[PATCH v2 2/2] include: xfuncs: employ compiler attributes to aid GCC warnings

[Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx>]

From: Ahmad Fatoum <ahmad@xxxxxx>

We already use __alloc_size and __realloc_size in <malloc.h>, so GCC can
warn about some types of memory safety issues at build-time.

Let's have the same for xfuncs.h as well and additionally specify
__returns_nonnull, so the compiler could provide better diagnostics.

Signed-off-by: Ahmad Fatoum <ahmad@xxxxxx>
---
v1 -> v2:
  - spell attribute the same in __has_attribute and __attribute__
  - drop __returns_nonnull from strdup style functions that return
    NULL if the argument is NULL
---
 include/linux/compiler_types.h   |  9 +++++++++
 include/xfuncs.h                 | 17 +++++++++--------
 scripts/include/linux/compiler.h |  9 +++++++++
 3 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index d925b3da296d..a713459f6e47 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -157,6 +157,12 @@ struct ftrace_likely_data {
 # define __no_stack_protector
 #endif
 
+#if __has_attribute(__returns_nonnull__)
+#define __returns_nonnull		__attribute__((__returns_nonnull__))
+#else
+#define __returns_nonnull
+#endif
+
 #endif /* __KERNEL__ */
 
 #endif /* __ASSEMBLY__ */
@@ -212,6 +218,9 @@ struct ftrace_likely_data {
 # define __realloc_size(x, ...)
 #endif
 
+# define __xalloc_size(args...)		__returns_nonnull __alloc_size(args)
+# define __xrealloc_size(args...)	__returns_nonnull __realloc_size(args)
+
 /* Are two types/vars the same type (ignoring qualifiers)? */
 #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 
diff --git a/include/xfuncs.h b/include/xfuncs.h
index a9132d378722..60ec220bd9b8 100644
--- a/include/xfuncs.h
+++ b/include/xfuncs.h
@@ -3,18 +3,19 @@
 #define __XFUNCS_H
 
 #include <linux/types.h>
+#include <linux/compiler.h>
 #include <stdarg.h>
 #include <wchar.h>
 
-void *xmalloc(size_t size);
-void *xrealloc(void *ptr, size_t size);
-void *xzalloc(size_t size);
+void *xmalloc(size_t size) __xalloc_size(1);
+void *xrealloc(void *ptr, size_t size) __xrealloc_size(2);
+void *xzalloc(size_t size) __xalloc_size(1);
 char *xstrdup(const char *s);
-char *xstrndup(const char *s, size_t size);
-void* xmemalign(size_t alignment, size_t bytes);
-void* xmemdup(const void *orig, size_t size);
-char *xasprintf(const char *fmt, ...) __attribute__ ((format(__printf__, 1, 2)));
-char *xvasprintf(const char *fmt, va_list ap);
+char *xstrndup(const char *s, size_t size) __returns_nonnull;
+void* xmemalign(size_t alignment, size_t bytes) __xalloc_size(2);
+void* xmemdup(const void *orig, size_t size) __returns_nonnull;
+char *xasprintf(const char *fmt, ...) __attribute__ ((format(__printf__, 1, 2))) __returns_nonnull;
+char *xvasprintf(const char *fmt, va_list ap) __returns_nonnull;
 
 wchar_t *xstrdup_wchar(const wchar_t *src);
 wchar_t *xstrdup_char_to_wchar(const char *src);
diff --git a/scripts/include/linux/compiler.h b/scripts/include/linux/compiler.h
index fa7208a32d76..780ccec21a3c 100644
--- a/scripts/include/linux/compiler.h
+++ b/scripts/include/linux/compiler.h
@@ -39,6 +39,15 @@
 # define unlikely(x)		__builtin_expect(!!(x), 0)
 #endif
 
+#ifndef __returns_nonnull
+# define __returns_nonnull
+#endif
+
+# define __alloc_size(x, ...)
+# define __realloc_size(x, ...)
+# define __xalloc_size(args...)		__returns_nonnull __alloc_size(args)
+# define __xrealloc_size(args...)	__returns_nonnull __realloc_size(args)
+
 #define ACCESS_ONCE(x) (*(volatile typeof(x) *)&(x))
 
 #include <linux/types.h>
-- 
2.39.2