| Message ID | 20210830173424.1385796-4-memxor@gmail.com (mailing list archive) |
|---|---|
| State | RFC |
| Delegated to: | BPF |
| Headers | show |
| Series | Support kernel module function calls from eBPF | expand |
On Mon, Aug 30, 2021 at 10:34 AM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote: > -ENOCOMMITMESSAGE? > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> > --- > tools/lib/bpf/bpf.c | 3 ++ > tools/lib/bpf/libbpf.c | 71 +++++++++++++++++++++++++++++++-- > tools/lib/bpf/libbpf_internal.h | 2 + > 3 files changed, 73 insertions(+), 3 deletions(-) > [...] > @@ -515,6 +521,13 @@ struct bpf_object { > void *priv; > bpf_object_clear_priv_t clear_priv; > > + struct { > + struct hashmap *map; > + int *fds; > + size_t cap_cnt; > + __u32 n_fds; > + } kfunc_btf_fds; > + > char path[]; > }; > #define obj_elf_valid(o) ((o)->efile.elf) > @@ -5327,6 +5340,7 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog) > ext = &obj->externs[relo->sym_off]; > insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL; > insn[0].imm = ext->ksym.kernel_btf_id; > + insn[0].off = ext->ksym.offset; Just a few lines above we use insn[1].imm = ext->ksym.kernel_btf_obj_fd; for EXT_KSYM (for variables). Why are you inventing a new form if we already have a pretty consistent pattern? > break; > case RELO_SUBPROG_ADDR: > if (insn[0].src_reg != BPF_PSEUDO_FUNC) { [...]
On Wed, Sep 01, 2021 at 06:25:14AM IST, Andrii Nakryiko wrote: > On Mon, Aug 30, 2021 at 10:34 AM Kumar Kartikeya Dwivedi > <memxor@gmail.com> wrote: > > > > -ENOCOMMITMESSAGE? > > > Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> > > --- > > tools/lib/bpf/bpf.c | 3 ++ > > tools/lib/bpf/libbpf.c | 71 +++++++++++++++++++++++++++++++-- > > tools/lib/bpf/libbpf_internal.h | 2 + > > 3 files changed, 73 insertions(+), 3 deletions(-) > > > > [...] > > > @@ -515,6 +521,13 @@ struct bpf_object { > > void *priv; > > bpf_object_clear_priv_t clear_priv; > > > > + struct { > > + struct hashmap *map; > > + int *fds; > > + size_t cap_cnt; > > + __u32 n_fds; > > + } kfunc_btf_fds; > > + > > char path[]; > > }; > > #define obj_elf_valid(o) ((o)->efile.elf) > > @@ -5327,6 +5340,7 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog) > > ext = &obj->externs[relo->sym_off]; > > insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL; > > insn[0].imm = ext->ksym.kernel_btf_id; > > + insn[0].off = ext->ksym.offset; > > Just a few lines above we use insn[1].imm = > ext->ksym.kernel_btf_obj_fd; for EXT_KSYM (for variables). Why are you > inventing a new form if we already have a pretty consistent pattern? > That makes sense. This is all new to me, so I went with what was described in e6ac2450d6de (bpf: Support bpf program calling kernel function), but I'll rework it to encode the btf fd like that in the next spin. It also makes the everything far simpler. > > break; > > case RELO_SUBPROG_ADDR: > > if (insn[0].src_reg != BPF_PSEUDO_FUNC) { > > [...] -- Kartikeya
On Tue, Aug 31, 2021 at 7:27 PM Kumar Kartikeya Dwivedi <memxor@gmail.com> wrote: > > > @@ -5327,6 +5340,7 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog) > > > ext = &obj->externs[relo->sym_off]; > > > insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL; > > > insn[0].imm = ext->ksym.kernel_btf_id; > > > + insn[0].off = ext->ksym.offset; > > > > Just a few lines above we use insn[1].imm = > > ext->ksym.kernel_btf_obj_fd; for EXT_KSYM (for variables). Why are you > > inventing a new form if we already have a pretty consistent pattern? > > > > That makes sense. This is all new to me, so I went with what was described in > e6ac2450d6de (bpf: Support bpf program calling kernel function), but I'll rework > it to encode the btf fd like that in the next spin. It also makes the everything > far simpler. Hmm. kfunc call is a call insn. There is no imm[1].
