208 lines
7.7 KiB
C
208 lines
7.7 KiB
C
/* Definitions for Dwarf2 EH unwind support for Windows32 targets
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Copyright (C) 2007-2019 Free Software Foundation, Inc.
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Contributed by Pascal Obry <obry@adacore.com>
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This file is part of GCC.
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GCC is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free
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Software Foundation; either version 3, or (at your option) any later
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version.
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GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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Under Section 7 of GPL version 3, you are granted additional
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permissions described in the GCC Runtime Library Exception, version
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3.1, as published by the Free Software Foundation.
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You should have received a copy of the GNU General Public License and
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a copy of the GCC Runtime Library Exception along with this program;
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see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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<http://www.gnu.org/licenses/>. */
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/* This file implements the md_fallback_frame_state_for routine for
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Windows, triggered when the GCC table based unwinding process hits a
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frame for which no unwind info has been registered. This typically
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occurs when raising an exception from a signal handler, because the
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handler is actually called from the OS kernel.
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The basic idea is to detect that we are indeed trying to unwind past a
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signal handler and to fill out the GCC internal unwinding structures for
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the OS kernel frame as if it had been directly called from the
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interrupted context.
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This is all assuming that the code to set the handler asked the kernel
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to pass a pointer to such context information.
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There is three main parts.
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1) The first thing to do is to check if we are in a signal context. If
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not we can just return as there is nothing to do. We are probably on
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some foreign code for which no unwind frame can be found. If this is
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a call from the Windows signal handler, then:
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2) We must get the signal context information.
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* With the standard exception filter:
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This is on Windows pointed to by an EXCEPTION_POINTERS. We know that
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the signal handle will call an UnhandledExceptionFilter with this
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parameter. The spec for this routine is:
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LONG WINAPI UnhandledExceptionFilter(struct _EXCEPTION_POINTERS*);
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So the pointer to struct _EXCEPTION_POINTERS must be somewhere on the
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stack.
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This was found experimentally to always be at offset 0 of the context
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frame in all cases handled by this implementation.
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* With the SEH exception handler:
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In this case the signal context is directly on the stack as the SEH
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exception handler has the following prototype:
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DWORD
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SEH_error_handler (PEXCEPTION_RECORD ExceptionRecord,
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PVOID EstablisherFrame,
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PCONTEXT ContextRecord,
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PVOID DispatcherContext)
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This was found experimentally to always be at offset 56 of the
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context frame in all cases handled by this implementation.
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3) When we have the signal context we just have to save some registers
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and set the return address based on the program counter (Eip).
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Note that this implementation follows closely the same principles as the
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GNU/Linux and OSF ones. */
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#ifndef __MINGW64__
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#define WIN32_MEAN_AND_LEAN
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#include <windows.h>
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/* Patterns found experimentally to be on a Windows signal handler */
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/* In a standard exception filter */
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#define SIG_PAT1 \
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(pc_[-2] == 0xff && pc_[-1] == 0xd0 /* call %eax */ \
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&& pc_[0] == 0x83 && pc_[1] == 0xf8) /* cmp 0xdepl,%eax */
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#define SIG_PAT2 \
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(pc_[-5] == 0xe8 && pc_[-4] == 0x68 /* call (depl16) */ \
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&& pc_[0] == 0xc3) /* ret */
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/* In a Win32 SEH handler */
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#define SIG_SEH1 \
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(pc_[-5] == 0xe8 /* call addr */ \
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&& pc_[0] == 0x83 && pc_[1] == 0xc4 /* add 0xval,%esp */ \
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&& pc_[3] == 0xb8) /* mov 0xval,%eax */
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#define SIG_SEH2 \
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(pc_[-5] == 0x8b && pc_[-4] == 0x4d /* mov depl(%ebp),%ecx */ \
