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lguest: fix guest kernel stack overflow when TF bit set.

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The symptoms are that running gdb on a binary causes the guest to
overflow the kernels stack (after some period of time), resulting in
it finally being killed with a "Bad address" message.

Reported-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2013-09-05 17:45:53 +09:30
parent 4623c28e22
commit 98fb4e5e6b
1 changed files with 10 additions and 0 deletions
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10
drivers/lguest/interrupts_and_traps.c
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@ -139,6 +139,16 @@ static void set_guest_interrupt(struct lg_cpu *cpu, u32 lo, u32 hi,
cpu->regs->cs = (__KERNEL_CS|GUEST_PL);
cpu->regs->eip = idt_address(lo, hi);
/*
* Trapping always clears these flags:
* TF: Trap flag
* VM: Virtual 8086 mode
* RF: Resume
* NT: Nested task.
*/
cpu->regs->eflags &=
~(X86_EFLAGS_TF|X86_EFLAGS_VM|X86_EFLAGS_RF|X86_EFLAGS_NT);
/*
* There are two kinds of interrupt handlers: 0xE is an "interrupt
* gate" which expects interrupts to be disabled on entry.