linux-kernel - [PATCH] lguest: Fix guest crash when CONFIG_X86_USE

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Date:	Tue, 11 Sep 2007 17:06:37 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Michael Rasenberger <michael.rasenberger@...glemail.com>
Cc:	lguest@...abs.org, Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	lkml - Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] lguest: Fix guest crash when CONFIG_X86_USE_3DNOW=y

One of the very first things lguest_init() does is a memcpy.  On
Athlon/Duron/K7 or CyrixIII/VIA-C3 or Geode GX/LX, this tries to use
MMX.

memcpy -> _mmx_memcpy -> kernel_fpu_begin -> clts -> paravirt_ops.clts

But we haven't set paravirt_ops.clts yet, so we do the native version
and crash.  The simplest solution is to use __memcpy.

Thanks to Michael Rasenberger for the bug report.

Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>

diff -r 1b28730fea64 drivers/lguest/lguest.c
--- a/drivers/lguest/lguest.c	Tue Sep 11 13:53:31 2007 +1000
+++ b/drivers/lguest/lguest.c	Tue Sep 11 16:28:49 2007 +1000
@@ -964,11 +964,12 @@ __init void lguest_init(void *boot)
 {
 	/* Copy boot parameters first: the Launcher put the physical location
 	 * in %esi, and head.S converted that to a virtual address and handed
-	 * it to us. */
-	memcpy(&boot_params, boot, PARAM_SIZE);
+	 * it to us.  We use "__memcpy" because "memcpy" sometimes tries to do
+	 * tricky things to go faster, and we're not ready for that. */
+	__memcpy(&boot_params, boot, PARAM_SIZE);
 	/* The boot parameters also tell us where the command-line is: save
 	 * that, too. */
-	memcpy(boot_command_line, __va(boot_params.hdr.cmd_line_ptr),
+	__memcpy(boot_command_line, __va(boot_params.hdr.cmd_line_ptr),
 	       COMMAND_LINE_SIZE);
 
 	/* We're under lguest, paravirt is enabled, and we're running at


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