On Tue, Jul 19, 2022 at 02:10AM +0200, andrey.konovalov@xxxxxxxxx wrote:
> From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>
> Instead of using a large static array, allocate the stack ring dynamically
> via memblock_alloc().
>
> The size of the stack ring is controlled by a new kasan.stack_ring_size
> command-line parameter. When kasan.stack_ring_size is not provided, the
> default value of 32 << 10 is used.
>
> When the stack trace collection is disabled via kasan.stacktrace=off,
> the stack ring is not allocated.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
>
> ---
>
> Changes v1->v2:
> - This is a new patch.
> ---
> mm/kasan/kasan.h | 5 +++--
> mm/kasan/report_tags.c | 4 ++--
> mm/kasan/tags.c | 22 +++++++++++++++++++++-
> 3 files changed, 26 insertions(+), 5 deletions(-)
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 447baf1a7a2e..4afe4db751da 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -252,12 +252,13 @@ struct kasan_stack_ring_entry {
> bool is_free;
> };
>
> -#define KASAN_STACK_RING_SIZE (32 << 10)
> +#define KASAN_STACK_RING_SIZE_DEFAULT (32 << 10)
>
This could be moved to tags.c, as there are no other users elsewhere.
> struct kasan_stack_ring {
> rwlock_t lock;
> + size_t size;
> atomic64_t pos;
> - struct kasan_stack_ring_entry entries[KASAN_STACK_RING_SIZE];
> + struct kasan_stack_ring_entry *entries;
> };
>
> #endif /* CONFIG_KASAN_SW_TAGS || CONFIG_KASAN_HW_TAGS */
> diff --git a/mm/kasan/report_tags.c b/mm/kasan/report_tags.c
> index a996489e6dac..7e267e69ce19 100644
> --- a/mm/kasan/report_tags.c
> +++ b/mm/kasan/report_tags.c
> @@ -56,11 +56,11 @@ void kasan_complete_mode_report_info(struct kasan_report_info *info)
> * entries relevant to the buggy object can be overwritten.
> */
>
> - for (u64 i = pos - 1; i != pos - 1 - KASAN_STACK_RING_SIZE; i--) {
> + for (u64 i = pos - 1; i != pos - 1 - stack_ring.size; i--) {
> if (alloc_found && free_found)
> break;
>
> - entry = &stack_ring.entries[i % KASAN_STACK_RING_SIZE];
> + entry = &stack_ring.entries[i % stack_ring.size];
>
> /* Paired with smp_store_release() in save_stack_info(). */
> ptr = (void *)smp_load_acquire(&entry->ptr);
> diff --git a/mm/kasan/tags.c b/mm/kasan/tags.c
> index 0eb6cf6717db..fd8c5f919156 100644
> --- a/mm/kasan/tags.c
> +++ b/mm/kasan/tags.c
> @@ -10,6 +10,7 @@
> #include <linux/init.h>
> #include <linux/kasan.h>
> #include <linux/kernel.h>
> +#include <linux/memblock.h>
> #include <linux/memory.h>
> #include <linux/mm.h>
> #include <linux/static_key.h>
> @@ -52,6 +53,16 @@ static int __init early_kasan_flag_stacktrace(char *arg)
> }
> early_param("kasan.stacktrace", early_kasan_flag_stacktrace);
>
> +/* kasan.stack_ring_size=32768 */
What does that comment say? Is it "kasan.stack_ring_size=<entries>"?
Is it already in the documentation?
> +static int __init early_kasan_flag_stack_ring_size(char *arg)
> +{
> + if (!arg)
> + return -EINVAL;
> +
> + return kstrtoul(arg, 0, &stack_ring.size);
> +}
> +early_param("kasan.stack_ring_size", early_kasan_flag_stack_ring_size);
> +
> void __init kasan_init_tags(void)
> {
> switch (kasan_arg_stacktrace) {
> @@ -65,6 +76,15 @@ void __init kasan_init_tags(void)
> static_branch_enable(&kasan_flag_stacktrace);
> break;
> }
> +
> + if (kasan_stack_collection_enabled()) {
> + if (!stack_ring.size)
> + stack_ring.size = KASAN_STACK_RING_SIZE_DEFAULT;
> + stack_ring.entries = memblock_alloc(
> + sizeof(stack_ring.entries[0]) *
> + stack_ring.size,
> + SMP_CACHE_BYTES);
memblock_alloc() can fail. Because unlikely, stack collection should
probably just be disabled.
(minor: excessive line breaks makes the above unreadable.)
> + }
> }
>
> static void save_stack_info(struct kmem_cache *cache, void *object,
> @@ -86,7 +106,7 @@ static void save_stack_info(struct kmem_cache *cache, void *object,
>
> next:
> pos = atomic64_fetch_add(1, &stack_ring.pos);
> - entry = &stack_ring.entries[pos % KASAN_STACK_RING_SIZE];
> + entry = &stack_ring.entries[pos % stack_ring.size];
>
> /* Detect stack ring entry slots that are being written to. */
> old_ptr = READ_ONCE(entry->ptr);
> --
> 2.25.1
