diff options
Diffstat (limited to 'arch/arm/kernel/sigreturn_codes.S')
| -rw-r--r-- | arch/arm/kernel/sigreturn_codes.S | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/arch/arm/kernel/sigreturn_codes.S b/arch/arm/kernel/sigreturn_codes.S new file mode 100644 index 000000000000..b84d0cb13682 --- /dev/null +++ b/arch/arm/kernel/sigreturn_codes.S @@ -0,0 +1,102 @@ +/* + * 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/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 + +#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 + + /* + * Note on addtional space: setup_return in signal.c + * algorithm uses two words copy regardless whether + * it is thumb case or not, so we need additional + * word after real last entry. + */ + arm_slot 2 + .space 4 + + .size sigreturn_codes, . - sigreturn_codes |