[PATCH v3 1/2] printk: Add function to return log buffer address and size

[Vasant Hegde <hegdevasant@linux.vnet.ibm.com>]

Platforms like IBM Power Systems supports service processor
assisted dump. It provides interface to add memory region to
be captured when system is crashed.

During initialization/running we can add kernel memory region
to be collected.

Presently we don't have a way to get the log buffer base address
and size. This patch adds support to return log buffer address
and size.

Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

---
Next patch extends arch specific code to add log buffer to platform
dump.

Changes in v3:
  As Andrew suggested changed function names and return type.
  (https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-August/119802.html).

Ben,
  - This patchset applies cleanly on powerpc next branch.
  - Andrew Morton suggested to include this patch in powerpc tree.
    (https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-August/119802.html)


 include/linux/printk.h |    3 +++
 kernel/printk/printk.c |   12 ++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/include/linux/printk.h b/include/linux/printk.h
index 319ff7e..b8c0316 100644
--- a/include/linux/printk.h
+++ b/include/linux/printk.h
@@ -10,6 +10,9 @@
 extern const char linux_banner[];
 extern const char linux_proc_banner[];
 
+extern char *log_buf_addr_get(void);
+extern u32 log_buf_len_get(void);
+
 static inline int printk_get_level(const char *buffer)
 {
 	if (buffer[0] == KERN_SOH_ASCII && buffer[1]) {
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index ea2d5f6..d6a984c 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -270,6 +270,18 @@ static char __log_buf[__LOG_BUF_LEN] __aligned(LOG_ALIGN);
 static char *log_buf = __log_buf;
 static u32 log_buf_len = __LOG_BUF_LEN;
 
+/* Return log buffer address */
+char *log_buf_addr_get(void)
+{
+	return log_buf;
+}
+
+/* Return log buffer size */
+u32 log_buf_len_get(void)
+{
+	return log_buf_len;
+}
+
 /* human readable text of the record */
 static char *log_text(const struct printk_log *msg)
 {