From 3b6424407025aad39b00e60bd0d711b67272513f Mon Sep 17 00:00:00 2001
From: Hugo Wen <wenhug@amazon.com>
Date: Fri, 24 Mar 2023 16:06:11 +0000
Subject: [PATCH] Handle meaningless addr2line results and increase timeout

MariaDB server prints the stack information if a crash happens.

It traverses the stack frames in function `print_with_addr_resolve`.
For *EACH* frame, it tries to parse the file name and line number of the
frame using `addr2line`, or prints `backtrace_symbols_fd` if `addr2line`
fails.

1. Logic in `addr_resolve` function uses addr2line to get the file name
   and line numbers. It has a timeout of 500ms to wait for the response
   from addr2line. However, that's not enough on small instances
   especially if the debug information is in a separate file or
   compressed.

   Increase the timeout to 5 seconds to support some edge cases, as
   experiments showed addr2line may take 2-3 seconds on some frames.

2. While parsing a frame inside of a shared library using `addr2line`,
   the file name and line numbers could be `??`, empty or `0` if the
   debug info is not loaded.
   It's easy to reproduce when glibc-debuginfo is not installed.

   Instead of printing a meaningless frame like:

       :0(__GI___poll)[0x1505e9197639]
       ...
       ??:0(__libc_start_main)[0x7ffff6c8913a]

   We want to print the frame information using `backtrace_symbols_fd`,
   with the shared library name and a hexadecimal offset.
   Stacktrace example on a real instance with this commit:

       /lib64/libc.so.6(__poll+0x49)[0x145cbf71a639]
       ...
       /lib64/libc.so.6(__libc_start_main+0xea)[0x7f4d0034d13a]

   `addr_resolve` has considered the case of meaningless combination of
   file name and line number returned by `addr2line`. e.g. `??:?`
   However, conditions like `:0` and `??:0` are not handled. So now the
   function will rollback to `backtrace_symbols_fd` in above cases.

All new code of the whole pull request, including one or several files
that are either new files or modified ones, are contributed under the
BSD-new license. I am contributing on behalf of my employer Amazon Web
Services, Inc.
---
 mysys/my_addr_resolve.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/mysys/my_addr_resolve.c b/mysys/my_addr_resolve.c
index ac1bdae187c..52fcaaf67bb 100644
--- a/mysys/my_addr_resolve.c
+++ b/mysys/my_addr_resolve.c
@@ -252,10 +252,10 @@ int my_addr_resolve(void *ptr, my_addr_loc *loc)
     return 3;
 
 
-  /* 500 ms should be plenty of time for addr2line to issue a response. */
+  /* 5000 ms should be plenty of time for addr2line to issue a response. */
   /* Read in a loop till all the output from addr2line is complete. */
   while (parsed == total_bytes_read &&
-         (ret= poll(&poll_fds, 1, 500)))
+         (ret= poll(&poll_fds, 1, 5000)))
   {
     /* error during poll */
     if (ret < 0)
@@ -299,7 +299,8 @@ int my_addr_resolve(void *ptr, my_addr_loc *loc)
   loc->line= atoi(output + line_number_start);
 
   /* Addr2line was unable to extract any meaningful information. */
-  if (strcmp(loc->file, "??") == 0)
+  if ((strcmp(loc->file, "??") == 0 || strcmp(loc->file, "") == 0) &&
+      (loc->func[0] == '?' || loc->line == 0))
     return 6;
 
   loc->file= strip_path(loc->file);