Commit 63592308 authored by Vincent Donnefort's avatar Vincent Donnefort Committed by Steven Rostedt (Google)
Browse files

tracing: load/unload page callbacks for simple_ring_buffer 

Add load/unload callback used for each admitted page in the ring-buffer.
This will be later useful for the pKVM hypervisor which uses a different
VA space and need to dynamically map/unmap the ring-buffer pages.

Link: https://patch.msgid.link/20260309162516.2623589-18-vdonnefort@google.com


Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarVincent Donnefort <vdonnefort@google.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent c88d5105

include/linux/simple_ring_buffer.h

+8 −0
Original line number Diff line number Diff line
@@ -54,4 +54,12 @@ int simple_ring_buffer_reset(struct simple_rb_per_cpu *cpu_buffer); 


int simple_ring_buffer_swap_reader_page(struct simple_rb_per_cpu *cpu_buffer);



int simple_ring_buffer_init_mm(struct simple_rb_per_cpu *cpu_buffer,

			       struct simple_buffer_page *bpages,

			       const struct ring_buffer_desc *desc,

			       void *(*load_page)(unsigned long va),

			       void (*unload_page)(void *va));



void simple_ring_buffer_unload_mm(struct simple_rb_per_cpu *cpu_buffer,

				  void (*unload_page)(void *));

#endif

kernel/trace/simple_ring_buffer.c

+72 −19
Original line number Diff line number Diff line
@@ -71,7 +71,7 @@ static void simple_bpage_reset(struct simple_buffer_page *bpage) 
	local_set(&bpage->page->commit, 0);

}



static void simple_bpage_init(struct simple_buffer_page *bpage, unsigned long page)

static void simple_bpage_init(struct simple_buffer_page *bpage, void *page)

{

	INIT_LIST_HEAD(&bpage->link);

	bpage->page = (struct buffer_data_page *)page;
@@ -372,18 +372,15 @@ int simple_ring_buffer_reset(struct simple_rb_per_cpu *cpu_buffer) 
}

EXPORT_SYMBOL_GPL(simple_ring_buffer_reset);



/**

 * simple_ring_buffer_init - Init @cpu_buffer based on @desc

 * @cpu_buffer:	A simple_rb_per_cpu buffer to init, allocated by the caller.

 * @bpages:	Array of simple_buffer_pages, with as many elements as @desc->nr_page_va

 * @desc:	A ring_buffer_desc

 *

 * Returns 0 on success or -EINVAL if the content of @desc is invalid

 */

int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_buffer_page *bpages,

			    const struct ring_buffer_desc *desc)

int simple_ring_buffer_init_mm(struct simple_rb_per_cpu *cpu_buffer,

			       struct simple_buffer_page *bpages,

			       const struct ring_buffer_desc *desc,

			       void *(*load_page)(unsigned long va),

			       void (*unload_page)(void *va))

{

	struct simple_buffer_page *bpage = bpages;

	int ret = 0;

	void *page;

	int i;



	/* At least 1 reader page and two pages in the ring-buffer */
@@ -392,15 +389,22 @@ int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_ 


	memset(cpu_buffer, 0, sizeof(*cpu_buffer));



	cpu_buffer->bpages = bpages;

	cpu_buffer->meta = load_page(desc->meta_va);

	if (!cpu_buffer->meta)

		return -EINVAL;



	cpu_buffer->meta = (void *)desc->meta_va;

	memset(cpu_buffer->meta, 0, sizeof(*cpu_buffer->meta));

	cpu_buffer->meta->meta_page_size = PAGE_SIZE;

	cpu_buffer->meta->nr_subbufs = cpu_buffer->nr_pages;



	/* The reader page is not part of the ring initially */

	simple_bpage_init(bpage, desc->page_va[0]);

	page = load_page(desc->page_va[0]);

	if (!page) {

		unload_page(cpu_buffer->meta);

		return -EINVAL;

	}



	simple_bpage_init(bpage, page);

	bpage->id = 0;



	cpu_buffer->nr_pages = 1;
@@ -410,7 +414,13 @@ int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_ 
	cpu_buffer->head_page = bpage + 1;



	for (i = 1; i < desc->nr_page_va; i++) {

		simple_bpage_init(++bpage, desc->page_va[i]);

		page = load_page(desc->page_va[i]);

		if (!page) {

			ret = -EINVAL;

			break;

		}



		simple_bpage_init(++bpage, page);



		bpage->link.next = &(bpage + 1)->link;

		bpage->link.prev = &(bpage - 1)->link;
@@ -419,6 +429,14 @@ int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_ 
		cpu_buffer->nr_pages = i + 1;

	}



	if (ret) {

		for (i--; i >= 0; i--)

			unload_page((void *)desc->page_va[i]);

		unload_page(cpu_buffer->meta);



		return ret;

	}



	/* Close the ring */

	bpage->link.next = &cpu_buffer->tail_page->link;

	cpu_buffer->tail_page->link.prev = &bpage->link;
@@ -426,23 +444,58 @@ int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_ 
	/* The last init'ed page points to the head page */

	simple_bpage_set_head_link(bpage);



	cpu_buffer->bpages = bpages;



	return 0;

}

EXPORT_SYMBOL_GPL(simple_ring_buffer_init);



static void *__load_page(unsigned long page)

{

	return (void *)page;

}



static void __unload_page(void *page) { }



/**

 * simple_ring_buffer_unload - Prepare @cpu_buffer for deletion

 * @cpu_buffer:	A simple_rb_per_cpu that will be deleted.

 * simple_ring_buffer_init - Init @cpu_buffer based on @desc

 * @cpu_buffer:	A simple_rb_per_cpu buffer to init, allocated by the caller.

 * @bpages:	Array of simple_buffer_pages, with as many elements as @desc->nr_page_va

 * @desc:	A ring_buffer_desc

 *

 * Returns 0 on success or -EINVAL if the content of @desc is invalid

 */

void simple_ring_buffer_unload(struct simple_rb_per_cpu *cpu_buffer)

int simple_ring_buffer_init(struct simple_rb_per_cpu *cpu_buffer, struct simple_buffer_page *bpages,

			    const struct ring_buffer_desc *desc)

{

	return simple_ring_buffer_init_mm(cpu_buffer, bpages, desc, __load_page, __unload_page);

}

EXPORT_SYMBOL_GPL(simple_ring_buffer_init);



void simple_ring_buffer_unload_mm(struct simple_rb_per_cpu *cpu_buffer,

				  void (*unload_page)(void *))

{

	int p;



	if (!simple_rb_loaded(cpu_buffer))

		return;



	simple_rb_enable_tracing(cpu_buffer, false);



	unload_page(cpu_buffer->meta);

	for (p = 0; p < cpu_buffer->nr_pages; p++)

		unload_page(cpu_buffer->bpages[p].page);



	cpu_buffer->bpages = NULL;

}



/**

 * simple_ring_buffer_unload - Prepare @cpu_buffer for deletion

 * @cpu_buffer:	A simple_rb_per_cpu that will be deleted.

 */

void simple_ring_buffer_unload(struct simple_rb_per_cpu *cpu_buffer)

{

	return simple_ring_buffer_unload_mm(cpu_buffer, __unload_page);

}

EXPORT_SYMBOL_GPL(simple_ring_buffer_unload);



/**