| /* Definitions for Dwarf2 EH unwind support for Windows32 targets |
| Copyright (C) 2007-2023 Free Software Foundation, Inc. |
| Contributed by Pascal Obry <obry@adacore.com> |
| |
| 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/>. */ |
| |
| |
| /* This file implements the md_fallback_frame_state_for routine for |
| Windows, triggered when the GCC table based unwinding process hits a |
| frame for which no unwind info has been registered. This typically |
| occurs when raising an exception from a signal handler, because the |
| handler is actually called from the OS kernel. |
| |
| The basic idea is to detect that we are indeed trying to unwind past a |
| signal handler and to fill out the GCC internal unwinding structures for |
| the OS kernel frame as if it had been directly called from the |
| interrupted context. |
| |
| This is all assuming that the code to set the handler asked the kernel |
| to pass a pointer to such context information. |
| |
| There is three main parts. |
| |
| 1) The first thing to do is to check if we are in a signal context. If |
| not we can just return as there is nothing to do. We are probably on |
| some foreign code for which no unwind frame can be found. If this is |
| a call from the Windows signal handler, then: |
| |
| 2) We must get the signal context information. |
| |
| * With the standard exception filter: |
| |
| This is on Windows pointed to by an EXCEPTION_POINTERS. We know that |
| the signal handle will call an UnhandledExceptionFilter with this |
| parameter. The spec for this routine is: |
| |
| LONG WINAPI UnhandledExceptionFilter(struct _EXCEPTION_POINTERS*); |
| |
| So the pointer to struct _EXCEPTION_POINTERS must be somewhere on the |
| stack. |
| |
| This was found experimentally to always be at offset 0 of the context |
| frame in all cases handled by this implementation. |
| |
| * With the SEH exception handler: |
| |
| In this case the signal context is directly on the stack as the SEH |
| exception handler has the following prototype: |
| |
| DWORD |
| SEH_error_handler (PEXCEPTION_RECORD ExceptionRecord, |
| PVOID EstablisherFrame, |
| PCONTEXT ContextRecord, |
| PVOID DispatcherContext) |
| |
| This was found experimentally to always be at offset 56 of the |
| context frame in all cases handled by this implementation. |
| |
| 3) When we have the signal context we just have to save some registers |
| and set the return address based on the program counter (Eip). |
| |
| Note that this implementation follows closely the same principles as the |
| GNU/Linux and OSF ones. */ |
| |
| #ifndef __MINGW64__ |
| |
| #define WIN32_MEAN_AND_LEAN |
| #include <windows.h> |
| /* Patterns found experimentally to be on a Windows signal handler */ |
| |
| /* In a standard exception filter */ |
| |
| #define SIG_PAT1 \ |
| (pc_[-2] == 0xff && pc_[-1] == 0xd0 /* call %eax */ \ |
| && pc_[0] == 0x83 && pc_[1] == 0xf8) /* cmp 0xdepl,%eax */ |
| |
| #define SIG_PAT2 \ |
| (pc_[-5] == 0xe8 && pc_[-4] == 0x68 /* call (depl16) */ \ |
| && pc_[0] == 0xc3) /* ret */ |
| |
| /* In a Win32 SEH handler */ |
| |
| #define SIG_SEH1 \ |
| (pc_[-5] == 0xe8 /* call addr */ \ |
| && pc_[0] == 0x83 && pc_[1] == 0xc4 /* add 0xval,%esp */ \ |
| && pc_[3] == 0xb8) /* mov 0xval,%eax */ |
| |
| #define SIG_SEH2 \ |
| (pc_[-5] == 0x8b && pc_[-4] == 0x4d /* mov depl(%ebp),%ecx */ \ |
| && pc_[0] == 0x64 && pc_[1] == 0x8b) /* mov %fs:(0),<reg> */ \ |
