projects/linux·commit 5c4e0a21

string: uninline memcpy_and_pad

5c4e0a21 · Guenter Roeck <[email protected]> · 2021-11-02 07:24:20 -07:00

When building m68k:allmodconfig, recent versions of gcc generate the
following error if the length of UTS_RELEASE is less than 8 bytes.

  In function 'memcpy_and_pad',
    inlined from 'nvmet_execute_disc_identify' at
      drivers/nvme/target/discovery.c:268:2: arch/m68k/include/asm/string.h:72:25: error:
	'__builtin_memcpy' reading 8 bytes from a region of size 7

Discussions around the problem suggest that this only happens if an
architecture does not provide strlen(), if -ffreestanding is provided as
compiler option, and if CONFIG_FORTIFY_SOURCE=n. All of this is the case
for m68k. The exact reasons are unknown, but seem to be related to the
ability of the compiler to evaluate the return value of strlen() and
the resulting execution flow in memcpy_and_pad(). It would be possible
to work around the problem by using sizeof(UTS_RELEASE) instead of
strlen(UTS_RELEASE), but that would only postpone the problem until the
function is called in a similar way. Uninline memcpy_and_pad() instead
to solve the problem for good.

Suggested-by: Linus Torvalds <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Acked-by: Andy Shevchenko <[email protected]>
Signed-off-by: Guenter Roeck <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Commit
5c4e0a21fae877a7ef89be6dcc6263ec672372b8
Parents
655fedaa

Changes

2 files changed · +22 −17

FileStatusAddDelContent
include/linux/string.hmodified+2−17View file
lib/string_helpers.cmodified+20−0View file

include/linux/string.h

View file
diff --git a/include/linux/string.h b/include/linux/string.h
index 5a36608..b6572ae 100644
--- a/include/linux/string.h
+++ b/include/linux/string.h
@@ -253,23 +253,8 @@ static inline const char *kbasename(const char *path)
#include <linux/fortify-string.h>
#endif
-/**
- * memcpy_and_pad - Copy one buffer to another with padding
- * @dest: Where to copy to
- * @dest_len: The destination buffer size
- * @src: Where to copy from
- * @count: The number of bytes to copy
- * @pad: Character to use for padding if space is left in destination.
- */
-static inline void memcpy_and_pad(void *dest, size_t dest_len,
- const void *src, size_t count, int pad)
-{
- if (dest_len > count) {
- memcpy(dest, src, count);
- memset(dest + count, pad, dest_len - count);
- } else
- memcpy(dest, src, dest_len);
-}
+void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count,
+ int pad);
/**
* memset_after - Set a value after a struct member to the end of a struct

lib/string_helpers.c

View file
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index faa9d8e..d5d008f 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -883,6 +883,26 @@ char *strreplace(char *s, char old, char new)
}
EXPORT_SYMBOL(strreplace);
+/**
+ * memcpy_and_pad - Copy one buffer to another with padding
+ * @dest: Where to copy to
+ * @dest_len: The destination buffer size
+ * @src: Where to copy from
+ * @count: The number of bytes to copy
+ * @pad: Character to use for padding if space is left in destination.
+ */
+void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count,
+ int pad)
+{
+ if (dest_len > count) {
+ memcpy(dest, src, count);
+ memset(dest + count, pad, dest_len - count);
+ } else {
+ memcpy(dest, src, dest_len);
+ }
+}
+EXPORT_SYMBOL(memcpy_and_pad);
+
#ifdef CONFIG_FORTIFY_SOURCE
void fortify_panic(const char *name)
{