| Message ID | 1626180159-112996-2-git-send-email-chengshuyi@linux.alibaba.com |
|---|---|
| State | New |
| Headers | show |
| Series | Add btf_custom_path in bpf_obj_open_opts | expand |
On Tue, Jul 13, 2021 at 5:43 AM Shuyi Cheng <chengshuyi@linux.alibaba.com> wrote: > > btf_custom_path allows developers to load custom BTF, and subsequent > CO-RE will use custom BTF for relocation. > > Learn from Andrii's comments in [0], add the btf_custom_path parameter > to bpf_obj_open_opts, you can directly use the skeleton's > <objname>_bpf__open_opts function to pass in the btf_custom_path > parameter. > > Prior to this, there was also a developer who provided a patch with > similar functions. It is a pity that the follow-up did not continue to > advance. See [1]. > > [0]https://lore.kernel.org/bpf/CAEf4BzbJZLjNoiK8_VfeVg_Vrg=9iYFv+po-38SMe=UzwDKJ=Q@mail.gmail.com/#t > [1]https://yhbt.net/lore/all/CAEf4Bzbgw49w2PtowsrzKQNcxD4fZRE6AKByX-5-dMo-+oWHHA@mail.gmail.com/ > > Signed-off-by: Shuyi Cheng <chengshuyi@linux.alibaba.com> > --- > tools/lib/bpf/libbpf.c | 36 ++++++++++++++++++++++++++++++------ > tools/lib/bpf/libbpf.h | 9 ++++++++- > 2 files changed, 38 insertions(+), 7 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index 1e04ce7..6e11a7b 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -498,6 +498,13 @@ struct bpf_object { > * it at load time. > */ > struct btf *btf_vmlinux; > + /* Path to the custom BTF to be used for BPF CO-RE relocations. > + * This custom BTF completely replaces the use of vmlinux BTF > + * for the purpose of CO-RE relocations. > + * NOTE: any other BPF feature (e.g., fentry/fexit programs, > + * struct_ops, etc) will need actual kernel BTF at /sys/kernel/btf/vmlinux. > + */ this comment completely duplicates the one from bpf_object_open_opts, I'll remove or shorten it > + char *btf_custom_path; > /* vmlinux BTF override for CO-RE relocations */ > struct btf *btf_vmlinux_override; > /* Lazily initialized kernel module BTFs */ > @@ -2645,10 +2652,6 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) > struct bpf_program *prog; > int i; > > - /* CO-RE relocations need kernel BTF */ > - if (obj->btf_ext && obj->btf_ext->core_relo_info.len) > - return true; > - > /* Support for typed ksyms needs kernel BTF */ > for (i = 0; i < obj->nr_extern; i++) { > const struct extern_desc *ext; > @@ -2665,6 +2668,13 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) > return true; > } > > + /* CO-RE relocations need kernel BTF, only when btf_custom_path > + * is not specified > + */ > + if (obj->btf_ext && obj->btf_ext->core_relo_info.len > + && !obj->btf_custom_path) > + return true; not sure why you moved it, I'll move it back to minimize code churn > + > return false; > } > [...]
