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-rw-r--r--toys/pending/dmesg.c167
1 files changed, 167 insertions, 0 deletions
diff --git a/toys/pending/dmesg.c b/toys/pending/dmesg.c
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+/* dmesg.c - display/control kernel ring buffer.
+ *
+ * Copyright 2006, 2007 Rob Landley <rob@landley.net>
+ *
+ * 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 <level markers>)
+ -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 <sys/klog.h>
+
+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);
+}