lkml.org 
[lkml]   [2005]   [Mar]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: More trouble with i386 EFLAGS and ptrace
On Sun, Mar 06, 2005 at 12:03:22PM -0800, Linus Torvalds wrote:
> I _think_ your test-case would work right if you just moved that code from
> the special-case in do_debug(), and moved it to the top of
> setup_sigcontext() instead. I've not tested it, though, and haven't really
> given it any "deep thought". Maybe somebody smarter can say "yeah, that's
> obviously the right thing to do" or "no, that won't work because.."

I bought it, but the GDB testsuite didn't. Both copies seem to be
necessary; there's generally no signal handler for SIGTRAP, so moving
it disables the test in the most common case. I didn't poke at it long
enough to figure out what the failing case was, but it introduced a
different situation which could leave TF enabled. This, however,
worked:

If a debugger set the TF bit, make sure to clear it when creating a
signal context. Otherwise, TF will be incorrectly restored by
sigreturn.

Signed-off-by: Daniel Jacobowitz <dan@debian.org>

===== arch/i386/kernel/signal.c 1.53 vs edited =====
--- 1.53/arch/i386/kernel/signal.c 2005-01-31 01:20:14 -05:00
+++ edited/arch/i386/kernel/signal.c 2005-03-06 15:36:41 -05:00
@@ -277,6 +277,18 @@
{
int tmp, err = 0;

+ /*
+ * If TF is set due to a debugger (PT_DTRACE), clear the TF
+ * flag so that register information in the sigcontext is
+ * correct.
+ */
+ if (unlikely(regs->eflags & TF_MASK)) {
+ if (likely(current->ptrace & PT_DTRACE)) {
+ current->ptrace &= ~PT_DTRACE;
+ regs->eflags &= ~TF_MASK;
+ }
+ }
+
tmp = 0;
__asm__("movl %%gs,%0" : "=r"(tmp): "0"(tmp));
err |= __put_user(tmp, (unsigned int __user *)&sc->gs);
--
Daniel Jacobowitz
CodeSourcery, LLC
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 14:10    [W:0.153 / U:0.104 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site