powerpc/kprobes: Skip livepatch_handler() for jprobes

ftrace_caller() depends on a modified regs->nip to detect if a certain
function has been livepatched. However, with KPROBES_ON_FTRACE, it is
possible for regs->nip to have been modified by the kprobes pre_handler
(jprobes, for instance). In this case, we do not want to invoke the
livepatch_handler so as not to consume the livepatch stack.

To distinguish between the two (kprobes and livepatch), we check if
there is an active kprobe on the current function. If there is, then we
know for sure that it must have modified the NIP as we don't support
livepatching a kprobe'd function. In this case, we simply skip the
livepatch_handler and branch to the new NIP. Otherwise, the
livepatch_handler is invoked.

Fixes: ead514d5fb30 ("powerpc/kprobes: Add support for KPROBES_ON_FTRACE")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

1 files changed, 6 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 5075a4d6f1d7..01addfb0ed0a 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -43,6 +43,12 @@ DEFINE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);
 
 struct kretprobe_blackpoint kretprobe_blacklist[] = {{NULL, NULL}};
 
+int is_current_kprobe_addr(unsigned long addr)
+{
+	struct kprobe *p = kprobe_running();
+	return (p && (unsigned long)p->addr == addr) ? 1 : 0;
+}
+
 bool arch_within_kprobe_blacklist(unsigned long addr)
 {
 	return  (addr >= (unsigned long)__kprobes_text_start &&