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-rw-r--r--include/linux/kernel.h6
-rw-r--r--kernel/printk.c52
2 files changed, 58 insertions, 0 deletions
diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 5fdbc814c2e..c680e1e6e9a 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -172,6 +172,9 @@ asmlinkage int vprintk(const char *fmt, va_list args)
__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)));
@@ -179,6 +182,9 @@ static inline int vprintk(const char *s, va_list args) { return 0; }
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 --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.