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&& pc_[0] == 0x64 && pc_[1] == 0x8b) /* mov %fs:(0),<reg> */ \
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/* In the GCC alloca (stack probing) */
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#define SIG_ALLOCA \
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(pc_[-1] == 0x83 /* orl $0x0,(%ecx) */ \
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&& pc_[0] == 0x9 && pc_[1] == 0 \
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&& pc_[2] == 0x2d && pc_[3] == 0 /* subl $0x1000,%eax */ \
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&& pc_[4] == 0x10 && pc_[5] == 0)
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#define MD_FALLBACK_FRAME_STATE_FOR i386_w32_fallback_frame_state
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static _Unwind_Reason_Code
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i386_w32_fallback_frame_state (struct _Unwind_Context *context,
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_Unwind_FrameState *fs)
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{
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void * ctx_ra_ = (void *)(context->ra); /* return address */
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void * ctx_cfa_ = (void *)(context->cfa); /* context frame address */
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unsigned char * pc_ = (unsigned char *) ctx_ra_;
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/* In the test below we look for two specific patterns found
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experimentally to be in the Windows signal handler. */
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if (SIG_PAT1 || SIG_PAT2 || SIG_SEH1 || SIG_SEH2)
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{
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PEXCEPTION_POINTERS weinfo_;
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PCONTEXT proc_ctx_;
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long new_cfa_;
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if (SIG_SEH1)
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proc_ctx_ = (PCONTEXT) (*(int*)(ctx_cfa_ + 56));
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else if (SIG_SEH2)
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proc_ctx_ = (PCONTEXT) (*(int*)(ctx_cfa_ + 8));
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else
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{
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weinfo_ = (PEXCEPTION_POINTERS) (*(int*)ctx_cfa_);
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proc_ctx_ = weinfo_->ContextRecord;
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}
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/* The new context frame address is the stack pointer. */
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new_cfa_ = proc_ctx_->Esp;
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fs->regs.cfa_how = CFA_REG_OFFSET;
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fs->regs.cfa_reg = __builtin_dwarf_sp_column();
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fs->regs.cfa_offset = new_cfa_ - (long) ctx_cfa_;
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/* Restore registers. */
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fs->regs.reg[0].how = REG_SAVED_OFFSET;
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fs->regs.reg[0].loc.offset = (long)&proc_ctx_->Eax - new_cfa_;
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fs->regs.reg[3].how = REG_SAVED_OFFSET;
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fs->regs.reg[3].loc.offset = (long)&proc_ctx_->Ebx - new_cfa_;
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fs->regs.reg[1].how = REG_SAVED_OFFSET;
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fs->regs.reg[1].loc.offset = (long)&proc_ctx_->Ecx - new_cfa_;
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fs->regs.reg[2].how = REG_SAVED_OFFSET;
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fs->regs.reg[2].loc.offset = (long)&proc_ctx_->Edx - new_cfa_;
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fs->regs.reg[6].how = REG_SAVED_OFFSET;
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fs->regs.reg[6].loc.offset = (long)&proc_ctx_->Esi - new_cfa_;
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fs->regs.reg[7].how = REG_SAVED_OFFSET;
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fs->regs.reg[7].loc.offset = (long)&proc_ctx_->Edi - new_cfa_;
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fs->regs.reg[5].how = REG_SAVED_OFFSET;
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fs->regs.reg[5].loc.offset = (long)&proc_ctx_->Ebp - new_cfa_;
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fs->regs.reg[8].how = REG_SAVED_OFFSET;
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fs->regs.reg[8].loc.offset = (long)&proc_ctx_->Eip - new_cfa_;
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fs->retaddr_column = 8;
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fs->signal_frame = 1;
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return _URC_NO_REASON;
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}
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/* Unwinding through _alloca, propagating from a trap triggered by
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one of it's probes prior to the real SP adjustment. The only
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operations of interest performed is "pushl %ecx", followed by
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ecx clobbering. */
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else if (SIG_ALLOCA)
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{
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/* Only one push between entry in _alloca and the probe trap. */
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long new_cfa_ = (long) ctx_cfa_ + 4;
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fs->regs.cfa_how = CFA_REG_OFFSET;
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fs->regs.cfa_reg = __builtin_dwarf_sp_column();
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fs->regs.cfa_offset = new_cfa_ - (long) ctx_cfa_;
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/* The saved value of %ecx is at CFA - 4 */
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fs->regs.reg[1].how = REG_SAVED_OFFSET;
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fs->regs.reg[1].loc.offset = -4;
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/* and what is stored at the CFA is the return address. */
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fs->retaddr_column = 8;
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fs->regs.reg[8].how = REG_SAVED_OFFSET;
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fs->regs.reg[8].loc.offset = 0;
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fs->signal_frame = 1;
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return _URC_NO_REASON;
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}
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else
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return _URC_END_OF_STACK;
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}
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#endif /* !__MINGW64__ */
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