kprobes: Blacklist symbols in arch-defined prohibited area

Blacklist symbols in arch-defined probe-prohibited areas.
With this change, user can see all symbols which are prohibited
to probe in debugfs.

All archtectures which have custom prohibit areas should define
its own arch_populate_kprobe_blacklist() function, but unless that,
all symbols marked __kprobes are blacklisted.

Reported-by: Andrea Righi <righi.andrea@gmail.com>
Tested-by: Andrea Righi <righi.andrea@gmail.com>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: David S. Miller <davem@davemloft.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Yonghong Song <yhs@fb.com>
Link: http://lkml.kernel.org/r/154503485491.26176.15823229545155174796.stgit@devbox
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2 files changed, 56 insertions, 14 deletions

diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index e909413e4e38..5da8a1de2187 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -242,10 +242,13 @@ extern int arch_init_kprobes(void);
 extern void show_registers(struct pt_regs *regs);
 extern void kprobes_inc_nmissed_count(struct kprobe *p);
 extern bool arch_within_kprobe_blacklist(unsigned long addr);
+extern int arch_populate_kprobe_blacklist(void);
 extern bool arch_kprobe_on_func_entry(unsigned long offset);
 extern bool kprobe_on_func_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset);
 
 extern bool within_kprobe_blacklist(unsigned long addr);
+extern int kprobe_add_ksym_blacklist(unsigned long entry);
+extern int kprobe_add_area_blacklist(unsigned long start, unsigned long end);
 
 struct kprobe_insn_cache {
         struct mutex mutex;
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 90e98e233647..90569aec0f24 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -2093,6 +2093,47 @@ void dump_kprobe(struct kprobe *kp)
 }
 NOKPROBE_SYMBOL(dump_kprobe);
 
+int kprobe_add_ksym_blacklist(unsigned long entry)
+{
+        struct kprobe_blacklist_entry *ent;
+        unsigned long offset = 0, size = 0;
+
+        if (!kernel_text_address(entry) ||
+            !kallsyms_lookup_size_offset(entry, &size, &offset))
+                return -EINVAL;
+
+        ent = kmalloc(sizeof(*ent), GFP_KERNEL);
+        if (!ent)
+                return -ENOMEM;
+        ent->start_addr = entry;
+        ent->end_addr = entry + size;
+        INIT_LIST_HEAD(&ent->list);
+        list_add_tail(&ent->list, &kprobe_blacklist);
+
+        return (int)size;
+}
+
+/* Add all symbols in given area into kprobe blacklist */
+int kprobe_add_area_blacklist(unsigned long start, unsigned long end)
+{
+        unsigned long entry;
+        int ret = 0;
+
+        for (entry = start; entry < end; entry += ret) {
+                ret = kprobe_add_ksym_blacklist(entry);
+                if (ret < 0)
+                        return ret;
+                if (ret == 0)   /* In case of alias symbol */
+                        ret = 1;
+        }
+        return 0;
+}
+
+int __init __weak arch_populate_kprobe_blacklist(void)
+{
+        return 0;
+}
+
 /*
  * Lookup and populate the kprobe_blacklist.
  *
@@ -2104,26 +2145,24 @@ NOKPROBE_SYMBOL(dump_kprobe);
 static int __init populate_kprobe_blacklist(unsigned long *start,
                                              unsigned long *end)
 {
+        unsigned long entry;
         unsigned long *iter;
-        struct kprobe_blacklist_entry *ent;
-        unsigned long entry, offset = 0, size = 0;
+        int ret;
 
         for (iter = start; iter < end; iter++) {
                 entry = arch_deref_entry_point((void *)*iter);
-
-                if (!kernel_text_address(entry) ||
-                    !kallsyms_lookup_size_offset(entry, &size, &offset))
+                ret = kprobe_add_ksym_blacklist(entry);
+                if (ret == -EINVAL)
                         continue;
-
-                ent = kmalloc(sizeof(*ent), GFP_KERNEL);
-                if (!ent)
-                        return -ENOMEM;
-                ent->start_addr = entry;
-                ent->end_addr = entry + size;
-                INIT_LIST_HEAD(&ent->list);
-                list_add_tail(&ent->list, &kprobe_blacklist);
+                if (ret < 0)
+                        return ret;
         }
-        return 0;
+
+        /* Symbols in __kprobes_text are blacklisted */
+        ret = kprobe_add_area_blacklist((unsigned long)__kprobes_text_start,
+                                        (unsigned long)__kprobes_text_end);
+
+        return ret ? : arch_populate_kprobe_blacklist();
 }
 
 /* Module notifier call back, checking kprobes on the module */