printk: honor the max_reason field in kmsg_dumper (b1f6f161) · Commits · 戴 / test

kmsg_dump() allows to dump kmesg buffer for various system events: oops, panic, reboot, etc. It provides an interface to register a callback call for clients, and in that callback interface there is a field "max_reason", but it was getting ignored when set to any "reason" higher than KMSG_DUMP_OOPS unless "always_kmsg_dump" was passed as kernel parameter. Allow clients to actually control their "max_reason", and keep the current behavior when "max_reason" is not set. Signed-off-by:

Pavel Tatashin <pasha.tatashin@soleen.com> Link: https://lore.kernel.org/lkml/20200515184434.8470-3-keescook@chromium.org/ Reviewed-by:

Petr Mladek <pmladek@suse.com> Signed-off-by:

Kees Cook <keescook@chromium.org>

include/linux/kmsg_dump.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -26,6 +26,7 @@ enum kmsg_dump_reason {
		KMSG_DUMP_OOPS,
		KMSG_DUMP_EMERG,
		KMSG_DUMP_SHUTDOWN,
		KMSG_DUMP_MAX
		};

		/**

kernel/printk/printk.c

+11 −4

Original line number	Diff line number	Diff line
		@@ -3157,12 +3157,19 @@ void kmsg_dump(enum kmsg_dump_reason reason)
		struct kmsg_dumper *dumper;
		unsigned long flags;

		if ((reason > KMSG_DUMP_OOPS) && !always_kmsg_dump)
		return;

		rcu_read_lock();
		list_for_each_entry_rcu(dumper, &dump_list, list) {
		if (dumper->max_reason && reason > dumper->max_reason)
		enum kmsg_dump_reason max_reason = dumper->max_reason;

		/*
		* If client has not provided a specific max_reason, default
		* to KMSG_DUMP_OOPS, unless always_kmsg_dump was set.
		*/
		if (max_reason == KMSG_DUMP_UNDEF) {
		max_reason = always_kmsg_dump ? KMSG_DUMP_MAX :
		KMSG_DUMP_OOPS;
		}
		if (reason > max_reason)
		continue;

		/* initialize iterator with data about the stored records */

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