Promote dmesg back to lsb.

1 files changed, 182 insertions, 0 deletions

diff --git a/toys/lsb/dmesg.c b/toys/lsb/dmesg.c
new file mode 100644
index 00000000..30f90e3a
--- /dev/null
+++ b/toys/lsb/dmesg.c
@@ -0,0 +1,182 @@
+/* dmesg.c - display/control kernel ring buffer.
+ *
+ * Copyright 2006, 2007 Rob Landley <rob@landley.net>
+ *
+ * See http://refspecs.linuxfoundation.org/LSB_4.1.0/LSB-Core-generic/LSB-Core-generic/dmesg.html
+ *
+ * Don't ask me why the horrible new dmesg API is still in "testing":
+ * http://kernel.org/doc/Documentation/ABI/testing/dev-kmsg
+
+// We care that FLAG_c is 1, so keep c at the end.
+USE_DMESG(NEWTOY(dmesg, "w(follow)CSTtrs#<1n#c[!Ttr][!Cc][!Sw]", TOYFLAG_BIN))
+
+config DMESG
+  bool "dmesg"
+  default y
+  help
+    usage: dmesg [-Cc] [-r|-t|-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	Use syslog(2) rather than /dev/kmsg
+    -s	Show the last SIZE many bytes
+    -T	Show human-readable timestamps
+    -t	Don't print 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 use_color;
+  time_t tea;
+)
+
+static void color(int c)
+{
+  if (TT.use_color) printf("\033[%dm", c);
+}
+
+static void format_message(char *msg, int new)
+{
+  unsigned long long time_s, time_us;
+  int facpri, subsystem, pos;
+  char *p, *text;
+
+  // The new /dev/kmsg and the old syslog(2) formats differ slightly.
+  if (new) {
+    if (sscanf(msg, "%u,%*u,%llu,%*[^;]; %n", &facpri, &time_us, &pos) != 2)
+      return;
+
+    time_s = time_us/1000000;
+    time_us %= 1000000;
+  } else if (sscanf(msg, "<%u>[%llu.%llu] %n",
+                    &facpri, &time_s, &time_us, &pos) != 3) return;
+
+  // Drop extras after end of message text.
+  if ((p = strchr(text = msg+pos, '\n'))) *p = 0;
+
+  // Is there a subsystem? (The ": " is just a convention.)
+  p = strstr(text, ": ");
+  subsystem = p ? (p-text) : 0;
+
+  // To get "raw" output for /dev/kmsg we need to add priority to each line
+  if (toys.optflags&FLAG_r) {
+    color(0);
+    printf("<%d>", facpri);
+  }
+
+  // Format the time.
+  if (!(toys.optflags&FLAG_t)) {
+    color(32);
+    if (toys.optflags&FLAG_T) {
+      time_t t = TT.tea+time_s;
+      char *ts = ctime(&t);
+
+      printf("[%.*s] ", (int)(strlen(ts)-1), ts);
+    } else printf("[%5lld.%06lld] ", time_s, time_us);
+  }
+
+  // Errors (or worse) are shown in red, subsystems are shown in yellow.
+  if (subsystem) {
+    color(33);
+    printf("%.*s", subsystem, text);
+    text += subsystem;
+  }
+  color(31*((facpri&7)<=3));
+  xputs(text);
+}
+
+static int xklogctl(int type, char *buf, int len)
+{
+  int rc = klogctl(type, buf, len);
+
+  if (rc<0) perror_exit("klogctl");
+
+  return rc;
+}
+
+static void dmesg_cleanup(void)
+{
+  color(0);
+}
+
+void dmesg_main(void)
+{
+  TT.use_color = isatty(1);
+
+  if (TT.use_color) sigatexit(dmesg_cleanup);
+  // If we're displaying output, is it klogctl or /dev/kmsg?
+  if (toys.optflags & (FLAG_C|FLAG_n)) goto no_output;
+
+  if (toys.optflags&FLAG_T) {
+    struct sysinfo info;
+
+    sysinfo(&info);
+    TT.tea = time(0)-info.uptime;
+  }
+
+  if (!(toys.optflags&FLAG_S)) {
+    char msg[8193]; // CONSOLE_EXT_LOG_MAX+1
+    ssize_t len;
+    int fd;
+
+    // Each read returns one message. By default, we block when there are no
+    // more messages (--follow); O_NONBLOCK is needed for for usual behavior.
+    fd = open("/dev/kmsg", O_RDONLY|(O_NONBLOCK*!(toys.optflags&FLAG_w)));
+    if (fd == -1) goto klogctl_mode;
+
+    // SYSLOG_ACTION_CLEAR(5) doesn't actually remove anything from /dev/kmsg,
+    // you need to seek to the last clear point.
+    lseek(fd, 0, SEEK_DATA);
+
+    for (;;) {
+      // why does /dev/kmesg return EPIPE instead of EAGAIN if oldest message
+      // expires as we read it?
+      if (-1==(len = read(fd, msg, sizeof(msg))) && errno==EPIPE) continue;
+      // read() from kmsg always fails on a pre-3.5 kernel.
+      if (len==-1 && errno==EINVAL) goto klogctl_mode;
+      if (len<1) break;
+
+      msg[len] = 0;
+      format_message(msg, 1);
+    }
+    close(fd);
+  } else {
+    char *data, *to, *from, *end;
+    int size;
+
+klogctl_mode:
+    // Figure out how much data we need, and fetch it.
+    if (!(size = TT.size)) size = xklogctl(10, 0, 0);
+    data = from = xmalloc(size+1);
+    data[size = xklogctl(3+(toys.optflags&FLAG_c), data, size)] = 0;
+
+    // Send each line to format_message.
+    to = data + size;
+    while (from < to) {
+      if (!(end = memchr(from, '\n', to-from))) break;
+      *end = 0;
+      format_message(from, 0);
+      from = end + 1;
+    }
+
+    if (CFG_TOYBOX_FREE) free(data);
+  }
+
+no_output:
+  // 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);
+}