tjh.dev
+30
arch/x86/kernel/cet.c
+30
arch/x86/kernel/cet.c
···
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static __ro_after_init bool ibt_fatal = true;
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+
/*
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* By definition, all missing-ENDBRANCH #CPs are a result of WFE && !ENDBR.
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*
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* For the kernel IBT no ENDBR selftest where #CPs are deliberately triggered,
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* the WFE state of the interrupted context needs to be cleared to let execution
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* continue. Otherwise when the CPU resumes from the instruction that just
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* caused the previous #CP, another missing-ENDBRANCH #CP is raised and the CPU
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* enters a dead loop.
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*
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* This is not a problem with IDT because it doesn't preserve WFE and IRET doesn't
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* set WFE. But FRED provides space on the entry stack (in an expanded CS area)
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* to save and restore the WFE state, thus the WFE state is no longer clobbered,
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* so software must clear it.
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*/
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static void ibt_clear_fred_wfe(struct pt_regs *regs)
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{
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/*
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* No need to do any FRED checks.
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*
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* For IDT event delivery, the high-order 48 bits of CS are pushed
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* as 0s into the stack, and later IRET ignores these bits.
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*
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* For FRED, a test to check if fred_cs.wfe is set would be dropped
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* by compilers.
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*/
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regs->fred_cs.wfe = 0;
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}
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+
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static void do_kernel_cp_fault(struct pt_regs *regs, unsigned long error_code)
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{
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if ((error_code & CP_EC) != CP_ENDBR) {
···
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90
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if (unlikely(regs->ip == (unsigned long)&ibt_selftest_noendbr)) {
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regs->ax = 0;
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+
ibt_clear_fred_wfe(regs);
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return;
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}
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96
···
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if (!ibt_fatal) {
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printk(KERN_DEFAULT CUT_HERE);
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__warn(__FILE__, __LINE__, (void *)regs->ip, TAINT_WARN, regs, NULL);
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ibt_clear_fred_wfe(regs);
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return;
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}
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BUG();
+1
-3
drivers/virt/coco/tdx-guest/tdx-guest.c
+1
-3
drivers/virt/coco/tdx-guest/tdx-guest.c