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bpf: Enable bpf_iter targets registering ctx argument types

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Commit b121b341e5 ("bpf: Add PTR_TO_BTF_ID_OR_NULL
support") adds a field btf_id_or_null_non0_off to
bpf_prog->aux structure to indicate that the
first ctx argument is PTR_TO_BTF_ID reg_type and
all others are PTR_TO_BTF_ID_OR_NULL.
This approach does not really scale if we have
other different reg types in the future, e.g.,
a pointer to a buffer.

This patch enables bpf_iter targets registering ctx argument
reg types which may be different from the default one.
For example, for pointers to structures, the default reg_type
is PTR_TO_BTF_ID for tracing program. The target can register
a particular pointer type as PTR_TO_BTF_ID_OR_NULL which can
be used by the verifier to enforce accesses.

Signed-off-by: Yonghong Song <yhs@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200513180221.2949882-1-yhs@fb.com
This commit is contained in:
Yonghong Song
2020-05-13 11:02:21 -07:00
committed by Alexei Starovoitov
parent ab2ee4fcb9
commit 3c32cc1bce
10 changed files with 60 additions and 12 deletions
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12
include/linux/bpf.h
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@@ -643,6 +643,12 @@ struct bpf_jit_poke_descriptor {
u16 reason;
};
/* reg_type info for ctx arguments */
struct bpf_ctx_arg_aux {
u32 offset;
enum bpf_reg_type reg_type;
};
struct bpf_prog_aux {
atomic64_t refcnt;
u32 used_map_cnt;
@@ -654,12 +660,13 @@ struct bpf_prog_aux {
u32 func_cnt; /* used by non-func prog as the number of func progs */
u32 func_idx; /* 0 for non-func prog, the index in func array for func prog */
u32 attach_btf_id; /* in-kernel BTF type id to attach to */
u32 ctx_arg_info_size;
const struct bpf_ctx_arg_aux *ctx_arg_info;
struct bpf_prog *linked_prog;
bool verifier_zext; /* Zero extensions has been inserted by verifier. */
bool offload_requested;
bool attach_btf_trace; /* true if attaching to BTF-enabled raw tp */
bool func_proto_unreliable;
bool btf_id_or_null_non0_off;
enum bpf_tramp_prog_type trampoline_prog_type;
struct bpf_trampoline *trampoline;
struct hlist_node tramp_hlist;
@@ -1139,12 +1146,15 @@ int bpf_obj_get_user(const char __user *pathname, int flags);
typedef int (*bpf_iter_init_seq_priv_t)(void *private_data);
typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data);
#define BPF_ITER_CTX_ARG_MAX 2
struct bpf_iter_reg {
const char *target;
const struct seq_operations *seq_ops;
bpf_iter_init_seq_priv_t init_seq_private;
bpf_iter_fini_seq_priv_t fini_seq_private;
u32 seq_priv_size;
u32 ctx_arg_info_size;
struct bpf_ctx_arg_aux ctx_arg_info[BPF_ITER_CTX_ARG_MAX];
};
struct bpf_iter_meta {