x86/int3: Ensure that poke_int3_handler() is not traced

In order to ensure poke_int3_handler() is completely self contained -- this
is called while modifying other text, imagine the fun of hitting another
INT3 -- ensure that everything it uses is not traced.

The primary means here is to force inlining; bsearch() is notrace because
all of lib/ is.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505135313.410702173@linutronix.de

arch/x86/include/asm/ptrace.h

@@ -123,7 +123,7 @@ static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
  * On x86_64, vm86 mode is mercifully nonexistent, and we don't need
  * the extra check.
  */
-static inline int user_mode(struct pt_regs *regs)
+static __always_inline int user_mode(struct pt_regs *regs)
 {
 #ifdef CONFIG_X86_32
 	return ((regs->cs & SEGMENT_RPL_MASK) | (regs->flags & X86_VM_MASK)) >= USER_RPL;

arch/x86/include/asm/text-patching.h

@@ -64,7 +64,7 @@ extern void text_poke_finish(void);
 
 #define DISP32_SIZE		4
 
-static inline int text_opcode_size(u8 opcode)
+static __always_inline int text_opcode_size(u8 opcode)
 {
 	int size = 0;
 
@@ -118,12 +118,14 @@ extern __ro_after_init struct mm_struct *poking_mm;
 extern __ro_after_init unsigned long poking_addr;
 
 #ifndef CONFIG_UML_X86
-static inline void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
+static __always_inline
+void int3_emulate_jmp(struct pt_regs *regs, unsigned long ip)
 {
 	regs->ip = ip;
 }
 
-static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val)
+static __always_inline
+void int3_emulate_push(struct pt_regs *regs, unsigned long val)
 {
 	/*
 	 * The int3 handler in entry_64.S adds a gap between the
@@ -138,7 +140,8 @@ static inline void int3_emulate_push(struct pt_regs *regs, unsigned long val)
 	*(unsigned long *)regs->sp = val;
 }
 
-static inline void int3_emulate_call(struct pt_regs *regs, unsigned long func)
+static __always_inline
+void int3_emulate_call(struct pt_regs *regs, unsigned long func)
 {
 	int3_emulate_push(regs, regs->ip - INT3_INSN_SIZE + CALL_INSN_SIZE);
 	int3_emulate_jmp(regs, func);

arch/x86/kernel/alternative.c

@@ -1011,7 +1011,8 @@ struct bp_patching_desc {
 
 static struct bp_patching_desc *bp_desc;
 
-static inline struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp)
+static __always_inline
+struct bp_patching_desc *try_get_desc(struct bp_patching_desc **descp)
 {
 	struct bp_patching_desc *desc = READ_ONCE(*descp); /* rcu_dereference */
 
@@ -1021,18 +1022,18 @@ static inline struct bp_patching_desc *try_get_desc(struct bp_patching_desc **de
 	return desc;
 }
 
-static inline void put_desc(struct bp_patching_desc *desc)
+static __always_inline void put_desc(struct bp_patching_desc *desc)
 {
 	smp_mb__before_atomic();
 	atomic_dec(&desc->refs);
 }
 
-static inline void *text_poke_addr(struct text_poke_loc *tp)
+static __always_inline void *text_poke_addr(struct text_poke_loc *tp)
 {
 	return _stext + tp->rel_addr;
 }
 
-static int notrace patch_cmp(const void *key, const void *elt)
+static int noinstr patch_cmp(const void *key, const void *elt)
 {
 	struct text_poke_loc *tp = (struct text_poke_loc *) elt;
 
@@ -1042,9 +1043,8 @@ static int notrace patch_cmp(const void *key, const void *elt)
 		return 1;
 	return 0;
 }
-NOKPROBE_SYMBOL(patch_cmp);
 
-int notrace poke_int3_handler(struct pt_regs *regs)
+int noinstr poke_int3_handler(struct pt_regs *regs)
 {
 	struct bp_patching_desc *desc;
 	struct text_poke_loc *tp;
@@ -1118,7 +1118,6 @@ int notrace poke_int3_handler(struct pt_regs *regs)
 	put_desc(desc);
 	return ret;
 }
-NOKPROBE_SYMBOL(poke_int3_handler);
 
 #define TP_VEC_MAX (PAGE_SIZE / sizeof(struct text_poke_loc))
 static struct text_poke_loc tp_vec[TP_VEC_MAX];