Merge tag 'arm-dt-6.0' of git://git.kernel.org/pub/scm/linux/kernel/git/soc/soc

[linux-2.6-microblaze.git] / arch / x86 / kernel / static_call.c

diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c
index aa72cef..aaaba85 100644 (file)
--- a/arch/x86/kernel/static_call.c
+++ b/arch/x86/kernel/static_call.c
@@ -11,6 +11,13 @@ enum insn_type {
        RET = 3,  /* tramp / site cond-tail-call */
 };
 
+/*
+ * ud1 %esp, %ecx - a 3 byte #UD that is unique to trampolines, chosen such
+ * that there is no false-positive trampoline identification while also being a
+ * speculation stop.
+ */
+static const u8 tramp_ud[] = { 0x0f, 0xb9, 0xcc };
+
 /*
  * cs cs cs xorl %eax, %eax - a single 5 byte instruction that clears %[er]ax
  */
@@ -18,7 +25,8 @@ static const u8 xor5rax[] = { 0x2e, 0x2e, 0x2e, 0x31, 0xc0 };
 
 static const u8 retinsn[] = { RET_INSN_OPCODE, 0xcc, 0xcc, 0xcc, 0xcc };
 
-static void __ref __static_call_transform(void *insn, enum insn_type type, void *func)
+static void __ref __static_call_transform(void *insn, enum insn_type type,
+                                         void *func, bool modinit)
 {
        const void *emulate = NULL;
        int size = CALL_INSN_SIZE;
@@ -43,14 +51,17 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, void
                break;
 
        case RET:
-               code = &retinsn;
+               if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
+                       code = text_gen_insn(JMP32_INSN_OPCODE, insn, &__x86_return_thunk);
+               else
+                       code = &retinsn;
                break;
        }
 
        if (memcmp(insn, code, size) == 0)
                return;
 
-       if (unlikely(system_state == SYSTEM_BOOTING))
+       if (system_state == SYSTEM_BOOTING || modinit)
                return text_poke_early(insn, code, size);
 
        text_poke_bp(insn, code, size, emulate);
@@ -60,7 +71,7 @@ static void __static_call_validate(void *insn, bool tail, bool tramp)
 {
        u8 opcode = *(u8 *)insn;
 
-       if (tramp && memcmp(insn+5, "SCT", 3)) {
+       if (tramp && memcmp(insn+5, tramp_ud, 3)) {
                pr_err("trampoline signature fail");
                BUG();
        }
@@ -104,14 +115,42 @@ void arch_static_call_transform(void *site, void *tramp, void *func, bool tail)
 
        if (tramp) {
                __static_call_validate(tramp, true, true);
-               __static_call_transform(tramp, __sc_insn(!func, true), func);
+               __static_call_transform(tramp, __sc_insn(!func, true), func, false);
        }
 
        if (IS_ENABLED(CONFIG_HAVE_STATIC_CALL_INLINE) && site) {
                __static_call_validate(site, tail, false);
-               __static_call_transform(site, __sc_insn(!func, tail), func);
+               __static_call_transform(site, __sc_insn(!func, tail), func, false);
        }
 
        mutex_unlock(&text_mutex);
 }
 EXPORT_SYMBOL_GPL(arch_static_call_transform);
+
+#ifdef CONFIG_RETHUNK
+/*
+ * This is called by apply_returns() to fix up static call trampolines,
+ * specifically ARCH_DEFINE_STATIC_CALL_NULL_TRAMP which is recorded as
+ * having a return trampoline.
+ *
+ * The problem is that static_call() is available before determining
+ * X86_FEATURE_RETHUNK and, by implication, running alternatives.
+ *
+ * This means that __static_call_transform() above can have overwritten the
+ * return trampoline and we now need to fix things up to be consistent.
+ */
+bool __static_call_fixup(void *tramp, u8 op, void *dest)
+{
+       if (memcmp(tramp+5, tramp_ud, 3)) {
+               /* Not a trampoline site, not our problem. */
+               return false;
+       }
+
+       mutex_lock(&text_mutex);
+       if (op == RET_INSN_OPCODE || dest == &__x86_return_thunk)
+               __static_call_transform(tramp, RET, NULL, true);
+       mutex_unlock(&text_mutex);
+
+       return true;
+}
+#endif