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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2024-02-25 10:22:21 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2024-02-25 10:22:21 -0800 |
| commit | 1eee4ef38ca15137379028a5a7b0f859bd1bb9b0 (patch) | |
| tree | 7e017de2e623925c05132fda5d6912d7211f13ac /arch/x86/entry/entry.S | |
| parent | 8c46ed3740e27aeba30866ea3da4bc41b08f98a4 (diff) | |
| parent | 43fb862de8f628c5db5e96831c915b9aebf62d33 (diff) | |
Merge tag 'x86_urgent_for_v6.8_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull x86 fixes from Borislav Petkov:
- Make sure clearing CPU buffers using VERW happens at the latest
possible point in the return-to-userspace path, otherwise memory
accesses after the VERW execution could cause data to land in CPU
buffers again
* tag 'x86_urgent_for_v6.8_rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
KVM/VMX: Move VERW closer to VMentry for MDS mitigation
KVM/VMX: Use BT+JNC, i.e. EFLAGS.CF to select VMRESUME vs. VMLAUNCH
x86/bugs: Use ALTERNATIVE() instead of mds_user_clear static key
x86/entry_32: Add VERW just before userspace transition
x86/entry_64: Add VERW just before userspace transition
x86/bugs: Add asm helpers for executing VERW
Diffstat (limited to 'arch/x86/entry/entry.S')
| -rw-r--r-- | arch/x86/entry/entry.S | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/arch/x86/entry/entry.S b/arch/x86/entry/entry.S index 8c8d38f0cb1d..003379049924 100644 --- a/arch/x86/entry/entry.S +++ b/arch/x86/entry/entry.S @@ -6,6 +6,9 @@ #include <linux/export.h> #include <linux/linkage.h> #include <asm/msr-index.h> +#include <asm/unwind_hints.h> +#include <asm/segment.h> +#include <asm/cache.h> .pushsection .noinstr.text, "ax" @@ -20,3 +23,23 @@ SYM_FUNC_END(entry_ibpb) EXPORT_SYMBOL_GPL(entry_ibpb); .popsection + +/* + * Define the VERW operand that is disguised as entry code so that + * it can be referenced with KPTI enabled. This ensure VERW can be + * used late in exit-to-user path after page tables are switched. + */ +.pushsection .entry.text, "ax" + +.align L1_CACHE_BYTES, 0xcc +SYM_CODE_START_NOALIGN(mds_verw_sel) + UNWIND_HINT_UNDEFINED + ANNOTATE_NOENDBR + .word __KERNEL_DS +.align L1_CACHE_BYTES, 0xcc +SYM_CODE_END(mds_verw_sel); +/* For KVM */ +EXPORT_SYMBOL_GPL(mds_verw_sel); + +.popsection + |