lkml.org 
[lkml]   [2011]   [Sep]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: try_to_freeze() called with IRQs disabled on ARM
On Fri, Sep 02, 2011 at 04:47:35PM +0200, Ulrich Weigand wrote:
> Assume the scenario you initally describe, where a first signal is
> ignored and leads to system call restart. With your latest patch,
> you call into syscall_restart which sets everything up to restart
> the call (with interrupts disabled).

I don't think SIG_IGN signals even set the TIF work flag, so they
never even cause a call into do_signal(). Therefore, as far as
syscalls go, attempting to send a process (eg) a SIGINT which its
handler is set to SIG_IGN results in the process not even being
notified about the attempt - we won't even wake up while the
syscall is sleeping.

> To really fix this case would probably require some way for the
> debugger to save and restore the restore_block saved state. This
> is not quite trivial, since it would expose that state to user space,
> effectively creating a new ABI (and probably requiring sanity checks
> to ensure a valid state is restored). This probably cannot be fixed
> by one architecture for itself, but would need support from common
> kernel code.

Such state would have to be crytographically signed or kept entirely
within the kernel, as it would otherwise mean that you could redirect
the kernel PC to anywhere...


\
 
 \ /
  Last update: 2011-09-02 19:29    [W:0.085 / U:0.224 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site