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| author | Andrii Nakryiko <andriin@fb.com> | 2020-08-13 23:49:40 +0300 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-08-14 02:45:41 +0300 |
| commit | 44ad23dfbccbcd26d6ca504eba1ac55755864969 (patch) | |
| tree | c084f7613c5f37093196b24f057fe96657a24aae /tools/lib/bpf/btf_dump.c | |
| parent | 15728ad3e71c120278105f20fa65b3735e715e0f (diff) | |
| download | linux-44ad23dfbccbcd26d6ca504eba1ac55755864969.tar.xz | |
libbpf: Handle BTF pointer sizes more carefully
With libbpf and BTF it is pretty common to have libbpf built for one
architecture, while BTF information was generated for a different architecture
(typically, but not always, BPF). In such case, the size of a pointer might
differ betweem architectures. libbpf previously was always making an
assumption that pointer size for BTF is the same as native architecture
pointer size, but that breaks for cases where libbpf is built as 32-bit
library, while BTF is for 64-bit architecture.
To solve this, add heuristic to determine pointer size by searching for `long`
or `unsigned long` integer type and using its size as a pointer size. Also,
allow to override the pointer size with a new API btf__set_pointer_size(), for
cases where application knows which pointer size should be used. User
application can check what libbpf "guessed" by looking at the result of
btf__pointer_size(). If it's not 0, then libbpf successfully determined a
pointer size, otherwise native arch pointer size will be used.
For cases where BTF is parsed from ELF file, use ELF's class (32-bit or
64-bit) to determine pointer size.
Fixes: 8a138aed4a80 ("bpf: btf: Add BTF support to libbpf")
Fixes: 351131b51c7a ("libbpf: add btf_dump API for BTF-to-C conversion")
Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200813204945.1020225-5-andriin@fb.com
Diffstat (limited to 'tools/lib/bpf/btf_dump.c')
| -rw-r--r-- | tools/lib/bpf/btf_dump.c | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/tools/lib/bpf/btf_dump.c b/tools/lib/bpf/btf_dump.c index ac81f3f8957a..fe39bd774697 100644 --- a/tools/lib/bpf/btf_dump.c +++ b/tools/lib/bpf/btf_dump.c @@ -61,6 +61,7 @@ struct btf_dump { const struct btf_ext *btf_ext; btf_dump_printf_fn_t printf_fn; struct btf_dump_opts opts; + int ptr_sz; bool strip_mods; /* per-type auxiliary state */ @@ -139,6 +140,7 @@ struct btf_dump *btf_dump__new(const struct btf *btf, d->btf_ext = btf_ext; d->printf_fn = printf_fn; d->opts.ctx = opts ? opts->ctx : NULL; + d->ptr_sz = btf__pointer_size(btf) ? : sizeof(void *); d->type_names = hashmap__new(str_hash_fn, str_equal_fn, NULL); if (IS_ERR(d->type_names)) { @@ -804,7 +806,7 @@ static void btf_dump_emit_bit_padding(const struct btf_dump *d, int align, int lvl) { int off_diff = m_off - cur_off; - int ptr_bits = sizeof(void *) * 8; + int ptr_bits = d->ptr_sz * 8; if (off_diff <= 0) /* no gap */ |