| |
| /* In the GCC alloca (stack probing) */ |
| |
| #define SIG_ALLOCA \ |
| (pc_[-1] == 0x83 /* orl $0x0,(%ecx) */ \ |
| && pc_[0] == 0x9 && pc_[1] == 0 \ |
| && pc_[2] == 0x2d && pc_[3] == 0 /* subl $0x1000,%eax */ \ |
| && pc_[4] == 0x10 && pc_[5] == 0) |
| |
| |
| #define MD_FALLBACK_FRAME_STATE_FOR i386_w32_fallback_frame_state |
| |
| static _Unwind_Reason_Code |
| i386_w32_fallback_frame_state (struct _Unwind_Context *context, |
| _Unwind_FrameState *fs) |
| |
| { |
| void * ctx_ra_ = (void *)(context->ra); /* return address */ |
| void * ctx_cfa_ = (void *)(context->cfa); /* context frame address */ |
| unsigned char * pc_ = (unsigned char *) ctx_ra_; |
| |
| /* In the test below we look for two specific patterns found |
| experimentally to be in the Windows signal handler. */ |
| if (SIG_PAT1 || SIG_PAT2 || SIG_SEH1 || SIG_SEH2) |
| { |
| PEXCEPTION_POINTERS weinfo_; |
| PCONTEXT proc_ctx_; |
| long new_cfa_; |
| |
| if (SIG_SEH1) |
| proc_ctx_ = (PCONTEXT) (*(int*)(ctx_cfa_ + 56)); |
| else if (SIG_SEH2) |
| proc_ctx_ = (PCONTEXT) (*(int*)(ctx_cfa_ + 8)); |
| else |
| { |
| weinfo_ = (PEXCEPTION_POINTERS) (*(int*)ctx_cfa_); |
| proc_ctx_ = weinfo_->ContextRecord; |
| } |
| |
| /* The new context frame address is the stack pointer. */ |
| new_cfa_ = proc_ctx_->Esp; |
| fs->regs.cfa_how = CFA_REG_OFFSET; |
| fs->regs.cfa_reg = __builtin_dwarf_sp_column(); |
| fs->regs.cfa_offset = new_cfa_ - (long) ctx_cfa_; |
| |
| /* Restore registers. */ |
| fs->regs.how[0] = REG_SAVED_OFFSET; |
| fs->regs.reg[0].loc.offset = (long)&proc_ctx_->Eax - new_cfa_; |
| fs->regs.how[3] = REG_SAVED_OFFSET; |
| fs->regs.reg[3].loc.offset = (long)&proc_ctx_->Ebx - new_cfa_; |
| fs->regs.how[1] = REG_SAVED_OFFSET; |
| fs->regs.reg[1].loc.offset = (long)&proc_ctx_->Ecx - new_cfa_; |
| fs->regs.how[2] = REG_SAVED_OFFSET; |
| fs->regs.reg[2].loc.offset = (long)&proc_ctx_->Edx - new_cfa_; |
| fs->regs.how[6] = REG_SAVED_OFFSET; |
| fs->regs.reg[6].loc.offset = (long)&proc_ctx_->Esi - new_cfa_; |
| fs->regs.how[7] = REG_SAVED_OFFSET; |
| fs->regs.reg[7].loc.offset = (long)&proc_ctx_->Edi - new_cfa_; |
| fs->regs.how[5] = REG_SAVED_OFFSET; |
| fs->regs.reg[5].loc.offset = (long)&proc_ctx_->Ebp - new_cfa_; |
| fs->regs.how[8] = REG_SAVED_OFFSET; |
| fs->regs.reg[8].loc.offset = (long)&proc_ctx_->Eip - new_cfa_; |
| fs->retaddr_column = 8; |
| fs->signal_frame = 1; |
| |
| return _URC_NO_REASON; |
| } |
| |
| /* Unwinding through _alloca, propagating from a trap triggered by |
| one of it's probes prior to the real SP adjustment. The only |
| operations of interest performed is "pushl %ecx", followed by |
| ecx clobbering. */ |
| else if (SIG_ALLOCA) |
| { |
| /* Only one push between entry in _alloca and the probe trap. */ |
| long new_cfa_ = (long) ctx_cfa_ + 4; |
| |
| fs->regs.cfa_how = CFA_REG_OFFSET; |
| fs->regs.cfa_reg = __builtin_dwarf_sp_column(); |
| fs->regs.cfa_offset = new_cfa_ - (long) ctx_cfa_; |
| |
| /* The saved value of %ecx is at CFA - 4 */ |
| fs->regs.how[1] = REG_SAVED_OFFSET; |
| fs->regs.reg[1].loc.offset = -4; |
| |
| /* and what is stored at the CFA is the return address. */ |
| fs->retaddr_column = 8; |
| fs->regs.how[8] = REG_SAVED_OFFSET; |
| fs->regs.reg[8].loc.offset = 0; |
| fs->signal_frame = 1; |
| |
| return _URC_NO_REASON; |
| } |
| else |
| return _URC_END_OF_STACK; |
| } |
| |
| #endif /* !__MINGW64__ */ |
