Messages in this thread Patch in this message | | | Date | Sun, 6 Mar 2005 16:14:26 -0500 | From | Daniel Jacobowitz <> | Subject | Re: More trouble with i386 EFLAGS and ptrace |
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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/
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