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Safe all clobbered volatile registers when using alternate stack 

* exceptions.cc (_cygtls::call_signal_handler): Drop subtracting 16
	bytes from the alternate stack, it's not necessary.  Safe all clobbered
	registers.  Safe one on the orignal stack, the others on the alternate
	stack on both platforms.

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
This commit is contained in:
Corinna Vinschen 2015-06-21 13:58:57 +02:00
parent 44745e3165
commit b6c18f2a64
2 changed files with 54 additions and 22 deletions
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7
winsup/cygwin/ChangeLog
View File

@ -1,3 +1,10 @@
2015-06-21 Corinna Vinschen <corinna@vinschen.de>
* exceptions.cc (_cygtls::call_signal_handler): Drop subtracting 16
bytes from the alternate stack, it's not necessary. Safe all clobbered
registers. Safe one on the orignal stack, the others on the alternate
stack on both platforms.
2015-06-20 Corinna Vinschen <corinna@vinschen.de> 2015-06-20 Corinna Vinschen <corinna@vinschen.de>
* exceptions.cc (_cygtls::call_signal_handler): Implement alternate * exceptions.cc (_cygtls::call_signal_handler): Implement alternate

69
winsup/cygwin/exceptions.cc
View File

@ -1594,29 +1594,49 @@ _cygtls::call_signal_handler ()
If the current code does not work as expected in the "usual" If the current code does not work as expected in the "usual"
POSIX circumstances, this problem must be revisited. */ POSIX circumstances, this problem must be revisited. */
/* Compute new stackbase. We start from the high address, subtract /* Compute new stackbase. We start from the high address, aligned
16 bytes (safe/sorry) and align to 16 byte. */ to 16 byte. */
uintptr_t new_sp = (uintptr_t) _my_tls.altstack.ss_sp uintptr_t new_sp = (uintptr_t) _my_tls.altstack.ss_sp
+ _my_tls.altstack.ss_size - 0x10; + _my_tls.altstack.ss_size;
new_sp &= ~0xf; new_sp &= ~0xf;
/* Mark alternate stack as used. */ /* Mark alternate stack as used. */
_my_tls.altstack.ss_flags = SS_ONSTACK; _my_tls.altstack.ss_flags = SS_ONSTACK;
/* Move to alternate stack, call thisfunc, revert stack regs. */ /* In assembler: Save regs on new stack, move to alternate stack,
call thisfunc, revert stack regs. */
#ifdef __x86_64__ #ifdef __x86_64__
/* Clobbered regs: rax, rcx, rdx, r8, r9, r10, r11, rbp, rsp */
__asm__ ("\n\ __asm__ ("\n\
movq %[NEW_SP], %%r10 # Load alt stack into r10 \n\ pushq %%r9 # Push r9 on orig stack \n\
movq %[NEW_SP], %%r9 # Load alt stack into r9 \n\
subq $0x40, %%r9 # Make room on alt stack to \n\
# save clobbered regs \n\
movq %%rax, (%%r9) # Save other clobbered regs \n\
movq %%rcx, 0x8(%%r9) \n\
movq %%rdx, 0x10(%%r9) \n\
movq %%r8, 0x18(%%r9) \n\
movq %%r10, 0x20(%%r9) \n\
movq %%r11, 0x28(%%r9) \n\
movq %%rbp, 0x30(%%r9) \n\
movq %%rsp, 0x38(%%r9) \n\
movl %[SIG], %%ecx # thissig to 1st arg reg \n\ movl %[SIG], %%ecx # thissig to 1st arg reg \n\
movq %[SI], %%rdx # &thissi to 2nd arg reg \n\ movq %[SI], %%rdx # &thissi to 2nd arg reg \n\
