linux-kernel - Re: 32-bit poweroc compile failure in v4.19-rc7-166-g7ec21823634d

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Date:   Mon, 15 Oct 2018 21:33:49 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Meelis Roos <mroos@...ux.ee>, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: 32-bit poweroc compile failure in v4.19-rc7-166-g7ec21823634d

Meelis Roos <mroos@...ux.ee> writes:
> I tried to test the fix to 32-bit poweroc boot hang but found that current git does not compile on 32bit poweroc at all for me:

That's GCC 8 I think?

I have seen that but couldn't work out what the hell GCC is thinking.

I don't think there's an actual bug, the size of the copy is bounded by
the count parameter, which *doesn't* come from user space, it's hard
coded.

I suspect the logic is just to convoluted for GCC.

We should fix it somehow, but I haven't worked out what's the best option.

cheers


>    CC      arch/powerpc/kernel/ptrace.o
> In file included from ./include/linux/bitmap.h:9,
>                   from ./include/linux/cpumask.h:12,
>                   from ./include/linux/rcupdate.h:44,
>                   from ./include/linux/rculist.h:11,
>                   from ./include/linux/pid.h:5,
>                   from ./include/linux/sched.h:14,
>                   from arch/powerpc/kernel/ptrace.c:19:
> In function ‘memcpy’,
>      inlined from ‘user_regset_copyin’ at ./include/linux/regset.h:295:4,
>      inlined from ‘vr_set’ at arch/powerpc/kernel/ptrace.c:619:9:
> ./include/linux/string.h:345:9: error: ‘__builtin_memcpy’ offset [-527, -529] is out of the bounds [0, 16] of object ‘vrsave’ with type ‘union <anonymous>’ [-Werror=array-bounds]
>    return __builtin_memcpy(p, q, size);
>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/powerpc/kernel/ptrace.c: In function ‘vr_set’:
> arch/powerpc/kernel/ptrace.c:614:5: note: ‘vrsave’ declared here
>     } vrsave;
>       ^~~~~~
> In file included from ./include/linux/bitmap.h:9,
>                   from ./include/linux/cpumask.h:12,
>                   from ./include/linux/rcupdate.h:44,
>                   from ./include/linux/rculist.h:11,
>                   from ./include/linux/pid.h:5,
>                   from ./include/linux/sched.h:14,
>                   from arch/powerpc/kernel/ptrace.c:19:
> In function ‘memcpy’,
>      inlined from ‘user_regset_copyout’ at ./include/linux/regset.h:270:4,
>      inlined from ‘vr_get’ at arch/powerpc/kernel/ptrace.c:572:9:
> ./include/linux/string.h:345:9: error: ‘__builtin_memcpy’ offset [-527, -529] is out of the bounds [0, 16] of object ‘vrsave’ with type ‘union <anonymous>’ [-Werror=array-bounds]
>    return __builtin_memcpy(p, q, size);
>           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> arch/powerpc/kernel/ptrace.c: In function ‘vr_get’:
> arch/powerpc/kernel/ptrace.c:567:5: note: ‘vrsave’ declared here
>     } vrsave;
>       ^~~~~~
> cc1: all warnings being treated as errors
> make[1]: *** [scripts/Makefile.build:306: arch/powerpc/kernel/ptrace.o] Error 1
> make: *** [Makefile:1052: arch/powerpc/kernel] Error 2
>
> -- 
> Meelis Roos <mroos@...ux.ee>