On Fri, Jul 23, 2021 at 2:31 AM Quentin Monnet <quentin@xxxxxxxxxxxxx> wrote: > > 2021-07-22 17:39 UTC-0700 ~ Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> > > On Wed, Jul 21, 2021 at 8:38 AM Quentin Monnet <quentin@xxxxxxxxxxxxx> 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! > > OK will do. > I've seen other folks detailing the changes on individual patches, and > done so in the past, although it's true the current trend is to have it > in the cover letter (and I understand the motivation). > > > > >> > >> Signed-off-by: Quentin Monnet <quentin@xxxxxxxxxxxxx> > >> Acked-by: John Fastabend <john.fastabend@xxxxxxxxx> > >> --- > >> 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 > > I can do that, but I'll need to uncouple btf__get_from_id() from the new > function. If it calls btf__load_from_kernel_by_id() and > LIBBPF_STRICT_CLEAN_PTRS is set, it would change its return value. No it won't, if libbpf_get_error() is used right after the API call. With CLEAN_PTRS the result pointer is NULL but actual error is passed through errno. libbpf_get_error() knows about this and extracts error from errno if passed NULL pointer. With returning ERR_PTR(-errno) from btf__load_from_kernel_by_id() you are breaking CLEAN_PTRS guarantees. > > > > >> + > >> + 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). > > I thought about that but wasn't sure, OK will do. Ok, thanks. > > > > >> 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. > > Oh right, I saw that err was initialised at -EINVAL and did not notice > it was changed for the info_linear. I'll address it. cool, thanks
