1 files changed, 167 insertions, 0 deletions
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 <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);
+}