LXR linux/arch/arm/kernel/sigreturn

   1/*
   2 * sigreturn_codes.S - code sinpets for sigreturn syscalls
   3 *
   4 * Created by:  Victor Kamensky, 2013-08-13
   5 * Copyright:   (C) 2013  Linaro Limited
   6 *
   7 * This program is free software; you can redistribute it and/or modify
   8 * it under the terms of the GNU General Public License version 2 as
   9 * published by the Free Software Foundation.
  10 *
  11 * This program is distributed in the hope that it will be useful,
  12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 * GNU General Public License for more details.
  15 */
  16
  17#include <asm/unistd.h>
  18
  19/*
  20 * For ARM syscalls, we encode the syscall number into the instruction.
  21 * With EABI, the syscall number has to be loaded into r7. As result
  22 * ARM syscall sequence snippet will have move and svc in .arm encoding
  23 *
  24 * For Thumb syscalls, we pass the syscall number via r7.  We therefore
  25 * need two 16-bit instructions in .thumb encoding
  26 *
  27 * Please note sigreturn_codes code are not executed in place. Instead
  28 * they just copied by kernel into appropriate places. Code inside of
  29 * arch/arm/kernel/signal.c is very sensitive to layout of these code
  30 * snippets.
  31 */
  32
  33/*
  34 * In CPU_THUMBONLY case kernel arm opcodes are not allowed.
  35 * Note in this case codes skips those instructions but it uses .org
  36 * directive to keep correct layout of sigreturn_codes array.
  37 */
  38#ifndef CONFIG_CPU_THUMBONLY
  39#define ARM_OK(code...) code
  40#else
  41#define ARM_OK(code...)
  42#endif
  43
  44        .macro arm_slot n
  45        .org    sigreturn_codes + 12 * (\n)
  46ARM_OK( .arm    )
  47        .endm
  48
  49        .macro thumb_slot n
  50        .org    sigreturn_codes + 12 * (\n) + 8
  51        .thumb
  52        .endm
  53
  54#if __LINUX_ARM_ARCH__ <= 4
  55        /*
  56         * Note we manually set minimally required arch that supports
  57         * required thumb opcodes for early arch versions. It is OK
  58         * for this file to be used in combination with other
  59         * lower arch variants, since these code snippets are only
  60         * used as input data.
  61         */
  62        .arch armv4t
  63#endif
  64
  65        .section .rodata
  66        .global sigreturn_codes
  67        .type   sigreturn_codes, #object
  68
  69        .align
  70
  71sigreturn_codes:
  72
  73        /* ARM sigreturn syscall code snippet */
  74        arm_slot 0
  75ARM_OK( mov     r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)       )
  76ARM_OK( swi     #(__NR_sigreturn)|(__NR_OABI_SYSCALL_BASE)      )
  77
  78        /* Thumb sigreturn syscall code snippet */
  79        thumb_slot 0
  80        movs    r7, #(__NR_sigreturn - __NR_SYSCALL_BASE)
  81        swi     #0
  82
  83        /* ARM sigreturn_rt syscall code snippet */
  84        arm_slot 1
  85ARM_OK( mov     r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)    )
  86ARM_OK( swi     #(__NR_rt_sigreturn)|(__NR_OABI_SYSCALL_BASE)   )
  87
  88        /* Thumb sigreturn_rt syscall code snippet */
  89        thumb_slot 1
  90        movs    r7, #(__NR_rt_sigreturn - __NR_SYSCALL_BASE)
  91        swi     #0
  92
  93        /*
  94         * Note on addtional space: setup_return in signal.c
  95         * algorithm uses two words copy regardless whether
  96         * it is thumb case or not, so we need additional
  97         * word after real last entry.
  98         */
  99        arm_slot 2
 100        .space  4
 101
 102        .size   sigreturn_codes, . - sigreturn_codes
 103