lguest: workaround cmpxchg8b_emu by ignoring cli in the guest.

[safe/jmp/linux-2.6] / drivers / lguest / x86 / core.c

diff --git a/drivers/lguest/x86/core.c b/drivers/lguest/x86/core.c
index fb2b7ef..b4eb675 100644 (file)
--- a/drivers/lguest/x86/core.c
+++ b/drivers/lguest/x86/core.c
@@ -288,6 +288,18 @@ static int emulate_insn(struct lg_cpu *cpu)
        insn = lgread(cpu, physaddr, u8);
 
        /*
+        * Around 2.6.33, the kernel started using an emulation for the
+        * cmpxchg8b instruction in early boot on many configurations.  This
+        * code isn't paravirtualized, and it tries to disable interrupts.
+        * Ignore it, which will Mostly Work.
+        */
+       if (insn == 0xfa) {
+               /* "cli", or Clear Interrupt Enable instruction.  Skip it. */
+               cpu->regs->eip++;
+               return 1;
+       }
+
+       /*
         * 0x66 is an "operand prefix".  It means it's using the upper 16 bits
         * of the eax register.
         */