From: Mark Wielaard <mark@klomp.org>
To: frysk@sourceware.org
Subject: [patch] Check for SYSCALL on x86_64 after "spurious" step/trap
Date: Fri, 06 Jul 2007 15:02:00 -0000 [thread overview]
Message-ID: <1183734114.3651.82.camel@dijkstra.wildebeest.org> (raw)
[-- Attachment #1: Type: text/plain, Size: 920 bytes --]
Hi,
On some x86_64 kernels you will get a trapped event after a step out of
a syscall, but the stepping flag isn't set in that case. This is at
least the case at least on 2.6.18-8.1.6.el5, but not on any of the
Fedora kernels I ever tested with, currently 2.6.20-1.2962.fc6.
Luckily the Isa has a way to signal such an event and this patch updates
the X86_64 Isa as follows to handle this:
2007-07-06 Mark Wielaard <mwielaard@redhat.com>
* IsaX8664.java hasExecutedSpuriousTrap): Check for SYSCALL
instruction.
This makes the following testcases PASS on such kernels and doesn't
change the results on any other system I tested on:
testSteppingtestHitAndRun(frysk.proc.TestBreakpoints) ...PASS
testSteppingtestInsertRemove(frysk.proc.TestBreakpoints) ...PASS
testSteppingAddLots(frysk.proc.TestBreakpoints) ...PASS
testStepSigReturn(frysk.proc.TestTaskObserverInstructionSigReturn) ...PASS
Cheers,
Mark
[-- Attachment #2: Type: text/x-patch, Size: 1031 bytes --]
Index: frysk-core/frysk/proc/IsaX8664.java
===================================================================
RCS file: /cvs/frysk/frysk-core/frysk/proc/IsaX8664.java,v
retrieving revision 1.18
diff -u -r1.18 IsaX8664.java
--- frysk-core/frysk/proc/IsaX8664.java 5 Jul 2007 12:40:28 -0000 1.18
+++ frysk-core/frysk/proc/IsaX8664.java 6 Jul 2007 14:49:25 -0000
@@ -336,12 +336,15 @@
* attributed to entering a signal handler or a normal step
* instruction notification.
*
- * x86_64 doesn't generate spurious trap events and this method
- * always returns false on this architecture.
+ * On some kernels x86_64 doesn't generate spurious trap events (or
+ * rather doesn't set the stepping flag) after returning from a
+ * SYSCALL instruction.
*/
public boolean hasExecutedSpuriousTrap(Task task)
{
- return false;
+ long address = pc(task);
+ return (task.getMemory().getByte(address - 1) == (byte) 0x05
+ && task.getMemory().getByte(address - 2) == (byte) 0x0f);
}
/**
reply other threads:[~2007-07-06 15:02 UTC|newest]
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