From 0b15d04af3dd996035d8fa81fc849d049171f9c3 Mon Sep 17 00:00:00 2001 From: Mike Frysinger Date: Tue, 16 Oct 2007 23:26:43 -0700 Subject: [PATCH] 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 Cc: Robin Getz Cc: Greg Ungerer Cc: Russell King Cc: Paul Mundt Acked-by: Tim Bird Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/kernel.h | 6 +++++ kernel/printk.c | 52 ++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 58 insertions(+) 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 @@ -219,6 +219,58 @@ 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: * -- 2.41.1