On Thu, Jul 15, 2021 at 8:15 AM Alan Maguire <alan.maguire@xxxxxxxxxx> 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@xxxxxxxxxx>
> ---
> 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;
> + }
> +
[...]
