5c16595353
Signal handlers are not direct function pointers but pointers to function descriptor in that case. Therefore we must retrieve the actual function address and load the GOT value into r9 from the descriptor before branching to the actual handler. If a restorer is provided, we also have to load its address and GOT from its descriptor. That descriptor address and the code to load it is pushed onto the stack to be executed as soon as the signal handler returns. However, to be compatible with NX stacks, the FDPIC bounce code is also copied to the signal page along with the other code stubs. Therefore this code must get at the descriptor address whether it executes from the stack or the signal page. To do so we use the stack pointer which points at the signal stack frame where the descriptor address was stored. Because the rt signal frame is different from the simpler frame, two versions of the bounce code are needed, and two variants (ARM and Thumb) as well. The asm-offsets facility is used to determine the actual offset in the signal frame for each version, meaning that struct sigframe and rt_sigframe had to be moved to a separate file. Signed-off-by: Nicolas Pitre <nico@linaro.org> Acked-by: Mickael GUENE <mickael.guene@st.com> Tested-by: Vincent Abriou <vincent.abriou@st.com> Tested-by: Andras Szemzo <szemzo.andras@gmail.com>
149 lines
3.8 KiB
ArmAsm
149 lines
3.8 KiB
ArmAsm
/*
|
|
* sigreturn_codes.S - code sinpets for sigreturn syscalls
|
|
*
|
|
* Created by: Victor Kamensky, 2013-08-13
|
|
* Copyright: (C) 2013 Linaro Limited
|
|
*
|
|
* 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.
|
|
*/
|
|
|
|
#include <asm/assembler.h>
|
|
#include <asm/asm-offsets.h>
|
|
#include <asm/unistd.h>
|
|
|
|
/*
|
|
* For ARM syscalls, we encode the syscall number into the instruction.
|
|
* With EABI, the syscall number has to be loaded into r7. As result
|
|
* ARM syscall sequence snippet will have move and svc in .arm encoding
|
|
*
|
|
* For Thumb syscalls, we pass the syscall number via r7. We therefore
|
|
* need two 16-bit instructions in .thumb encoding
|
|
*
|
|
* Please note sigreturn_codes code are not executed in place. Instead
|
|
* they just copied by kernel into appropriate places. Code inside of
|
|
* arch/arm/kernel/signal.c is very sensitive to layout of these code
|
|
* snippets.
|
|
*/
|
|
|
|
/*
|
|
* In CPU_THUMBONLY case kernel arm opcodes are not allowed.
|
|
* Note in this case codes skips those instructions but it uses .org
|
|
* directive to keep correct layout of sigreturn_codes array.
|
|
*/
|
|
#ifndef CONFIG_CPU_THUMBONLY
|
|
#define ARM_OK(code...) code
|
|
#else
|
|
#define ARM_OK(code...)
|
|
#endif
|
|
|
|
.macro arm_slot n
|
|
.org sigreturn_codes + 12 * (\n)
|
|
ARM_OK( .arm )
|
|
.endm
|
|
|
|
.macro thumb_slot n
|
|
.org sigreturn_codes + 12 * (\n) + 8
|
|
.thumb
|
|
.endm
|
|
|
|
.macro arm_fdpic_slot n
|
|
.org sigreturn_codes + 24 + 20 * (\n)
|
|
ARM_OK( .arm )
|
|
.endm
|
|
|
|
.macro thumb_fdpic_slot n
|
|
.org sigreturn_codes + 24 + 20 * (\n) + 12
|
|
.thumb
|
|
.endm
|
|
|
|
|
|
#if __LINUX_ARM_ARCH__ <= 4
|
|
/*
|
|
* Note we manually set minimally required arch that supports
|
|
* required thumb opcodes for early arch versions. It is OK
|
|
* for this file to be used in combination with other
|
|
* lower arch variants, since these code snippets are only
|
|
* used as input data.
|
|
*/
|
|
.arch armv4t
|
|
#endif
|
|
|
|
.section .rodata
|
|
.global sigreturn_codes
|
|
.type sigreturn_codes, #object
|
|
|
|
.align
|
|
|
|
sigreturn_codes:
|
|
|
|
/* ARM sigreturn syscall code snippet */
|
|
arm_slot 0
|
|
ARM_OK( mov r7, #(__NR_sigreturn - __NR_SYSCALL_BASE) )
|
|
ARM_OK( swi #(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE) )
|
|
|
|
/* Thumb sigreturn syscall code snippet */
|
|
thumb_slot 0
|
|
movs r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
|
|
swi #0
|
|
|
|
/* ARM sigreturn_rt syscall code snippet */
|
|
arm_slot 1
|
|
ARM_OK( mov r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE) )
|
|
ARM_OK( swi #(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE) )
|
|
|
|
/* Thumb sigreturn_rt syscall code snippet */
|
|
thumb_slot 1
|
|
movs r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
|
|
swi #0
|
|
|
|
/* ARM sigreturn restorer FDPIC bounce code snippet */
|
|
arm_fdpic_slot 0
|
|
ARM_OK( ldr r3, [sp, #SIGFRAME_RC3_OFFSET] )
|
|
ARM_OK( ldmia r3, {r3, r9} )
|
|
#ifdef CONFIG_ARM_THUMB
|
|
ARM_OK( bx r3 )
|
|
#else
|
|
ARM_OK( ret r3 )
|
|
#endif
|
|
|
|
/* Thumb sigreturn restorer FDPIC bounce code snippet */
|
|
thumb_fdpic_slot 0
|
|
ldr r3, [sp, #SIGFRAME_RC3_OFFSET]
|
|
ldmia r3, {r2, r3}
|
|
mov r9, r3
|
|
bx r2
|
|
|
|
/* ARM sigreturn_rt restorer FDPIC bounce code snippet */
|
|
arm_fdpic_slot 1
|
|
ARM_OK( ldr r3, [sp, #RT_SIGFRAME_RC3_OFFSET] )
|
|
ARM_OK( ldmia r3, {r3, r9} )
|
|
#ifdef CONFIG_ARM_THUMB
|
|
ARM_OK( bx r3 )
|
|
#else
|
|
ARM_OK( ret r3 )
|
|
#endif
|
|
|
|
/* Thumb sigreturn_rt restorer FDPIC bounce code snippet */
|
|
thumb_fdpic_slot 1
|
|
ldr r3, [sp, #RT_SIGFRAME_RC3_OFFSET]
|
|
ldmia r3, {r2, r3}
|
|
mov r9, r3
|
|
bx r2
|
|
|
|
/*
|
|
* Note on additional space: setup_return in signal.c
|
|
* always copies the same number of words regardless whether
|
|
* it is thumb case or not, so we need one additional padding
|
|
* word after the last entry.
|
|
*/
|
|
.space 4
|
|
|
|
.size sigreturn_codes, . - sigreturn_codes
|