[PATCH -tip v2 09/10] x86/unwind/orc: Fixup kretprobe trampoline entry

[Masami Hiramatsu]

Since the kretprobe replaces the function return address with
the kretprobe_trampoline on the stack, the ORC unwinder can not
continue the stack unwinding at that point.

To fix this issue, correct state->ip as like as function-graph
tracer in the unwind_next_frame().

Signed-off-by: Masami Hiramatsu <mhira...@kernel.org>
---
  Changes in v2:
   - Remove kretprobe wrapper functions from unwind_orc.c
   - Do not fixup state->ip when unwinding with regs because
     kretprobe fixup instruction pointer before calling handler.
---
 arch/x86/include/asm/unwind.h |    4 ++++
 arch/x86/kernel/unwind_orc.c  |   16 ++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/arch/x86/include/asm/unwind.h b/arch/x86/include/asm/unwind.h
index 70fc159ebe69..ab5e45b848d5 100644
--- a/arch/x86/include/asm/unwind.h
+++ b/arch/x86/include/asm/unwind.h
@@ -4,6 +4,7 @@
 
 #include <linux/sched.h>
 #include <linux/ftrace.h>
+#include <linux/llist.h>
 #include <asm/ptrace.h>
 #include <asm/stacktrace.h>
 
@@ -20,6 +21,9 @@ struct unwind_state {
        bool signal, full_regs;
        unsigned long sp, bp, ip;
        struct pt_regs *regs, *prev_regs;
+#if defined(CONFIG_KRETPROBES)
+       struct llist_node *kr_iter;
+#endif
 #elif defined(CONFIG_UNWINDER_FRAME_POINTER)
        bool got_irq;
        unsigned long *bp, *orig_sp, ip;
diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
index 2a1d47f47eee..1d1b9388a1b1 100644
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -2,6 +2,7 @@
 #include <linux/objtool.h>
 #include <linux/module.h>
 #include <linux/sort.h>
+#include <linux/kprobes.h>
 #include <asm/ptrace.h>
 #include <asm/stacktrace.h>
 #include <asm/unwind.h>
@@ -536,6 +537,21 @@ bool unwind_next_frame(struct unwind_state *state)
 
                state->ip = ftrace_graph_ret_addr(state->task, 
&state->graph_idx,
                                                  state->ip, (void *)ip_p);
+               /*
+                * When the stack unwinder is called from the kretprobe handler
+                * or the interrupt handler which occurs in the kretprobe
+                * trampoline code, %sp is shown on the stack instead of the
+                * return address because kretprobe_trampoline() does
+                * "push %sp" at first.
+                * And also the unwinder may find the kretprobe_trampoline
+                * instead of the real return address on stack.
+                * In those cases, find the correct return address from
+                * task->kretprobe_instances list.
+                */
+               if (state->ip == sp ||
+                   is_kretprobe_trampoline(state->ip))
+                       state->ip = kretprobe_find_ret_addr(state->task,
+                                                           &state->kr_iter);
 
                state->sp = sp;
                state->regs = NULL;