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mm/bpf: Add bpf_get_kmem_cache() kfunc

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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: Vlastimil 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: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20241010232505.1339892-3-namhyung@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Namhyung Kim
2024-10-10 16:25:04 -07:00
committed by Alexei Starovoitov
parent 4971266e15
commit a992d7a397
3 changed files with 25 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
kernel/bpf/helpers.c
View File

@@ -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 = {

5
kernel/bpf/verifier.c
View File

@@ -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;

19
mm/slab_common.c
View File

@@ -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);