Re: [PATCH v2] printk: Add a short description string to kmsg_dump()

From: Jocelyn Falempe
Date: Fri Jul 12 2024 - 05:59:48 EST

On 02/07/2024 14:26, Jocelyn Falempe wrote:
kmsg_dump doesn't forward the panic reason string to the kmsg_dumper
callback.
This patch adds a new struct kmsg_dump_detail, that will hold the
reason and description, and pass it to the dump() callback.

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.

v2:
* Use a struct kmsg_dump_detail to hold the reason and description
pointer, for more flexibility if we want to add other parameters.
(Kees Cook)
* Fix powerpc/nvram_64 build, as I didn't update the forward
declaration of oops_to_nvram()

Signed-off-by: Jocelyn Falempe <jfalempe@xxxxxxxxxx>
---
arch/powerpc/kernel/nvram_64.c | 8 ++++----
arch/powerpc/platforms/powernv/opal-kmsg.c | 4 ++--
arch/um/kernel/kmsg_dump.c | 2 +-
drivers/gpu/drm/drm_panic.c | 4 ++--
drivers/hv/hv_common.c | 4 ++--
drivers/mtd/mtdoops.c | 2 +-
fs/pstore/platform.c | 10 +++++-----
include/linux/kmsg_dump.h | 22 +++++++++++++++++++---
kernel/panic.c | 2 +-
kernel/printk/printk.c | 11 ++++++++---
10 files changed, 45 insertions(+), 24 deletions(-)

