Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: outside array bounds error on ppc64_defconfig, GCC 12.1.0 | Date | Tue, 07 Jun 2022 12:05:18 +1000 |
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Bagas Sanjaya <bagasdotme@gmail.com> writes: > Hi, > > I'm trying to verify Drop ppc_inst_as_str() patch on [1] by performing > ppc64_defconfig build with powerpc64-unknown-linux-gnu-gcc (GCC 12.1.0). > The patch is applied on top of powerpc tree, next branch.
Yeah I see it too.
> I got outside array bounds error: > > CC arch/powerpc/kernel/dbell.o > In function 'do_byte_reverse', > inlined from 'do_vec_store' at arch/powerpc/lib/sstep.c:722:3, > inlined from 'emulate_loadstore' at arch/powerpc/lib/sstep.c:3509:9: > arch/powerpc/lib/sstep.c:286:25: error: array subscript [3, 4] is outside array bounds of 'union <anonymous>[1]' [-Werror=array-bounds] > 286 | up[0] = byterev_8(up[3]); > | ^~~~~~~~~~~~~~~~ > > arch/owerpc/lib/sstep.c: In function 'emulate_loadstore': > arch/powerpc/lib/sstep.c:708:11: note: at offset [24, 39] into object 'u' of size 16 > 708 | } u; > | ^ > In function 'do_byte_reverse', > inlined from 'do_vec_store' at arch/powerpc/lib/sstep.c:722:3, > inlined from 'emulate_loadstore' at arch/powerpc/lib/sstep.c:3509:9: > arch/powerpc/lib/sstep.c:287:23: error: array subscript [3, 4] is outside array bounds of 'union <anonymous>[1]' [-Werror=array-bounds] > 287 | up[3] = tmp; > | ~~~~~~^~~~~
This happens because we have a generic byte reverse function (do_byte_reverse()), that takes a size as a parameter. So it will reverse 8, 16, 32 bytes etc.
In some cases the compiler can see that we're passing a pointer to storage that is smaller than 32 bytes, but it isn't convinced that the size parameter is also smaller than 32 bytes.
Which I think is reasonable, the code that sets the size is separate from this code, so the compiler can't really deduce that it's safe.
I don't see a really simple fix. I tried clamping the size parameter to do_byte_reverse() with max(), but that didn't work :/
cheers
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