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authorMike Frysinger <vapier.adi@gmail.com>2007-10-16 23:26:43 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-17 08:42:50 -0700
commit0b15d04af3dd996035d8fa81fc849d049171f9c3 (patch)
treecb0dc973b6485edb6fdf0bcdf4a2eeef9a48adad /kernel/printk.c
parentd823e3e7541c39b4dfe9c79dbf052b4c39da2965 (diff)
downloadlinux-0b15d04af3dd996035d8fa81fc849d049171f9c3.tar.gz
printk: add interfaces for external access to the log buffer
Add two new functions for reading the kernel log buffer. The intention is for them to be used by recovery/dump/debug code so the kernel log can be easily retrieved/parsed in a crash scenario, but they are generic enough for other people to dream up other fun uses. [akpm@linux-foundation.org: buncha fixes] Signed-off-by: Mike Frysinger <vapier@gentoo.org> Cc: Robin Getz <rgetz@blackfin.uclinux.org> Cc: Greg Ungerer <gerg@snapgear.com> Cc: Russell King <rmk@arm.linux.org.uk> Cc: Paul Mundt <lethal@linux-sh.org> Acked-by: Tim Bird <tim.bird@am.sony.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/printk.c')
-rw-r--r--kernel/printk.c52
1 files changed, 52 insertions, 0 deletions
diff --git a/kernel/printk.c b/kernel/printk.c
index b2b5c3a22a3..52493474f0a 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -220,6 +220,58 @@ static inline void boot_delay_msec(void)
#endif
/*
+ * Return the number of unread characters in the log buffer.
+ */
+int log_buf_get_len(void)
+{
+ return logged_chars;
+}
+
+/*
+ * Copy a range of characters from the log buffer.
+ */
+int log_buf_copy(char *dest, int idx, int len)
+{
+ int ret, max;
+ bool took_lock = false;
+
+ if (!oops_in_progress) {
+ spin_lock_irq(&logbuf_lock);
+ took_lock = true;
+ }
+
+ max = log_buf_get_len();
+ if (idx < 0 || idx >= max) {
+ ret = -1;
+ } else {
+ if (len > max)
+ len = max;
+ ret = len;
+ idx += (log_end - max);
+ while (len-- > 0)
+ dest[len] = LOG_BUF(idx + len);
+ }
+
+ if (took_lock)
+ spin_unlock_irq(&logbuf_lock);
+
+ return ret;
+}
+
+/*
+ * Extract a single character from the log buffer.
+ */
+int log_buf_read(int idx)
+{
+ char ret;
+
+ if (log_buf_copy(&ret, idx, 1) == 1)
+ return ret;
+ else
+ return -1;
+}
+
+/*
* Commands to do_syslog:
*
* 0 -- Close the log. Currently a NOP.