From: David Carlier <devnexen@gmail.com>
Date: Sat, 9 Dec 2017 22:28:21 +0000 (+0000)
Subject: Improve explicit_bzero implementation
X-Git-Tag: php-7.3.0alpha1~779
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=e835e3c1324bd5e285afd8403f7554c7a2fe3f4f;p=php

Improve explicit_bzero implementation

Using the weak symbol explicit_bzero_hook does not work if LTO is
enabled. Instead avoid memset optimizations using an asm memory
barrier.

Use a fallback implementation where the memory is zeroed through
volatile.
---

diff --git a/main/explicit_bzero.c b/main/explicit_bzero.c
index e99e082e6d..a6d99337fb 100644
--- a/main/explicit_bzero.c
+++ b/main/explicit_bzero.c
@@ -30,15 +30,18 @@
 
 #include <string.h>
 
-__attribute__((weak)) void
-__explicit_bzero_hook(void *dst, size_t siz)
-{
-}
-
 PHPAPI void php_explicit_bzero(void *dst, size_t siz)
 {
+#ifdef __GNUC__
 	memset(dst, 0, siz);
-	__explicit_bzero_hook(dst, siz);
+	asm __volatile__("" :: "r"(dst) : "memory"); 
+#else
+	size_t i = 0;
+	volatile unsigned char *buf = (volatile unsigned char *)dst;
+
+	for (; i < siz; i ++)
+		buf[i] = 0;
+#endif
 }
 #endif
 /*