movq %[CTX], %%r8 # thiscontext to 3rd arg reg \n\ movq %[CTX], %%r8 # thiscontext to 3rd arg reg \n\
movq %[FUNC], %%rax # thisfunc to rax \n\ movq %[FUNC], %%rax # thisfunc to rax \n\
movq %%rbp, %%r12 # Save rbp in r12 \n\ movq %%r9, %%rsp # Move alt stack into rsp \n\
movq %%rsp, %%r13 # Save rsp in r13 \n\
movq %%r10, %%rsp # Move alt stack into rsp \n\
xorq %%rbp, %%rbp # Set rbp to 0 \n\ xorq %%rbp, %%rbp # Set rbp to 0 \n\
subq $32, %%rsp # Setup shadow space \n\ subq $0x20, %%rsp # Setup shadow space \n\
call *%%rax # Call thisfunc \n\ call *%%rax # Call thisfunc \n\
movq %%r12, %%rbp # Restore rbp \n\ addq $0x20, %%rsp # Revert shadow space \n\
movq %%r13, %%rsp # Restore rsp \n" movq %%rsp, %%r9 # Restore clobbered regs \n\
movq 0x38(%%r9), %%rsp \n\
movq 0x30(%%r9), %%rbp \n\
movq 0x28(%%r9), %%r11 \n\
movq 0x20(%%r9), %%r10 \n\
movq 0x18(%%r9), %%r8 \n\
movq 0x10(%%r9), %%rdx \n\
movq 0x8(%%r9), %%rcx \n\
movq (%%r9), %%rax \n\
popq %%r9 \n"
: : [NEW_SP] "o" (new_sp), : : [NEW_SP] "o" (new_sp),
[SIG] "o" (thissig), [SIG] "o" (thissig),
[SI] "p" (&thissi), [SI] "p" (&thissi),
@ -1624,11 +1644,17 @@ _cygtls::call_signal_handler ()
[FUNC] "o" (thisfunc) [FUNC] "o" (thisfunc)
: "memory"); : "memory");
#else #else
/* Clobbered regs: eax, ecx, edx, ebp, esp */
__asm__ ("\n\ __asm__ ("\n\
push %%ecx # Save ecx on orig stack \n\ push %%ecx # Push ecx on orig stack \n\
push %%edx # Save edx on orig stack \n\
movl %[NEW_SP], %%ecx # Load alt stack into ecx \n\ movl %[NEW_SP], %%ecx # Load alt stack into ecx \n\
subl $20, %%ecx # Make room on new stack \n\ subl $28, %%ecx # Make room on alt stack for \n\
# clobbered regs and args to \n\
# signal handler \n\
movl %%eax, 12(%%ecx) # Save other clobbered regs \n\
movl %%edx, 16(%%ecx) \n\
movl %%ebp, 20(%%ecx) \n\
movl %%esp, 24(%%ecx) \n\
movl %[SIG], %%edx # thissig to 1st arg slot \n\ movl %[SIG], %%edx # thissig to 1st arg slot \n\
movl %%edx, (%%ecx) \n\ movl %%edx, (%%ecx) \n\
movl %[SI], %%edx # &thissi to 2nd arg slot \n\ movl %[SI], %%edx # &thissi to 2nd arg slot \n\
@ -1636,16 +1662,15 @@ _cygtls::call_signal_handler ()
movl %[CTX], %%edx # thiscontext to 3rd arg slot\n\ movl %[CTX], %%edx # thiscontext to 3rd arg slot\n\
movl %%edx, 8(%%ecx) \n\ movl %%edx, 8(%%ecx) \n\
movl %[FUNC], %%eax # thisfunc to eax \n\ movl %[FUNC], %%eax # thisfunc to eax \n\
movl %%ebp, 12(%%ecx) # Save ebp on alt stack \n\ movl %%ecx, %%esp # Move alt stack into esp \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\ xorl %%ebp, %%ebp # Set ebp to 0 \n\
call *%%eax # Call thisfunc \n\ call *%%eax # Call thisfunc \n\
movl %%esp, %%ecx # Move alt stack to ecx \n\ movl %%esp, %%ecx # Restore clobbered regs \n\
movl 12(%%ecx), %%ebp # Restore ebp \n\ movl 24(%%ecx), %%esp \n\
movl 16(%%ecx), %%esp # Restore esp \n\ movl 20(%%ecx), %%ebp \n\
popl %%edx # Restore edx from orig stack\n\ movl 16(%%ecx), %%edx \n\
popl %%ecx # Restore ecx from orig stack\n" movl 12(%%ecx), %%eax \n\
popl %%ecx \n"
: : [NEW_SP] "o" (new_sp), : : [NEW_SP] "o" (new_sp),
[SIG] "o" (thissig), [SIG] "o" (thissig),
[SI] "p" (&thissi), [SI] "p" (&thissi),