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/* Return backtrace of current program state. Arch-specific bits.
Copyright (C) 2020-2021 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#ifndef _UNWIND_ARCH_H
#define _UNWIND_ARCH_H
#include <stdint.h>
/* MIPS fallback code handle a frame where its FDE can not be obtained
(for instance a signal frame) by reading the kernel allocated signal frame
and adding '2' to the value of 'sc_pc' [1]. The added value is used to
recognize an end of an EH region on mips16 [2].
The idea here is to adjust the obtained signal frame ADDR value and remove
the libgcc added value by checking if the previous frame is a signal frame
one.
[1] libgcc/config/mips/linux-unwind.h from gcc code.
[2] gcc/config/mips/mips.h from gcc code. */
static inline void *
unwind_arch_adjustment (void *prev, void *addr)
{
uint32_t *pc = (uint32_t *) prev;
if (pc == NULL)
return addr;
/* For MIPS16 or microMIPS frame libgcc makes no adjustment. */
if ((uintptr_t) pc & 0x3)
return addr;
/* The vDSO containes either
24021061 li v0, 0x1061 (rt_sigreturn)
0000000c syscall
or
24021017 li v0, 0x1017 (sigreturn)
0000000c syscall */
if (pc[1] != 0x0000000c)
return addr;
#if _MIPS_SIM == _ABIO32
if (pc[0] == (0x24020000 | __NR_sigreturn))
return (void *) ((uintptr_t) addr - 2);
#endif
if (pc[0] == (0x24020000 | __NR_rt_sigreturn))
return (void *) ((uintptr_t) addr - 2);
return addr;
}
#endif
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