From bb86986253dac6027c793b7f9f5822bb458f4787 Mon Sep 17 00:00:00 2001
From: Willy Tarreau <w@1wt.eu>
Date: Thu, 16 Apr 2020 10:52:41 +0200
Subject: [PATCH] MINOR: init: report the haproxy version and executable path
 once on errors

If haproxy fails to start and emits an alert, then it can be useful
to have it also emit the version and the path used to load it. Some
users may be mistakenly launching the wrong binary due to a misconfigured
PATH variable and this will save them some troubleshooting time when it
reports that some keywords are not understood.

What we do here is that we *try* to extract the binary name from the
AUX vector on glibc, and we report this as a NOTICE tag before the
very first alert is emitted.
---
 include/common/standard.h |  1 +
 include/types/global.h    |  1 +
 src/log.c                 |  9 +++++++++
 src/standard.c            | 20 ++++++++++++++++++++
 4 files changed, 31 insertions(+)

diff --git a/include/common/standard.h b/include/common/standard.h
index cf8f1f046..80a1fc234 100644
--- a/include/common/standard.h
+++ b/include/common/standard.h
@@ -1496,6 +1496,7 @@ void dump_addr_and_bytes(struct buffer *buf, const char *pfx, const void *addr,
 void dump_hex(struct buffer *out, const char *pfx, const void *buf, int len, int unsafe);
 int may_access(const void *ptr);
 void *resolve_sym_name(struct buffer *buf, const char *pfx, void *addr);
+const char *get_exec_path();
 
 #if defined(USE_BACKTRACE)
 /* Note that this may result in opening libgcc() on first call, so it may need
diff --git a/include/types/global.h b/include/types/global.h
index 407fbff60..592d28867 100644
--- a/include/types/global.h
+++ b/include/types/global.h
@@ -245,6 +245,7 @@ extern unsigned char boot_seed[20];  // per-boot random seed (160 bits initially
 /* bit values to go with "warned" above */
 #define WARN_ANY                    0x00000001 /* any warning was emitted */
 #define WARN_FORCECLOSE_DEPRECATED  0x00000002
+#define WARN_EXEC_PATH              0x00000004 /* executable path already reported */
 
 
 /* to be used with warned and WARN_* */
diff --git a/src/log.c b/src/log.c
index 50b5080c4..2d926649e 100644
--- a/src/log.c
+++ b/src/log.c
@@ -29,6 +29,7 @@
 #include <common/initcall.h>
 #include <common/standard.h>
 #include <common/time.h>
+#include <common/version.h>
 
 #include <types/cli.h>
 #include <types/global.h>
@@ -1109,6 +1110,14 @@ void ha_alert(const char *fmt, ...)
 	va_list argp;
 
 	if (!(global.mode & MODE_QUIET) || (global.mode & (MODE_VERBOSE | MODE_STARTING))) {
+		if (!(warned & WARN_EXEC_PATH)) {
+			const char *path = get_exec_path();
+
+			warned |= WARN_EXEC_PATH;
+			ha_notice("haproxy version is %s\n", haproxy_version);
+			if (path)
+				ha_notice("path to executable is %s\n", path);
+		}
 		va_start(argp, fmt);
 		print_message("ALERT", fmt, argp);
 		va_end(argp);
diff --git a/src/standard.c b/src/standard.c
index 3afaf5a99..eba79101b 100644
--- a/src/standard.c
+++ b/src/standard.c
@@ -16,6 +16,10 @@
 #include <link.h>
 #endif
 
+#if (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 16))
+#include <sys/auxv.h>
+#endif
+
 #include <ctype.h>
 #include <errno.h>
 #include <netdb.h>
@@ -4335,6 +4339,22 @@ void debug_hexdump(FILE *out, const char *pfx, const char *buf,
 	}
 }
 
+/* Tries to report the executable path name on platforms supporting this. If
+ * not found or not possible, returns NULL.
+ */
+const char *get_exec_path()
+{
+	const char *ret = NULL;
+
+#if (__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 16))
+	long execfn = getauxval(AT_EXECFN);
+
+	if (execfn && execfn != ENOENT)
+		ret = (const char *)execfn;
+#endif
+	return ret;
+}
+
 #ifdef __ELF__
 /* calls dladdr() or dladdr1() on <addr> and <dli>. If dladdr1 is available,
  * also returns the symbol size in <size>, otherwise returns 0 there.