Commit bc47ee48 authored by Steven Rostedt (Google)'s avatar Steven Rostedt (Google)
Browse files

tracing/user_events: Use alloc_pages instead of kzalloc() for register pages 

kzalloc virtual addresses do not work with SetPageReserved, use the actual
page virtual addresses instead via alloc_pages.

The issue is reported when booting with user_events and
DEBUG_VM_PGFLAGS=y.

Also make the number of events based on the ORDER.

Link: https://lore.kernel.org/all/CADYN=9+xY5Vku3Ws5E9S60SM5dCFfeGeRBkmDFbcxX0ZMoFing@mail.gmail.com/
Link: https://lore.kernel.org/all/20220311223028.1865-1-beaub@linux.microsoft.com/



Cc: Beau Belgrave <beaub@linux.microsoft.com>
Reported-by: default avatarAnders Roxell <anders.roxell@linaro.org>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 380af29b

kernel/trace/trace_events_user.c

+8 −6
Original line number Diff line number Diff line
@@ -30,9 +30,10 @@ 


/*

 * Limits how many trace_event calls user processes can create:

 * Must be multiple of PAGE_SIZE.

 * Must be a power of two of PAGE_SIZE.

 */

#define MAX_PAGES 1

#define MAX_PAGE_ORDER 0

#define MAX_PAGES (1 << MAX_PAGE_ORDER)

#define MAX_EVENTS (MAX_PAGES * PAGE_SIZE)



/* Limit how long of an event name plus args within the subsystem. */
@@ -1622,16 +1623,17 @@ static void set_page_reservations(bool set) 


static int __init trace_events_user_init(void)

{

	struct page *pages;

	int ret;



	/* Zero all bits beside 0 (which is reserved for failures) */

	bitmap_zero(page_bitmap, MAX_EVENTS);

	set_bit(0, page_bitmap);



	register_page_data = kzalloc(MAX_EVENTS, GFP_KERNEL);



	if (!register_page_data)

	pages = alloc_pages(GFP_KERNEL | __GFP_ZERO, MAX_PAGE_ORDER);

	if (!pages)

		return -ENOMEM;

	register_page_data = page_address(pages);



	set_page_reservations(true);
@@ -1640,7 +1642,7 @@ static int __init trace_events_user_init(void) 
	if (ret) {

		pr_warn("user_events could not register with tracefs\n");

		set_page_reservations(false);

		kfree(register_page_data);

		__free_pages(pages, MAX_PAGE_ORDER);

		return ret;

	}