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@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/lguest/lguest.c b/drivers/lguest/lguest.c
index 6e135ac0834f..ee1c6d05c3d3 100644
--- a/drivers/lguest/lguest.c
+++ b/drivers/lguest/lguest.c
@@ -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