diff --git a/arch/powerpc/kernel/nvram_64.c b/arch/powerpc/kernel/nvram_64.c
index e385d3164648..f9c6568a9137 100644
--- a/arch/powerpc/kernel/nvram_64.c
+++ b/arch/powerpc/kernel/nvram_64.c
@@ -73,7 +73,7 @@ static const char *nvram_os_partitions[] = {
};
static void oops_to_nvram(struct kmsg_dumper *dumper,
- enum kmsg_dump_reason reason);
+ struct kmsg_dump_detail *detail);
static struct kmsg_dumper nvram_kmsg_dumper = {
.dump = oops_to_nvram
@@ -643,7 +643,7 @@ 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)
+ struct kmsg_dump_detail *detail)
{
struct oops_log_info *oops_hdr = (struct oops_log_info *)oops_buf;
static unsigned int oops_count = 0;
@@ -655,7 +655,7 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
unsigned int err_type = ERR_TYPE_KERNEL_PANIC_GZ;
int rc = -1;
- switch (reason) {
+ switch (detail->reason) {
case KMSG_DUMP_SHUTDOWN:
/* These are almost always orderly shutdowns. */
return;
@@ -671,7 +671,7 @@ static void oops_to_nvram(struct kmsg_dumper *dumper,
break;
default:
pr_err("%s: ignoring unrecognized KMSG_DUMP_* reason %d\n",
- __func__, (int) reason);
+ __func__, (int) detail->reason);
return;
}
diff --git a/arch/powerpc/platforms/powernv/opal-kmsg.c b/arch/powerpc/platforms/powernv/opal-kmsg.c
index 6c3bc4b4da98..bb4218fa796e 100644
--- a/arch/powerpc/platforms/powernv/opal-kmsg.c
+++ b/arch/powerpc/platforms/powernv/opal-kmsg.c
@@ -20,13 +20,13 @@
* 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)
+ struct kmsg_dump_detail *detail)
{
/*
* Outside of a panic context the pollers will continue to run,
* so we don't need to do any special flushing.
*/
- if (reason != KMSG_DUMP_PANIC)
+ if (detail->reason != KMSG_DUMP_PANIC)
return;
opal_flush_console(0);
diff --git a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
index 4382cf02a6d1..419021175272 100644
--- a/arch/um/kernel/kmsg_dump.c
+++ b/arch/um/kernel/kmsg_dump.c
@@ -8,7 +8,7 @@
#include <os.h>
static void kmsg_dumper_stdout(struct kmsg_dumper *dumper,
- enum kmsg_dump_reason reason)
+ struct kmsg_dump_detail *detail)
{
static struct kmsg_dump_iter iter;
static DEFINE_SPINLOCK(lock);
diff --git a/drivers/gpu/drm/drm_panic.c b/drivers/gpu/drm/drm_panic.c
index 948aed00595e..8794c7f6c0ee 100644
--- a/drivers/gpu/drm/drm_panic.c
+++ b/drivers/gpu/drm/drm_panic.c
@@ -655,11 +655,11 @@ 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, struct kmsg_dump_detail *detail)
{
struct drm_plane *plane = to_drm_plane(dumper);
- if (reason == KMSG_DUMP_PANIC)
+ if (detail->reason == KMSG_DUMP_PANIC)
draw_panic_plane(plane);
}
diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
index 9c452bfbd571..7a35c82976e0 100644
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -207,13 +207,13 @@ 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)
+ struct kmsg_dump_detail *detail)
{
struct kmsg_dump_iter iter;
size_t bytes_written;
/* We are only interested in panics. */
- if (reason != KMSG_DUMP_PANIC || !sysctl_record_panic_msg)
+ if (detail->reason != KMSG_DUMP_PANIC || !sysctl_record_panic_msg)
return;
/*
diff --git a/drivers/mtd/mtdoops.c b/drivers/mtd/mtdoops.c
index 2f11585b5613..86d49db9196d 100644
--- a/drivers/mtd/mtdoops.c
+++ b/drivers/mtd/mtdoops.c
@@ -298,7 +298,7 @@ static void find_next_position(struct mtdoops_context *cxt)
}
static void mtdoops_do_dump(struct kmsg_dumper *dumper,
- enum kmsg_dump_reason reason)
+ struct kmsg_dump_detail *detail)
{
struct mtdoops_context *cxt = container_of(dumper,
struct mtdoops_context, dump);
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 3497ede88aa0..9c6b7c97fa3c 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -275,7 +275,7 @@ 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)
+ struct kmsg_dump_detail *detail)
{
struct kmsg_dump_iter iter;
unsigned long total = 0;
@@ -285,9 +285,9 @@ static void pstore_dump(struct kmsg_dumper *dumper,
int saved_ret = 0;
int ret;
- why = kmsg_dump_reason_str(reason);
+ why = kmsg_dump_reason_str(detail->reason);
- if (pstore_cannot_block_path(reason)) {
+ if (pstore_cannot_block_path(detail->reason)) {
if (!spin_trylock_irqsave(&psinfo->buf_lock, flags)) {
pr_err("dump skipped in %s path because of concurrent dump\n",
in_nmi() ? "NMI" : why);
@@ -311,7 +311,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
pstore_record_init(&record, psinfo);
record.type = PSTORE_TYPE_DMESG;
record.count = oopscount;
- record.reason = reason;
+ record.reason = detail->reason;
record.part = part;
record.buf = psinfo->buf;
@@ -352,7 +352,7 @@ static void pstore_dump(struct kmsg_dumper *dumper,
}
ret = psinfo->write(&record);
- if (ret == 0 && reason == KMSG_DUMP_OOPS) {
+ if (ret == 0 && detail->reason == KMSG_DUMP_OOPS) {
pstore_new_entry = 1;
pstore_timer_kick();
} else {
diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
index 906521c2329c..65f5a47727bc 100644
--- a/include/linux/kmsg_dump.h
+++ b/include/linux/kmsg_dump.h
@@ -39,6 +39,17 @@ struct kmsg_dump_iter {
u64 next_seq;
};
+/**
+ *struct kmsg_dump_detail - kernel crash detail
+ * @reason: reason for the crash, see kmsg_dump_reason.
+ * @description: optional short string, to provide additional information.
+ */
+
+struct kmsg_dump_detail {
+ enum kmsg_dump_reason reason;
+ const char *description;
+};
+
/**
* struct kmsg_dumper - kernel crash message dumper structure
* @list: Entry in the dumper list (private)
@@ -49,13 +60,13 @@ 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, struct kmsg_dump_detail *detail);
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 +82,7 @@ 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 +118,9 @@ 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 0843a275531a..0a8b29c44f3c 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 5dcc05e1aa56..19bc414be5f0 100644
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -4272,16 +4272,21 @@ 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;
+ struct kmsg_dump_detail detail = {
+ .reason = reason,
+ .description = desc};
rcu_read_lock();
list_for_each_entry_rcu(dumper, &dump_list, list) {
@@ -4299,7 +4304,7 @@ void kmsg_dump(enum kmsg_dump_reason reason)
continue;
/* invoke dumper which will iterate over records */
- dumper->dump(dumper, reason);
+ dumper->dump(dumper, &detail);
}
rcu_read_unlock();
}

base-commit: 82e4255305c554b0bb18b7ccf2db86041b4c8b6e

Gentle ping, I need reviews from powerpc, usermod linux, mtd, pstore and hyperv, to be able to push it in the drm-misc tree.

Best regards,

--

Jocelyn