Messages in this thread Patch in this message | | | From | Lai Jiangshan <> | Subject | [PATCH V5 17/50] x86/entry: Add C user_entry_swapgs_and_fence() | Date | Wed, 10 Nov 2021 19:57:03 +0800 |
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From: Lai Jiangshan <laijs@linux.alibaba.com>
The C user_entry_swapgs_and_fence() implements the ASM code: swapgs FENCE_SWAPGS_USER_ENTRY
It will be used in the user entry swapgs code path, doing the swapgs and lfence to prevent a speculative swapgs when coming from kernel space.
Cc: Josh Poimboeuf <jpoimboe@redhat.com> Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> --- arch/x86/entry/entry64.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/arch/x86/entry/entry64.c b/arch/x86/entry/entry64.c index bdc9540f25d3..3db503ea0703 100644 --- a/arch/x86/entry/entry64.c +++ b/arch/x86/entry/entry64.c @@ -49,6 +49,9 @@ static __always_inline void switch_to_kernel_cr3(void) {} * 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. + * + * user_entry_swapgs_and_fence is a wrapper of swapgs and fence for user entry + * code path. */ static __always_inline void fence_swapgs_user_entry(void) { @@ -59,3 +62,9 @@ static __always_inline void fence_swapgs_kernel_entry(void) { alternative("", "lfence", X86_FEATURE_FENCE_SWAPGS_KERNEL); } + +static __always_inline void user_entry_swapgs_and_fence(void) +{ + native_swapgs(); + fence_swapgs_user_entry(); +} -- 2.19.1.6.gb485710b
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