Commit e645535a authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

tracing: Add option to use memmapped memory for trace boot instance 

Add an option to the trace_instance kernel command line parameter that
allows it to use the reserved memory from memmap boot parameter.

  memmap=12M$0x284500000 trace_instance=boot_mapped@0x284500000:12M

The above will reserves 12 megs at the physical address 0x284500000.
The second parameter will create a "boot_mapped" instance and use the
memory reserved as the memory for the ring buffer.

That will create an instance called "boot_mapped":

  /sys/kernel/tracing/instances/boot_mapped

Note, because the ring buffer is using a defined memory ranged, it will
act just like a memory mapped ring buffer. It will not have a snapshot
buffer, as it can't swap out the buffer. The snapshot files as well as any
tracers that uses a snapshot will not be present in the boot_mapped
instance.

Link: https://lkml.kernel.org/r/20240612232026.329660169@goodmis.org



Cc: linux-mm@kvack.org
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Daniel Bristot de Oliveira <bristot@redhat.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineeth Pillai <vineeth@bitbyteword.org>
Cc: Youssef Esmat <youssefesmat@google.com>
Cc: Beau Belgrave <beaub@linux.microsoft.com>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "Paul E. McKenney" <paulmck@kernel.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Ross Zwisler <zwisler@google.com>
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 5f3b6e83

Documentation/admin-guide/kernel-parameters.txt

+9 −0
Original line number Diff line number Diff line
@@ -6754,6 +6754,15 @@ 
			the same thing would happen if it was left off). The irq_handler_entry

			event, and all events under the "initcall" system.



			If memory has been reserved (see memmap for x86), the instance

			can use that memory:



				memmap=12M$0x284500000 trace_instance=boot_map@0x284500000:12M



			The above will create a "boot_map" instance that uses the physical

			memory at 0x284500000 that is 12Megs. The per CPU buffers of that

			instance will be split up accordingly.



	trace_options=[option-list]

			[FTRACE] Enable or disable tracer options at boot.

			The option-list is a comma delimited list of options

kernel/trace/trace.c

+69 −6
Original line number Diff line number Diff line
@@ -9504,6 +9504,31 @@ static int instance_mkdir(const char *name) 
	return ret;

}



static u64 map_pages(u64 start, u64 size)

{

	struct page **pages;

	phys_addr_t page_start;

	unsigned int page_count;

	unsigned int i;

	void *vaddr;



	page_count = DIV_ROUND_UP(size, PAGE_SIZE);



	page_start = start;

	pages = kmalloc_array(page_count, sizeof(struct page *), GFP_KERNEL);

	if (!pages)

		return 0;



	for (i = 0; i < page_count; i++) {

		phys_addr_t addr = page_start + i * PAGE_SIZE;

		pages[i] = pfn_to_page(addr >> PAGE_SHIFT);

	}

	vaddr = vmap(pages, page_count, VM_MAP, PAGE_KERNEL);

	kfree(pages);



	return (u64)(unsigned long)vaddr;

}



/**

 * trace_array_get_by_name - Create/Lookup a trace array, given its name.

 * @name: The name of the trace array to be looked up/created.
@@ -10350,6 +10375,7 @@ __init static void enable_instances(void) 
{

	struct trace_array *tr;

	char *curr_str;

	char *name;

	char *str;

	char *tok;
@@ -10358,18 +10384,55 @@ __init static void enable_instances(void) 
	str = boot_instance_info;



	while ((curr_str = strsep(&str, "\t"))) {

		unsigned long start = 0;

		unsigned long size = 0;

		unsigned long addr = 0;



		tok = strsep(&curr_str, ",");

		name = strsep(&tok, "@");

		if (tok) {

			start = memparse(tok, &tok);

			if (!start) {

				pr_warn("Tracing: Invalid boot instance address for %s\n",

					name);

				continue;

			}

		}



		if (start) {

			if (*tok != ':') {

				pr_warn("Tracing: No size specified for instance %s\n", name);

				continue;

			}

			tok++;

			size = memparse(tok, &tok);

			if (!size) {

				pr_warn("Tracing: Invalid boot instance size for %s\n",

					name);

				continue;

			}

			addr = map_pages(start, size);

			if (addr) {

				pr_info("Tracing: mapped boot instance %s at physical memory 0x%lx of size 0x%lx\n",

					name, start, size);

			} else {

				pr_warn("Tracing: Failed to map boot instance %s\n", name);

				continue;

			}

		} else {

			/* Only non mapped buffers have snapshot buffers */

			if (IS_ENABLED(CONFIG_TRACER_MAX_TRACE))

			do_allocate_snapshot(tok);

				do_allocate_snapshot(name);

		}



		tr = trace_array_get_by_name(tok, NULL);

		tr = trace_array_create_systems(name, NULL, addr, size);

		if (!tr) {

			pr_warn("Failed to create instance buffer %s\n", curr_str);

			pr_warn("Tracing: Failed to create instance buffer %s\n", curr_str);

			continue;

		}

		/* Allow user space to delete it */



		/* Only allow non mapped buffers to be deleted */

		if (!start)

			trace_array_put(tr);



		while ((tok = strsep(&curr_str, ","))) {