Messages in this thread Patch in this message | | | From | Lai Jiangshan <> | Subject | [PATCH V3 16/49] x86/traps: Add fence_swapgs_{user,kernel}_entry() | Date | Thu, 14 Oct 2021 11:33:39 +0800 |
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From: Lai Jiangshan <laijs@linux.alibaba.com>
fence_swapgs_{user,kernel}_entry() in entry64.c are the same as the ASM macro FENCE_SWAPGS_{USER,KERNEL}_ENTRY.
fence_swapgs_user_entry is used in the user entry swapgs code path, to prevent a speculative swapgs when coming from kernel space.
fence_swapgs_kernel_entry is used in the kernel entry code path, to prevent the swapgs from getting speculatively skipped when coming from user space.
Cc: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> --- arch/x86/entry/entry64.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)
diff --git a/arch/x86/entry/entry64.c b/arch/x86/entry/entry64.c index 9a5c535b1ddf..bdc9540f25d3 100644 --- a/arch/x86/entry/entry64.c +++ b/arch/x86/entry/entry64.c @@ -38,3 +38,24 @@ static __always_inline void switch_to_kernel_cr3(void) #else static __always_inline void switch_to_kernel_cr3(void) {} #endif + +/* + * Mitigate Spectre v1 for conditional swapgs code paths. + * + * fence_swapgs_user_entry is used in the user entry swapgs code path, to + * prevent a speculative swapgs when coming from kernel space. It must be + * used with switch_to_kernel_cr3() in the same path. + * + * fence_swapgs_kernel_entry is used in the kernel entry code path without + * CR3 write or with conditinal CR3 write only, to prevent the swapgs from + * getting speculatively skipped when coming from user space. + */ +static __always_inline void fence_swapgs_user_entry(void) +{ + alternative("", "lfence", X86_FEATURE_FENCE_SWAPGS_USER); +} + +static __always_inline void fence_swapgs_kernel_entry(void) +{ + alternative("", "lfence", X86_FEATURE_FENCE_SWAPGS_KERNEL); +} -- 2.19.1.6.gb485710b
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