arch/arm64/kernel/vdso32/sigreturn.S

   1 /*
   2  * Sigreturn trampolines for returning from a signal when the SA_RESTORER
   3  * flag is not set.
   4  *
   5  * Copyright (C) 2016 ARM 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  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  *
  19  * Based on glibc's arm sa_restorer. While this is not strictly necessary, we
  20  * provide both A32 and T32 versions, in accordance with the arm sigreturn
  21  * code.
  22  */
  23
  24 #include <linux/linkage.h>
  25 #include <asm/asm-offsets.h>
  26 #include <asm/unistd32.h>
  27
  28 .macro sigreturn_trampoline name, syscall, regs_offset
  29         /*
  30          * We provide directives for enabling stack unwinding through the
  31          * trampoline. On arm, CFI directives are only used for debugging (and
  32          * the vDSO is stripped of debug information), so only the arm-specific
  33          * unwinding directives are useful here.
  34          */
  35         .fnstart
  36         .save {r0-r15}
  37         .pad #\regs_offset
  38         /*
  39          * It is necessary to start the unwind tables at least one instruction
  40          * before the trampoline, as the unwinder will assume that the signal
  41          * handler has been called from the trampoline, that is just before
  42          * where the signal handler returns (mov r7, ...).
  43          */
  44         nop
  45 ENTRY(\name)
  46         mov     r7, #\syscall
  47         svc     #0
  48         .fnend
  49         /*
  50          * We would like to use ENDPROC, but the macro uses @ which is a
  51          * comment symbol for arm assemblers, so directly use .type with %
  52          * instead.
  53          */
  54         .type \name, %function
  55 END(\name)
  56 .endm
  57
  58         .text
  59
  60         .arm
  61         sigreturn_trampoline __kernel_sigreturn_arm, \
  62                              __NR_sigreturn, \
  63                              COMPAT_SIGFRAME_REGS_OFFSET
  64
  65         sigreturn_trampoline __kernel_rt_sigreturn_arm, \
  66                              __NR_rt_sigreturn, \
  67                              COMPAT_RT_SIGFRAME_REGS_OFFSET
  68
  69         .thumb
  70         sigreturn_trampoline __kernel_sigreturn_thumb, \
  71                              __NR_sigreturn, \
  72                              COMPAT_SIGFRAME_REGS_OFFSET
  73
  74         sigreturn_trampoline __kernel_rt_sigreturn_thumb, \
  75                              __NR_rt_sigreturn, \
  76                              COMPAT_RT_SIGFRAME_REGS_OFFSET