/* _Unwind_Frames_Extra with shadow stack for x86-64 and x86. Copyright (C) 2017-2020 Free Software Foundation, Inc. This file is part of GCC. GCC is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3, or (at your option) any later version. GCC 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 General Public License for more details. Under Section 7 of GPL version 3, you are granted additional permissions described in the GCC Runtime Library Exception, version 3.1, as published by the Free Software Foundation. You should have received a copy of the GNU General Public License and a copy of the GCC Runtime Library Exception along with this program; see the files COPYING3 and COPYING.RUNTIME respectively. If not, see <http://www.gnu.org/licenses/>. */ /* NB: We need _get_ssp and _inc_ssp from <cetintrin.h>. But we can't include <x86intrin.h> which ends up including <mm_malloc.h>, which includes <stdlib.h> and <errno.h> unconditionally. But we can't include any libc system headers unconditionally from libgcc. Avoid including <mm_malloc.h> here by defining _IMMINTRIN_H_INCLUDED. */ #define _IMMINTRIN_H_INCLUDED #include <cetintrin.h> #undef _IMMINTRIN_H_INCLUDED /* Unwind the shadow stack for EH. */ #undef _Unwind_Frames_Extra #define _Unwind_Frames_Extra(x) \ do \ { \ _Unwind_Word ssp = _get_ssp (); \ if (ssp != 0) \ { \ _Unwind_Word tmp = (x); \ while (tmp > 255) \ { \ _inc_ssp (255); \ tmp -= 255; \ } \ _inc_ssp (tmp); \ } \ } \ while (0) /* Linux CET kernel places a restore token on shadow stack for signal handler to enhance security. The restore token is 8 byte and aligned to 8 bytes. It is usually transparent to user programs since kernel will pop the restore token when signal handler returns. But when an exception is thrown from a signal handler, now we need to pop the restore token from shadow stack. For x86-64, we just need to treat the signal frame as normal frame. For i386, we need to search for the restore token to check if the original shadow stack is 8 byte aligned. If the original shadow stack is 8 byte aligned, we just need to pop 2 slots, one restore token, from shadow stack. Otherwise, we need to pop 3 slots, one restore token + 4 byte padding, from shadow stack. */ #ifndef __x86_64__ #undef _Unwind_Frames_Increment #define _Unwind_Frames_Increment(context, frames) \ if (_Unwind_IsSignalFrame (context)) \ do \ { \ _Unwind_Word ssp, prev_ssp, token; \ ssp = _get_ssp (); \ if (ssp != 0) \ { \ /* Align shadow stack pointer to the next \ 8 byte aligned boundary. */ \ ssp = (ssp + 4) & ~7; \ do \ { \ /* Look for a restore token. */ \ token = (*(_Unwind_Word *) (ssp - 8)); \ prev_ssp = token & ~7; \ if (prev_ssp == ssp) \ break; \ ssp += 8; \ } \ while (1); \ frames += (token & 0x4) ? 3 : 2; \ } \ } \ while (0); \ else \ frames++; #endif |