Commit a992d7a3 authored by Namhyung Kim's avatar Namhyung Kim Committed by Alexei Starovoitov
Browse files

mm/bpf: Add bpf_get_kmem_cache() kfunc 



The bpf_get_kmem_cache() is to get a slab cache information from a
virtual address like virt_to_cache().  If the address is a pointer
to a slab object, it'd return a valid kmem_cache pointer, otherwise
NULL is returned.

It doesn't grab a reference count of the kmem_cache so the caller is
responsible to manage the access.  The returned point is marked as
PTR_UNTRUSTED.

The intended use case for now is to symbolize locks in slab objects
from the lock contention tracepoints.

Suggested-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev> (mm/*)
Acked-by: Vlastimil Babka <vbabka@suse.cz> #mm/slab
Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20241010232505.1339892-3-namhyung@kernel.org


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 4971266e

kernel/bpf/helpers.c

+1 −0
Original line number Diff line number Diff line
@@ -3090,6 +3090,7 @@ BTF_ID_FLAGS(func, bpf_iter_bits_new, KF_ITER_NEW) 
BTF_ID_FLAGS(func, bpf_iter_bits_next, KF_ITER_NEXT | KF_RET_NULL)

BTF_ID_FLAGS(func, bpf_iter_bits_destroy, KF_ITER_DESTROY)

BTF_ID_FLAGS(func, bpf_copy_from_user_str, KF_SLEEPABLE)

BTF_ID_FLAGS(func, bpf_get_kmem_cache)

BTF_KFUNCS_END(common_btf_ids)



static const struct btf_kfunc_id_set common_kfunc_set = {

kernel/bpf/verifier.c

+5 −0
Original line number Diff line number Diff line
@@ -11259,6 +11259,7 @@ enum special_kfunc_type { 
	KF_bpf_preempt_enable,

	KF_bpf_iter_css_task_new,

	KF_bpf_session_cookie,

	KF_bpf_get_kmem_cache,

};









BTF_SET_START(special_kfunc_set)








@@ -11324,6 +11325,7 @@ BTF_ID(func, bpf_session_cookie)







#else









BTF_ID_UNUSED









#endif









BTF_ID(func, bpf_get_kmem_cache)

















static bool is_kfunc_ret_null(struct bpf_kfunc_call_arg_meta *meta)









{








@@ -12834,6 +12836,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,







			regs[BPF_REG_0].type = PTR_TO_BTF_ID;









			regs[BPF_REG_0].btf_id = ptr_type_id;

















			if (meta.func_id == special_kfunc_list[KF_bpf_get_kmem_cache])









				regs[BPF_REG_0].type |= PTR_UNTRUSTED;

















			if (is_iter_next_kfunc(&meta)) {









				struct bpf_reg_state *cur_iter;








































mm/slab_common.c



+19
−0






























Original line number
Diff line number
Diff line







@@ -1322,6 +1322,25 @@ size_t ksize(const void *objp)







}









EXPORT_SYMBOL(ksize);



















#ifdef CONFIG_BPF_SYSCALL









#include <linux/btf.h>



















__bpf_kfunc_start_defs();



















__bpf_kfunc struct kmem_cache *bpf_get_kmem_cache(u64 addr)









{









	struct slab *slab;



















	if (!virt_addr_valid((void *)(long)addr))









		return NULL;



















	slab = virt_to_slab((void *)(long)addr);









	return slab ? slab->slab_cache : NULL;









}



















__bpf_kfunc_end_defs();









#endif /* CONFIG_BPF_SYSCALL */



















/* Tracepoints definitions. */









EXPORT_TRACEPOINT_SYMBOL(kmalloc);









EXPORT_TRACEPOINT_SYMBOL(kmem_cache_alloc);