[parisc-linux] 2.5 fix for user level page fault problems

[parisc-linux] 2.5 fix for user level page fault problems

[James Bottomley]

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It seems that going from 2.4 to 2.5 there was an over zealous removal of the 
check signals return path.  The problem is that if a user application takes a 
page fault, that can result in a signal being posted (specifically SEGV for 
illegal memory access).  If we never check the signals, the instruction is 
retried and re-faults ad infinitum (well actually, it seems to terminate with 
an unaligned instruction trap in this case after a few hundred faults).

The attached path makes signal posting on page fault work again

James


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===== entry.S 1.8 vs edited =====
--- 1.8/arch/parisc/kernel/entry.S	Sun Nov 24 17:36:53 2002
+++ edited/entry.S	Mon Dec 16 22:09:59 2002
@@ -944,11 +944,11 @@
 	ldo		-16(%r30),%r29	/* Reference param save area */
 #endif
 
-	ldil		L%intr_restore, %r2
+	ldil		L%intr_check_sig, %r2
 	copy		%r25, %r16	/* save pt_regs */
 
 	b		handle_interruption
-	ldo		R%intr_restore(%r2), %r2
+	ldo		R%intr_check_sig(%r2), %r2
 
 
 	/*

Re: [parisc-linux] 2.5 fix for user level page fault problems

[Randolph Chung]

In reference to a message from James Bottomley, dated Dec 18:
> It seems that going from 2.4 to 2.5 there was an over zealous removal of the 
> check signals return path.  The problem is that if a user application takes a 
> page fault, that can result in a signal being posted (specifically SEGV for 
> illegal memory access).  If we never check the signals, the instruction is 
> retried and re-faults ad infinitum (well actually, it seems to terminate with 
> an unaligned instruction trap in this case after a few hundred faults).

thanks James. I've commited this to our 2.5 tree. We had fixed this in
2.4 a couple of weeks ago but I forgot to commit this to 2.5 too.

randolph
-- 
Randolph Chung
Debian GNU/Linux Developer, hppa/ia64 ports
http://www.tausq.org/