https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=0cbf19283b1d82a6ad2bed51674cea56cea5c31c
commit 0cbf19283b1d82a6ad2bed51674cea56cea5c31c Author: Corinna Vinschen <[email protected]> Date: Sat Jun 20 20:21:02 2015 +0200 Implement using alternate signal stack in Cygwin * exceptions.cc (_cygtls::call_signal_handler): Implement alternate signal stack handling. Signed-off-by: Corinna Vinschen <[email protected]> Diff: --- winsup/cygwin/exceptions.cc | 121 +++++++++++++++++++++++++++++++++++++++----- 1 file changed, 108 insertions(+), 13 deletions(-) diff --git a/winsup/cygwin/exceptions.cc b/winsup/cygwin/exceptions.cc index 112d792..895d57f 100644 --- a/winsup/cygwin/exceptions.cc +++ b/winsup/cygwin/exceptions.cc @@ -1537,19 +1537,26 @@ _cygtls::call_signal_handler () RtlCaptureContext ((CONTEXT *) &context.uc_mcontext); } - /* FIXME: If/when sigaltstack is implemented, this will need to do - something more complicated */ - context.uc_stack.ss_sp = NtCurrentTeb ()->Tib.StackBase; - context.uc_stack.ss_flags = 0; - if (!NtCurrentTeb ()->DeallocationStack) - context.uc_stack.ss_size - = (uintptr_t) NtCurrentTeb ()->Tib.StackLimit - - (uintptr_t) NtCurrentTeb ()->Tib.StackBase; + if (this_sa_flags & SA_ONSTACK + && !_my_tls.altstack.ss_flags + && _my_tls.altstack.ss_sp) + { + context.uc_stack = _my_tls.altstack; + context.uc_stack.ss_flags = SS_ONSTACK; + } else - context.uc_stack.ss_size - = (uintptr_t) NtCurrentTeb ()->DeallocationStack - - (uintptr_t) NtCurrentTeb ()->Tib.StackBase; - + { + context.uc_stack.ss_sp = NtCurrentTeb ()->Tib.StackBase; + context.uc_stack.ss_flags = 0; + if (!NtCurrentTeb ()->DeallocationStack) + context.uc_stack.ss_size + = (uintptr_t) NtCurrentTeb ()->Tib.StackLimit + - (uintptr_t) NtCurrentTeb ()->Tib.StackBase; + else + context.uc_stack.ss_size + = (uintptr_t) NtCurrentTeb ()->DeallocationStack + - (uintptr_t) NtCurrentTeb ()->Tib.StackBase; + } context.uc_sigmask = context.uc_mcontext.oldmask = this_oldmask; context.uc_mcontext.cr2 = (thissi.si_signo == SIGSEGV @@ -1565,7 +1572,95 @@ _cygtls::call_signal_handler () sig = 0; /* Flag that we can accept another signal */ unlock (); /* unlock signal stack */ - thisfunc (thissig, &thissi, thiscontext); + /* Alternate signal stack requested for this signal and alternate signal + stack set up for this thread? */ + if (this_sa_flags & SA_ONSTACK + && !_my_tls.altstack.ss_flags + && _my_tls.altstack.ss_sp) + { + /* Yes, use alternate signal stack. + + NOTE: + + We DO NOT change the TEB's stack addresses and we DO NOT move the + _cygtls area to the alternate stack. This seems to work fine on + 32 and 64 bit, but there may be Windows functions not working + correctly under these circumstances. Especially 32 bit exception + handling may be broken. + + On the other hand, if a Windows function crashed and we're handling + this here, moving the TEB stack addresses may be fatal. + + If the current code does not work as expected in the "usual" + POSIX circumstances, this problem must be revisited. */ + + /* Compute new stackbase. We start from the high address, subtract + 16 bytes (safe/sorry) and align to 16 byte. */ + uintptr_t new_sp = (uintptr_t) _my_tls.altstack.ss_sp + + _my_tls.altstack.ss_size - 0x10; + new_sp &= ~0xf; + /* Mark alternate stack as used. */ + _my_tls.altstack.ss_flags = SS_ONSTACK; + /* Move to alternate stack, call thisfunc, revert stack regs. */ +#ifdef __x86_64__ + __asm__ ("\n\ + movq %[NEW_SP], %%r10 # Load alt stack into r10 \n\ + movl %[SIG], %%ecx # thissig to 1st arg reg \n\ + movq %[SI], %%rdx # &thissi to 2nd arg reg \n\ + movq %[CTX], %%r8 # thiscontext to 3rd arg reg \n\ + movq %[FUNC], %%rax # thisfunc to rax \n\ + movq %%rbp, %%r12 # Save rbp in r12 \n\ + movq %%rsp, %%r13 # Store rsp in r13 \n\ + movq %%r10, %%rsp # Move alt stack into rsp \n\ + xorq %%rbp, %%rbp # Set rbp to 0 \n\ + subq $32, %%rsp # Setup shadow space \n\ + call *%%rax # Call thisfunc \n\ + movq %%r12, %%rbp # Restore rbp \n\ + movq %%r13, %%rsp # Restore rsp \n" + : : [NEW_SP] "o" (new_sp), + [SIG] "o" (thissig), + [SI] "p" (&thissi), + [CTX] "o" (thiscontext), + [FUNC] "o" (thisfunc) + : "memory"); +#else + __asm__ ("\n\ + push %%ecx # Save ecx on orig stack \n\ + push %%edx # Save edx on orig stack \n\ + movl %[NEW_SP], %%ecx # Load alt stack into ecx \n\ + subl $20, %%ecx # Make room on new stack \n\ + movl %[SIG], %%edx # thissig to 1st arg slot \n\ + movl %%edx, (%%ecx) \n\ + movl %[SI], %%edx # &thissi to 2nd arg slot \n\ + movl %%edx, 4(%%ecx) \n\ + movl %[CTX], %%edx # thiscontext to 3rd arg slot\n\ + movl %%edx, 8(%%ecx) \n\ + movl %[FUNC], %%eax # thisfunc to eax \n\ + movl %%ebp, 12(%%ecx) # Save ebp on alt stack \n\ + movl %%esp, 16(%%ecx) # Save esp on alt stack \n\ + movl %%ecx, %%esp # Move stackbase into esp \n\ + xorl %%ebp, %%ebp # Set ebp to 0 \n\ + call *%%eax # Call thisfunc \n\ + movl %%esp, %%ecx # Move alt stack to ecx \n\ + movl 12(%%ecx), %%ebp # Restore ebp \n\ + movl 16(%%ecx), %%esp # Restore esp \n\ + popl %%edx # Restore edx from orig stack\n\ + popl %%ecx # Restore ecx from orig stack\n" + : : [NEW_SP] "o" (new_sp), + [SIG] "o" (thissig), + [SI] "p" (&thissi), + [CTX] "o" (thiscontext), + [FUNC] "o" (thisfunc) + : "memory"); +#endif + /* Revert altstack info to normal. */ + _my_tls.altstack.ss_flags = 0; + } + else + /* No alternate signal stack requested or available, just call + signal handler. */ + thisfunc (thissig, &thissi, thiscontext); + incyg = true; set_signal_mask (_my_tls.sigmask, this_oldmask);
