Re: [patch] kprobes: dont steal interrupts from vm86

[Prasanna S Panchamukhi]

Hi Stas,

> I've found yet another bug in this
> very same piece of code. Now I can
> reproduce the interrupt theft without
> using either vm86() or modify_ldt().

The patch below should fix this problem. Please
let me know if you any issues.

Regards
Prasanna



Stas repoted that kprobes steals int3 exceptions when not in 
virtual-8086 mode. This patch fixes the problem by returning 0,
if the int3 exceptions does not belong to kprobes.

Signed-off-by: Prasanna S Panchamukhi <prasanna@xxxxxxxxxx>


---

 linux-2.6.10-rc3-prasanna/arch/i386/kernel/kprobes.c |    6 +++---
 1 files changed, 3 insertions(+), 3 deletions(-)

diff -puN arch/i386/kernel/kprobes.c~kprobes-steals-int3 arch/i386/kernel/kprobes.c
--- linux-2.6.10-rc3/arch/i386/kernel/kprobes.c~kprobes-steals-int3	2004-12-07 11:20:33.000000000 +0530
+++ linux-2.6.10-rc3-prasanna/arch/i386/kernel/kprobes.c	2004-12-07 11:20:34.000000000 +0530
@@ -127,10 +127,10 @@ static inline int kprobe_handler(struct 
 			 * The breakpoint instruction was removed right
 			 * after we hit it.  Another cpu has removed
 			 * either a probepoint or a debugger breakpoint
-			 * at this address.  In either case, no further
-			 * handling of this interrupt is appropriate.
+			 * at this address. In either case, kprobes
+			 * need not handle it.
 			 */
-			ret = 1;
+			ret = 0;
 		}
 		/* Not one of ours: let kernel handle it */
 		goto no_kprobe;

_
-- 

Prasanna S Panchamukhi
Linux Technology Center
India Software Labs, IBM Bangalore
Ph: 91-80-25044636
<prasanna@xxxxxxxxxx>
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