Messages in this thread Patch in this message | | | From | William Cattey <> | Subject | Re: vm86.c audit_syscall_exit() call trashes registers | Date | Thu, 4 Oct 2007 19:58:37 -0400 |
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Thanks very much for thinking about this and providing a revised candidate patch.
Sadly, the effect of the patch is the same as the most recent candidate patch from Jeremy Fitzhardinge: The EDID transfer still comes up all zeros.
This is very perplexing to me. If I take the code that appears in 2.6.18's vm86.c, and simply put #if 0 around the call to audit_syscall_exit I get good data.
If this is indeed a correct minimal correction to the audit_syscall_exit code, then perhaps there's some other condition being exercised. I guess my next step is to take the whole pt_regs patch (commit 49d26b6eaa8e970c8cf6e299e6ccba2474191bf5) from kernel.org and see if that has a beneficial effect.
-Bill
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William Cattey Linux Platform Coordinator MIT Information Services & Technology
N42-040M, 617-253-0140, wdc@mit.edu http://web.mit.edu/wdc/www/
On Oct 2, 2007, at 12:44 PM, Chuck Ebbert wrote:
> On 09/25/2007 07:38 PM, William Cattey wrote: >> >> I'd feel a lot more confident we were on the right track if I >> could just >> correctly patch Fitzhardinge's cleanup into the test setup I have >> now. >> > > I think you need to zero both registers if you're using 2.6.16, and > force > %eax as the source so it doesn't choose %ebp? > > --- a/arch/i386/kernel/vm86.c > +++ b/arch/i386/kernel/vm86.c > @@ -306,19 +334,19 @@ static void do_sys_vm86(struct > kernel_vm86_struct *info, struct task_struct *tsk > tsk->thread.screen_bitmap = info->screen_bitmap; > if (info->flags & VM86_SCREEN_BITMAP) > mark_screen_rdonly(tsk->mm); > - __asm__ __volatile__("xorl %eax,%eax; movl %eax,%fs; movl %eax,%gs > \n\t"); > - __asm__ __volatile__("movl %%eax, %0\n" :"=r"(eax)); > > /*call audit_syscall_exit since we do not exit via the normal > paths */ > if (unlikely(current->audit_context)) > - audit_syscall_exit(AUDITSC_RESULT(eax), eax); > + audit_syscall_exit(AUDITSC_RESULT(0), 0); > > __asm__ __volatile__( > "movl %0,%%esp\n\t" > "movl %1,%%ebp\n\t" > + "mov %2, %%fs\n\t" > + "mov %2, %%gs\n\t" > "jmp resume_userspace" > : /* no outputs */ > - :"r" (&info->regs), "r" (task_thread_info(tsk))); > + :"r" (&info->regs), "r" (task_thread_info(tsk)), "a" (0)); > /* we never return here */ > } >
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