6.1-stable review patch. If anyone has any objections, please let me know.
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From: Peter Zijlstra peterz@infradead.org
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@infradead.org Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Link: https://lore.kernel.org/r/20220915111147.680469665@infradead.org Signed-off-by: Borislav Petkov (AMD) bp@alien8.de Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/nospec-branch.h | 6 ++++++ arch/x86/kernel/alternative.c | 19 ++++++++++++++----- arch/x86/kernel/ftrace.c | 2 +- arch/x86/kernel/static_call.c | 2 +- arch/x86/net/bpf_jit_comp.c | 2 +- 5 files changed, 23 insertions(+), 8 deletions(-)
--- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -222,6 +222,12 @@ 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
#define GEN(reg) \ --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -536,6 +536,11 @@ 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. * @@ -551,14 +556,18 @@ 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/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -361,7 +361,7 @@ 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 @@ -80,7 +80,7 @@ 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 @@ -432,7 +432,7 @@ 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))