From mboxrd@z Thu Jan 1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 65561] KVM:Entry failed on Single stepping sti instruction
Date: Sat, 24 May 2014 05:38:16 +0000
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https://bugzilla.kernel.org/show_bug.cgi?id=65561
--- Comment #20 from Jidong Xiao ---
Thanks Jatin, I actually tried some other instructions, like accessing cr
register. I use the following program:
linux:~/code/cvedr # cat getcr.c
#include
main(){
asm __volatile__ (
"mov %cr0, %eax\n"
"mov %cr3, %ebx\n"
);
printf("test cr\n");
}
In x86_emulate_insn(), there is a piece of code like this (the printk is added
by me.)
==================================
case 0x20: /* mov cr, reg */
printk(KERN_ERR "DEBUG: Passed %s %d
\n",__FUNCTION__,__LINE__);
if (c->modrm_mod != 3)
goto cannot_emulate;
c->regs[c->modrm_rm] =
realmode_get_cr(ctxt->vcpu, c->modrm_reg);
c->dst.type = OP_NONE; /* no writeback */
break;
==================================
My results show that the above c program does not trigger this printk statement
neither. I assume accessing cr should be a privileged operation, right? So I am
really curious that how to trigger these printk statements?
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