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bpf: verifier: refactor check_attach_btf_id()

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The check_attach_btf_id() function really does three things:

1. It performs a bunch of checks on the program to ensure that the
   attachment is valid.

2. It stores a bunch of state about the attachment being requested in
   the verifier environment and struct bpf_prog objects.

3. It allocates a trampoline for the attachment.

This patch splits out (1.) and (3.) into separate functions which will
perform the checks, but return the computed values instead of directly
modifying the environment. This is done in preparation for reusing the
checks when the actual attachment is happening, which will allow tracing
programs to have multiple (compatible) attachments.

This also fixes a bug where a bunch of checks were skipped if a trampoline
already existed for the tracing target.

Fixes: 6ba43b761c ("bpf: Attachment verification for BPF_MODIFY_RETURN")
Fixes: 1e6c62a882 ("bpf: Introduce sleepable BPF programs")
Acked-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Toke Høiland-Jørgensen
2020-09-25 23:25:02 +02:00
committed by Alexei Starovoitov
parent efc68158c4
commit f7b12b6fea
4 changed files with 146 additions and 93 deletions
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19
include/linux/bpf.h
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@@ -606,6 +606,13 @@ struct bpf_trampoline {
struct bpf_ksym ksym;
};
struct bpf_attach_target_info {
struct btf_func_model fmodel;
long tgt_addr;
const char *tgt_name;
const struct btf_type *tgt_type;
};
#define BPF_DISPATCHER_MAX 48 /* Fits in 2048B */
struct bpf_dispatcher_prog {
@@ -633,9 +640,10 @@ static __always_inline unsigned int bpf_dispatcher_nop_func(
return bpf_func(ctx, insnsi);
}
#ifdef CONFIG_BPF_JIT
struct bpf_trampoline *bpf_trampoline_lookup(u64 key);
int bpf_trampoline_link_prog(struct bpf_prog *prog);
int bpf_trampoline_unlink_prog(struct bpf_prog *prog);
struct bpf_trampoline *bpf_trampoline_get(u64 key,
struct bpf_attach_target_info *tgt_info);
void bpf_trampoline_put(struct bpf_trampoline *tr);
#define BPF_DISPATCHER_INIT(_name) { \
.mutex = __MUTEX_INITIALIZER(_name.mutex), \
@@ -680,10 +688,6 @@ void bpf_image_ksym_del(struct bpf_ksym *ksym);
void bpf_ksym_add(struct bpf_ksym *ksym);
void bpf_ksym_del(struct bpf_ksym *ksym);
#else
static inline struct bpf_trampoline *bpf_trampoline_lookup(u64 key)
{
return NULL;
}
static inline int bpf_trampoline_link_prog(struct bpf_prog *prog)
{
return -ENOTSUPP;
@@ -692,6 +696,11 @@ static inline int bpf_trampoline_unlink_prog(struct bpf_prog *prog)
{
return -ENOTSUPP;
}
static inline struct bpf_trampoline *bpf_trampoline_get(u64 key,
struct bpf_attach_target_info *tgt_info)
{
return ERR_PTR(-EOPNOTSUPP);
}
static inline void bpf_trampoline_put(struct bpf_trampoline *tr) {}
#define DEFINE_BPF_DISPATCHER(name)
#define DECLARE_BPF_DISPATCHER(name)