From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <martin.lau@kernel.org>,
Dave Marchevsky <davemarchevsky@meta.com>,
Delyan Kratunov <delyank@meta.com>
Subject: [PATCH bpf-next v6 18/26] bpf: Introduce bpf_obj_drop
Date: Sat, 12 Nov 2022 01:02:16 +0530 [thread overview]
Message-ID: <20221111193224.876706-19-memxor@gmail.com> (raw)
In-Reply-To: <20221111193224.876706-1-memxor@gmail.com>
Introduce bpf_obj_drop, which is the kfunc used to free allocated
objects (allocated using bpf_obj_new). Pairing with bpf_obj_new, it
implicitly destructs the fields part of object automatically without
user intervention.
Just like the previous patch, btf_struct_meta that is needed to free up
the special fields is passed as a hidden argument to the kfunc.
For the user, a convenience macro hides over the kernel side kfunc which
is named bpf_obj_drop_impl.
Continuing the previous example:
void prog(void) {
struct foo *f;
f = bpf_obj_new(typeof(*f));
if (!f)
return;
bpf_obj_drop(f);
}
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
kernel/bpf/helpers.c | 11 ++++
kernel/bpf/verifier.c | 66 +++++++++++++++----
.../testing/selftests/bpf/bpf_experimental.h | 13 ++++
3 files changed, 79 insertions(+), 11 deletions(-)
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index c4f1c22cc44c..71d803ca0c1d 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1770,6 +1770,16 @@ void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
return p;
}
+void bpf_obj_drop_impl(void *p__alloc, void *meta__ign)
+{
+ struct btf_struct_meta *meta = meta__ign;
+ void *p = p__alloc;
+
+ if (meta)
+ bpf_obj_free_fields(meta->record, p);
+ bpf_mem_free(&bpf_global_ma, p);
+}
+
__diag_pop();
BTF_SET8_START(generic_btf_ids)
@@ -1777,6 +1787,7 @@ BTF_SET8_START(generic_btf_ids)
BTF_ID_FLAGS(func, crash_kexec, KF_DESTRUCTIVE)
#endif
BTF_ID_FLAGS(func, bpf_obj_new_impl, KF_ACQUIRE | KF_RET_NULL)
+BTF_ID_FLAGS(func, bpf_obj_drop_impl, KF_RELEASE)
BTF_SET8_END(generic_btf_ids)
static const struct btf_kfunc_id_set generic_kfunc_set = {
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b7c663a2dbfa..5f98aa4c9d7c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7866,6 +7866,10 @@ struct bpf_kfunc_call_arg_meta {
u64 value;
bool found;
} arg_constant;
+ struct {
+ struct btf *btf;
+ u32 btf_id;
+ } arg_obj_drop;
};
static bool is_kfunc_acquire(struct bpf_kfunc_call_arg_meta *meta)
@@ -7944,6 +7948,11 @@ static bool is_kfunc_arg_sfx_ignore(const struct btf *btf, const struct btf_para
return __kfunc_param_match_suffix(btf, arg, "__ign");
}
+static bool is_kfunc_arg_alloc_obj(const struct btf *btf, const struct btf_param *arg)
+{
+ return __kfunc_param_match_suffix(btf, arg, "__alloc");
+}
+
static bool is_kfunc_arg_ret_buf_size(const struct btf *btf,
const struct btf_param *arg,
const struct bpf_reg_state *reg,
@@ -8044,6 +8053,7 @@ static u32 *reg2btf_ids[__BPF_REG_TYPE_MAX] = {
enum kfunc_ptr_arg_type {
KF_ARG_PTR_TO_CTX,
+ KF_ARG_PTR_TO_ALLOC_BTF_ID, /* Allocated object */
KF_ARG_PTR_TO_KPTR_STRONG, /* PTR_TO_KPTR but type specific */
KF_ARG_PTR_TO_DYNPTR,
KF_ARG_PTR_TO_BTF_ID, /* Also covers reg2btf_ids conversions */
@@ -8051,6 +8061,20 @@ enum kfunc_ptr_arg_type {
KF_ARG_PTR_TO_MEM_SIZE, /* Size derived from next argument, skip it */
};
+enum special_kfunc_type {
+ KF_bpf_obj_new_impl,
+ KF_bpf_obj_drop_impl,
+};
+
+BTF_SET_START(special_kfunc_set)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_ID(func, bpf_obj_drop_impl)
+BTF_SET_END(special_kfunc_set)
+
+BTF_ID_LIST(special_kfunc_list)
+BTF_ID(func, bpf_obj_new_impl)
