kprobes: support kretprobe blacklist

Introduce architecture dependent kretprobe blacklists to prohibit users
from inserting return probes on the function in which kprobes can be
inserted but kretprobes can not.

This patch also removes "__kprobes" mark from "__switch_to" on x86_64 and
registers "__switch_to" to the blacklist on x86-64, because that mark is to
prohibit user from inserting only kretprobe.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 15 insertions, 1 deletions

diff --git a/arch/x86/kernel/kprobes_32.c b/arch/x86/kernel/kprobes_32.c
index 06b86e5617f6..90f778c04b3f 100644
--- a/arch/x86/kernel/kprobes_32.c
+++ b/arch/x86/kernel/kprobes_32.c
@@ -41,6 +41,13 @@ void jprobe_return_end(void);
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
+struct kretprobe_blackpoint kretprobe_blacklist[] = {
+        {"__switch_to", }, /* This function switches only current task, but
+                             doesn't switch kernel stack.*/
+        {NULL, NULL}    /* Terminator */
+};
+const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
+
 /* insert a jmp code */
 static __always_inline void set_jmp_op(void *from, void *to)
 {
diff --git a/arch/x86/kernel/kprobes_64.c b/arch/x86/kernel/kprobes_64.c
index 7c16506d681f..681b801c5e26 100644
--- a/arch/x86/kernel/kprobes_64.c
+++ b/arch/x86/kernel/kprobes_64.c
@@ -48,6 +48,13 @@ static void __kprobes arch_copy_kprobe(struct kprobe *p);
 DEFINE_PER_CPU(struct kprobe *, current_kprobe) = NULL;
 DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
+struct kretprobe_blackpoint kretprobe_blacklist[] = {
+        {"__switch_to", }, /* This function switches only current task, but
+                              doesn't switch kernel stack.*/
+        {NULL, NULL}    /* Terminator */
+};
+const int kretprobe_blacklist_size = ARRAY_SIZE(kretprobe_blacklist);
+
 /*
  * returns non-zero if opcode modifies the interrupt flag.
  */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 7352d4b377e6..6309b275cb9c 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -581,7 +581,7 @@ static inline void __switch_to_xtra(struct task_struct *prev_p,
  *
  * Kprobes not supported here. Set the probe on schedule instead.
  */
-__kprobes struct task_struct *
+struct task_struct *
 __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
 {
         struct thread_struct *prev = &prev_p->thread,