[uml-devel] [PATCH 4/5] UML - Fix strace -f

[uml-devel] [PATCH 4/5] UML - Fix strace -f

[Jeff Dike]

It turns out that we need to check for pending signals when a newly forked 
process is run for the first time.  With strace -f, strace needs to know
about the forked process before it gets going.  If it doesn't, then it
ptraces some bogus values into its registers, and the process segfaults.
So, I added calls to interrupt_end, which does that, plus checks for 
reschedules.  There shouldn't be any of those, but x86 does the same thing,
so I'm copying that behavior to be safe.

Signed-off-by: Jeff Dike <jdike@addtoit.com>

Index: linux-2.6.12-rc/arch/um/kernel/skas/process_kern.c
===================================================================
--- linux-2.6.12-rc.orig/arch/um/kernel/skas/process_kern.c	2005-06-02 17:16:46.000000000 -0400
+++ linux-2.6.12-rc/arch/um/kernel/skas/process_kern.c	2005-06-02 17:16:50.000000000 -0400
@@ -68,8 +68,11 @@ void new_thread_handler(int sig)
 	 * 0 if it just exits
 	 */
 	n = run_kernel_thread(fn, arg, &current->thread.exec_buf);
-	if(n == 1)
+	if(n == 1){
+		/* Handle any immediate reschedules or signals */
+		interrupt_end();
 		userspace(&current->thread.regs.regs);
+	}
 	else do_exit(0);
 }
 
@@ -96,6 +99,8 @@ void fork_handler(int sig)
 	schedule_tail(current->thread.prev_sched);
 	current->thread.prev_sched = NULL;
 
+	/* Handle any immediate reschedules or signals */
+	interrupt_end();
 	userspace(&current->thread.regs.regs);
 }
 



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