Re: [PATCH v3 4/4] x86, mpx: extend siginfo structure to includebound violation information

From: Ren Qiaowei
Date: Sat Jan 25 2014 - 23:45:37 EST


On 01/26/2014 12:22 PM, David Rientjes wrote:
On Sun, 26 Jan 2014, Qiaowei Ren wrote:

This patch adds new fields about bound violation into siginfo
structure. si_lower and si_upper are respectively lower bound
and upper bound when bound violation is caused.

These fields will be set in #BR exception handler by decoding
the user instruction and constructing the faulting pointer.
A userspace application can get violation address, lower bound
and upper bound for bound violation from this new siginfo structure.

Signed-off-by: Qiaowei Ren <qiaowei.ren@xxxxxxxxx>

Same 32-bit warnings I reported for v2:

arch/x86/kernel/mpx.c: In function âdo_mpx_boundsâ:
arch/x86/kernel/mpx.c:407:3: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
arch/x86/kernel/mpx.c:409:3: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]

and the documentation says you explicitly want to support this config.

These types of warnings are usually indicative of real problems when
you're storing upper and lower bits in 32-bit fields after casting them
from 64-bit values.

I'm also not sure if the added fields to the generic struct siginfo can be
justified for this.

According to MPX spec, for 32-bit case, the upper 32-bits of 64-bits bound register are ignored, and so casting to pointer from 64-bit values should be not produce any problems.

Thanks,
Qiaowei
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/