Date: Wed, 26 Jun 2024 09:26:03 -0700
From: Kees Cook <kees@...nel.org>
To: Jocelyn Falempe <jfalempe@...hat.com>
Cc: Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	"Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>,
	Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
	Miquel Raynal <miquel.raynal@...tlin.com>,
	Richard Weinberger <richard@....at>,
	Vignesh Raghavendra <vigneshr@...com>,
	Tony Luck <tony.luck@...el.com>,
	"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
	Petr Mladek <pmladek@...e.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	John Ogness <john.ogness@...utronix.de>,
	Sergey Senozhatsky <senozhatsky@...omium.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jani Nikula <jani.nikula@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Kefeng Wang <wangkefeng.wang@...wei.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Uros Bizjak <ubizjak@...il.com>, linuxppc-dev@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linux-hyperv@...r.kernel.org, linux-mtd@...ts.infradead.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] printk: Add a short description string to kmsg_dump()

On Tue, Jun 25, 2024 at 02:39:29PM +0200, Jocelyn Falempe wrote:
> 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.

Seems reasonable. Given the prototype before/after:

dump(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason)

dump(struct kmsg_dumper *dumper, enum kmsg_dump_reason reason,
     const char *desc)

Perhaps this should instead be a struct that the panic fills in? Then
it'll be easy to adjust the struct in the future:

struct kmsg_dump_detail {
	enum kmsg_dump_reason reason;
	const char *description;
};

dump(struct kmsg_dumper *dumper, struct kmsg_dump *detail)

This .cocci could do the conversion:


@ dump_func @
identifier DUMPER, CALLBACK;
@@

  struct kmsg_dumper DUMPER = {
    .dump = CALLBACK,
  };

@ detail @
identifier dump_func.CALLBACK;
identifier DUMPER, REASON;
@@

	CALLBACK(struct kmsg_dumper *DUMPER,
-		 enum kmsg_dump_reason REASON
+		 struct kmsg_dump_detail *detail
		)
	{
		<...
-		REASON
+		detail->reason
		...>
	}


Also, just to double-check, doesn't the panic reason show up in the
kmsg_dump log itself (at the end?) I ask since for pstore, "desc" is
likely redundant since it's capturing the entire console log.

-Kees

Here's the patch from the above cocci:


diff -u -p a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
--- a/drivers/hv/hv_common.c
+++ b/drivers/hv/hv_common.c
@@ -207,13 +207,13 @@ static int hv_die_panic_notify_crash(str
  * 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 -u -p a/arch/powerpc/platforms/powernv/opal-kmsg.c b/arch/powerpc/platforms/powernv/opal-kmsg.c
--- 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 -u -p a/arch/powerpc/kernel/nvram_64.c b/arch/powerpc/kernel/nvram_64.c
--- 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(in
  * 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_du
 	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_du
 		break;
 	default:
 		pr_err("%s: ignoring unrecognized KMSG_DUMP_* reason %d\n",
-		       __func__, (int) reason);
+		       __func__, (int) detail->reason);
 		return;
 	}
 
warning: detail, node 59: record.reason = ... ;[1,2,21,22,32] in pstore_dump may be inconsistently modified
warning: detail, node 105: if[1,2,21,22,54] in pstore_dump may be inconsistently modified
diff -u -p a/fs/pstore/platform.c b/fs/pstore/platform.c
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -275,7 +275,7 @@ void pstore_record_init(struct pstore_re
  * 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_dump
 	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_dump
 		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_dump
 		}
 
 		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 -u -p a/arch/um/kernel/kmsg_dump.c b/arch/um/kernel/kmsg_dump.c
--- 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);

-- 
Kees Cook

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