Messages in this thread Patch in this message | | | From | Andy Lutomirski <> | Subject | [PATCH v2 12/18] x86/espfix/64: Stop assuming that pt_regs is on the entry stack | Date | Tue, 21 Nov 2017 20:44:07 -0800 |
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When we start using an entry trampoline, a #GP from userspace will be delivered on the entry stack, not on the task stack. Fix the espfix64 #DF fixup to set up #GP according to TSS.SP0, rather than assuming that pt_regs + 1 == SP0. This won't change anything without an entry stack, but it will make the code continue to work when an entry stack is added.
Signed-off-by: Andy Lutomirski <luto@kernel.org> --- arch/x86/kernel/traps.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 81841f27beff..1ea03027a4a9 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -358,7 +358,8 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code) regs->cs == __KERNEL_CS && regs->ip == (unsigned long)native_irq_return_iret) { - struct pt_regs *normal_regs = task_pt_regs(current); + struct pt_regs *normal_regs = + (struct pt_regs *)this_cpu_read(cpu_tss.x86_tss.sp0) - 1; /* Fake a #GP(0) from userspace. */ memmove(&normal_regs->ip, (void *)regs->sp, 5*8); @@ -389,7 +390,7 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code) * * Processors update CR2 whenever a page fault is detected. If a * second page fault occurs while an earlier page fault is being - * deliv- ered, the faulting linear address of the second fault will + * delivered, the faulting linear address of the second fault will * overwrite the contents of CR2 (replacing the previous * address). These updates to CR2 occur even if the page fault * results in a double fault or occurs during the delivery of a -- 2.13.6
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