busybox/util-linux/dmesg.c

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/* vi: set sw=4 ts=4: */
/*
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*
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* dmesg - display/control kernel ring buffer.
*
* Copyright 2006 Rob Landley <rob@landley.net>
* Copyright 2006 Bernhard Reutner-Fischer <rep.nop@aon.at>
*
* Licensed under GPLv2, see file LICENSE in this source tree.
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*/
//config:config DMESG
//config: bool "dmesg (3.7 kb)"
//config: default y
//config: select PLATFORM_LINUX
//config: help
//config: dmesg is used to examine or control the kernel ring buffer. When the
//config: Linux kernel prints messages to the system log, they are stored in
//config: the kernel ring buffer. You can use dmesg to print the kernel's ring
//config: buffer, clear the kernel ring buffer, change the size of the kernel
//config: ring buffer, and change the priority level at which kernel messages
//config: are also logged to the system console. Enable this option if you
//config: wish to enable the 'dmesg' utility.
//config:
//config:config FEATURE_DMESG_PRETTY
//config: bool "Pretty output"
//config: default y
//config: depends on DMESG
//config: help
//config: If you wish to scrub the syslog level from the output, say 'Y' here.
//config: The syslog level is a string prefixed to every line with the form
//config: "<#>".
//config:
//config: With this option you will see:
//config: # dmesg
//config: Linux version 2.6.17.4 .....
//config: BIOS-provided physical RAM map:
//config: BIOS-e820: 0000000000000000 - 000000000009f000 (usable)
//config:
//config: Without this option you will see:
//config: # dmesg
//config: <5>Linux version 2.6.17.4 .....
//config: <6>BIOS-provided physical RAM map:
//config: <6> BIOS-e820: 0000000000000000 - 000000000009f000 (usable)
//applet:IF_DMESG(APPLET(dmesg, BB_DIR_BIN, BB_SUID_DROP))
//kbuild:lib-$(CONFIG_DMESG) += dmesg.o
//usage:#define dmesg_trivial_usage
//usage: "[-c] [-n LEVEL] [-s SIZE]"
//usage:#define dmesg_full_usage "\n\n"
//usage: "Print or control the kernel ring buffer\n"
//usage: "\n -c Clear ring buffer after printing"
//usage: "\n -n LEVEL Set console logging level"
//usage: "\n -s SIZE Buffer size"
//usage: "\n -r Print raw message buffer"
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#include <sys/klog.h>
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#include "libbb.h"
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int dmesg_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int dmesg_main(int argc UNUSED_PARAM, char **argv)
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{
int len, level;
char *buf;
unsigned opts;
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enum {
OPT_c = 1 << 0,
OPT_s = 1 << 1,
OPT_n = 1 << 2,
OPT_r = 1 << 3
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};
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opts = getopt32(argv, "cs:+n:+r", &len, &level);
if (opts & OPT_n) {
if (klogctl(8, NULL, (long) level))
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>
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bb_simple_perror_msg_and_die("klogctl");
return EXIT_SUCCESS;
}
if (!(opts & OPT_s))
len = klogctl(10, NULL, 0); /* read ring buffer size */
if (len < 16*1024)
len = 16*1024;
if (len > 16*1024*1024)
len = 16*1024*1024;
buf = xmalloc(len);
len = klogctl(3 + (opts & OPT_c), buf, len); /* read ring buffer */
if (len < 0)
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>
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bb_simple_perror_msg_and_die("klogctl");
if (len == 0)
return EXIT_SUCCESS;
if (ENABLE_FEATURE_DMESG_PRETTY && !(opts & OPT_r)) {
int last = '\n';
int in = 0;
/* Skip <[0-9]+> at the start of lines */
while (1) {
if (last == '\n' && buf[in] == '<') {
while (buf[in++] != '>' && in < len)
;
} else {
last = buf[in++];
putchar(last);
}
if (in >= len)
break;
}
/* Make sure we end with a newline */
if (last != '\n')
bb_putchar('\n');
} else {
full_write(STDOUT_FILENO, buf, len);
if (buf[len-1] != '\n')
bb_putchar('\n');
}
if (ENABLE_FEATURE_CLEAN_UP) free(buf);
return EXIT_SUCCESS;
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}