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✅ All tests passed successfully. No issues detected. No action required from the submitter.
The upstream commit SHA1 provided is correct: a75bf27fe41abe658c53276a0c486c4bf9adecfc
Status in newer kernel trees: 6.14.y | Present (different SHA1: 308cb38001dc) 6.12.y | Present (different SHA1: 09f29041465a) 6.6.y | Present (different SHA1: 16103770be91) 6.1.y | Present (different SHA1: eb5018752a74)
Note: The patch differs from the upstream commit: --- 1: a75bf27fe41ab ! 1: 8baf62c74291b x86/its: Add support for ITS-safe return thunk @@ Metadata ## Commit message ## x86/its: Add support for ITS-safe return thunk
+ commit a75bf27fe41abe658c53276a0c486c4bf9adecfc upstream. + 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. @@ Commit message
- 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.
@@ Commit message Reviewed-by: Alexandre Chartre alexandre.chartre@oracle.com
## arch/x86/include/asm/alternative.h ## -@@ arch/x86/include/asm/alternative.h: static __always_inline int x86_call_depth_emit_accounting(u8 **pprog, - } - #endif +@@ arch/x86/include/asm/alternative.h: extern void apply_returns(s32 *start, s32 *end); + + struct module;
-+#if defined(CONFIG_MITIGATION_RETHUNK) && defined(CONFIG_OBJTOOL) ++#ifdef CONFIG_RETHUNK +extern bool cpu_wants_rethunk(void); +extern bool cpu_wants_rethunk_at(void *addr); +#else @@ arch/x86/include/asm/alternative.h: static __always_inline int x86_call_depth_em void *locks, void *locks_end,
## arch/x86/include/asm/nospec-branch.h ## -@@ arch/x86/include/asm/nospec-branch.h: static inline void srso_return_thunk(void) {} - static inline void srso_alias_return_thunk(void) {} +@@ arch/x86/include/asm/nospec-branch.h: extern void __x86_return_thunk(void); + static inline void __x86_return_thunk(void) {} #endif
+#ifdef CONFIG_MITIGATION_ITS @@ arch/x86/include/asm/nospec-branch.h: static inline void srso_return_thunk(void) ## arch/x86/kernel/alternative.c ## @@ arch/x86/kernel/alternative.c: void __init_or_module noinline apply_retpolines(s32 *start, s32 *end)
- #ifdef CONFIG_MITIGATION_RETHUNK + #ifdef CONFIG_RETHUNK
+bool cpu_wants_rethunk(void) +{ @@ arch/x86/kernel/alternative.c: static int patch_return(void *addr, struct insn * i = JMP32_INSN_SIZE; __text_gen_insn(bytes, JMP32_INSN_OPCODE, addr, x86_return_thunk, i); } else { -@@ arch/x86/kernel/alternative.c: void __init_or_module noinline apply_returns(s32 *start, s32 *end) - { - s32 *s; - -- if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) -+ if (cpu_wants_rethunk()) - static_call_force_reinit(); - - for (s = start; s < end; s++) {
## arch/x86/kernel/ftrace.c ## @@ arch/x86/kernel/ftrace.c: create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) @@ arch/x86/kernel/static_call.c: static void __ref __static_call_transform(void *i code = text_gen_insn(JMP32_INSN_OPCODE, insn, x86_return_thunk); else code = &retinsn; -@@ arch/x86/kernel/static_call.c: static void __ref __static_call_transform(void *insn, enum insn_type type, - case JCC: - if (!func) { - func = __static_call_return; -- if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) -+ if (cpu_wants_rethunk()) - func = x86_return_thunk; - } -
## arch/x86/kernel/vmlinux.lds.S ## -@@ arch/x86/kernel/vmlinux.lds.S: PROVIDE(__ref_stack_chk_guard = __stack_chk_guard); +@@ arch/x86/kernel/vmlinux.lds.S: INIT_PER_CPU(irq_stack_backing_store); . = ASSERT(__x86_indirect_its_thunk_array == __x86_indirect_its_thunk_rax, "Gap in ITS thunk array"); #endif
@@ arch/x86/kernel/vmlinux.lds.S: PROVIDE(__ref_stack_chk_guard = __stack_chk_guard + #endif /* CONFIG_X86_64 */
- /* + #ifdef CONFIG_KEXEC_CORE
## arch/x86/lib/retpoline.S ## @@ arch/x86/lib/retpoline.S: SYM_CODE_START(__x86_indirect_its_thunk_array) @@ arch/x86/lib/retpoline.S: SYM_CODE_START(__x86_indirect_its_thunk_array) + +#endif /* CONFIG_MITIGATION_ITS */
- /* - * This function name is magical and is used by -mfunction-return=thunk-extern + SYM_CODE_START(__x86_return_thunk) + UNWIND_HINT_FUNC
## arch/x86/net/bpf_jit_comp.c ## @@ arch/x86/net/bpf_jit_comp.c: static void emit_return(u8 **pprog, u8 *ip) ---
Results of testing on various branches:
| Branch | Patch Apply | Build Test | |---------------------------|-------------|------------| | stable/linux-6.1.y | Success | Success |