry.S,v 1.37 2004/06/11 13:02:46 doyu Exp $
*
* linux/arch/sh/entry.S
*
* Copyright (C) 1999, 2000, 2002 Niibe Yutaka
* Copyright (C) 2003 Paul Mundt
*
* This file is subject to the terms and conditions of the GNU General Public
* License. See the file "COPYING" in the main directory of this archive
* for more details.
*
*/
! NOTE:
! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
! to be jumped is too far, but it causes illegal slot exception.
/*
* entry.S contains the system-call and fault low-level handling routines.
* This also contains the timer-interrupt handler, as well as all interrupts
* and faults that can result in a task-switch.
*
* NOTE: This code handles signal-recognition, which happens every time
* after a timer-interrupt and after each system call.
*
* NOTE: This code uses a convention that instructions in the delay slot
* of a transfer-control instruction are indented by an extra space, thus:
*
* jmp @k0 ! control-transfer instruction
* ldc k1, ssr ! delay slot
*
* Stack layout in 'ret_from_syscall':
* ptrace needs to have all regs on the stack.
* if the order here is changed, it needs to be
* updated in ptrace.c and ptrace.h
*
* r0
* ...
* r15 = stack pointer
* spc
* pr
* ssr
* gbr
* mach
* macl
* syscall #
*
*/
#if defined(CONFIG_PREEMPT)
# define preempt_stop() cli
#else
# define preempt_stop()
# define resume_kernel __restore_all
#endif
#if defined(CONFIG_SH_STANDARD_BIOS) || defined(CONFIG_SH_KGDB)
! Handle kernel debug if either kgdb (SW) or gdb-stub (FW) is present.
! If both are configured, handle the debug traps (breakpoints) in SW,
! but still allow BIOS traps to FW.
.align 2
debug_kernel:
#if defined(CONFIG_SH_STANDARD_BIOS) && defined(CONFIG_SH_KGDB)
/* Force BIOS call to FW (debug_trap put TRA in r8) */
mov r8,r0
shlr2 r0
cmp/eq #0x3f,r0
bt debug_kernel_fw
#endif /* CONFIG_SH_STANDARD_BIOS && CONFIG_SH_KGDB */
debug_enter:
#if defined(CONFIG_SH_KGDB)
/* Jump to kgdb, pass stacked regs as arg */
debug_kernel_sw:
mov.l 3f, r0
jmp @r0
mov r15, r4
.align 2
3: .long kgdb_handle_exception
#endif /* CONFIG_SH_KGDB */
#endif /* CONFIG_SH_STANDARD_BIOS || CONFIG_SH_KGDB */
.align 2
debug_trap:
#if defined(CONFIG_SH_STANDARD_BIOS) || defined(CONFIG_SH_KGDB)
mov #OFF_SR, r0
mov.l @(r0,r15), r0 ! get status register
shll r0
shll r0 ! kernel space?
bt/s debug_kernel
#endif
mov.l @r15, r0 ! Restore R0 value
mov.l 1f, r8
jmp @r8
nop
.align 2
ENTRY(exception_error)
!
sti
mov.l 2f, r0
jmp @r0
nop
!
.align 2
1: .long break_point_trap_software
2: .long do_exception_error
.align 2
ret_from_exception:
preempt_stop()
ENTRY(ret_from_irq)
!
mov #OFF_SR, r0
mov.l @(r0,r15), r0 ! get status register
shll r0
shll r0 ! kernel space?
get_current_thread_info r8, r0
bt resume_kernel ! Yes, it's from kernel, go back soon
#ifdef CONFIG_PREEMPT
bra resume_userspace
nop
ENTRY(resume_kernel)
mov.l @(TI_PRE_COUNT,r8), r0 ! current_thread_info->preempt_count
tst r0, r0
bf noresched
need_resched:
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #_TIF_NEED_RESCHED, r0 ! need_resched set?
bt noresched
mov #OFF_SR, r0
mov.l @(r0,r15), r0 ! get status register
and #0xf0, r0 ! interrupts off (exception path)?
cmp/eq #0xf0, r0
bt noresched
mov.l 1f, r0
mov.l r0, @(TI_PRE_COUNT,r8)
sti
mov.l 2f, r0
jsr @r0
nop
mov #0, r0
mov.l r0, @(TI_PRE_COUNT,r8)
cli
bra need_resched
nop
noresched:
bra __restore_all
nop
.align 2
1: .long PREEMPT_ACTIVE
2: .long schedule
#endif
ENTRY(resume_userspace)
! r8: current_thread_info
cli
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #_TIF_WORK_MASK, r0
bt/s __restore_all
tst #_TIF_NEED_RESCHED, r0
.align 2
work_pending:
! r0: current_thread_info->flags
! r8: current_thread_info
! t: result of "tst #_TIF_NEED_RESCHED, r0"
bf/s work_resched
tst #(_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK), r0
work_notifysig:
bt/s __restore_all
mov r15, r4
mov r12, r5 ! set arg1(save_r0)
mov r0, r6
mov.l 2f, r1
mov.l 3f, r0
jmp @r1
lds r0, pr
work_resched:
#ifndef CONFIG_PREEMPT
! gUSA handling
mov.l @(OFF_SP,r15), r0 ! get user space stack pointer
mov r0, r1
shll r0
bf/s 1f
shll r0
bf/s 1f
mov #OFF_PC, r0
! SP >= 0xc0000000 : gUSA mark
mov.l @(r0,r15), r2 ! get user space PC (program counter)
mov.l @(OFF_R0,r15), r3 ! end point
cmp/hs r3, r2 ! r2 >= r3?
bt 1f
add r3, r1 ! rewind point #2
mov.l r1, @(r0,r15) ! reset PC to rewind point #2
!
