sysdeps/unix/sysv/linux/x86_64/sigaction.c

   1 /* POSIX.1 `sigaction' call for Linux/x86-64.
   2    Copyright (C) 2001-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <sysdep.h>
  20 #include <errno.h>
  21 #include <stddef.h>
  22 #include <signal.h>
  23 #include <string.h>
  24
  25 #include <sysdep.h>
  26 #include <sys/syscall.h>
  27
  28 /* The difference here is that the sigaction structure used in the
  29    kernel is not the same as we use in the libc.  Therefore we must
  30    translate it here.  */
  31 #include <kernel_sigaction.h>
  32
  33 #include "ucontext_i.h"
  34
  35 /* We do not globally define the SA_RESTORER flag so do it here.  */
  36 #define SA_RESTORER 0x04000000
  37
  38 /* Using the hidden attribute here does not change the code but it
  39    helps to avoid warnings.  */
  40 extern void restore_rt (void) asm ("__restore_rt") attribute_hidden;
  41
  42
  43 /* If ACT is not NULL, change the action for SIG to *ACT.
  44    If OACT is not NULL, put the old action for SIG in *OACT.  */
  45 int
  46 __libc_sigaction (int sig, const struct sigaction *act, struct sigaction *oact)
  47 {
  48   int result;
  49   struct kernel_sigaction kact, koact;
  50
  51   if (act)
  52     {
  53       kact.k_sa_handler = act->sa_handler;
  54       memcpy (&kact.sa_mask, &act->sa_mask, sizeof (sigset_t));
  55       kact.sa_flags = act->sa_flags | SA_RESTORER;
  56
  57       kact.sa_restorer = &restore_rt;
  58     }
  59
  60   /* XXX The size argument hopefully will have to be changed to the
  61      real size of the user-level sigset_t.  */
  62   result = INLINE_SYSCALL (rt_sigaction, 4,
  63                            sig, act ? &kact : NULL,
  64                            oact ? &koact : NULL, _NSIG / 8);
  65   if (oact && result >= 0)
  66     {
  67       oact->sa_handler = koact.k_sa_handler;
  68       memcpy (&oact->sa_mask, &koact.sa_mask, sizeof (sigset_t));
  69       oact->sa_flags = koact.sa_flags;
  70       oact->sa_restorer = koact.sa_restorer;
  71     }
  72   return result;
  73 }
  74 libc_hidden_def (__libc_sigaction)
  75
  76 #ifdef WRAPPER_INCLUDE
  77 # include WRAPPER_INCLUDE
  78 #endif
  79
  80 #ifndef LIBC_SIGACTION
  81 weak_alias (__libc_sigaction, __sigaction)
  82 libc_hidden_weak (__sigaction)
  83 weak_alias (__libc_sigaction, sigaction)
  84 #endif
  85
  86 /* NOTE: Please think twice before making any changes to the bits of
  87    code below.  GDB needs some intimate knowledge about it to
  88    recognize them as signal trampolines, and make backtraces through
  89    signal handlers work right.  Important are both the names
  90    (__restore_rt) and the exact instruction sequence.
  91    If you ever feel the need to make any changes, please notify the
  92    appropriate GDB maintainer.
  93
  94    The unwind information starts a byte before __restore_rt, so that
  95    it is found when unwinding, to get an address the unwinder assumes
  96    will be in the middle of a call instruction.  See the Linux kernel
  97    (the i386 vsyscall, in particular) for an explanation of the complex
  98    unwind information used here in order to get the traditional CFA.
