x86/static_call: Serialize __static_call_fixup() properly

__static_call_fixup() invokes __static_call_transform() without holding
text_mutex, which causes lockdep to complain in text_poke_bp().

Adding the proper locking cures that, but as this is either used during
early boot or during module finalizing, it's not required to use
text_poke_bp(). Add an argument to __static_call_transform() which tells
it to use text_poke_early() for it.

Fixes: ee88d363d156 ("x86,static_call: Use alternative RET encoding")
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>

diff --git a/arch/x86/kernel/static_call.c b/arch/x86/kernel/static_call.c
index be7038a..aaaba85 100644 (file)
--- a/arch/x86/kernel/static_call.c
+++ b/arch/x86/kernel/static_call.c
@@ -25,7 +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;
@@ -60,7 +61,7 @@ static void __ref __static_call_transform(void *insn, enum insn_type type, void
        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);
@@ -114,12 +115,12 @@ 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);
@@ -145,8 +146,10 @@ bool __static_call_fixup(void *tramp, u8 op, void *dest)
                return false;
        }
 
+       mutex_lock(&text_mutex);
        if (op == RET_INSN_OPCODE || dest == &__x86_return_thunk)
-               __static_call_transform(tramp, RET, NULL);
+               __static_call_transform(tramp, RET, NULL, true);
+       mutex_unlock(&text_mutex);
 
        return true;
 }