On Tue, 12 Mar 2019, I wrote:
... I did another experiment with the latter (forced inline) approach,
to see if some optimizations can still be used with -ffreestanding.
diff --git a/include/linux/string.h b/include/linux/string.h
index 7927b875f80c..25b5bf689018 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -436,6 +436,58 @@ __FORTIFY_INLINE char *strcpy(char *p, const char *q)
return p;
}
+#else
+
+//__FORTIFY_INLINE char *strncpy(char *p, const char *q, __kernel_size_t size)
+//{
+// return __builtin_strncpy(p, q, size);
+//}
+
+__FORTIFY_INLINE char *strcat(char *p, const char *q)
+{
+ return __builtin_strcat(p, q);
+}
+
+__FORTIFY_INLINE __kernel_size_t strlen(const char *p)
+{
+ return __builtin_strlen(p);
+}
+
+__FORTIFY_INLINE char *strncat(char *p, const char *q, __kernel_size_t count)
+{
+ return __builtin_strncat(p, q, count);
+}
+
+__FORTIFY_INLINE void *memset(void *p, int c, __kernel_size_t size)
+{
+ return __builtin_memset(p, c, size);
+}
+
+//__FORTIFY_INLINE void *memcpy(void *p, const void *q, __kernel_size_t size)
+//{
+// return __builtin_memcpy(p, q, size);
+//}
+
+__FORTIFY_INLINE void *memmove(void *p, const void *q, __kernel_size_t size)
+{
+ return __builtin_memmove(p, q, size);
+}
+
+__FORTIFY_INLINE int memcmp(const void *p, const void *q, __kernel_size_t size)
+{
+ return __builtin_memcmp(p, q, size);
+}
+
+__FORTIFY_INLINE void *memchr(const void *p, int c, __kernel_size_t size)
+{
+ return __builtin_memchr(p, c, size);
+}
+
+__FORTIFY_INLINE char *strcpy(char *p, const char *q)
+{
+ return __builtin_strcpy(p, q);
+}
+
#endif
/**
The result of this patch really is confusing. It still suppresses the
warning you raised:
arch/m68k/include/asm/string.h:72:25: warning: '__builtin_memcpy' forming
offset 8 is out of the bounds [0, 7] [-Warray-bounds]
#define memcpy(d, s, n) __builtin_memcpy(d, s, n)
^~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/string.h:456:3: note: in expansion of macro 'memcpy'
memcpy(dest, src, dest_len);
^~~~~~
But it also causes new ones, because of __builtin_memset():
drivers/video/fbdev/core/fbcvt.c: In function 'fb_find_mode_cvt':
drivers/video/fbdev/core/fbcvt.c:312:16: warning: 'cvt.flags' may be used uninit ialized in this function [-Wmaybe-uninitialized]
cvt.flags |= FB_CVT_FLAG_MARGINS;
^~
Apparently the compiler doesn't understand that __builtin_memset() has
the effect of initialization. Weird.
The other weird thing is that this warning doesn't show up when
CONFIG_FORTIFY_SOURCE=y, even though the technique is much the same, that
is, __builtin_memset() gets wrapped in a static inline memset() function.
Anyway, a quick and dirty microbenchmark under qemu-m68k shows that this
patch reduces system time for 'time find / -false' by approx. 10%.
Interestingly, the -ffreestanding option doesn't make much difference to
this particular microbenchmark.
--
