From fd866b2f058294cf51a6987a1786ff1bd9e6b1ea Mon Sep 17 00:00:00 2001 From: Rob Landley Date: Mon, 20 Feb 2017 21:42:58 -0600 Subject: Declaring todo bankruptcy, dmesg goes back into pending until I get a chance to unify the two codepaths in Elliott's rewrite. --- toys/pending/dmesg.c | 167 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 167 insertions(+) create mode 100644 toys/pending/dmesg.c (limited to 'toys/pending') diff --git a/toys/pending/dmesg.c b/toys/pending/dmesg.c new file mode 100644 index 00000000..40834b0c --- /dev/null +++ b/toys/pending/dmesg.c @@ -0,0 +1,167 @@ +/* dmesg.c - display/control kernel ring buffer. + * + * Copyright 2006, 2007 Rob Landley + * + * http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/dmesg.html + +// We care that FLAG_c is 1, so keep c at the end. +USE_DMESG(NEWTOY(dmesg, "w(follow)Ctrs#<1n#c[!tr][!Cc]", TOYFLAG_BIN)) + +config DMESG + bool "dmesg" + default n + help + usage: dmesg [-Cc] [-r|-t] [-n LEVEL] [-s SIZE] [-w] + + Print or control the kernel ring buffer. + + -C Clear ring buffer without printing + -c Clear ring buffer after printing + -n Set kernel logging LEVEL (1-9) + -r Raw output (with ) + -s Show the last SIZE many bytes + -t Don't print kernel's timestamps + -w Keep waiting for more output (aka --follow) +*/ + +#define FOR_dmesg +#include "toys.h" +#include + +GLOBALS( + long level; + long size; + + int color; +) + +static int xklogctl(int type, char *buf, int len) +{ + int rc = klogctl(type, buf, len); + + if (rc<0) perror_exit("klogctl"); + + return rc; +} + +// Use klogctl for reading if we're on a pre-3.5 kernel. +static void legacy_mode() +{ + char *data, *to, *from; + int size; + + // Figure out how much data we need, and fetch it. + if (!(size = TT.size)) size = xklogctl(10, 0, 0); + data = to = from = xmalloc(size+1); + data[size = xklogctl(3 + (toys.optflags & FLAG_c), data, size)] = 0; + + // Filter out level markers and optionally time markers + if (!(toys.optflags & FLAG_r)) while ((from - data) < size) { + if (from == data || from[-1] == '\n') { + char *to; + + if (*from == '<' && (to = strchr(from, '>'))) from = ++to; + if ((toys.optflags&FLAG_t) && *from == '[' && (to = strchr(from, ']'))) + from = to+1+(to[1]==' '); + } + *(to++) = *(from++); + } else to = data+size; + + // Write result. The odds of somebody requesting a buffer of size 3 and + // getting "<1>" are remote, but don't segfault if they do. + if (to != data) { + xwrite(1, data, to-data); + if (to[-1] != '\n') xputc('\n'); + } + if (CFG_TOYBOX_FREE) free(data); +} + +static void color(int c) +{ + if (TT.color) printf("\033[%dm", c); +} + +static void print_all(void) +{ + // http://kernel.org/doc/Documentation/ABI/testing/dev-kmsg + + // Each read returns one message. By default, we block when there are no + // more messages (--follow); O_NONBLOCK is needed for for usual behavior. + int fd = xopen("/dev/kmsg", O_RDONLY | ((toys.optflags&FLAG_w)?0:O_NONBLOCK)); + + // With /dev/kmsg, SYSLOG_ACTION_CLEAR (5) doesn't actually remove anything; + // you need to seek to the last clear point. + lseek(fd, 0, SEEK_DATA); + + while (1) { + char msg[8192]; // CONSOLE_EXT_LOG_MAX. + unsigned long long time_us; + int facpri, subsystem, pos; + char *p, *text; + ssize_t len; + + // kmsg fails with EPIPE if we try to read while the buffer moves under + // us; the next read will succeed and return the next available entry. + do { + len = read(fd, msg, sizeof(msg)); + } while (len == -1 && errno == EPIPE); + // All reads from kmsg fail if you're on a pre-3.5 kernel. + if (len == -1 && errno == EINVAL) { + close(fd); + return legacy_mode(); + } + if (len <= 0) break; + + msg[len] = 0; + + if (sscanf(msg, "%u,%*u,%llu,%*[^;];%n", &facpri, &time_us, &pos) != 2) + continue; + + // Drop extras after end of message text. + text = msg + pos; + if ((p = strchr(text, '\n'))) *p = 0; + + // Is there a subsystem? (The ": " is just a convention.) + p = strstr(text, ": "); + subsystem = p ? (p - text) : 0; + + // "Raw" is a lie for /dev/kmsg. In practice, it just means we show the + // syslog facility/priority at the start of each line. + if (toys.optflags&FLAG_r) printf("<%d>", facpri); + + if (!(toys.optflags&FLAG_t)) { + color(32); + printf("[%5lld.%06lld] ", time_us/1000000, time_us%1000000); + color(0); + } + + // Errors (or worse) are shown in red, subsystems are shown in yellow. + if (subsystem) { + color(33); + printf("%.*s", subsystem, text); + text += subsystem; + color(0); + } + if (!((facpri&7) <= 3)) xputs(text); + else { + color(31); + printf("%s", text); + color(0); + xputc('\n'); + } + } + close(fd); +} + +void dmesg_main(void) +{ + TT.color = isatty(1); + + if (!(toys.optflags & (FLAG_C|FLAG_n))) print_all(); + + // Set the log level? + if (toys.optflags & FLAG_n) xklogctl(8, 0, TT.level); + + // Clear the buffer? + if (toys.optflags & (FLAG_C|FLAG_c)) xklogctl(5, 0, 0); +} -- cgit v1.2.3