path: root/src/thread/i386/syscall_cp.s
diff options
authorRich Felker <>2011-04-17 15:30:08 -0400
committerRich Felker <>2011-04-17 15:30:08 -0400
commit09dae2b7b66f741b30aa7ce95ab395239da20762 (patch)
treeda94ed95c914ec60663aec3368e3642d8c41cfeb /src/thread/i386/syscall_cp.s
parentebf82447be4b30bedc19ad868c3a0662b1ba596d (diff)
fix bugs in cancellable syscall asm
x86_64 was just plain wrong in the cancel-flag-already-set path, and crashing. the more subtle error was not clearing the saved stack pointer before returning to c code. this could result in the signal handler misidentifying c code as the pre-syscall part of the asm, and acting on cancellation at the wrong time, and thus resource leak race conditions. also, now __cancel (in the c code) is responsible for clearing the saved sp in the already-cancelled branch. this means we have to use call rather than jmp to ensure the stack pointer in the c will never match what the asm saved.
Diffstat (limited to 'src/thread/i386/syscall_cp.s')
1 files changed, 4 insertions, 5 deletions
diff --git a/src/thread/i386/syscall_cp.s b/src/thread/i386/syscall_cp.s
index 6d8c354b..51905131 100644
--- a/src/thread/i386/syscall_cp.s
+++ b/src/thread/i386/syscall_cp.s
@@ -28,9 +28,8 @@ __syscall_cp_asm:
popl %edi
popl %esi
popl %ebx
+ xorl %edx,%edx
+ movl 4(%esp),%ecx
+ movl %edx,(%ecx)
-2: xorl %eax,%eax
- movl %eax,4(%ecx)
- movl %eax,(%ecx)
- pushl $-1
- call __cancel
+2: call __cancel