+BTF_ID(func, bpf_obj_drop_impl)
+
static enum kfunc_ptr_arg_type
get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
struct bpf_kfunc_call_arg_meta *meta,
@@ -8071,6 +8095,9 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env,
if (btf_get_prog_ctx_type(&env->log, meta->btf, t, resolve_prog_type(env->prog), argno))
return KF_ARG_PTR_TO_CTX;
+ if (is_kfunc_arg_alloc_obj(meta->btf, &args[argno]))
+ return KF_ARG_PTR_TO_ALLOC_BTF_ID;
+
if (is_kfunc_arg_kptr_get(meta, argno)) {
if (!btf_type_is_ptr(ref_t)) {
verbose(env, "arg#0 BTF type must be a double pointer for kptr_get kfunc\n");
@@ -8289,6 +8316,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
return kf_arg_type;
switch (kf_arg_type) {
+ case KF_ARG_PTR_TO_ALLOC_BTF_ID:
case KF_ARG_PTR_TO_BTF_ID:
if (!is_kfunc_trusted_args(meta))
break;
@@ -8325,6 +8353,21 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
return -EINVAL;
}
break;
+ case KF_ARG_PTR_TO_ALLOC_BTF_ID:
+ if (reg->type != (PTR_TO_BTF_ID | MEM_ALLOC)) {
+ verbose(env, "arg#%d expected pointer to allocated object\n", i);
+ return -EINVAL;
+ }
+ if (!reg->ref_obj_id) {
+ verbose(env, "allocated object must be referenced\n");
+ return -EINVAL;
+ }
+ if (meta->btf == btf_vmlinux &&
+ meta->func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+ meta->arg_obj_drop.btf = reg->btf;
+ meta->arg_obj_drop.btf_id = reg->btf_id;
+ }
+ break;
case KF_ARG_PTR_TO_KPTR_STRONG:
if (reg->type != PTR_TO_MAP_VALUE) {
verbose(env, "arg#0 expected pointer to map value\n");
@@ -8395,17 +8438,6 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_kfunc_call_
return 0;
}
-enum special_kfunc_type {
- KF_bpf_obj_new_impl,
-};
-
-BTF_SET_START(special_kfunc_set)
-BTF_ID(func, bpf_obj_new_impl)
-BTF_SET_END(special_kfunc_set)
-
-BTF_ID_LIST(special_kfunc_list)
-BTF_ID(func, bpf_obj_new_impl)
-
static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
int *insn_idx_p)
{
@@ -8532,6 +8564,10 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
env->insn_aux_data[insn_idx].obj_new_size = ret_t->size;
env->insn_aux_data[insn_idx].kptr_struct_meta =
btf_find_struct_meta(ret_btf, ret_btf_id);
+ } else if (meta.func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+ env->insn_aux_data[insn_idx].kptr_struct_meta =
+ btf_find_struct_meta(meta.arg_obj_drop.btf,
+ meta.arg_obj_drop.btf_id);
} else {
verbose(env, "kernel function %s unhandled dynamic return type\n",
meta.func_name);
@@ -14737,6 +14773,14 @@ static int fixup_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
insn_buf[2] = addr[1];
insn_buf[3] = *insn;
*cnt = 4;
+ } else if (desc->func_id == special_kfunc_list[KF_bpf_obj_drop_impl]) {
+ struct btf_struct_meta *kptr_struct_meta = env->insn_aux_data[insn_idx].kptr_struct_meta;
+ struct bpf_insn addr[2] = { BPF_LD_IMM64(BPF_REG_2, (long)kptr_struct_meta) };
+
+ insn_buf[0] = addr[0];
+ insn_buf[1] = addr[1];
+ insn_buf[2] = *insn;
+ *cnt = 3;
}
return 0;
}
diff --git a/tools/testing/selftests/bpf/bpf_experimental.h b/tools/testing/selftests/bpf/bpf_experimental.h
index aeb6a7fcb7c4..8473395a11af 100644
--- a/tools/testing/selftests/bpf/bpf_experimental.h
+++ b/tools/testing/selftests/bpf/bpf_experimental.h
@@ -22,4 +22,17 @@ extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
/* Convenience macro to wrap over bpf_obj_new_impl */
#define bpf_obj_new(type) ((type *)bpf_obj_new_impl(bpf_core_type_id_local(type), NULL))
+/* Description
+ * Free an allocated object. All fields of the object that require
+ * destruction will be destructed before the storage is freed.
