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author | Alan Maguire <alan.maguire@oracle.com> | 2020-09-28 12:31:05 +0100 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2020-09-28 18:26:58 -0700 |
commit | c4d0bfb45068d853a478b9067a95969b1886a30f (patch) | |
tree | 112e9bf23f951321551e59e731962057c34307a4 /include/linux/btf.h | |
parent | 31d0bc81637d8d974a6dad9827b765b4b70c89d7 (diff) | |
download | linux-stable-c4d0bfb45068d853a478b9067a95969b1886a30f.tar.gz linux-stable-c4d0bfb45068d853a478b9067a95969b1886a30f.tar.bz2 linux-stable-c4d0bfb45068d853a478b9067a95969b1886a30f.zip |
bpf: Add bpf_snprintf_btf helper
A helper is added to support tracing kernel type information in BPF
using the BPF Type Format (BTF). Its signature is
long bpf_snprintf_btf(char *str, u32 str_size, struct btf_ptr *ptr,
u32 btf_ptr_size, u64 flags);
struct btf_ptr * specifies
- a pointer to the data to be traced
- the BTF id of the type of data pointed to
- a flags field is provided for future use; these flags
are not to be confused with the BTF_F_* flags
below that control how the btf_ptr is displayed; the
flags member of the struct btf_ptr may be used to
disambiguate types in kernel versus module BTF, etc;
the main distinction is the flags relate to the type
and information needed in identifying it; not how it
is displayed.
For example a BPF program with a struct sk_buff *skb
could do the following:
static struct btf_ptr b = { };
b.ptr = skb;
b.type_id = __builtin_btf_type_id(struct sk_buff, 1);
bpf_snprintf_btf(str, sizeof(str), &b, sizeof(b), 0, 0);
Default output looks like this:
(struct sk_buff){
.transport_header = (__u16)65535,
.mac_header = (__u16)65535,
.end = (sk_buff_data_t)192,
.head = (unsigned char *)0x000000007524fd8b,
.data = (unsigned char *)0x000000007524fd8b,
.truesize = (unsigned int)768,
.users = (refcount_t){
.refs = (atomic_t){
.counter = (int)1,
},
},
}
Flags modifying display are as follows:
- BTF_F_COMPACT: no formatting around type information
- BTF_F_NONAME: no struct/union member names/types
- BTF_F_PTR_RAW: show raw (unobfuscated) pointer values;
equivalent to %px.
- BTF_F_ZERO: show zero-valued struct/union members;
they are not displayed by default
Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/1601292670-1616-4-git-send-email-alan.maguire@oracle.com
Diffstat (limited to 'include/linux/btf.h')
-rw-r--r-- | include/linux/btf.h | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/include/linux/btf.h b/include/linux/btf.h index d0f5d3c9ec3d..3e5cdc2ba963 100644 --- a/include/linux/btf.h +++ b/include/linux/btf.h @@ -6,6 +6,7 @@ #include <linux/types.h> #include <uapi/linux/btf.h> +#include <uapi/linux/bpf.h> #define BTF_TYPE_EMIT(type) ((void)(type *)0) @@ -59,10 +60,10 @@ const struct btf_type *btf_type_id_size(const struct btf *btf, * - BTF_SHOW_UNSAFE: skip use of bpf_probe_read() to safely read * data before displaying it. */ -#define BTF_SHOW_COMPACT (1ULL << 0) -#define BTF_SHOW_NONAME (1ULL << 1) -#define BTF_SHOW_PTR_RAW (1ULL << 2) -#define BTF_SHOW_ZERO (1ULL << 3) +#define BTF_SHOW_COMPACT BTF_F_COMPACT +#define BTF_SHOW_NONAME BTF_F_NONAME +#define BTF_SHOW_PTR_RAW BTF_F_PTR_RAW +#define BTF_SHOW_ZERO BTF_F_ZERO #define BTF_SHOW_UNSAFE (1ULL << 4) void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj, |