Optionally re-introduce bb_info_msg()

Between Busybox 1.24.2 and 1.25.0 the bb_info_msg() function was
eliminated and calls to it changed to be bb_error_msg(). The downside of
this is that daemons now log all messages to syslog at the LOG_ERR level
which makes it hard to filter errors from informational messages.

This change optionally re-introduces bb_info_msg(), controlled by a new
option FEATURE_SYSLOG_INFO, restores all the calls to bb_info_msg() that
were removed (only in applets that set logmode to LOGMODE_SYSLOG or
LOGMODE_BOTH), and also changes informational messages in ifplugd and
ntpd.

The code size change of this is as follows (using 'defconfig' on x86_64
with gcc 7.3.0-27ubuntu1~18.04)

function                                             old     new   delta
bb_info_msg                                            -     182    +182
bb_vinfo_msg                                           -      27     +27
static.log7                                          194     198      +4
log8                                                 190     191      +1
log5                                                 190     191      +1
crondlog                                              45       -     -45
------------------------------------------------------------------------------
(add/remove: 2/1 grow/shrink: 3/0 up/down: 215/-45)           Total: 170 bytes

If you don't care about everything being logged at LOG_ERR level
then when FEATURE_SYSLOG_INFO is disabled Busybox actually gets smaller:

function                                             old     new   delta
static.log7                                          194     200      +6
log8                                                 190     193      +3
log5                                                 190     193      +3
syslog_level                                           1       -      -1
bb_verror_msg                                        583     581      -2
crondlog                                              45       -     -45
------------------------------------------------------------------------------
(add/remove: 0/2 grow/shrink: 3/1 up/down: 12/-48)            Total: -36 bytes

Signed-off-by: James Byrne <james.byrne@origamienergy.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/include/libbb.h b/include/libbb.h
index a20d5e403..57cfce385 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -1316,7 +1316,6 @@ enum {
         LOGMODE_BOTH = LOGMODE_SYSLOG + LOGMODE_STDIO,
 };
 extern const char *msg_eol;
-extern smallint syslog_level;
 extern smallint logmode;
 extern uint8_t xfunc_error_retval;
 extern void (*die_func)(void);
@@ -1336,6 +1335,14 @@ void bb_verror_msg(const char *s, va_list p, const char *strerr) FAST_FUNC;
 void bb_die_memory_exhausted(void) NORETURN FAST_FUNC;
 void bb_logenv_override(void) FAST_FUNC;
 
+#if ENABLE_FEATURE_SYSLOG_INFO
+void bb_info_msg(const char *s, ...) __attribute__ ((format (printf, 1, 2))) FAST_FUNC;
+void bb_vinfo_msg(const char *s, va_list p) FAST_FUNC;
+#else
+#define bb_info_msg bb_error_msg
+#define bb_vinfo_msg(s,p) bb_verror_msg(s,p,NULL)
+#endif
+
 /* We need to export XXX_main from libbusybox
  * only if we build "individual" binaries
  */