Re: [tip:x86/x32] x32: Fix alignment fail in struct compat_siginfo
From: H.J. Lu
Date: Wed Apr 18 2012 - 14:33:21 EST
On Wed, Apr 18, 2012 at 11:21 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> On 04/18/2012 11:15 AM, H.J. Lu wrote:
>>
>> In x32 glibc, I have
>>
>> # if compile for X32
>> /* si_utime and si_stime must be 4 byte aligned for x32 to match the
>> kernel. We align siginfo_t to 8 bytes so that si_utime and si_stime
>> are actually aligned to 8 bytes since their offsets are multiple of
>> 8 bytes. */
>> typedef __clock_t __attribute__ ((__aligned__ (4))) __sigchld_clock_t;
>> # define __SI_ALIGNMENT __attribute__ ((__aligned__ (8)))
>> # else
>> typedef __clock_t __sigchld_clock_t;
>> # define __SI_ALIGNMENT
>> # endif
>>
>> typedef struct siginfo
>> {
>> ...
>> /* SIGCHLD. */
>> struct
>> {
>> __pid_t si_pid; /* Which child. */
>> __uid_t si_uid; /* Real user ID of sending process. */
>> int si_status; /* Exit value or signal. */
>> __sigchld_clock_t si_utime;
>> __sigchld_clock_t si_stime;
>> } _sigchld;
>> ...
>> } siginfo_t __SI_ALIGNMENT;
>>
>
> So in other words, a separate type just for this. However, the question
Yes.
> still holds: could we simply change __kernel_clock_t for x32 and be done
> with it? It would affect the alignment of struct tms, I guess; it
> wouldn't really affect the kernel directly since the kernel gets a
> pointer straight from userspace for times(2), but it would kind of mess
> up a userspace which uses __kernel_clock_t directly.
That is true.
> Urk, okay...
>
This is the best approach I can think of.
--
H.J.
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