From 9639948f3fdda4afcf25e7080aa87d8ad2fbeb34 Mon Sep 17 00:00:00 2001

From: Martin Milata <mmilata@redhat.com>

Date: Wed, 27 Aug 2014 13:55:50 +0200

Subject: [SATYR PATCH] Better handling of infinite recursion

unwind: Append threads/frames in O(1)

unwind: throw away the most recent frames

unwind: lower stacktrace length limit to 256

Fixes #179.

Signed-off-by: Martin Milata <mmilata@redhat.com>

---

 lib/core_unwind_elfutils.c | 36 ++++++++++++++++++++----------------

 1 file changed, 20 insertions(+), 16 deletions(-)

diff --git a/lib/core_unwind_elfutils.c b/lib/core_unwind_elfutils.c

index 43d66be..bbd4813 100644

--- a/lib/core_unwind_elfutils.c

+++ b/lib/core_unwind_elfutils.c

@@ -29,18 +29,18 @@

 #include <stdio.h>

 #include <string.h>

-#define FRAME_LIMIT 1024

+#define FRAME_LIMIT 256

 struct frame_callback_arg

 {

-    struct sr_core_thread *thread;

+    struct sr_core_frame **frames_tail;

     char *error_msg;

     unsigned nframes;

 };

 struct thread_callback_arg

 {

-    struct sr_core_stacktrace *stacktrace;

+    struct sr_core_thread **threads_tail;

     char *error_msg;

 };

@@ -70,15 +70,9 @@ frame_callback(Dwfl_Frame *frame, void *data)

         return CB_STOP_UNWIND;

     }

-    frame_arg->thread->frames =

-        sr_core_frame_append(frame_arg->thread->frames, result);

-

-    /* Avoid huge stacktraces from programs stuck in infinite recursion. */

+    *frame_arg->frames_tail = result;

+    frame_arg->frames_tail = &result->next;

     frame_arg->nframes++;

-    if (frame_arg->nframes >= FRAME_LIMIT)

-    {

-        return CB_STOP_UNWIND;

-    }

     return DWARF_CB_OK;

 }

@@ -99,7 +93,7 @@ unwind_thread(Dwfl_Thread *thread, void *data)

     struct frame_callback_arg frame_arg =

     {

-        .thread = result,

+        .frames_tail = &(result->frames),

         .error_msg = NULL,

         .nframes = 0

     };

@@ -121,14 +115,24 @@ unwind_thread(Dwfl_Thread *thread, void *data)

         goto abort;

     }

-    if (!error_msg && !frame_arg.thread->frames)

+    if (!error_msg && !result->frames)

     {

         set_error("No frames found for thread id %d", (int)result->id);

         goto abort;

     }

-    thread_arg->stacktrace->threads =

-        sr_core_thread_append(thread_arg->stacktrace->threads, result);

+    /* Truncate the stacktrace to FRAME_LIMIT least recent frames. */

+    while (result->frames && frame_arg.nframes > FRAME_LIMIT)

+    {

+        struct sr_core_frame *old_frame = result->frames;

+        result->frames = old_frame->next;

+        sr_core_frame_free(old_frame);

+        frame_arg.nframes--;

+    }

+

+    *thread_arg->threads_tail = result;

+    thread_arg->threads_tail = &result->next;

+

     return DWARF_CB_OK;

 abort:

@@ -166,7 +170,7 @@ sr_parse_coredump(const char *core_file,

     struct thread_callback_arg thread_arg =

     {

-        .stacktrace = stacktrace,

+        .threads_tail = &(stacktrace->threads),

         .error_msg = NULL

     };

-- 

1.9.3