Implement using alternate signal stack in Cygwin
* exceptions.cc (_cygtls::call_signal_handler): Implement alternate signal stack handling. Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen
parent
6442e914d9
commit
0cbf19283b
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@ -1537,8 +1537,15 @@ _cygtls::call_signal_handler ()
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RtlCaptureContext ((CONTEXT *) &context.uc_mcontext);
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}
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/* FIXME: If/when sigaltstack is implemented, this will need to do
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something more complicated */
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if (this_sa_flags & SA_ONSTACK
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&& !_my_tls.altstack.ss_flags
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&& _my_tls.altstack.ss_sp)
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{
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context.uc_stack = _my_tls.altstack;
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context.uc_stack.ss_flags = SS_ONSTACK;
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}
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else
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{
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context.uc_stack.ss_sp = NtCurrentTeb ()->Tib.StackBase;
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context.uc_stack.ss_flags = 0;
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if (!NtCurrentTeb ()->DeallocationStack)
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@ -1549,7 +1556,7 @@ _cygtls::call_signal_handler ()
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context.uc_stack.ss_size
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= (uintptr_t) NtCurrentTeb ()->DeallocationStack
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- (uintptr_t) NtCurrentTeb ()->Tib.StackBase;
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}
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context.uc_sigmask = context.uc_mcontext.oldmask = this_oldmask;
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context.uc_mcontext.cr2 = (thissi.si_signo == SIGSEGV
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@ -1565,7 +1572,95 @@ _cygtls::call_signal_handler ()
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sig = 0; /* Flag that we can accept another signal */
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unlock (); /* unlock signal stack */
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/* Alternate signal stack requested for this signal and alternate signal
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stack set up for this thread? */
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if (this_sa_flags & SA_ONSTACK
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&& !_my_tls.altstack.ss_flags
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&& _my_tls.altstack.ss_sp)
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{
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/* Yes, use alternate signal stack.
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NOTE:
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We DO NOT change the TEB's stack addresses and we DO NOT move the
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_cygtls area to the alternate stack. This seems to work fine on
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32 and 64 bit, but there may be Windows functions not working
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correctly under these circumstances. Especially 32 bit exception
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handling may be broken.
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On the other hand, if a Windows function crashed and we're handling
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this here, moving the TEB stack addresses may be fatal.
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If the current code does not work as expected in the "usual"
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POSIX circumstances, this problem must be revisited. */
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/* Compute new stackbase. We start from the high address, subtract
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16 bytes (safe/sorry) and align to 16 byte. */
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uintptr_t new_sp = (uintptr_t) _my_tls.altstack.ss_sp
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+ _my_tls.altstack.ss_size - 0x10;
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new_sp &= ~0xf;
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/* Mark alternate stack as used. */
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_my_tls.altstack.ss_flags = SS_ONSTACK;
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/* Move to alternate stack, call thisfunc, revert stack regs. */
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#ifdef __x86_64__
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__asm__ ("\n\
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movq %[NEW_SP], %%r10 # Load alt stack into r10 \n\
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movl %[SIG], %%ecx # thissig to 1st arg reg \n\
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movq %[SI], %%rdx # &thissi to 2nd arg reg \n\
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movq %[CTX], %%r8 # thiscontext to 3rd arg reg \n\
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movq %[FUNC], %%rax # thisfunc to rax \n\
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movq %%rbp, %%r12 # Save rbp in r12 \n\
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movq %%rsp, %%r13 # Store rsp in r13 \n\
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movq %%r10, %%rsp # Move alt stack into rsp \n\
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xorq %%rbp, %%rbp # Set rbp to 0 \n\
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subq $32, %%rsp # Setup shadow space \n\
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call *%%rax # Call thisfunc \n\
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movq %%r12, %%rbp # Restore rbp \n\
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movq %%r13, %%rsp # Restore rsp \n"
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: : [NEW_SP] "o" (new_sp),
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[SIG] "o" (thissig),
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[SI] "p" (&thissi),
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[CTX] "o" (thiscontext),
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[FUNC] "o" (thisfunc)
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: "memory");
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#else
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__asm__ ("\n\
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push %%ecx # Save ecx on orig stack \n\
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push %%edx # Save edx on orig stack \n\
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movl %[NEW_SP], %%ecx # Load alt stack into ecx \n\
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subl $20, %%ecx # Make room on new stack \n\
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movl %[SIG], %%edx # thissig to 1st arg slot \n\
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movl %%edx, (%%ecx) \n\
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movl %[SI], %%edx # &thissi to 2nd arg slot \n\
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movl %%edx, 4(%%ecx) \n\
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movl %[CTX], %%edx # thiscontext to 3rd arg slot\n\
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movl %%edx, 8(%%ecx) \n\
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movl %[FUNC], %%eax # thisfunc to eax \n\
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movl %%ebp, 12(%%ecx) # Save ebp on alt stack \n\
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movl %%esp, 16(%%ecx) # Save esp on alt stack \n\
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movl %%ecx, %%esp # Move stackbase into esp \n\
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xorl %%ebp, %%ebp # Set ebp to 0 \n\
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call *%%eax # Call thisfunc \n\
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movl %%esp, %%ecx # Move alt stack to ecx \n\
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movl 12(%%ecx), %%ebp # Restore ebp \n\
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movl 16(%%ecx), %%esp # Restore esp \n\
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popl %%edx # Restore edx from orig stack\n\
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popl %%ecx # Restore ecx from orig stack\n"
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: : [NEW_SP] "o" (new_sp),
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[SIG] "o" (thissig),
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[SI] "p" (&thissi),
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[CTX] "o" (thiscontext),
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[FUNC] "o" (thisfunc)
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: "memory");
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#endif
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/* Revert altstack info to normal. */
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_my_tls.altstack.ss_flags = 0;
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}
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else
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/* No alternate signal stack requested or available, just call
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signal handler. */
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thisfunc (thissig, &thissi, thiscontext);
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incyg = true;
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set_signal_mask (_my_tls.sigmask, this_oldmask);
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