lkml.org 
[lkml]   [2021]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] string: uninline memcpy_and_pad
On Mon, Nov 01, 2021 at 09:30:24PM -0700, Guenter Roeck wrote:
> 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.

Acked-by: Andy Shevchenko <andriy.shevchenko@intel.com>

> Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
> ---
> include/linux/string.h | 19 ++-----------------
> lib/string.c | 19 +++++++++++++++++++
> 2 files changed, 21 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 5e96d656be7a..d68097b4f600 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -262,23 +262,8 @@ void __write_overflow(void) __compiletime_error("detected write beyond size of o
> #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);
>
> /**
> * str_has_prefix - Test if a string has a given prefix
> diff --git a/lib/string.c b/lib/string.c
> index b2de45a581f4..ff13d6d77a05 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -1165,3 +1165,22 @@ void fortify_panic(const char *name)
> BUG();
> }
> EXPORT_SYMBOL(fortify_panic);
> +
> +/**
> + * 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);
> --
> 2.33.0
>

--
With Best Regards,
Andy Shevchenko


\
 
 \ /
  Last update: 2021-11-02 13:37    [W:0.040 / U:0.360 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site