[PATCH] printk: Add a short description string to kmsg_dump()

[Jocelyn Falempe <jfalempe@redhat.com>]

kmsg_dump doesn't forward the panic reason string to the kmsg_dumper
callback.
This patch adds a new parameter "const char *desc" to the kmsg_dumper
dump() callback, and update all drivers that are using it.

To avoid updating all kmsg_dump() call, it adds a kmsg_dump_desc()
function and a macro for backward compatibility.

I've written this for drm_panic, but it can be useful for other
kmsg_dumper.
It allows to see the panic reason, like "sysrq triggered crash"
or "VFS: Unable to mount root fs on xxxx" on the drm panic screen.

Signed-off-by: Jocelyn Falempe <jfalempe@redhat.com>
---
 arch/powerpc/kernel/nvram_64.c             |  3 ++-
 arch/powerpc/platforms/powernv/opal-kmsg.c |  3 ++-
 drivers/gpu/drm/drm_panic.c                |  3 ++-
 drivers/hv/hv_common.c                     |  3 ++-
 drivers/mtd/mtdoops.c                      |  3 ++-
 fs/pstore/platform.c                       |  3 ++-
 include/linux/kmsg_dump.h                  | 13 ++++++++++---
 kernel/panic.c                             |  2 +-
 kernel/printk/printk.c                     |  8 +++++---
 9 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/arch/powerpc/kernel/nvram_64.c b/arch/powerpc/kernel/nvram_64.c
index e385d3164648c..6b3a80d8cfa64 100644
--- a/arch/powerpc/kernel/nvram_64.c
+++ b/arch/powerpc/kernel/nvram_64.c
@@ -643,7 +643,8 @@ void __init nvram_init_oops_partition(int rtas_partition_exists)
  * partition.  If that's too much, go back and capture uncompressed text.
  */
 static void oops_to_nvram(struct kmsg_dumper *dumper,
-			  enum kmsg_dump_reason reason)
+			  enum kmsg_dump_reason reason,
+			  const char *desc)
 {
 	struct oops_log_info *oops_hdr = (struct oops_log_info *)oops_buf;
 	static unsigned int oops_count = 0;
diff --git a/arch/powerpc/platforms/powernv/opal-kmsg.c b/arch/powerpc/platforms/powernv/opal-kmsg.c
index 6c3bc4b4da983..49b60de6feb04 100644
--- a/arch/powerpc/platforms/powernv/opal-kmsg.c
+++ b/arch/powerpc/platforms/powernv/opal-kmsg.c
@@ -20,7 +20,8 @@
  * message, it just ensures that OPAL completely flushes the console buffer.
  */
 static void kmsg_dump_opal_console_flush(struct kmsg_dumper *dumper,
-				     enum kmsg_dump_reason reason)
+				     enum kmsg_dump_reason reason,
+				     const char *desc)
 {
 	/*
 	 * Outside of a panic context the pollers will continue to run,
diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
index 293d4dcbc80da..88e9359fe6d78 100644
--- a/drivers/gpu/drm/drm_panic.c
+++ b/drivers/gpu/drm/drm_panic.c
@@ -604,7 +604,8 @@ static struct drm_plane *to_drm_plane(struct kmsg_dumper *kd)
 	return container_of(kd, struct drm_plane, kmsg_panic);
 }
 
-static void drm_panic(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason)
+static void drm_panic(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason,
+		      const char *desc)
 {
 	struct drm_plane *plane = to_drm_plane(dumper);
 
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 9c452bfbd5719..b0786ee9c94e3 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -207,7 +207,8 @@ static int hv_die_panic_notify_crash(struct notifier_block *self,
  * buffer and call into Hyper-V to transfer the data.
  */
 static void hv_kmsg_dump(struct kmsg_dumper *dumper,
-			 enum kmsg_dump_reason reason)
+			 enum kmsg_dump_reason reason,
+			 const char *desc)
 {
 	struct kmsg_dump_iter iter;
 	size_t bytes_written;
diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index 2f11585b5613e..c618999a96832 100644
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -298,7 +298,8 @@ static void find_next_position(struct mtdoops_context *cxt)
 }
 
