lkml.org 
[lkml]   [2012]   [Jun]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v2] lib/decompress_unxz.c: removing all memory helper functions
On 2012-06-11 T Makphaibulchoke wrote:
> --- /dev/null
> +++ b/lib/boot/mem.c
> @@ -0,0 +1,58 @@
> +/*
> + * Small subset of simple memory helper functions required by different
> + * compressors for preboot environment.
> + */
> +
> +#include <linux/string.h>
> +
> +#ifndef __HAVE_PREBOOT_ARCH_MEMCPY
> +void *memcpy(void *__dest, __const void *__src, size_t __n)
> +{
> + return __builtin_memcpy(__dest, __src, __n);
> +}
> +#endif

GCC will replace __builtin_memcpy above with a call to memcpy, creating
an infinite loop. I confirmed this on x86_64 by first uncommenting the
memcpy from arch/x86/boot/compressed/string.c.

You need to provide a memcpy implementation yourself without using
__builtin functions. For example, copy the memcpy implementation from
lib/string.c.

> +#ifndef __HAVE_PREBOOT_ARCH_MEMMOVE
> +void *memmove(void *__dest, __const void *__src, size_t count)
> +{
> + unsigned char *d = __dest;
> + const unsigned char *s = __src;
> +
> + if (__dest == __src)
> + return __dest;
> +
> + if (__dest < __src)
> + return memcpy(__dest, __src, count);
> +
> + while (count--)
> + d[count] = s[count];
> + return __dest;
> +}
> +#endif

The use of memcpy when __dest < __src is OK with some memcpy
implementations, but in a generic case it isn't guaranteed to work.
I think it would be better to just copy memmove from lib/string.c.

--
Lasse Collin | IRC: Larhzu @ IRCnet & Freenode


\
 
 \ /
  Last update: 2012-06-12 19:01    [W:0.127 / U:0.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site