1:
#endif
mov.l 1f, r1
jsr @r1 ! schedule
nop
cli
!
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #_TIF_WORK_MASK, r0
bt __restore_all
bra work_pending
tst #_TIF_NEED_RESCHED, r0
.align 2
1: .long schedule
2: .long do_notify_resume
3: .long restore_all
.align 2
syscall_exit_work:
! r0: current_thread_info->flags
! r8: current_thread_info
tst #_TIF_SYSCALL_TRACE, r0
bt/s work_pending
tst #_TIF_NEED_RESCHED, r0
sti
! XXX setup arguments...
mov.l 4f, r0 ! do_syscall_trace
jsr @r0
nop
bra resume_userspace
nop
.align 2
syscall_trace_entry:
! Yes it is traced.
! XXX setup arguments...
mov.l 4f, r11 ! Call do_syscall_trace which notifies
jsr @r11 ! superior (will chomp R[0-7])
nop
! Reload R0-R4 from kernel stack, where the
! parent may have modified them using
! ptrace(POKEUSR). (Note that R0-R2 are
! used by the system call handler directly
! from the kernel stack anyway, so don't need
! to be reloaded here.) This allows the parent
! to rewrite system calls and args on the fly.
mov.l @(OFF_R4,r15), r4 ! arg0
mov.l @(OFF_R5,r15), r5
mov.l @(OFF_R6,r15), r6
mov.l @(OFF_R7,r15), r7 ! arg3
mov.l @(OFF_R3,r15), r3 ! syscall_nr
!
mov.l 2f, r10 ! Number of syscalls
cmp/hs r10, r3
bf syscall_call
mov #-ENOSYS, r0
bra syscall_exit
mov.l r0, @(OFF_R0,r15) ! Return value
__restore_all:
mov.l 1f,r0
jmp @r0
nop
.align 2
1: .long restore_all
.align 2
not_syscall_tra:
bra debug_trap
nop
.align 2
syscall_badsys: ! Bad syscall number
mov #-ENOSYS, r0
bra resume_userspace
mov.l r0, @(OFF_R0,r15) ! Return value
/*
* Syscall interface:
*
* Syscall #: R3
* Arguments #0 to #3: R4--R7
* Arguments #4 to #6: R0, R1, R2
* TRA: (number of arguments + 0x10) x 4
*
* This code also handles delegating other traps to the BIOS/gdb stub
* according to:
*
* Trap number
* (TRA>>2) Purpose
* -------- -------
* 0x0-0xf old syscall ABI
* 0x10-0x1f new syscall ABI
* 0x20-0xff delegated through debug_trap to BIOS/gdb stub.
*
* Note: When we're first called, the TRA value must be shifted
* right 2 bits in order to get the value that was used as the "trapa"
* argument.
*/
.align 2
.globl ret_from_fork
ret_from_fork:
mov.l 1f, r8
jsr @r8
mov r0, r4
bra syscall_exit
nop
.align 2
1: .long schedule_tail
!
ENTRY(system_call)
#if !defined(CONFIG_CPU_SH2)
mov.l 1f, r9
mov.l @r9, r8 ! Read from TRA (Trap Address) Register
#endif
!
! Is the trap argument >= 0x20? (TRA will be >= 0x80)
mov #0x7f, r9
cmp/hi r9, r8
bt/s not_syscall_tra
mov #OFF_TRA, r9
add r15, r9
mov.l r8, @r9 ! set TRA value to tra
sti
!
get_current_thread_info r8, r10
mov.l @(TI_FLAGS,r8), r8
mov #_TIF_SYSCALL_TRACE, r10
tst r10, r8
bf syscall_trace_entry
!
mov.l 2f, r8 ! Number of syscalls
cmp/hs r8, r3
bt syscall_badsys
!
syscall_call:
shll2 r3 ! x4
mov.l 3f, r8 ! Load the address of sys_call_table
add r8, r3
mov.l @r3, r8
jsr @r8 ! jump to specific syscall handler
nop
mov.l @(OFF_R0,r15), r12 ! save r0
mov.l r0, @(OFF_R0,r15) ! save the return value
!
syscall_exit:
cli
!
get_current_thread_info r8, r0
mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
tst #_TIF_ALLWORK_MASK, r0
bf syscall_exit_work
bra __restore_all
nop
.align 2
#if !defined(CONFIG_CPU_SH2)
1: .long TRA
#endif
2: .long NR_syscalls
3: .long sys_call_table
4: .long do_syscall_trace
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