Re: [PATCH v2 1/2] printk: Add function to return log buffer address and size

From: Vasant Hegde
Date: Fri Aug 01 2014 - 04:15:36 EST


On 08/01/2014 03:52 AM, Andrew Morton wrote:
On Thu, 31 Jul 2014 21:05:48 +0530 Vasant Hegde <hegdevasant@xxxxxxxxxxxxxxxxxx> wrote:

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.

...

--- 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 void *get_log_buf_addr(void);
+extern u32 get_log_buf_len(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 13e839d..4049f7b 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 */
+void *get_log_buf_addr(void)
+{
+ return log_buf;
+}
+
+/* Return log buffer size */
+u32 get_log_buf_len(void)
+{
+ return log_buf_len;
+}
+
/* human readable text of the record */
static char *log_text(const struct printk_log *msg)
{


Andrew,

Thanks for the review.. Shall I add your Ack?

Looks OK to me, although I think log_buf_addr_get() and
log_buf_len_get() would be better names. The kernel uses some
big-endian names and some little-endian-names and some middle-endian
names. It's all rather a mess. These symbols are already big-endian
(ie: decreasing significance):

log_buf -> addr -> get
log_buf -> len -> get

Sure . Will rename function as above.



The world wouldn't end if we simply made log_buf and log_buf_len global
symbols. The pros and cons are all minor.

It's probably better to make get_log_buf_addr() tell the truth and
return a char *.


Please include this in whatever tree carries "powerpc/powernv:
Interface to register/unregister opal dump region".

Sure.. Will work with BenH.

-Vasant

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