Commit d0f2d6e9 authored by Steven Rostedt's avatar Steven Rostedt Committed by Steven Rostedt (Google)
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ring-buffer: Add magic and struct size to boot up meta data 

Add a magic number as well as save the struct size of the ring_buffer_meta
structure in the meta data to also use as validation. Updating the magic
number could be used to force a invalidation between kernel versions, and
saving the structure size is also a good method to make sure the content
is what is expected.

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Link: https://lore.kernel.org/20240815115032.0c197b32@rorschach.local.home


Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent bca704f6

kernel/trace/ring_buffer.c

+14 −0
Original line number Diff line number Diff line
@@ -44,7 +44,11 @@ 


static void update_pages_handler(struct work_struct *work);



#define RING_BUFFER_META_MAGIC	0xBADFEED



struct ring_buffer_meta {

	int		magic;

	int		struct_size;

	unsigned long	text_addr;

	unsigned long	data_addr;

	unsigned long	first_buffer;
@@ -1627,6 +1631,13 @@ static bool rb_meta_valid(struct ring_buffer_meta *meta, int cpu, 
	unsigned long buffers_end;

	int i;



	/* Check the meta magic and meta struct size */

	if (meta->magic != RING_BUFFER_META_MAGIC ||

	    meta->struct_size != sizeof(*meta)) {

		pr_info("Ring buffer boot meta[%d] mismatch of magic or struct size\n", cpu);

		return false;

	}



	/* The subbuffer's size and number of subbuffers must match */

	if (meta->subbuf_size != subbuf_size ||

	    meta->nr_subbufs != nr_pages + 1) {
@@ -1858,6 +1869,9 @@ static void rb_range_meta_init(struct trace_buffer *buffer, int nr_pages) 


		memset(meta, 0, next_meta - (void *)meta);



		meta->magic = RING_BUFFER_META_MAGIC;

		meta->struct_size = sizeof(*meta);



		meta->nr_subbufs = nr_pages + 1;

		meta->subbuf_size = PAGE_SIZE;