Re: [PATCH bpf-next v2 2/5] libbpf: rename btf__get_from_id() as btf__load_from_kernel_by_id()
From: Andrii Nakryiko <hidden>
Date: 2021-07-23 00:39:58
Also in:
bpf
On Wed, Jul 21, 2021 at 8:38 AM Quentin Monnet [off-list ref] wrote:
Rename function btf__get_from_id() as btf__load_from_kernel_by_id() to better indicate what the function does. Change the new function so that, instead of requiring a pointer to the pointer to update and returning with an error code, it takes a single argument (the id of the BTF object) and returns the corresponding pointer. This is more in line with the existing constructors. The other tools calling the deprecated btf__get_from_id() function will be updated in a future commit. References: - https://github.com/libbpf/libbpf/issues/278 - https://github.com/libbpf/libbpf/wiki/Libbpf:-the-road-to-v1.0#btfh-apis v2: - Instead of a simple renaming, change the new function to make it return the pointer to the btf struct. - API v0.5.0 instead of v0.6.0.
We generally keep such version changes to cover letters. It keeps each individual commit clean and collects full history in the cover letter which becomes a body of merge commit when the whole patch set is applied. For next revision please consolidate the history in the cover letter. Thanks!
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Signed-off-by: Quentin Monnet <redacted> Acked-by: John Fastabend <john.fastabend@gmail.com> --- tools/lib/bpf/btf.c | 25 +++++++++++++++++-------- tools/lib/bpf/btf.h | 1 + tools/lib/bpf/libbpf.c | 5 +++-- tools/lib/bpf/libbpf.map | 1 + 4 files changed, 22 insertions(+), 10 deletions(-)diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c index 7e0de560490e..6654bdee7ad7 100644 --- a/tools/lib/bpf/btf.c +++ b/tools/lib/bpf/btf.c@@ -1383,21 +1383,30 @@ struct btf *btf_get_from_fd(int btf_fd, struct btf *base_btf) return btf; } +struct btf *btf__load_from_kernel_by_id(__u32 id) +{ + struct btf *btf; + int btf_fd; + + btf_fd = bpf_btf_get_fd_by_id(id); + if (btf_fd < 0) + return ERR_PTR(-errno);
please use libbpf_err_ptr() for consistency, see bpf_object__open_mem() for an example
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+ + btf = btf_get_from_fd(btf_fd, NULL); + close(btf_fd); + + return libbpf_ptr(btf); +} + int btf__get_from_id(__u32 id, struct btf **btf) { struct btf *res; - int err, btf_fd; + int err; *btf = NULL; - btf_fd = bpf_btf_get_fd_by_id(id); - if (btf_fd < 0) - return libbpf_err(-errno); - - res = btf_get_from_fd(btf_fd, NULL); + res = btf__load_from_kernel_by_id(id); err = libbpf_get_error(res); - close(btf_fd); - if (err) return libbpf_err(err);diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h index fd8a21d936ef..3db9446bc133 100644 --- a/tools/lib/bpf/btf.h +++ b/tools/lib/bpf/btf.h@@ -68,6 +68,7 @@ LIBBPF_API const void *btf__get_raw_data(const struct btf *btf, __u32 *size); LIBBPF_API const char *btf__name_by_offset(const struct btf *btf, __u32 offset); LIBBPF_API const char *btf__str_by_offset(const struct btf *btf, __u32 offset); LIBBPF_API int btf__get_from_id(__u32 id, struct btf **btf); +LIBBPF_API struct btf *btf__load_from_kernel_by_id(__u32 id);
let's move this definition to after btf__parse() to keep all "constructors" together (we can move btf__get_from_id() there for completeness as well, I suppose).
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LIBBPF_API int btf__get_map_kv_tids(const struct btf *btf, const char *map_name, __u32 expected_key_size, __u32 expected_value_size,diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 242e97892043..eff005b1eba1 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c@@ -9576,8 +9576,8 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd) { struct bpf_prog_info_linear *info_linear; struct bpf_prog_info *info; - struct btf *btf = NULL; int err = -EINVAL; + struct btf *btf; info_linear = bpf_program__get_prog_info_linear(attach_prog_fd, 0); err = libbpf_get_error(info_linear);@@ -9591,7 +9591,8 @@ static int libbpf_find_prog_btf_id(const char *name, __u32 attach_prog_fd) pr_warn("The target program doesn't have BTF\n"); goto out; } - if (btf__get_from_id(info->btf_id, &btf)) { + btf = btf__load_from_kernel_by_id(info->btf_id); + if (libbpf_get_error(btf)) {
there seems to be a bug in existing code and you are keeping it. On error err will be 0. Let's fix it. Same for above if (!info->btf_id), please fix that as well while you are at it.
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pr_warn("Failed to get BTF of the program\n"); goto out; }diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map index f7d52d76ca3a..ca8cc7a7faad 100644 --- a/tools/lib/bpf/libbpf.map +++ b/tools/lib/bpf/libbpf.map@@ -373,6 +373,7 @@ LIBBPF_0.5.0 { bpf_map__initial_value; bpf_map_lookup_and_delete_elem_flags; bpf_object__gen_loader; + btf__load_from_kernel_by_id; btf__load_into_kernel; btf_dump__dump_type_data; libbpf_set_strict_mode; --2.30.2