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SubjectRe: 2.1.111 fix for debugger ptrace(PTRACE_ATTACH, ...) side-effects
Date
From
> On Wed, 29 Jul 1998, Eric PAIRE wrote:
> > The summary of the bugs, the SMP-safe fix explanation and the patch file
> > are all available at http://www.gr.opengroup.org/java/jdk/linux/kernel1.htm
>
> I have seen additional problems which may or may not be related. I
> think that the debug registers are not being cleared during context
> switching, or at all for that matter? (I haven't looked into the
> kernel code yet)
>
I haven't made (yet) any test with hardware breakpoints; but by looking at
the kernel code, you were right in saying that the debug registers were not
cleared during context switching, and only replaced by new ones if used.

An obvious fix example is attached (for 2.1.111),
Eric
+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+ Eric PAIRE
Email : e.paire@gr.opengroup.org | The Open Group - Grenoble Research Institute
Phone : +33 (0) 476 63 48 71 | 2, avenue de Vignate
Fax : +33 (0) 476 51 05 32 | F-38610 Gieres FRANCE
------ Cut Here ------ Cut Here ------ Cut Here ------ Cut Here ------
--- arch/i386/kernel/process.c.OLD Mon Jul 27 09:38:08 1998
+++ arch/i386/kernel/process.c Wed Jul 29 18:01:38 1998
@@ -767,8 +767,8 @@
loaddebug(next,2);
loaddebug(next,3);
loaddebug(next,6);
- loaddebug(next,7);
}
+ loaddebug(next,7);
}

asmlinkage int sys_fork(struct pt_regs regs)
-
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