Hi Morimoto-san,
On Tue, Dec 17, 2019 at 7:09 AM Kuninori Morimoto
<kuninori.morimoto.gx@xxxxxxxxxxx> wrote:
> We get too many below strncpy() warning on SH.
> Can someone solve it ?
> I don't remember SH assembler code / can't test it...
I never touched SH assembler code at all.
But it looks a bit like RISCified m68k, so let's give it a try ;-)
> In file included from /home/morimoto/WORK/linux/arch/sh/include/asm/string.h:3,
> from /home/morimoto/WORK/linux/include/linux/string.h:20,
> from /home/morimoto/WORK/linux/include/linux/bitmap.h:9,
> from /home/morimoto/WORK/linux/include/linux/nodemask.h:95,
> from /home/morimoto/WORK/linux/include/linux/mmzone.h:17,
> from /home/morimoto/WORK/linux/include/linux/gfp.h:6,
> from /home/morimoto/WORK/linux/include/linux/slab.h:15,
> from /home/morimoto/WORK/linux/drivers/mmc/host/vub300.c:38:
> /home/morimoto/WORK/linux/drivers/mmc/host/vub300.c: In function 'new_system_port_status':
> /home/morimoto/WORK/linux/arch/sh/include/asm/string_32.h:51:42: warning: array subscript 80 is above array bounds of 'char[26]' [-Warray-bounds]
> : "0" (__dest), "1" (__src), "r" (__src+__n)
> ~~~~~^~~~
Yeah, these array warnings are (sometimes) a PITA.
> static inline char *strncpy(char *__dest, const char *__src, size_t __n)
> {
> register char *__xdest = __dest;
> unsigned long __dummy;
>
> if (__n == 0)
> return __xdest;
>
> __asm__ __volatile__(
> "1:\n"
> "mov.b @%1+, %2\n\t"
> "mov.b %2, @%0\n\t"
> "cmp/eq #0, %2\n\t"
> "bt/s 2f\n\t"
> " cmp/eq %5,%1\n\t"
> "bf/s 1b\n\t"
> " add #1, %0\n"
> "2:"
> : "=r" (__dest), "=r" (__src), "=&z" (__dummy)
> => : "0" (__dest), "1" (__src), "r" (__src+__n)
> : "memory", "t");
>
> return __xdest;
> }
My first thought was to just replace "__src+__n" by "__dest+__n", and
change the "cmp/eq" from "%1" (current src) to "%0" (current dst).
However, "%0" isn't incremented until the branch delay slot of the loop.
So I had to move the increment up, and fill the branch delay slot with a nop.
Untested (it-compiles-so-it-must-be-perfect ;-) whitespace-damaged patch:
--- a/arch/sh/include/asm/string_32.h
+++ b/arch/sh/include/asm/string_32.h
@@ -40,15 +40,15 @@ static inline char *strncpy(char *__dest, const
char *__src, size_t __n)
__asm__ __volatile__(
"1:\n"
"mov.b @%1+, %2\n\t"
- "mov.b %2, @%0\n\t"
+ "mov.b %2, @%0+\n\t"
"cmp/eq #0, %2\n\t"
"bt/s 2f\n\t"
- " cmp/eq %5,%1\n\t"
+ " cmp/eq %5,%0\n\t"
"bf/s 1b\n\t"
- " add #1, %0\n"
+ " nop\n"
"2:"
: "=r" (__dest), "=r" (__src), "=&z" (__dummy)
- : "0" (__dest), "1" (__src), "r" (__src+__n)
+ : "0" (__dest), "1" (__src), "r" (__dest+__n)
: "memory", "t");
return __xdest;
Does this make sense?
Can it be improved, by putting something useful in the delay slot?
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
