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Merge pull request #244 from qnighy/dynamic-stack-probing

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Fix segfault on probestack with dynamic alloca.
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Alex Crichton 2018-05-28 11:54:19 -05:00 committed by GitHub
commit 6eb8f8d710
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1 changed files with 12 additions and 0 deletions
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12
src/probestack.rs
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@ -64,6 +64,13 @@ pub unsafe extern fn __rust_probestack() {
// bytes pushed on the stack orginally with our return address. Using
// `8(%rsp)` simulates us testing the stack pointer in the caller's
// context.
// It's usually called when %rax >= 0x1000, but that's not always true.
// Dynamic stack allocation, which is needed to implement unsized
// rvalues, triggers stackprobe even if %rax < 0x1000.
// Thus we have to check %r11 first to avoid segfault.
cmp $$0x1000,%r11
jna 3f
2:
sub $$0x1000,%rsp
test %rsp,8(%rsp)
@ -71,6 +78,7 @@ pub unsafe extern fn __rust_probestack() {
cmp $$0x1000,%r11
ja 2b
3:
// Finish up the last remaining stack space requested, getting the last
// bits out of r11
sub %r11,%rsp
@ -98,6 +106,9 @@ pub unsafe extern fn __rust_probestack() {
asm!("
push %ecx
mov %eax,%ecx
cmp $$0x1000,%ecx
jna 3f
2:
sub $$0x1000,%esp
test %esp,8(%esp)
@ -105,6 +116,7 @@ pub unsafe extern fn __rust_probestack() {
cmp $$0x1000,%ecx
ja 2b
3:
sub %ecx,%esp
test %esp,8(%esp)