 static void mtdoops_do_dump(struct kmsg_dumper *dumper,
-			    enum kmsg_dump_reason reason)
+			    enum kmsg_dump_reason reason,
+			    const char *desc)
 {
 	struct mtdoops_context *cxt = container_of(dumper,
 			struct mtdoops_context, dump);
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 3497ede88aa01..a6ed5d56021ef 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -275,7 +275,8 @@ void pstore_record_init(struct pstore_record *record,
  * end of the buffer.
  */
 static void pstore_dump(struct kmsg_dumper *dumper,
-			enum kmsg_dump_reason reason)
+			enum kmsg_dump_reason reason,
+			const char *desc)
 {
 	struct kmsg_dump_iter iter;
 	unsigned long	total = 0;
diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
index 906521c2329ca..a8f8a6204542d 100644
--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -49,13 +49,15 @@ struct kmsg_dump_iter {
  */
 struct kmsg_dumper {
 	struct list_head list;
-	void (*dump)(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason);
+	void (*dump)(struct kmsg_dumper *dumper,
+		     enum kmsg_dump_reason reason,
+		     const char *desc);
 	enum kmsg_dump_reason max_reason;
 	bool registered;
 };
 
 #ifdef CONFIG_PRINTK
-void kmsg_dump(enum kmsg_dump_reason reason);
+void kmsg_dump_desc(enum kmsg_dump_reason reason, const char *desc);
 
 bool kmsg_dump_get_line(struct kmsg_dump_iter *iter, bool syslog,
 			char *line, size_t size, size_t *len);
@@ -71,7 +73,7 @@ int kmsg_dump_unregister(struct kmsg_dumper *dumper);
 
 const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason);
 #else
-static inline void kmsg_dump(enum kmsg_dump_reason reason)
+static inline void kmsg_dump_desc(enum kmsg_dump_reason reason, const char *desc)
 {
 }
 
@@ -107,4 +109,9 @@ static inline const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason)
 }
 #endif
 
+static inline void kmsg_dump(enum kmsg_dump_reason reason)
+{
+	kmsg_dump_desc(reason, NULL);
+}
+
 #endif /* _LINUX_KMSG_DUMP_H */
diff --git a/kernel/panic.c b/kernel/panic.c
index 0843a275531a7..0a8b29c44f3c1 100644
--- a/kernel/panic.c
+++ b/kernel/panic.c
@@ -378,7 +378,7 @@ void panic(const char *fmt, ...)
 
 	panic_print_sys_info(false);
 
-	kmsg_dump(KMSG_DUMP_PANIC);
+	kmsg_dump_desc(KMSG_DUMP_PANIC, buf);
 
 	/*
 	 * If you doubt kdump always works fine in any situation,
diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index d0bff0b0abfdb..2e7195894e41a 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -4287,14 +4287,16 @@ const char *kmsg_dump_reason_str(enum kmsg_dump_reason reason)
 EXPORT_SYMBOL_GPL(kmsg_dump_reason_str);
 
 /**
- * kmsg_dump - dump kernel log to kernel message dumpers.
+ * kmsg_dump_desc - dump kernel log to kernel message dumpers.
  * @reason: the reason (oops, panic etc) for dumping
+ * @desc: a short string to describe what caused the panic or oops. Can be NULL
+ * if no additional description is available.
  *
  * Call each of the registered dumper's dump() callback, which can
  * retrieve the kmsg records with kmsg_dump_get_line() or
  * kmsg_dump_get_buffer().
  */
-void kmsg_dump(enum kmsg_dump_reason reason)
+void kmsg_dump_desc(enum kmsg_dump_reason reason, const char *desc)
 {
 	struct kmsg_dumper *dumper;
 
@@ -4314,7 +4316,7 @@ void kmsg_dump(enum kmsg_dump_reason reason)
 			continue;
 
 		/* invoke dumper which will iterate over records */
-		dumper->dump(dumper, reason);
+		dumper->dump(dumper, reason, desc);
 	}
 	rcu_read_unlock();
 }

base-commit: f76698bd9a8ca01d3581236082d786e9a6b72bb7
-- 
2.45.1