sysdeps/mips/unwind-arch.h

   1 /* Dynamic loading of the libgcc unwinder.  MIPS customization.
   2    Copyright (C) 2020-2024 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    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _ARCH_UNWIND_LINK_H
  20 #define _ARCH_UNWIND_LINK_H
  21
  22 #include <stdint.h>
  23 #include <sys/syscall.h>
  24
  25 #define UNWIND_LINK_GETIP 1
  26 #define UNWIND_LINK_FRAME_STATE_FOR 1
  27 #define UNWIND_LINK_FRAME_ADJUSTMENT 1
  28 #define UNWIND_LINK_EXTRA_FIELDS
  29 #define UNWIND_LINK_EXTRA_INIT
  30
  31 /* MIPS fallback code handle a frame where its FDE can not be obtained
  32    (for instance a signal frame) by reading the kernel allocated signal frame
  33    and adding '2' to the value of 'sc_pc' [1].  The added value is used to
  34    recognize an end of an EH region on mips16 [2].
  35
  36    The idea here is to adjust the obtained signal frame ADDR value and remove
  37    the libgcc added value by checking if the previous frame is a signal frame
  38    one.
  39
  40    [1] libgcc/config/mips/linux-unwind.h from gcc code.
  41    [2] gcc/config/mips/mips.h from gcc code.  */
  42
  43 static inline void *
  44 unwind_arch_adjustment (void *prev, void *addr)
  45 {
  46   uint32_t *pc = (uint32_t *) prev;
  47
  48   if (pc == NULL)
  49     return addr;
  50
  51   /* For MIPS16 or microMIPS frame libgcc makes no adjustment.  */
  52   if ((uintptr_t) pc & 0x3)
  53     return addr;
  54
  55   /* The vDSO contains either
  56
  57      24021061 li v0, 0x1061 (rt_sigreturn)
  58      0000000c syscall
  59         or
  60      24021017 li v0, 0x1017 (sigreturn)
  61      0000000c syscall  */
  62   if (pc[1] != 0x0000000c)
  63     return addr;
  64 #if _MIPS_SIM == _ABIO32
  65   if (pc[0] == (0x24020000 | __NR_sigreturn))
  66     return (void *) ((uintptr_t) addr - 2);
  67 #endif
  68   if (pc[0] == (0x24020000 | __NR_rt_sigreturn))
  69     return (void *) ((uintptr_t) addr - 2);
  70
  71   return addr;
  72 }
  73
  74 #endif /* _ARCH_UNWIND_LINK_H */