libbb: reduce the overhead of single parameter bb_error_msg() calls

Back in 2007, commit 0c97c9d43707 ("'simple' error message functions by
Loic Grenie") introduced bb_simple_perror_msg() to allow for a lower
overhead call to bb_perror_msg() when only a string was being printed
with no parameters. This saves space for some CPU architectures because
it avoids the overhead of a call to a variadic function. However there
has never been a simple version of bb_error_msg(), and since 2007 many
new calls to bb_perror_msg() have been added that only take a single
parameter and so could have been using bb_simple_perror_message().

This changeset introduces 'simple' versions of bb_info_msg(),
bb_error_msg(), bb_error_msg_and_die(), bb_herror_msg() and
bb_herror_msg_and_die(), and replaces all calls that only take a
single parameter, or use something like ("%s", arg), with calls to the
corresponding 'simple' version.

Since it is likely that single parameter calls to the variadic functions
may be accidentally reintroduced in the future a new debugging config
option WARN_SIMPLE_MSG has been introduced. This uses some macro magic
which will cause any such calls to generate a warning, but this is
turned off by default to avoid use of the unpleasant macros in normal
circumstances.

This is a large changeset due to the number of calls that have been
replaced. The only files that contain changes other than simple
substitution of function calls are libbb.h, libbb/herror_msg.c,
libbb/verror_msg.c and libbb/xfuncs_printf.c. In miscutils/devfsd.c,
networking/udhcp/common.h and util-linux/mdev.c additonal macros have
been added for logging so that single parameter and multiple parameter
logging variants exist.

The amount of space saved varies considerably by architecture, and was
found to be as follows (for 'defconfig' using GCC 7.4):

Arm:     -92 bytes
MIPS:    -52 bytes
PPC:   -1836 bytes
x86_64: -938 bytes

Note that for the MIPS architecture only an exception had to be made
disabling the 'simple' calls for 'udhcp' (in networking/udhcp/common.h)
because it made these files larger on MIPS.

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

1 files changed, 10 insertions, 5 deletions

diff --git a/miscutils/devfsd.c b/miscutils/devfsd.c
index e4d104d0c..f3d935b2e 100644
--- a/miscutils/devfsd.c
+++ b/miscutils/devfsd.c
@@ -344,14 +344,19 @@ static const char bb_msg_variable_not_found[] ALIGN1 = "variable: %s not found";
 /* Busybox stuff */
 #if ENABLE_DEVFSD_VERBOSE || ENABLE_DEBUG
 #define info_logger(p, fmt, args...)                 bb_info_msg(fmt, ## args)
+#define simple_info_logger(p, msg)                   bb_simple_info_msg(msg)
 #define msg_logger(p, fmt, args...)                  bb_error_msg(fmt, ## args)
+#define simple_msg_logger(p, msg)                    bb_simple_error_msg(msg)
 #define msg_logger_and_die(p, fmt, args...)          bb_error_msg_and_die(fmt, ## args)
+#define simple_msg_logger_and_die(p, msg)            bb_simple_error_msg_and_die(msg)
 #define error_logger(p, fmt, args...)                bb_perror_msg(fmt, ## args)
 #define error_logger_and_die(p, fmt, args...)        bb_perror_msg_and_die(fmt, ## args)
 #else
 #define info_logger(p, fmt, args...)
 #define msg_logger(p, fmt, args...)
+#define simple_msg_logger(p, msg)
 #define msg_logger_and_die(p, fmt, args...)           exit(EXIT_FAILURE)
+#define simple_msg_logger_and_die(p, msg)             exit(EXIT_FAILURE)
 #define error_logger(p, fmt, args...)
 #define error_logger_and_die(p, fmt, args...)         exit(EXIT_FAILURE)
 #endif
@@ -727,7 +732,7 @@ static int do_servicing(int fd, unsigned long event_mask)
                 caught_sighup = FALSE;
                 return c_sighup;
         }
-        msg_logger_and_die(LOG_ERR, "read error on control file");
+        simple_msg_logger_and_die(LOG_ERR, "read error on control file");
 }   /*  End Function do_servicing  */
 
 static void service_name(const struct devfsd_notify_struct *info)
@@ -786,7 +791,7 @@ static void service_name(const struct devfsd_notify_struct *info)
                                 action_compat(info, entry->action.what);
                                 break;
                         default:
-                                msg_logger_and_die(LOG_ERR, "Unknown action");
+                                simple_msg_logger_and_die(LOG_ERR, "Unknown action");
                 }
         }
 }   /*  End Function service_name  */
@@ -1691,7 +1696,7 @@ int st_expr_expand(char *output, unsigned int length, const char *input,
         }
         return FALSE;
 st_expr_expand_out:
-        info_logger(LOG_INFO, bb_msg_small_buffer);
+        simple_info_logger(LOG_INFO, bb_msg_small_buffer);
         return FALSE;
 }   /*  End Function st_expr_expand  */
 
@@ -1775,7 +1780,7 @@ static const char *expand_variable(char *buffer, unsigned int length,
                 return input + len;
         }
         if (ch != ':' || ptr[1] != '-') {
-                info_logger(LOG_INFO, "illegal char in var name");
+                simple_info_logger(LOG_INFO, "illegal char in var name");
                 return NULL;
         }
         /*  It's that handy "${var:-word}" expression. Check if var is defined  */
@@ -1838,7 +1843,7 @@ static const char *expand_variable(char *buffer, unsigned int length,
         *out_pos += len;
         return input;
 expand_variable_out:
-        info_logger(LOG_INFO, bb_msg_small_buffer);
+        simple_info_logger(LOG_INFO, bb_msg_small_buffer);
         return NULL;
 }   /*  End Function expand_variable  */