The patch titled
printk: add interfaces for external access to the log buffer
has been added to the -mm tree. Its filename is
early_printk-accessing-__log_buf.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: printk: add interfaces for external access to the log buffer
From: Mike Frysinger <vapier.adi@xxxxxxxxx>
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.
Signed-off-by: Mike Frysinger <vapier@xxxxxxxxxx>
Cc: Robin Getz <rgetz@xxxxxxxxxxxxxxxxxxxx>
Cc: Greg Ungerer <gerg@xxxxxxxxxxxx>
Cc: Russell King <rmk@xxxxxxxxxxxxxxxx>
Cc: Paul Mundt <lethal@xxxxxxxxxxxx>
Cc: Tim Bird <tim.bird@xxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/kernel.h | 6 ++++
kernel/printk.c | 49 +++++++++++++++++++++++++++++++++++++++
2 files changed, 55 insertions(+)
diff -puN include/linux/kernel.h~early_printk-accessing-__log_buf include/linux/kernel.h
--- a/include/linux/kernel.h~early_printk-accessing-__log_buf
+++ a/include/linux/kernel.h
@@ -157,6 +157,9 @@ asmlinkage int vprintk(const char *fmt,
__attribute__ ((format (printf, 1, 0)));
asmlinkage int printk(const char * fmt, ...)
__attribute__ ((format (printf, 1, 2))) __cold;
+extern int log_buf_get_len(void);
+extern int log_buf_read(int idx);
+extern int log_buf_copy(char *dest, int idx, int len);
#else
static inline int vprintk(const char *s, va_list args)
__attribute__ ((format (printf, 1, 0)));
@@ -164,6 +167,9 @@ static inline int vprintk(const char *s,
static inline int printk(const char *s, ...)
__attribute__ ((format (printf, 1, 2)));
static inline int __cold printk(const char *s, ...) { return 0; }
+static inline int log_buf_get_len(void) { return 0; }
+static inline int log_buf_read(int idx); { return 0; }
+static inline int log_buf_copy(char *dest, int idx, int len) { return 0; }
#endif
unsigned long int_sqrt(unsigned long);
diff -puN kernel/printk.c~early_printk-accessing-__log_buf kernel/printk.c
--- a/kernel/printk.c~early_printk-accessing-__log_buf
+++ a/kernel/printk.c
@@ -220,6 +220,55 @@ 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 log_end - log_start;
+}
+
+/*
+ * Copy a range of characters from the log buffer.
+ */
+int log_buf_copy(char *dest, int idx, int len)
+{
+ int ret, max;
+
+ if (!oops_in_progress)
+ spin_lock_irq(&logbuf_lock);
+
+ max = log_buf_get_len();
+ if (idx < 0 || idx >= max)
+ ret = -1;
+ else {
+ if (len > max)
+ len = max;
+ ret = len;
+ while (len-- > 0) {
+ *dest = LOG_BUF(idx++);
+ ++dest;
+ }
+ }
+
+ if (!oops_in_progress)
+ 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.
_
Patches currently in -mm which might be from vapier.adi@xxxxxxxxx are
early_printk-accessing-__log_buf.patch
early_printk-accessing-__log_buf-fix.patch
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