Add macro to disable address safety instrumentation

j-naylor · j-naylor · commit db17594ad73a · 2024-04-06T12:20:40.000+07:00
fasthash_accum_cstring_aligned() uses a technique, found in various strlen() implementations, to detect a string's NUL terminator by reading a word at at time. That triggers failures when testing with "-fsanitize=address", at least with frontend code. To enable using this function anywhere, add a function attribute macro to disable such testing. Reviewed by Jeff Davis Discussion: https://postgr.es/m/CANWCAZbwvp7oUEkbw-xP4L0_S_WNKq-J-ucP4RCNDPJnrakUPw%40mail.gmail.com
diff --git a/src/include/c.h b/src/include/c.h
@@ -135,6 +135,19 @@
 #define pg_nodiscard
 #endif
 
+/*
+ * This macro will disable address safety instrumentation for a function
+ * when running with "-fsanitize=address". Think twice before using this!
+ */
+#if defined(__clang__) || __GNUC__ >= 8
+#define pg_attribute_no_sanitize_address() __attribute__((no_sanitize("address")))
+#elif __has_attribute(no_sanitize_address)
+/* This would work for clang, but it's deprecated. */
+#define pg_attribute_no_sanitize_address() __attribute__((no_sanitize_address))
+#else
+#define pg_attribute_no_sanitize_address()
+#endif
+
 /*
  * Place this macro before functions that should be allowed to make misaligned
  * accesses.  Think twice before using it on non-x86-specific code!
diff --git a/src/include/common/hashfn_unstable.h b/src/include/common/hashfn_unstable.h
@@ -213,8 +213,11 @@ fasthash_accum_cstring_unaligned(fasthash_state *hs, const char *str)
  *
  * With an aligned pointer, we consume the string a word at a time.
  * Loading the word containing the NUL terminator cannot segfault since
- * allocation boundaries are suitably aligned.
+ * allocation boundaries are suitably aligned. To keep from setting
+ * off alarms with address sanitizers, exclude this function from
+ * such testing.
  */
+pg_attribute_no_sanitize_address()
 static inline size_t
 fasthash_accum_cstring_aligned(fasthash_state *hs, const char *str)
 {

Original file line number	Diff line number	Diff line change
`@@ -213,8 +213,11 @@ fasthash_accum_cstring_unaligned(fasthash_state hs, const char str)`
`213`	`213`	`*`
`214`	`214`	`* With an aligned pointer, we consume the string a word at a time.`
`215`	`215`	`* Loading the word containing the NUL terminator cannot segfault since`
`216`		`- * allocation boundaries are suitably aligned.`
	`216`	`+ * allocation boundaries are suitably aligned. To keep from setting`
	`217`	`+ * off alarms with address sanitizers, exclude this function from`
	`218`	`+ * such testing.`
`217`	`219`	`*/`
	`220`	`+pg_attribute_no_sanitize_address()`
`218`	`221`	`static inline size_t`
`219`	`222`	`fasthash_accum_cstring_aligned(fasthash_state hs, const char str)`
`220`	`223`	`{`