[PATCH 1/2] tools/nolibc: fix WIFSIGNALED() for status 0

[Danish Khateeb <danishkhateeb03@gmail.com>]

WIFSIGNALED() needs the subtraction to wrap around for status 0, so that
only 1 to 0xff, a terminating signal with or without the core dump flag,
pass the check. But status is an int, and 0 - 1 is -1, which is less
than 0xff. A child that exits with 0 is therefore reported as both
exited and killed, and a caller that tests WIFSIGNALED() first sees
"killed by signal 0".

Make the subtraction unsigned, as musl does in the same macro.

Fixes: 8c934d4822c7 ("tools/nolibc: add helpers for wait() signal exits")
Cc: stable@vger.kernel.org # v6.4+
Assisted-by: LLM
Signed-off-by: Danish Khateeb <danishkhateeb03@gmail.com>
---
 tools/include/nolibc/types.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/include/nolibc/types.h b/tools/include/nolibc/types.h
index 8f3cb18df7f1..4373bd8a5b5f 100644
--- a/tools/include/nolibc/types.h
+++ b/tools/include/nolibc/types.h
@@ -119,7 +119,7 @@ struct timeval {
 #define WEXITSTATUS(status) (((status) & 0xff00) >> 8)
 #define WIFEXITED(status)   (((status) & 0x7f) == 0)
 #define WTERMSIG(status)    ((status) & 0x7f)
-#define WIFSIGNALED(status) ((status) - 1 < 0xff)
+#define WIFSIGNALED(status) ((status) - 1U < 0xff)
 
 /* standard exit() codes */
 #define EXIT_SUCCESS 0
-- 
2.55.0