[PATCH v3 2/4] kprobes: split blacklist into common and arch

[Oskar Andero]

Some blackpoints are only valid for specific architectures. To let each
architecture specify its own blackpoints the list has been split in two
lists: common and arch. The common list is kept in kernel/kprobes.c and
the arch list is kept in the arch/ directory.

Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Cc: linux-arch@xxxxxxxxxxxxxxx
Signed-off-by: Oskar Andero <oskar.andero@xxxxxxxxxxxxxx>
---
 kernel/kprobes.c | 88 +++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 59 insertions(+), 29 deletions(-)

diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index c8c2281..2458ae1 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -68,7 +68,6 @@
 #endif
 
 static int kprobes_initialized;
-static bool kprobe_blacklist_initialized;
 static struct hlist_head kprobe_table[KPROBE_TABLE_SIZE];
 static struct hlist_head kretprobe_inst_table[KPROBE_TABLE_SIZE];
 
@@ -94,31 +93,64 @@ static raw_spinlock_t *kretprobe_table_lock_ptr(unsigned long hash)
  *
  * For such cases, we now have a blacklist
  */
-static struct kprobe_blackpoint kprobe_blacklist[] = {
-	{"preempt_schedule",},
-	{"native_get_debugreg",},
-	{"irq_entries_start",},
-	{"common_interrupt",},
-	{"mcount",},	/* mcount can be called from everywhere */
-	{NULL}    /* Terminator */
+static const char * const common_kprobes_blacksyms[] = {
+	"preempt_schedule",
+	"native_get_debugreg",
+	"irq_entries_start",
+	"common_interrupt",
+	"mcount",       /* mcount can be called from everywhere */
 };
+static const size_t common_kprobes_blacksyms_size =
+			ARRAY_SIZE(common_kprobes_blacksyms);
+
+/*
+ * These weak symbols can be overridden from the arch/ directory for
+ * architecure specific blackpoints.
+ */
+const char * const __weak arch_kprobes_blacksyms[] = {};
+const size_t __weak arch_kprobes_blacksyms_size;
+
+static struct kprobe_blackpoint *kprobe_blacklist;
+static size_t kprobe_blacklist_size;
+
+static void init_kprobe_blacklist_entry(struct kprobe_blackpoint *kb,
+					const char * const name)
+{
+	const char *symbol_name;
+	char *modname, namebuf[128];
+	void *addr;
+	unsigned long offset = 0, size = 0;
+
+	kb->name = name;
+	kprobe_lookup_name(kb->name, addr);
+	if (!addr)
+		return;
+
+	kb->start_addr = (unsigned long)addr;
+	symbol_name = kallsyms_lookup(kb->start_addr,
+			&size, &offset, &modname, namebuf);
+	if (!symbol_name)
+		kb->range = 0;
+	else
+		kb->range = size;
+}
 
 /* it can take some time ( > 100ms ) to initialise the
  * blacklist so we delay this until we actually need it
  */
 static void init_kprobe_blacklist(void)
 {
-	int i;
-	unsigned long offset = 0, size = 0;
-	char *modname, namebuf[128];
-	const char *symbol_name;
-	void *addr;
+	int i, j = 0;
 	struct kprobe_blackpoint *kb;
 
 	mutex_lock(&kprobe_mutex);
-	if (kprobe_blacklist_initialized)
+	if (kprobe_blacklist)
 		goto out;
 
+	kprobe_blacklist_size = common_kprobes_blacksyms_size +
+				arch_kprobes_blacksyms_size;
+	kb = kzalloc(sizeof(*kb) * kprobe_blacklist_size, GFP_KERNEL);
+
 	/*
 	 * Lookup and populate the kprobe_blacklist.
 	 *
@@ -127,18 +159,14 @@ static void init_kprobe_blacklist(void)
 	 * since a kprobe need not necessarily be at the beginning
 	 * of a function.
 	 */
-	for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
-		kprobe_lookup_name(kb->name, addr);
-		if (!addr)
-			continue;
+	for (i = 0; i < common_kprobes_blacksyms_size; i++, j++) {
+		init_kprobe_blacklist_entry(&kb[j],
+					    common_kprobes_blacksyms[i]);
+	}
 
-		kb->start_addr = (unsigned long)addr;
-		symbol_name = kallsyms_lookup(kb->start_addr,
-				&size, &offset, &modname, namebuf);
-		if (!symbol_name)
-			kb->range = 0;
-		else
-			kb->range = size;
+	for (i = 0; i < arch_kprobes_blacksyms_size; i++, j++) {
+		init_kprobe_blacklist_entry(&kb[j],
+					    arch_kprobes_blacksyms[i]);
 	}
 
 	if (kretprobe_blacklist_size) {
@@ -153,7 +181,7 @@ static void init_kprobe_blacklist(void)
 	}
 
 	smp_wmb();
-	kprobe_blacklist_initialized = true;
+	kprobe_blacklist = kb;
 
 out:
 	mutex_unlock(&kprobe_mutex);
@@ -1384,18 +1412,20 @@ out:
 static int __kprobes in_kprobes_functions(unsigned long addr)
 {
 	struct kprobe_blackpoint *kb;
+	int i;
 
 	if (addr >= (unsigned long)__kprobes_text_start &&
 	    addr < (unsigned long)__kprobes_text_end)
 		return -EINVAL;
 
-	if (unlikely(!kprobe_blacklist_initialized))
+	if (unlikely(!kprobe_blacklist))
 		init_kprobe_blacklist();
 	/*
 	 * If there exists a kprobe_blacklist, verify and
 	 * fail any probe registration in the prohibited area
 	 */
-	for (kb = kprobe_blacklist; kb->name != NULL; kb++) {
+	for (i = 0; i < kprobe_blacklist_size; i++) {
+		kb = &kprobe_blacklist[i];
 		if (kb->start_addr) {
 			if (addr >= kb->start_addr &&
 			    addr < (kb->start_addr + kb->range))
@@ -1876,7 +1906,7 @@ int __kprobes register_kretprobe(struct kretprobe *rp)
 	void *addr;
 
 	if (kretprobe_blacklist_size) {
-		if (unlikely(!kprobe_blacklist_initialized))
+		if (unlikely(!kprobe_blacklist))
 			init_kprobe_blacklist();
 		addr = kprobe_addr(&rp->kp);
 		if (IS_ERR(addr))
-- 
1.8.1.5

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