Commit 62a898b0 authored by Hou Tao's avatar Hou Tao Committed by Alexei Starovoitov
Browse files

bpf: Add bpf_mem_alloc_check_size() helper 



Introduce bpf_mem_alloc_check_size() to check whether the allocation
size exceeds the limitation for the kmalloc-equivalent allocator. The
upper limit for percpu allocation is LLIST_NODE_SZ bytes larger than
non-percpu allocation, so a percpu argument is added to the helper.

The helper will be used in the following patch to check whether the size
parameter passed to bpf_mem_alloc() is too big.

Signed-off-by: default avatarHou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20241030100516.3633640-3-houtao@huaweicloud.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 101ccfba

include/linux/bpf_mem_alloc.h

+3 −0
Original line number Diff line number Diff line
@@ -33,6 +33,9 @@ int bpf_mem_alloc_percpu_init(struct bpf_mem_alloc *ma, struct obj_cgroup *objcg 
int bpf_mem_alloc_percpu_unit_init(struct bpf_mem_alloc *ma, int size);

void bpf_mem_alloc_destroy(struct bpf_mem_alloc *ma);



/* Check the allocation size for kmalloc equivalent allocator */

int bpf_mem_alloc_check_size(bool percpu, size_t size);



/* kmalloc/kfree equivalent: */

void *bpf_mem_alloc(struct bpf_mem_alloc *ma, size_t size);

void bpf_mem_free(struct bpf_mem_alloc *ma, void *ptr);

kernel/bpf/memalloc.c

+13 −1
Original line number Diff line number Diff line
@@ -35,6 +35,8 @@ 
 */

#define LLIST_NODE_SZ sizeof(struct llist_node)



#define BPF_MEM_ALLOC_SIZE_MAX 4096



/* similar to kmalloc, but sizeof == 8 bucket is gone */

static u8 size_index[24] __ro_after_init = {

	3,	/* 8 */
@@ -65,7 +67,7 @@ static u8 size_index[24] __ro_after_init = { 


static int bpf_mem_cache_idx(size_t size)

{

	if (!size || size > 4096)

	if (!size || size > BPF_MEM_ALLOC_SIZE_MAX)

		return -1;



	if (size <= 192)
@@ -1005,3 +1007,13 @@ void notrace *bpf_mem_cache_alloc_flags(struct bpf_mem_alloc *ma, gfp_t flags) 


	return !ret ? NULL : ret + LLIST_NODE_SZ;

}



int bpf_mem_alloc_check_size(bool percpu, size_t size)

{

	/* The size of percpu allocation doesn't have LLIST_NODE_SZ overhead */

	if ((percpu && size > BPF_MEM_ALLOC_SIZE_MAX) ||

	    (!percpu && size > BPF_MEM_ALLOC_SIZE_MAX - LLIST_NODE_SZ))

		return -E2BIG;



	return 0;

}