5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Upstream commit: 770ae1b709528a6a173b5c7b183818ee9b45e376 In preparation for call depth tracking on Intel SKL CPUs, make it possible to patch in a SKL specific return thunk. Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20220915111147.680469665@xxxxxxxxxxxxx Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/include/asm/nospec-branch.h | 6 ++++++ arch/x86/kernel/alternative.c | 19 ++++++++++++++----- arch/x86/kernel/cpu/bugs.c | 2 ++ arch/x86/kernel/ftrace.c | 2 +- arch/x86/kernel/static_call.c | 2 +- arch/x86/net/bpf_jit_comp.c | 2 +- 6 files changed, 25 insertions(+), 8 deletions(-) --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -207,6 +207,12 @@ extern void srso_alias_untrain_ret(void) extern void entry_untrain_ret(void); extern void entry_ibpb(void); +#ifdef CONFIG_CALL_THUNKS +extern void (*x86_return_thunk)(void); +#else +#define x86_return_thunk (&__x86_return_thunk) +#endif + #ifdef CONFIG_RETPOLINE typedef u8 retpoline_thunk_t[RETPOLINE_THUNK_SIZE]; --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -521,6 +521,11 @@ void __init_or_module noinline apply_ret } #ifdef CONFIG_RETHUNK + +#ifdef CONFIG_CALL_THUNKS +void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk; +#endif + /* * Rewrite the compiler generated return thunk tail-calls. * @@ -536,14 +541,18 @@ static int patch_return(void *addr, stru { int i = 0; - if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) - return -1; - - bytes[i++] = RET_INSN_OPCODE; + if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) { + if (x86_return_thunk == __x86_return_thunk) + return -1; + + i = JMP32_INSN_SIZE; + __text_gen_insn(bytes, JMP32_INSN_OPCODE, addr, x86_return_thunk, i); + } else { + bytes[i++] = RET_INSN_OPCODE; + } for (; i < insn->length;) bytes[i++] = INT3_INSN_OPCODE; - return i; } --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -62,7 +62,9 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd); static DEFINE_MUTEX(spec_ctrl_mutex); +#ifdef CONFIG_CALL_THUNKS void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk; +#endif /* Update SPEC_CTRL MSR and its cached copy unconditionally */ static void update_spec_ctrl(u64 val) --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -368,7 +368,7 @@ create_trampoline(struct ftrace_ops *ops ip = trampoline + size; if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) - __text_gen_insn(ip, JMP32_INSN_OPCODE, ip, &__x86_return_thunk, JMP32_INSN_SIZE); + __text_gen_insn(ip, JMP32_INSN_OPCODE, ip, x86_return_thunk, JMP32_INSN_SIZE); else memcpy(ip, retq, sizeof(retq)); --- a/arch/x86/kernel/static_call.c +++ b/arch/x86/kernel/static_call.c @@ -52,7 +52,7 @@ static void __ref __static_call_transfor case RET: if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) - code = text_gen_insn(JMP32_INSN_OPCODE, insn, &__x86_return_thunk); + code = text_gen_insn(JMP32_INSN_OPCODE, insn, x86_return_thunk); else code = &retinsn; break; --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -411,7 +411,7 @@ static void emit_return(u8 **pprog, u8 * u8 *prog = *pprog; if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) { - emit_jump(&prog, &__x86_return_thunk, ip); + emit_jump(&prog, x86_return_thunk, ip); } else { EMIT1(0xC3); /* ret */ if (IS_ENABLED(CONFIG_SLS))