On 7/16/21 12:51 PM, Andrii Nakryiko wrote: > On Tue, Jul 13, 2021 at 5:43 AM Shuyi Cheng > <chengshuyi@linux.alibaba.com> wrote: >> >> btf_custom_path allows developers to load custom BTF, and subsequent >> CO-RE will use custom BTF for relocation. >> >> Learn from Andrii's comments in [0], add the btf_custom_path parameter >> to bpf_obj_open_opts, you can directly use the skeleton's >> <objname>_bpf__open_opts function to pass in the btf_custom_path >> parameter. >> >> Prior to this, there was also a developer who provided a patch with >> similar functions. It is a pity that the follow-up did not continue to >> advance. See [1]. >> >> [0]https://lore.kernel.org/bpf/CAEf4BzbJZLjNoiK8_VfeVg_Vrg=9iYFv+po-38SMe=UzwDKJ=Q@mail.gmail.com/#t >> [1]https://yhbt.net/lore/all/CAEf4Bzbgw49w2PtowsrzKQNcxD4fZRE6AKByX-5-dMo-+oWHHA@mail.gmail.com/ >> >> Signed-off-by: Shuyi Cheng <chengshuyi@linux.alibaba.com> >> --- >> tools/lib/bpf/libbpf.c | 36 ++++++++++++++++++++++++++++++------ >> tools/lib/bpf/libbpf.h | 9 ++++++++- >> 2 files changed, 38 insertions(+), 7 deletions(-) >> >> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c >> index 1e04ce7..6e11a7b 100644 >> --- a/tools/lib/bpf/libbpf.c >> +++ b/tools/lib/bpf/libbpf.c >> @@ -498,6 +498,13 @@ struct bpf_object { >> * it at load time. >> */ >> struct btf *btf_vmlinux; >> + /* Path to the custom BTF to be used for BPF CO-RE relocations. >> + * This custom BTF completely replaces the use of vmlinux BTF >> + * for the purpose of CO-RE relocations. >> + * NOTE: any other BPF feature (e.g., fentry/fexit programs, >> + * struct_ops, etc) will need actual kernel BTF at /sys/kernel/btf/vmlinux. >> + */ > > this comment completely duplicates the one from bpf_object_open_opts, > I'll remove or shorten it > >> + char *btf_custom_path; >> /* vmlinux BTF override for CO-RE relocations */ >> struct btf *btf_vmlinux_override; >> /* Lazily initialized kernel module BTFs */ >> @@ -2645,10 +2652,6 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) >> struct bpf_program *prog; >> int i; >> >> - /* CO-RE relocations need kernel BTF */ >> - if (obj->btf_ext && obj->btf_ext->core_relo_info.len) >> - return true; >> - >> /* Support for typed ksyms needs kernel BTF */ >> for (i = 0; i < obj->nr_extern; i++) { >> const struct extern_desc *ext; >> @@ -2665,6 +2668,13 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) >> return true; >> } >> >> + /* CO-RE relocations need kernel BTF, only when btf_custom_path >> + * is not specified >> + */ >> + if (obj->btf_ext && obj->btf_ext->core_relo_info.len >> + && !obj->btf_custom_path) >> + return true; > > not sure why you moved it, I'll move it back to minimize code churn You're right. 👍 regards, Shuyi > >> + >> return false; >> } >> > > [...] >
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 1e04ce7..6e11a7b 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -498,6 +498,13 @@ struct bpf_object { * it at load time. */ struct btf *btf_vmlinux; + /* Path to the custom BTF to be used for BPF CO-RE relocations. + * This custom BTF completely replaces the use of vmlinux BTF + * for the purpose of CO-RE relocations. + * NOTE: any other BPF feature (e.g., fentry/fexit programs, + * struct_ops, etc) will need actual kernel BTF at /sys/kernel/btf/vmlinux. + */ + char *btf_custom_path; /* vmlinux BTF override for CO-RE relocations */ struct btf *btf_vmlinux_override; /* Lazily initialized kernel module BTFs */ @@ -2645,10 +2652,6 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) struct bpf_program *prog; int i; - /* CO-RE relocations need kernel BTF */ - if (obj->btf_ext && obj->btf_ext->core_relo_info.len) - return