Revert "x86/ibt,ftrace: Search for __fentry__ location"

This reverts commit f6f1a8e333.

arch/x86/kernel/kprobes/core.c

@@ -194,10 +194,17 @@ static unsigned long
 __recover_probed_insn(kprobe_opcode_t *buf, unsigned long addr)
 {
 	struct kprobe *kp;
-	bool faddr;
+	unsigned long faddr;
 
 	kp = get_kprobe((void *)addr);
-	faddr = ftrace_location(addr) == addr;
+	faddr = ftrace_location(addr);
+	/*
+	 * Addresses inside the ftrace location are refused by
+	 * arch_check_ftrace_location(). Something went terribly wrong
+	 * if such an address is checked here.
+	 */
+	if (WARN_ON(faddr && faddr != addr))
+		return 0UL;
 	/*
 	 * Use the current code if it is not modified by Kprobe
 	 * and it cannot be modified by ftrace.

kernel/bpf/trampoline.c

@@ -89,6 +89,18 @@ out:
 	return tr;
 }
 
+static int is_ftrace_location(void *ip)
+{
+	long addr;
+
+	addr = ftrace_location((long)ip);
+	if (!addr)
+		return 0;
+	if (WARN_ON_ONCE(addr != (long)ip))
+		return -EFAULT;
+	return 1;
+}
+
 static int unregister_fentry(struct bpf_trampoline *tr, void *old_addr)
 {
 	void *ip = tr->func.addr;
@@ -117,12 +129,12 @@ static int modify_fentry(struct bpf_trampoline *tr, void *old_addr, void *new_ad
 static int register_fentry(struct bpf_trampoline *tr, void *new_addr)
 {
 	void *ip = tr->func.addr;
-	unsigned long faddr;
 	int ret;
 
-	faddr = ftrace_location((unsigned long)ip);
-	if (faddr)
-		tr->func.ftrace_managed = true;
+	ret = is_ftrace_location(ip);
+	if (ret < 0)
+		return ret;
+	tr->func.ftrace_managed = ret;
 
 	if (tr->func.ftrace_managed)
 		ret = register_ftrace_direct((long)ip, (long)new_addr);

kernel/kprobes.c

@@ -1611,10 +1611,14 @@ static inline int check_kprobe_rereg(struct kprobe *p)
 
 int __weak arch_check_ftrace_location(struct kprobe *p)
 {
-	unsigned long addr = (unsigned long)p->addr;
+	unsigned long ftrace_addr;
 
-	if (ftrace_location(addr) == addr) {
+	ftrace_addr = ftrace_location((unsigned long)p->addr);
+	if (ftrace_addr) {
 #ifdef CONFIG_KPROBES_ON_FTRACE
+		/* Given address is not on the instruction boundary */
+		if ((unsigned long)p->addr != ftrace_addr)
+			return -EILSEQ;
 		p->flags |= KPROBE_FLAG_FTRACE;
 #else	/* !CONFIG_KPROBES_ON_FTRACE */
 		return -EINVAL;

kernel/trace/ftrace.c

@@ -1575,34 +1575,17 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end)
 }
 
 /**
- * ftrace_location - return the ftrace location
+ * ftrace_location - return true if the ip giving is a traced location
  * @ip: the instruction pointer to check
  *
- * If @ip matches the ftrace location, return @ip.
- * If @ip matches sym+0, return sym's ftrace location.
- * Otherwise, return 0.
+ * Returns rec->ip if @ip given is a pointer to a ftrace location.
+ * That is, the instruction that is either a NOP or call to
+ * the function tracer. It checks the ftrace internal tables to
+ * determine if the address belongs or not.
  */
 unsigned long ftrace_location(unsigned long ip)
 {
-	struct dyn_ftrace *rec;
-	unsigned long offset;
-	unsigned long size;
-
-	rec = lookup_rec(ip, ip);
-	if (!rec) {
-		if (!kallsyms_lookup_size_offset(ip, &size, &offset))
-			goto out;
-
-		/* map sym+0 to __fentry__ */
-		if (!offset)
-			rec = lookup_rec(ip, ip + size - 1);
-	}
-
-	if (rec)
-		return rec->ip;
-
-out:
-	return 0;
+	return ftrace_location_range(ip, ip);
 }
 
 /**
@@ -4965,8 +4948,7 @@ ftrace_match_addr(struct ftrace_hash *hash, unsigned long ip, int remove)
 {
 	struct ftrace_func_entry *entry;
 
-	ip = ftrace_location(ip);
-	if (!ip)
+	if (!ftrace_location(ip))
 		return -EINVAL;
 
 	if (remove) {
@@ -5114,16 +5096,11 @@ int register_ftrace_direct(unsigned long ip, unsigned long addr)
 	struct ftrace_func_entry *entry;
 	struct ftrace_hash *free_hash = NULL;
 	struct dyn_ftrace *rec;
-	int ret = -ENODEV;
+	int ret = -EBUSY;
 
 	mutex_lock(&direct_mutex);
 
-	ip = ftrace_location(ip);
-	if (!ip)
-		goto out_unlock;
-
 	/* See if there's a direct function at @ip already */
-	ret = -EBUSY;
 	if (ftrace_find_rec_direct(ip))
 		goto out_unlock;
 
@@ -5252,10 +5229,6 @@ int unregister_ftrace_direct(unsigned long ip, unsigned long addr)
 
 	mutex_lock(&direct_mutex);
 
-	ip = ftrace_location(ip);
-	if (!ip)
-		goto out_unlock;
-
 	entry = find_direct_entry(&ip, NULL);
 	if (!entry)
 		goto out_unlock;
@@ -5387,11 +5360,6 @@ int modify_ftrace_direct(unsigned long ip,
 	mutex_lock(&direct_mutex);
 
 	mutex_lock(&ftrace_lock);
-
-	ip = ftrace_location(ip);
-	if (!ip)
-		goto out_unlock;
-
 	entry = find_direct_entry(&ip, &rec);
 	if (!entry)
 		goto out_unlock;