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x86/entry: Fix AC assertion
The WARN added in commit3c73b81a91
("x86/entry, selftests: Further improve user entry sanity checks") unconditionally triggers on a IVB machine because it does not support SMAP. For !SMAP hardware the CLAC/STAC instructions are patched out and thus if userspace sets AC, it is still have set after entry. Fixes:3c73b81a91
("x86/entry, selftests: Further improve user entry sanity checks") Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Tested-by: Daniel Thompson <daniel.thompson@linaro.org> Acked-by: Andy Lutomirski <luto@kernel.org> Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20200902133200.666781610@infradead.org
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@ -18,8 +18,16 @@ static __always_inline void arch_check_user_regs(struct pt_regs *regs)
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* state, not the interrupt state as imagined by Xen.
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*/
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unsigned long flags = native_save_fl();
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WARN_ON_ONCE(flags & (X86_EFLAGS_AC | X86_EFLAGS_DF |
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X86_EFLAGS_NT));
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unsigned long mask = X86_EFLAGS_DF | X86_EFLAGS_NT;
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/*
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* For !SMAP hardware we patch out CLAC on entry.
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*/
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if (boot_cpu_has(X86_FEATURE_SMAP) ||
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(IS_ENABLED(CONFIG_64_BIT) && boot_cpu_has(X86_FEATURE_XENPV)))
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mask |= X86_EFLAGS_AC;
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WARN_ON_ONCE(flags & mask);
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/* We think we came from user mode. Make sure pt_regs agrees. */
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WARN_ON_ONCE(!user_mode(regs));
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