Re: [Qemu-devel] [PULL 00/11] Ide patches

[John Snow <jsnow@redhat.com>]

On 01/11/2016 06:18 AM, Peter Maydell wrote:
> On 9 January 2016 at 00:51, John Snow <jsnow@redhat.com> wrote:
>> The following changes since commit 38a762fec63fd5c035aae29ba9a77d357e21e4a7:
>>
>>   Merge remote-tracking branch 'remotes/berrange/tags/pull-crypto-fixes-2015-12-23-1' into staging (2015-12-23 13:53:32 +0000)
>>
>> are available in the git repository at:
>>
>>   https://github.com/jnsnow/qemu.git tags/ide-pull-request
>>
>> for you to fetch changes up to 4160ad843841df21de296016fb77f986e693bed2:
>>
>>   libqos/ahci: organize header (2016-01-08 15:22:34 -0500)
>>
>> ----------------------------------------------------------------
>>
>> ----------------------------------------------------------------
> 
> These seem to result in some new clang sanitizer runtime warnings
> during a 'make check':
> 
> /home/petmay01/linaro/qemu-for-merges/tests/libqos/ahci.c:963:9:
> runtime error: store to misaligned address 0x2adacfbaacd7 for type
> 'uint16_t' (aka 'unsigned short'), which requires 2 byte alignment
> 0x2adacfbaacd7: note: pointer points here
>  00 00 00 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  21
> 00 00 00 00 00 00 00  6c 6f 6e
>              ^
> /home/petmay01/linaro/qemu-for-merges/tests/libqos/ahci.c:907:9:
> runtime error: store to misaligned address 0x2adacfbaacd2 for type
> 'uint32_t' (aka 'unsigned int'), which requires 4 byte alignment
> 0x2adacfbaacd2: note: pointer points here
>  00 00  28 00 00 00 00 00 00 00  01 00 00 00 00 00 00 00  00 00 00 00
> 00 00 00 00  21 00 00 00 00 00
>               ^
> 
> This kind of thing:
> 

"This kind of thing" as one might say while holding up a rotting fish
with just two fingers, held at arm's length.

>     unsigned char *cbd = cmd->atapi_cmd;
>     uint32_t *lba32;
> 
>         lba32 = (uint32_t *)&(cbd[2]);
>         *lba32 = cpu_to_be32(lba);
> 
> isn't valid. You probably want
>  stl_be_p(&cbd[2], lba);
> 
> (defined in qemu/bswap.h).
> 
> thanks
> -- PMM
> 

Thanks for the pointer. Out of curiosity, is there no standard way to
perform this kind of operation in C? I want to adjust my bad habits. In
QEMU I can remember to use these macros now that I know they're there,
but not sure what I'd use in other projects. memcpy directly?

--js