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

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Date:	Sat, 09 Aug 2014 11:15:30 +0530
From:	Vasant Hegde <hegdevasant@...ux.vnet.ibm.com>
To:	linuxppc-dev@...ts.ozlabs.org
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 1/2] printk: Add function to return log buffer address
 and size

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@...ux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@...nel.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)
 {

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