x86/returnthunk: Allow different return thunks

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>

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index 940c15ee5650f46028fd420010c03d4786b2f2bd..e28237f7063f7f7fe36f04378b64af4b27f13f82 100644 (file)
--- 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];

diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index aea88d0d83523c0954c51da69b83aa394a077591..08e1f1011ff4fe3a954c635e01a0e29772e2d612 100644 (file)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -521,6 +521,11 @@ void __init_or_module noinline apply_retpolines(s32 *start, s32 *end)
 }
 
 #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, struct insn *insn, u8 *bytes)
 {
        int i = 0;
 
-       if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
-               return -1;
+       if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) {
+               if (x86_return_thunk == __x86_return_thunk)
+                       return -1;
 
-       bytes[i++] = RET_INSN_OPCODE;
+               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;
 }
 

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d1ba55ea46a7b7f98b7598ff7ba0a03cedb249f0..038732b4e408da7eab71e076ac94e9f6ea2d05f4 100644 (file)
--- 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)

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index a809a3693ac59a71b7988e4c0f850aa5c9bd1eac..85c09843df1b9e373039572a9e1441e5d20e33da 100644 (file)
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -368,7 +368,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
 
        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));
 

diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c
index b48b659ccf6fb7372d368e877ea0eea0c754d5f1..e25050c7ff1ea9f7cc060855951be0d967fb9969 100644 (file)
--- a/arch/x86/kernel/static_call.c
+++ b/arch/x86/kernel/static_call.c
@@ -52,7 +52,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type,
 
        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;

diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index ee6e3cda173885c6ea3284562552d92f444fae73..f7a0e9708418d369889950b90c69c031ab89bb67 100644 (file)
--- 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 *ip)
        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))