MINOR: debug: start to create a new struct post_mortem

The goal here is to accumulate precious debugging information in a
struct that is easy to find in memory. It's aligned to 256-byte as
it also helps. We'll progressively add a lot of info about the
startup conditions, the operating system, the hardware and hypervisor
so as to limit the number of round trips between developers and users
during debugging sessions. Also, opening a core file with an hex editor
should often be sufficient to extract most of the info.

In addition, a new "show dev" command will show these information so
that they can be checked at runtime without having to wait for a crash
(e.g. if a limit is bad in a container, better know it early).

For now the struct only contains utsname that's fed at boot time.

diff --git a/src/debug.c b/src/debug.c
index 9417a9613c4e888504694b49a4ef7072b9d6bcd0..7a98ffce65b7dbd4eb17efab738225f1e5650f03 100644 (file)
--- a/src/debug.c
+++ b/src/debug.c
@@ -20,6 +20,7 @@
 #include <syslog.h>
 #include <sys/stat.h>
 #include <sys/types.h>
+#include <sys/utsname.h>
 #include <sys/wait.h>
 #include <unistd.h>
 #ifdef USE_EPOLL
@@ -66,6 +67,20 @@
 #define THREAD_DUMP_FSYNC     0x00008000U
 #define THREAD_DUMP_PMASK     0x7FFF0000U
 
+/* This is a collection of information that are centralized to help with core
+ * dump analysis. It must be used with a public variable and gather elements
+ * as much as possible without dereferences so that even when identified in a
+ * core dump it's possible to get the most out of it even if the core file is
+ * not much exploitable. It's aligned to 256 so that it's easy to spot, given
+ * that being that large it will not change its size much.
+ */
+struct post_mortem {
+       /* platform-specific information */
+       struct {
+               struct utsname utsname; // OS name+ver+arch+hostname
+       } platform;
+} post_mortem ALIGNED(256) = { };
+
 /* Points to a copy of the buffer where the dump functions should write, when
  * non-null. It's only used by debuggers for core dump analysis.
  */
@@ -421,6 +436,29 @@ static int debug_parse_cli_show_libs(char **args, char *payload, struct appctx *
 }
 #endif
 
+/* parse a "show dev" command. It returns 1 if it emits anything otherwise zero. */
+static int debug_parse_cli_show_dev(char **args, char *payload, struct appctx *appctx, void *private)
+{
+       if (*args[2])
+               return cli_err(appctx, "This command takes no argument.\n");
+
+       chunk_reset(&trash);
+
+       chunk_appendf(&trash, "Platform info\n");
+       if (*post_mortem.platform.utsname.sysname)
+               chunk_appendf(&trash, "  OS name: %s\n", post_mortem.platform.utsname.sysname);
+       if (*post_mortem.platform.utsname.release)
+               chunk_appendf(&trash, "  OS release: %s\n", post_mortem.platform.utsname.release);
+       if (*post_mortem.platform.utsname.version)
+               chunk_appendf(&trash, "  OS version: %s\n", post_mortem.platform.utsname.version);
+       if (*post_mortem.platform.utsname.machine)
+               chunk_appendf(&trash, "  OS architecture: %s\n", post_mortem.platform.utsname.machine);
+       if (*post_mortem.platform.utsname.nodename)
+               chunk_appendf(&trash, "  node name: %s\n", HA_ANON_CLI(post_mortem.platform.utsname.nodename));
+
+       return cli_msg(appctx, LOG_INFO, trash.area);
+}
+
 /* Dumps a state of all threads into the trash and on fd #2, then aborts.
  * A copy will be put into a trash chunk that's assigned to thread_dump_buffer
  * so that the debugger can easily find it. This buffer might be truncated if
@@ -1838,6 +1876,16 @@ REGISTER_PER_THREAD_INIT(init_debug_per_thread);
 
 #endif /* USE_THREAD_DUMP */
 
+
+static int feed_post_mortem()
+{
+       /* kernel type, version and arch */
+       uname(&post_mortem.platform.utsname);
+       return ERR_NONE;
+}
+
+REGISTER_POST_CHECK(feed_post_mortem);
+
 /* register cli keywords */
 static struct cli_kw_list cli_kws = {{ },{
        {{ "debug", "dev", "bug", NULL },      "debug dev bug                           : call BUG_ON() and crash",                 debug_parse_cli_bug,   NULL, NULL, NULL, ACCESS_EXPERT },
@@ -1867,6 +1915,7 @@ static struct cli_kw_list cli_kws = {{ },{
        {{ "debug", "dev", "warn",  NULL },    "debug dev warn                          : call WARN_ON() and possibly crash",       debug_parse_cli_warn,  NULL, NULL, NULL, ACCESS_EXPERT },
        {{ "debug", "dev", "write", NULL },    "debug dev write  [size]                 : write that many bytes in return",         debug_parse_cli_write, NULL, NULL, NULL, ACCESS_EXPERT },
 
+       {{ "show", "dev", NULL, NULL },        "show dev                                : show debug info for developers",          debug_parse_cli_show_dev, NULL, NULL },
 #if defined(HA_HAVE_DUMP_LIBS)
        {{ "show", "libs", NULL, NULL },       "show libs                               : show loaded object files and libraries", debug_parse_cli_show_libs, NULL, NULL },
 #endif