On Thu, Jul 15, 2021 at 8:15 AM Alan Maguire alan.maguire@oracle.com wrote:
Add a BTF dumper for typed data, so that the user can dump a typed version of the data provided.
The API is
int btf_dump__dump_type_data(struct btf_dump *d, __u32 id, void *data, size_t data_sz, const struct btf_dump_type_data_opts *opts);
...where the id is the BTF id of the data pointed to by the "void *" argument; for example the BTF id of "struct sk_buff" for a "struct skb *" data pointer. Options supported are
- a starting indent level (indent_lvl)
- a user-specified indent string which will be printed once per indent level; if NULL, tab is chosen but any string <= 32 chars can be provided.
- a set of boolean options to control dump display, similar to those used for BPF helper bpf_snprintf_btf(). Options are - compact : omit newlines and other indentation - skip_names: omit member names - emit_zeroes: show zero-value members
Default output format is identical to that dumped by bpf_snprintf_btf(), for example a "struct sk_buff" representation would look like this:
struct sk_buff){ (union){ (struct){ .next = (struct sk_buff *)0xffffffffffffffff, .prev = (struct sk_buff *)0xffffffffffffffff, (union){ .dev = (struct net_device *)0xffffffffffffffff, .dev_scratch = (long unsigned int)18446744073709551615, }, }, ...
If the data structure is larger than the *data_sz* number of bytes that are available in *data*, as much of the data as possible will be dumped and -E2BIG will be returned. This is useful as tracers will sometimes not be able to capture all of the data associated with a type; for example a "struct task_struct" is ~16k. Being able to specify that only a subset is available is important for such cases. On success, the amount of data dumped is returned.
Signed-off-by: Alan Maguire alan.maguire@oracle.com
tools/lib/bpf/btf.h | 19 ++ tools/lib/bpf/btf_dump.c | 819 ++++++++++++++++++++++++++++++++++++++++++++++- tools/lib/bpf/libbpf.map | 1 + 3 files changed, 834 insertions(+), 5 deletions(-)
[...]
+/* return size of type, or if base type overflows, return -E2BIG. */ +static int btf_dump_type_data_check_overflow(struct btf_dump *d,
const struct btf_type *t,__u32 id,const void *data,__u8 bits_offset)+{
__s64 size = btf__resolve_size(d->btf, id);if (size < 0 || size >= INT_MAX) {pr_warn("unexpected size [%lld] for id [%u]\n",size, id);
ppc64le arch doesn't like the %lld:
In file included from btf_dump.c:22: btf_dump.c: In function 'btf_dump_type_data_check_overflow': libbpf_internal.h:111:22: error: format '%lld' expects argument of type 'long long int', but argument 3 has type '__s64' {aka 'long int'} [-Werror=format=] 111 | libbpf_print(level, "libbpf: " fmt, ##__VA_ARGS__); \ | ^~~~~~~~~~ libbpf_internal.h:114:27: note: in expansion of macro '__pr' 114 | #define pr_warn(fmt, ...) __pr(LIBBPF_WARN, fmt, ##__VA_ARGS__) | ^~~~ btf_dump.c:1992:3: note: in expansion of macro 'pr_warn' 1992 | pr_warn("unexpected size [%lld] for id [%u]\n", | ^~~~~~~ btf_dump.c:1992:32: note: format string is defined here 1992 | pr_warn("unexpected size [%lld] for id [%u]\n", | ~~~^ | | | long long int | %ld
Cast to size_t and use %zu.
return -EINVAL;}
[...]