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| author |   Pawan Gupta <pawan.kumar.gupta@linux.intel.com> | 2024-06-21 21:17:21 -0700 |
|---|---|---|
| committer |   Dave Hansen <dave.hansen@linux.intel.com> | 2025-05-09 13:22:05 -0700 |
| commit | a75bf27fe41abe658c53276a0c486c4bf9adecfc (patch) | |
| tree | 0898216e1eb51992a199696ed652042942ac11f9 /arch/x86/lib | |
| parent | x86/its: Add support for ITS-safe indirect thunk (diff) | |
| download | wireguard-linux-a75bf27fe41abe658c53276a0c486c4bf9adecfc.tar.xz wireguard-linux-a75bf27fe41abe658c53276a0c486c4bf9adecfc.zip | |
x86/its: Add support for ITS-safe return thunk
RETs in the lower half of cacheline may be affected by ITS bug,
specifically when the RSB-underflows. Use ITS-safe return thunk for such
RETs.
RETs that are not patched:
- RET in retpoline sequence does not need to be patched, because the
sequence itself fills an RSB before RET.
- RET in Call Depth Tracking (CDT) thunks __x86_indirect_{call|jump}_thunk
and call_depth_return_thunk are not patched because CDT by design
prevents RSB-underflow.
- RETs in .init section are not reachable after init.
- RETs that are explicitly marked safe with ANNOTATE_UNRET_SAFE.
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Diffstat (limited to 'arch/x86/lib')
| -rw-r--r-- | arch/x86/lib/retpoline.S | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index a06891892853..ebca28fe7e31 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -393,7 +393,18 @@ SYM_CODE_START(__x86_indirect_its_thunk_array) .align 64, 0xcc SYM_CODE_END(__x86_indirect_its_thunk_array) -#endif +.align 64, 0xcc +.skip 32, 0xcc +SYM_CODE_START(its_return_thunk) + UNWIND_HINT_FUNC + ANNOTATE_NOENDBR + ANNOTATE_UNRET_SAFE + ret + int3 +SYM_CODE_END(its_return_thunk) +EXPORT_SYMBOL(its_return_thunk) + +#endif /* CONFIG_MITIGATION_ITS */ /* * This function name is magical and is used by -mfunction-return=thunk-extern |