linux-kernel - [patch] i386: fix recursive fault in page-fault handler

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Message-ID: <200607171322_MC3-1-C53B-6253@compuserve.com>
Date:	Mon, 17 Jul 2006 13:19:16 -0400
From:	Chuck Ebbert <76306.1226@...puserve.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	Krzysztof Halasa <khc@...waw.pl>, Andi Kleen <ak@...e.de>,
	Andrew Morton <akpm@...l.org>,
	Linus Torvalds <torvalds@...l.org>
Subject: [patch] i386: fix recursive fault in page-fault handler

Krzysztof Halasa reported recursive faults in do_page_fault()
causing a stream of partial oops messages on the console. Fix
by adding a fixup for that code.

Signed-off-by: Chuck Ebbert <76306.1226@...puserve.com>

---

x86_64 looks like it has the same problem.

--- 2.6.18-rc1-32.orig/arch/i386/mm/fault.c
+++ 2.6.18-rc1-32/arch/i386/mm/fault.c
@@ -585,9 +585,20 @@ no_context:
 		printk(KERN_ALERT "*pte = %08lx\n", page);
 	}
 #endif
-	tsk->thread.cr2 = address;
-	tsk->thread.trap_no = 14;
-	tsk->thread.error_code = error_code;
+	asm (	"# set task data without causing another oops\n"
+		"1:\t"
+		"movl %3,%0\n\t"
+		"movl $14,%1\n\t"
+		"movl %4,%2\n"
+		"2:\n"
+		".section __ex_table,\"a\"\n\t"
+		".align 4\n\t"
+		".long 1b,2b\n"
+		".previous"
+		: "=m" (tsk->thread.cr2), "=m" (tsk->thread.trap_no),
+		  "=m" (tsk->thread.error_code)
+		: "r" (address), "r" (error_code)
+	);
 	die("Oops", regs, error_code);
 	bust_spinlocks(0);
 	do_exit(SIGKILL);
-- 
And did you exchange a walk-on part in the war for a lead role in a cage?
        --Roger Waters
-
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