properly access mcontext_t program counter in cancellation handler

[oweals/musl.git] / src / thread / pthread_cancel.c

diff --git a/src/thread/pthread_cancel.c b/src/thread/pthread_cancel.c
index 0151a1ae5f93fba0d322dbea4f259ea0b899dddf..6eaf72c45c90e82b9e4bbe5bc2314111d39bc977 100644 (file)
--- a/src/thread/pthread_cancel.c
+++ b/src/thread/pthread_cancel.c
@@ -1,3 +1,4 @@
+#define _GNU_SOURCE
 #include <string.h>
 #include "pthread_impl.h"
 #include "syscall.h"
@@ -61,15 +62,15 @@ static void cancel_handler(int sig, siginfo_t *si, void *ctx)
 {
        pthread_t self = __pthread_self();
        ucontext_t *uc = ctx;
-       const char *ip = ((char **)&uc->uc_mcontext)[CANCEL_REG_IP];
+       uintptr_t pc = uc->uc_mcontext.MC_PC;
 
        a_barrier();
        if (!self->cancel || self->canceldisable == PTHREAD_CANCEL_DISABLE) return;
 
        _sigaddset(&uc->uc_sigmask, SIGCANCEL);
 
-       if (self->cancelasync || ip >= __cp_begin && ip < __cp_end) {
-               ((char **)&uc->uc_mcontext)[CANCEL_REG_IP] = (char *)__cp_cancel;
+       if (self->cancelasync || pc >= (uintptr_t)__cp_begin && pc < (uintptr_t)__cp_end) {
+               uc->uc_mcontext.MC_PC = (uintptr_t)__cp_cancel;
                return;
        }