Use syscall directly in write_validate to avoid ASAN errors

ASAN will complain about this write call with the following error:

ERROR: AddressSanitizer: stack-buffer-underflow on address
HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext

This is similar to what google's abseil does to work around the issue.

Reported-by: qiwang@fb.com

2 files changed, 6 insertions, 2 deletions

diff --git a/src/s390x/Ginit.c b/src/s390x/Ginit.c
index 8f3e369e..f0886ac9 100644
--- a/src/s390x/Ginit.c
+++ b/src/s390x/Ginit.c
@@ -35,6 +35,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include <stdlib.h>
 #include <string.h>
 #include <sys/mman.h>
+#include <sys/syscall.h>
 
 #include "unwind_i.h"
 
@@ -131,7 +132,8 @@ write_validate (void *addr)
 
   do
     {
-      ret = write (mem_validate_pipe[1], addr, 1);
+      /* use syscall insteadof write() so that ASAN does not complain */
+      ret = syscall (SYS_write, mem_validate_pipe[1], addr, 1);
     }
   while ( errno == EINTR );
 
diff --git a/src/x86_64/Ginit.c b/src/x86_64/Ginit.c
index 6281b767..2a84a1ee 100644
--- a/src/x86_64/Ginit.c
+++ b/src/x86_64/Ginit.c
@@ -34,6 +34,7 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.  */
 #include <stdlib.h>
 #include <string.h>
 #include <sys/mman.h>
+#include <sys/syscall.h>
 
 #include "unwind_i.h"
 
@@ -107,7 +108,8 @@ write_validate (void *addr)
 
   do
     {
-      ret = write (mem_validate_pipe[1], addr, 1);
+      /* use syscall insteadof write() so that ASAN does not complain */
+      ret = syscall (SYS_write, mem_validate_pipe[1], addr, 1);
     }
   while ( errno == EINTR );