  99    We do not restore cs - it's only stored as two bytes here so that's
 100    a bit tricky.  We don't use the gas cfi directives, so that we can
 101    reliably add .cfi_signal_frame.  */
 102
 103 #define do_cfa_expr                                             \
 104   "     .byte 0x0f\n"           /* DW_CFA_def_cfa_expression */ \
 105   "     .uleb128 2f-1f\n"       /* length */                    \
 106   "1:   .byte 0x77\n"           /* DW_OP_breg7 */               \
 107   "     .sleb128 " CFI_STRINGIFY (oRSP) "\n"                    \
 108   "     .byte 0x06\n"           /* DW_OP_deref */               \
 109   "2:"
 110
 111 #define do_expr(regno, offset)                                  \
 112   "     .byte 0x10\n"           /* DW_CFA_expression */         \
 113   "     .uleb128 " CFI_STRINGIFY (regno) "\n"                   \
 114   "     .uleb128 2f-1f\n"       /* length */                    \
 115   "1:   .byte 0x77\n"           /* DW_OP_breg7 */               \
 116   "     .sleb128 " CFI_STRINGIFY (offset) "\n"                  \
 117   "2:"
 118
 119 #define RESTORE(name, syscall) RESTORE2 (name, syscall)
 120 # define RESTORE2(name, syscall) \
 121 asm                                                                     \
 122   (                                                                     \
 123    /* `nop' for debuggers assuming `call' should not disalign the code.  */ \
 124    "    nop\n"                                                          \
 125    ".align 16\n"                                                        \
 126    ".LSTART_" #name ":\n"                                               \
 127    "    .type __" #name ",@function\n"                                  \
 128    "__" #name ":\n"                                                     \
 129    "    movq $" #syscall ", %rax\n"                                     \
 130    "    syscall\n"                                                      \
 131    ".LEND_" #name ":\n"                                                 \
 132    ".section .eh_frame,\"a\",@progbits\n"                               \
 133    ".LSTARTFRAME_" #name ":\n"                                          \
 134    "    .long .LENDCIE_" #name "-.LSTARTCIE_" #name "\n"                \
 135    ".LSTARTCIE_" #name ":\n"                                            \
 136    "    .long 0\n"      /* CIE ID */                                    \
 137    "    .byte 1\n"      /* Version number */                            \
 138    "    .string \"zRS\"\n" /* NUL-terminated augmentation string */     \
 139    "    .uleb128 1\n"   /* Code alignment factor */                     \
 140    "    .sleb128 -8\n"  /* Data alignment factor */                     \
 141    "    .uleb128 16\n"  /* Return address register column (rip) */      \
 142    /* Augmentation value length */                                      \
 143    "    .uleb128 .LENDAUGMNT_" #name "-.LSTARTAUGMNT_" #name "\n"       \
 144    ".LSTARTAUGMNT_" #name ":\n"                                         \
 145    "    .byte 0x1b\n"   /* DW_EH_PE_pcrel|DW_EH_PE_sdata4. */           \
 146    ".LENDAUGMNT_" #name ":\n"                                           \
 147    "    .align " LP_SIZE "\n"                                           \
 148    ".LENDCIE_" #name ":\n"                                              \
 149    "    .long .LENDFDE_" #name "-.LSTARTFDE_" #name "\n" /* FDE len */  \
 150    ".LSTARTFDE_" #name ":\n"                                            \
 151    "    .long .LSTARTFDE_" #name "-.LSTARTFRAME_" #name "\n" /* CIE */  \
 152    /* `LSTART_' is subtracted 1 as debuggers assume a `call' here.  */  \
 153    "    .long (.LSTART_" #name "-1)-.\n" /* PC-relative start addr.  */ \
 154    "    .long .LEND_" #name "-(.LSTART_" #name "-1)\n"                  \
 155    "    .uleb128 0\n"                   /* FDE augmentation length */   \
 156    do_cfa_expr                                                          \
 157    do_expr (8 /* r8 */, oR8)                                            \
 158    do_expr (9 /* r9 */, oR9)                                            \
 159    do_expr (10 /* r10 */, oR10)                                         \
 160    do_expr (11 /* r11 */, oR11)                                         \
 161    do_expr (12 /* r12 */, oR12)                                         \
 162    do_expr (13 /* r13 */, oR13)                                         \
 163    do_expr (14 /* r14 */, oR14)                                         \
 164    do_expr (15 /* r15 */, oR15)                                         \
 165    do_expr (5 /* rdi */, oRDI)                                          \
 166    do_expr (4 /* rsi */, oRSI)                                          \
 167    do_expr (6 /* rbp */, oRBP)                                          \
 168    do_expr (3 /* rbx */, oRBX)                                          \
 169    do_expr (1 /* rdx */, oRDX)                                          \
 170    do_expr (0 /* rax */, oRAX)                                          \
 171    do_expr (2 /* rcx */, oRCX)                                          \
 172    do_expr (7 /* rsp */, oRSP)                                          \
 173    do_expr (16 /* rip */, oRIP)                                         \
 174    /* libgcc-4.1.1 has only `DWARF_FRAME_REGISTERS == 17'.  */          \
 175    /* do_expr (49 |* rflags *|, oEFL) */                                \
 176    /* `cs'/`ds'/`fs' are unaligned and a different size.  */            \
 177    /* gas: Error: register save offset not a multiple of 8  */          \
 178    "    .align " LP_SIZE "\n"                                           \
 179    ".LENDFDE_" #name ":\n"                                              \
 180    "    .previous\n"                                                    \
 181    );
 182 /* The return code for realtime-signals.  */
 183 RESTORE (restore_rt, __NR_rt_sigreturn)