* [PATCH] user_events: Use alloc_pages instead of kzalloc for register pages
@ 2022-03-11 22:30 Beau Belgrave
2022-03-11 23:33 ` Steven Rostedt
0 siblings, 1 reply; 4+ messages in thread
From: Beau Belgrave @ 2022-03-11 22:30 UTC (permalink / raw)
To: rostedt, mhiramat
Cc: anders.roxell, linux-trace-devel, linux-kernel, linux-next, beaub
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.
Link: https://lore.kernel.org/linux-trace-devel/CADYN=9+xY5Vku3Ws5E9S60SM5dCFfeGeRBkmDFbcxX0ZMoFing@mail.gmail.com/#R
Reported-by: Anders Roxell <anders.roxell@linaro.org>
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
---
kernel/trace/trace_events_user.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 2b5e9fdb63a0..59c900789757 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -1587,16 +1587,20 @@ static void set_page_reservations(bool set)
static int __init trace_events_user_init(void)
{
int ret;
+ struct page *register_pages;
/* 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);
+ register_pages = alloc_pages(GFP_KERNEL | __GFP_ZERO,
+ get_order(MAX_EVENTS));
- if (!register_page_data)
+ if (!register_pages)
return -ENOMEM;
+ register_page_data = page_address(register_pages);
+
set_page_reservations(true);
ret = create_user_tracefs();
@@ -1604,7 +1608,7 @@ 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(register_pages, get_order(MAX_EVENTS));
return ret;
}
base-commit: 864ea0e10cc90416a01b46f0d47a6f26dc020820
--
2.17.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] user_events: Use alloc_pages instead of kzalloc for register pages
2022-03-11 22:30 [PATCH] user_events: Use alloc_pages instead of kzalloc for register pages Beau Belgrave
@ 2022-03-11 23:33 ` Steven Rostedt
2022-03-11 23:44 ` Steven Rostedt
0 siblings, 1 reply; 4+ messages in thread
From: Steven Rostedt @ 2022-03-11 23:33 UTC (permalink / raw)
To: Beau Belgrave
Cc: mhiramat, anders.roxell, linux-trace-devel, linux-kernel, linux-next
On Fri, 11 Mar 2022 14:30:28 -0800
Beau Belgrave <beaub@linux.microsoft.com> wrote:
> diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> index 2b5e9fdb63a0..59c900789757 100644
> --- a/kernel/trace/trace_events_user.c
> +++ b/kernel/trace/trace_events_user.c
> @@ -1587,16 +1587,20 @@ static void set_page_reservations(bool set)
> static int __init trace_events_user_init(void)
> {
> int ret;
> + struct page *register_pages;
The int ret should come last.
>
> /* 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);
> + register_pages = alloc_pages(GFP_KERNEL | __GFP_ZERO,
> + get_order(MAX_EVENTS));
>
> - if (!register_page_data)
> + if (!register_pages)
> return -ENOMEM;
>
> + register_page_data = page_address(register_pages);
> +
> set_page_reservations(true);
>
> ret = create_user_tracefs();
> @@ -1604,7 +1608,7 @@ 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(register_pages, get_order(MAX_EVENTS));
> return ret;
> }
>
I tried it slightly differently. Why waist bits if MAX_EVENTS is greater
than the order. That is, make MAX_EVENTS depend on the order, not the other
way around.
-- Steve
diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 4febc1d6ae72..6941d0794347 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -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. */
@@ -1606,41 +1607,25 @@ static int create_user_tracefs(void)
return -ENODEV;
}
-static void set_page_reservations(bool set)
-{
- int page;
-
- for (page = 0; page < MAX_PAGES; ++page) {
- void *addr = register_page_data + (PAGE_SIZE * page);
-
- if (set)
- SetPageReserved(virt_to_page(addr));
- else
- ClearPageReserved(virt_to_page(addr));
- }
-}
-
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;
-
- set_page_reservations(true);
+ register_page_data = page_address(pages);
ret = create_user_tracefs();
if (ret) {
pr_warn("user_events could not register with tracefs\n");
- set_page_reservations(false);
- kfree(register_page_data);
+ free_page((unsigned long)register_page_data);
return ret;
}
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] user_events: Use alloc_pages instead of kzalloc for register pages
2022-03-11 23:33 ` Steven Rostedt
@ 2022-03-11 23:44 ` Steven Rostedt
2022-03-11 23:55 ` Beau Belgrave
0 siblings, 1 reply; 4+ messages in thread
From: Steven Rostedt @ 2022-03-11 23:44 UTC (permalink / raw)
To: Beau Belgrave
Cc: mhiramat, anders.roxell, linux-trace-devel, linux-kernel, linux-next
On Fri, 11 Mar 2022 18:33:43 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:
> I tried it slightly differently. Why waist bits if MAX_EVENTS is greater
> than the order. That is, make MAX_EVENTS depend on the order, not the other
> way around.
Here's a version that keeps the reserving part as well as some bug fixes (I
didn't even compile the previous version ;-)
-- Steve
diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
index 4febc1d6ae72..e10ad057e797 100644
--- a/kernel/trace/trace_events_user.c
+++ b/kernel/trace/trace_events_user.c
@@ -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;
}
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] user_events: Use alloc_pages instead of kzalloc for register pages
2022-03-11 23:44 ` Steven Rostedt
@ 2022-03-11 23:55 ` Beau Belgrave
0 siblings, 0 replies; 4+ messages in thread
From: Beau Belgrave @ 2022-03-11 23:55 UTC (permalink / raw)
To: Steven Rostedt
Cc: mhiramat, anders.roxell, linux-trace-devel, linux-kernel, linux-next
On Fri, Mar 11, 2022 at 06:44:40PM -0500, Steven Rostedt wrote:
> On Fri, 11 Mar 2022 18:33:43 -0500
> Steven Rostedt <rostedt@goodmis.org> wrote:
>
> > I tried it slightly differently. Why waist bits if MAX_EVENTS is greater
> > than the order. That is, make MAX_EVENTS depend on the order, not the other
> > way around.
>
> Here's a version that keeps the reserving part as well as some bug fixes (I
> didn't even compile the previous version ;-)
>
> -- Steve
>
> diff --git a/kernel/trace/trace_events_user.c b/kernel/trace/trace_events_user.c
> index 4febc1d6ae72..e10ad057e797 100644
> --- a/kernel/trace/trace_events_user.c
> +++ b/kernel/trace/trace_events_user.c
> @@ -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;
> }
>
This looks good to me, I agree having the max events aligning to page
order makes more sense going forward.
Thanks,
-Beau
^ permalink raw reply [flat|nested] 4+ messages in thread
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2022-03-11 22:30 [PATCH] user_events: Use alloc_pages instead of kzalloc for register pages Beau Belgrave
2022-03-11 23:33 ` Steven Rostedt
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2022-03-11 23:55 ` Beau Belgrave
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