true; - /* Support for typed ksyms needs kernel BTF */ for (i = 0; i < obj->nr_extern; i++) { const struct extern_desc *ext; @@ -2665,6 +2668,13 @@ static bool obj_needs_vmlinux_btf(const struct bpf_object *obj) return true; } + /* CO-RE relocations need kernel BTF, only when btf_custom_path + * is not specified + */ + if (obj->btf_ext && obj->btf_ext->core_relo_info.len + && !obj->btf_custom_path) + return true; + return false; } @@ -7554,7 +7564,7 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver) __bpf_object__open(const char *path, const void *obj_buf, size_t obj_buf_sz, const struct bpf_object_open_opts *opts) { - const char *obj_name, *kconfig; + const char *obj_name, *kconfig, *btf_tmp_path; struct bpf_program *prog; struct bpf_object *obj; char tmp_name[64]; @@ -7584,6 +7594,19 @@ int bpf_program__load(struct bpf_program *prog, char *license, __u32 kern_ver) obj = bpf_object__new(path, obj_buf, obj_buf_sz, obj_name); if (IS_ERR(obj)) return obj; + + btf_tmp_path = OPTS_GET(opts, btf_custom_path, NULL); + if (btf_tmp_path) { + if (strlen(btf_tmp_path) >= PATH_MAX) { + err = -ENAMETOOLONG; + goto out; + } + obj->btf_custom_path = strdup(btf_tmp_path); + if (!obj->btf_custom_path) { + err = -ENOMEM; + goto out; + } + } kconfig = OPTS_GET(opts, kconfig, NULL); if (kconfig) { @@ -8055,7 +8078,7 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr) err = err ? : bpf_object__sanitize_maps(obj); err = err ? : bpf_object__init_kern_struct_ops_maps(obj); err = err ? : bpf_object__create_maps(obj); - err = err ? : bpf_object__relocate(obj, attr->target_btf_path); + err = err ? : bpf_object__relocate(obj, obj->btf_custom_path ? : attr->target_btf_path); err = err ? : bpf_object__load_progs(obj, attr->log_level); if (obj->gen_loader) { @@ -8702,6 +8725,7 @@ void bpf_object__close(struct bpf_object *obj) for (i = 0; i < obj->nr_maps; i++) bpf_map__destroy(&obj->maps[i]); + zfree(&obj->btf_custom_path); zfree(&obj->kconfig); zfree(&obj->externs); obj->nr_extern = 0; diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 6e61342..102ee8e 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -94,8 +94,15 @@ struct bpf_object_open_opts { * system Kconfig for CONFIG_xxx externs. */ const char *kconfig; + /* Path to the custom BTF to be used for BPF CO-RE relocations. + * This custom BTF completely replaces the use of vmlinux BTF + * for the purpose of CO-RE relocations. + * NOTE: any other BPF feature (e.g., fentry/fexit programs, + * struct_ops, etc) will need actual kernel BTF at /sys/kernel/btf/vmlinux. + */ + char *btf_custom_path; }; -#define bpf_object_open_opts__last_field kconfig +#define bpf_object_open_opts__last_field btf_custom_path LIBBPF_API struct bpf_object *bpf_object__open(const char *path); LIBBPF_API struct bpf_object *
btf_custom_path allows developers to load custom BTF, and subsequent CO-RE will use custom BTF for relocation. Learn from Andrii's comments in [0], add the btf_custom_path parameter to bpf_obj_open_opts, you can directly use the skeleton's <objname>_bpf__open_opts function to pass in the btf_custom_path parameter. Prior to this, there was also a developer who provided a patch with similar functions. It is a pity that the follow-up did not continue to advance. See [1]. [0]https://lore.kernel.org/bpf/CAEf4BzbJZLjNoiK8_VfeVg_Vrg=9iYFv+po-38SMe=UzwDKJ=Q@mail.gmail.com/#t [1]https://yhbt.net/lore/all/CAEf4Bzbgw49w2PtowsrzKQNcxD4fZRE6AKByX-5-dMo-+oWHHA@mail.gmail.com/ Signed-off-by: Shuyi Cheng <chengshuyi@linux.alibaba.com> --- tools/lib/bpf/libbpf.c | 36 ++++++++++++++++++++++++++++++------ tools/lib/bpf/libbpf.h | 9 ++++++++- 2 files changed, 38 insertions(+), 7 deletions(-)