+ *
+ * The 'meta' parameter is a hidden argument that is ignored.
+ * Returns
+ * Void.
+ */
+extern void bpf_obj_drop_impl(void *kptr, void *meta) __ksym;
+
+/* Convenience macro to wrap over bpf_obj_drop_impl */
+#define bpf_obj_drop(kptr) bpf_obj_drop_impl(kptr, NULL)
+
#endif
--
2.38.1
next prev parent reply other threads:[~2022-11-11 19:34 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-11 19:31 [PATCH bpf-next v6 00/26] Allocated objects, BPF linked lists Kumar Kartikeya Dwivedi
2022-11-11 19:31 ` [PATCH bpf-next v6 01/26] bpf: Remove local kptr references in documentation Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 02/26] bpf: Remove BPF_MAP_OFF_ARR_MAX Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 03/26] bpf: Fix copy_map_value, zero_map_value Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 04/26] bpf: Support bpf_list_head in map values Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 05/26] bpf: Rename RET_PTR_TO_ALLOC_MEM Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 06/26] bpf: Rename MEM_ALLOC to MEM_RINGBUF Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 07/26] bpf: Refactor btf_struct_access Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 08/26] bpf: Introduce allocated objects support Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 09/26] bpf: Recognize lock and list fields in allocated objects Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 10/26] bpf: Verify ownership relationships for user BTF types Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 11/26] bpf: Allow locking bpf_spin_lock in allocated objects Kumar Kartikeya Dwivedi
2022-11-14 8:25 ` Dan Carpenter
2022-11-14 9:11 ` Kumar Kartikeya Dwivedi
2022-11-14 9:38 ` Dan Carpenter
2022-11-11 19:32 ` [PATCH bpf-next v6 12/26] bpf: Allow locking bpf_spin_lock global variables Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 13/26] bpf: Allow locking bpf_spin_lock in inner map values Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 14/26] bpf: Rewrite kfunc argument handling Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 15/26] bpf: Drop kfunc bits from btf_check_func_arg_match Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 16/26] bpf: Support constant scalar arguments for kfuncs Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 17/26] bpf: Introduce bpf_obj_new Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` Kumar Kartikeya Dwivedi [this message]
2022-11-11 19:32 ` [PATCH bpf-next v6 19/26] bpf: Permit NULL checking pointer with non-zero fixed offset Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 20/26] bpf: Introduce single ownership BPF linked list API Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 21/26] bpf: Add 'release on unlock' logic for bpf_list_push_{front,back} Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 22/26] selftests/bpf: Add __contains macro to bpf_experimental.h Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 23/26] selftests/bpf: Update spinlock selftest Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 24/26] selftests/bpf: Add failure test cases for spin lock pairing Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 25/26] selftests/bpf: Add BPF linked list API tests Kumar Kartikeya Dwivedi
2022-11-11 19:32 ` [PATCH bpf-next v6 26/26] selftests/bpf: Add BTF sanity tests Kumar Kartikeya Dwivedi
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