Re: i386 singlestep is borken

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On Thu, 16 Feb 2006, Chuck Ebbert wrote:
> 
> 2. Makes vsyscall; debug trap occurs in kernel mode and TF
>    is cleared.  TIF_SINGLESTEP gets set so kernel will remember
>    to re-enable TF on return to user.  But when user eflags
>    is saved on the stack, TF has already been cleared.

This is exactly correct. 

TF should be re-enabled by the "is there work to be done at system call 
return time?" logic, which should mean that we go through 
do_notify_resume() (which will set TF_MASK) and return with an "iret".

We can't return with a sysexit in the TF case, and setting TF on the stack 
is thus useless.

> 3. When user gets control back, TF is not re-enabled.

Sounds like something is broken, but I don't see what.

I did check single-step over sysenter at some point (a long time ago), so 
this has worked.

		Linus
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux