On Sat, Dec 18, 2021 at 09:13:57PM +0100, Paul Menzel wrote:
> Dear Kevin,
>
>
> Am 18.12.21 um 19:10 schrieb Kevin O'Connor:
> > Use a different definition for the linker script symbol to avoid a gcc
> > warning.
>
> What GCC version did you use, and which warning is it exactly?
$ gcc --version
gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1)
src/post.c: In function 'reloc_preinit':
src/post.c:248:34: warning: array subscript 'u32 {aka unsigned int}[0]' is
partly outside array bounds of 'char[1]' [-Warray-bounds]
248 | *((u32*)(dest + *reloc)) += delta;
| ^~
In file included from src/biosvar.h:11,
from src/post.c:8:
src/post.c:278:26: note: while referencing 'code32flat_start'
278 | updateRelocs(VSYMBOL(code32flat_start), VSYMBOL(_reloc_init_start)
| ^~~~~~~~~~~~~~~~
src/memmap.h:18:36: note: in definition of macro 'SYMBOL'
18 | #define SYMBOL(SYM) ({ extern char SYM; (u32)&SYM; })
| ^~~
>
> > Signed-off-by: Kevin O'Connor <[email protected]>
> > ---
> > src/memmap.h | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/src/memmap.h b/src/memmap.h
> > index 22bd4bc..32ca265 100644
> > --- a/src/memmap.h
> > +++ b/src/memmap.h
> > @@ -15,7 +15,7 @@ static inline void *memremap(u32 addr, u32 len) {
> > }
> > // Return the value of a linker script symbol (see scripts/layoutrom.py)
> > -#define SYMBOL(SYM) ({ extern char SYM; (u32)&SYM; })
> > +#define SYMBOL(SYM) ({ extern char SYM[]; (u32)SYM; })
> > #define VSYMBOL(SYM) ((void*)SYMBOL(SYM))
> > #endif // memmap.h
>
> gcc (Debian 11.2.0-13) 11.2.0 still shows a lot of:
>
> Compile checking out/src/fw/smm.o
> In file included from src/fw/smm.c:18:
> src/fw/smm.c: In function 'smm_save_and_copy':
> src/string.h:23:16: warning: '__builtin_memcpy' offset [0, 511] is out
> of the bounds [0, 0] [-Warray-bounds]
> 23 | #define memcpy __builtin_memcpy
> src/fw/smm.c:148:5: note: in expansion of macro 'memcpy'
> 148 | memcpy(&smm->cpu, &initsmm->cpu, sizeof(smm->cpu));
> | ^~~~~~
>
Yes - I see that as well in smm.c. Alas, I don't have a fix for it.
It seems to me that gcc is producing bogus warnings here. It looks
like anything of the form "memcpy((void*)0x1234, p, n)" where n is
greater than 8 produces this warning. It's a requirement to memcpy to
a physical memory address. Disabling the warning would require adding
both "-Wno-array-bounds -Wno-stringop-overflow" to the build.
Maybe someone else has an idea on how to suppress this warning.
-Kevin
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