Messages in this thread Patch in this message | | | Date | Sat, 19 Feb 2022 10:58:27 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH 00/29] x86: Kernel IBT |
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On Sat, Feb 19, 2022 at 01:29:45AM +0000, Edgecombe, Rick P wrote: > On Fri, 2022-02-18 at 17:49 +0100, Peter Zijlstra wrote: > > This is an (almost!) complete Kernel IBT implementation. It's been > > self-hosting > > for a few days now. That is, it runs on IBT enabled hardware > > (Tigerlake) and is > > capable of building the next kernel. > > > > It is also almost clean on allmodconfig using GCC-11.2. > > > > The biggest TODO item at this point is Clang, I've not yet looked at > > that. > > Do you need to turn this off before kexec?
Probably... :-) I've never looked at that code though; so I'm not exactly sure where to put things.
I'm assuming kexec does a hot-unplug of all but the boot-cpu which then leaves only a single CPU with state in machine_kexec() ? Does the below look reasonable?
--- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -638,6 +638,12 @@ static __always_inline void setup_cet(st } } +void cet_disable(void) +{ + cr4_clear_bits(X86_CR4_CET); + wrmsrl(MSR_IA32_S_CET, 0); +} + /* * Some CPU features depend on higher CPUID levels, which may not always * be available due to CPUID level capping or broken virtualization diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index 33d41e350c79..cf26356db53e 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -72,4 +72,7 @@ void init_ia32_feat_ctl(struct cpuinfo_x86 *c); #else static inline void init_ia32_feat_ctl(struct cpuinfo_x86 *c) {} #endif + +extern void cet_disable(void); + #endif /* _ASM_X86_CPU_H */ diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c index f5da4a18070a..29a2a1732605 100644 --- a/arch/x86/kernel/machine_kexec_64.c +++ b/arch/x86/kernel/machine_kexec_64.c @@ -310,6 +310,7 @@ void machine_kexec(struct kimage *image) /* Interrupts aren't acceptable while we reboot */ local_irq_disable(); hw_breakpoint_disable(); + cet_disable(); if (image->preserve_context) { #ifdef CONFIG_X86_IO_APIC
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