MINOR: debug: store important pointers in post_mortem

Dealing with a core and a stripped executable is a pain when it comes
to finding pools, proxies or thread contexts. Let's put a pointer to
these heads and arrays in the post_mortem struct for easier location.
Other critical lists like this could possibly benefit from being added
later.

Here we now have:
  - tgroup_info
  - thread_info
  - tgroup_ctx
  - thread_ctx
  - pools
  - proxies

Example:
  $ objdump -h haproxy|grep post
   34 _post_mortem  000014b0  0000000000cfd400  0000000000cfd400  008fc400  2**8

  (gdb) set $pm=(struct post_mortem*)0x0000000000cfd400

  (gdb) p $pm->tgroup_ctx[0]
  $8 = {
    threads_harmless = 254,
    threads_idle = 254,
    stopping_threads = 0,
    timers = {
      b = {0x0, 0x0}
    },
    niced_tasks = 0,
    __pad = 0xf5662c <ha_tgroup_ctx+44> "",
    __end = 0xf56640 <ha_tgroup_ctx+64> ""
  }

  (gdb) info thr
    Id   Target Id                         Frame
  * 1    Thread 0x7f9e7706a440 (LWP 21169) 0x00007f9e76a9c868 in raise () from /lib64/libc.so.6
    2    Thread 0x7f9e76a60640 (LWP 21175) 0x00007f9e76b343c7 in wait4 () from /lib64/libc.so.6
    3    Thread 0x7f9e7613d640 (LWP 21176) 0x00007f9e76b343c7 in wait4 () from /lib64/libc.so.6
    4    Thread 0x7f9e7493a640 (LWP 21179) 0x00007f9e76b343c7 in wait4 () from /lib64/libc.so.6
    5    Thread 0x7f9e7593c640 (LWP 21177) 0x00007f9e76b343c7 in wait4 () from /lib64/libc.so.6
    6    Thread 0x7f9e7513b640 (LWP 21178) 0x00007f9e76b343c7 in wait4 () from /lib64/libc.so.6
    7    Thread 0x7f9e6ffff640 (LWP 21180) 0x00007f9e76b343c7 in wait4 () from /lib64/libc.so.6
    8    Thread 0x7f9e6f7fe640 (LWP 21181) 0x00007f9e76b343c7 in wait4 () from /lib64/libc.so.6
  (gdb) p/x $pm->thread_info[0].pth_id
  $12 = 0x7f9e7706a440
  (gdb) p/x $pm->thread_info[1].pth_id
  $13 = 0x7f9e76a60640

  (gdb) set $px = *$pm->proxies
  while ($px != 0)
     printf "%#lx %s served=%u\n", $px, $px->id, $px->served
     set $px = ($px)->next
  end

  0x125eda0 GLOBAL served=0
  0x12645b0 stats served=0
  0x1266940 comp served=0
  0x1268e10 comp_bck served=0
  0x1260cf0 <OCSP-UPDATE> served=0
  0x12714c0 <HTTPCLIENT> served=0

Author: wtarreau

src/debug.c

@@ -45,6 +45,7 @@
 #include <haproxy/log.h>
 #include <haproxy/net_helper.h>
 #include <haproxy/sc_strm.h>
+#include <haproxy/proxy.h>
 #include <haproxy/stconn.h>
 #include <haproxy/task.h>
 #include <haproxy/thread.h>
@@ -149,6 +150,12 @@ struct post_mortem {
 	/* information about dynamic shared libraries involved */
 	char *libs;                      // dump of one addr / path per line, or NULL
 #endif
+	struct tgroup_info *tgroup_info; // pointer to ha_tgroup_info
+	struct thread_info *thread_info; // pointer to ha_thread_info
+	struct tgroup_ctx  *tgroup_ctx;  // pointer to ha_tgroup_ctx
+	struct thread_ctx  *thread_ctx;  // pointer to ha_thread_ctx
+	struct list *pools;              // pointer to the head of the pools list
+	struct proxy **proxies;          // pointer to the head of the proxies list
 
 	/* info about identified distinct components (executable, shared libs, etc).
 	 * These can be all listed at once in gdb using:
@@ -2543,6 +2550,13 @@ static int feed_post_mortem()
 		post_mortem.libs = strdup(trash.area);
 #endif
 
+	post_mortem.tgroup_info = ha_tgroup_info;
+	post_mortem.thread_info = ha_thread_info;
+	post_mortem.tgroup_ctx  = ha_tgroup_ctx;
+	post_mortem.thread_ctx  = ha_thread_ctx;
+	post_mortem.pools = &pools;
+	post_mortem.proxies = &proxies_list;
+
 	return ERR_NONE;
 }