On Tue, Aug 31, 2021 at 7:59 PM Alexei Starovoitov <alexei.starovoitov@gmail.com> wrote: > > On Tue, Aug 31, 2021 at 7:27 PM Kumar Kartikeya Dwivedi > <memxor@gmail.com> wrote: > > > > @@ -5327,6 +5340,7 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog) > > > > ext = &obj->externs[relo->sym_off]; > > > > insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL; > > > > insn[0].imm = ext->ksym.kernel_btf_id; > > > > + insn[0].off = ext->ksym.offset; > > > > > > Just a few lines above we use insn[1].imm = > > > ext->ksym.kernel_btf_obj_fd; for EXT_KSYM (for variables). Why are you > > > inventing a new form if we already have a pretty consistent pattern? > > > > > > > That makes sense. This is all new to me, so I went with what was described in > > e6ac2450d6de (bpf: Support bpf program calling kernel function), but I'll rework > > it to encode the btf fd like that in the next spin. It also makes the everything > > far simpler. > > Hmm. kfunc call is a call insn. There is no imm[1]. Doh, right :( Never mind, we'll need to use fd_array for this. Either way, I don't think hashmap use is warranted here to find a BTF slot. Let's just do linear search, it's not like we are going to have thousands of module BTFs used by any single BPF program, right?
diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c index 2401fad090c5..df2d1ceba146 100644 --- a/tools/lib/bpf/bpf.c +++ b/tools/lib/bpf/bpf.c @@ -265,6 +265,9 @@ int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr) attr.line_info_cnt = load_attr->line_info_cnt; attr.line_info = ptr_to_u64(load_attr->line_info); + attr.kfunc_btf_fds = ptr_to_u64(load_attr->kfunc_btf_fds); + attr.kfunc_btf_fds_cnt = load_attr->kfunc_btf_fds_cnt; + if (load_attr->name) memcpy(attr.prog_name, load_attr->name, min(strlen(load_attr->name), (size_t)BPF_OBJ_NAME_LEN - 1)); diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 88d8825fc6f6..c4677ef97caa 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -419,6 +419,12 @@ struct extern_desc { /* local btf_id of the ksym extern's type. */ __u32 type_id; + /* offset to be patched in for insn->off, + * this is 0 for btf_vmlinux, and index + 1 + * for module BTF, where index is BTF index in + * obj->kfunc_btf_fds.fds array + */ + __u32 offset; } ksym; }; }; @@ -515,6 +521,13 @@ struct bpf_object { void *priv; bpf_object_clear_priv_t clear_priv; + struct { + struct hashmap *map; + int *fds; + size_t cap_cnt; + __u32 n_fds; + } kfunc_btf_fds; + char path[]; }; #define obj_elf_valid(o) ((o)->efile.elf) @@ -5327,6 +5340,7 @@ bpf_object__relocate_data(struct bpf_object *obj, struct bpf_program *prog) ext = &obj->externs[relo->sym_off]; insn[0].src_reg = BPF_PSEUDO_KFUNC_CALL; insn[0].imm = ext->ksym.kernel_btf_id; + insn[0].off = ext->ksym.offset; break; case RELO_SUBPROG_ADDR: if (insn[0].src_reg != BPF_PSEUDO_FUNC) { @@ -6122,6 +6136,11 @@ load_program(struct bpf_program *prog, struct bpf_insn *insns, int insns_cnt, load_attr.log_level = prog->log_level; load_attr.prog_flags = prog->prog_flags; + if (prog->obj->kfunc_btf_fds.n_fds) { + load_attr.kfunc_btf_fds = prog->obj->kfunc_btf_fds.fds; + load_attr.kfunc_btf_fds_cnt = prog->obj->kfunc_btf_fds.n_fds; + } + if (prog->obj->gen_loader) { bpf_gen__prog_load(prog->obj->gen_loader, &load_attr, prog - prog->obj->programs); @@ -6723,9 +6742,49 @@ static int bpf_object__resolve_ksym_func_btf_id(struct bpf_object *obj, } if (kern_btf != obj->btf_vmlinux) { - pr_warn("extern (func ksym) '%s': function in kernel module is not supported\n", - ext->name); - return -ENOTSUP; + size_t index; + void *value; + + /* Lazy initialize btf->fd index map */ + if (!obj->kfunc_btf_fds.map) { + obj->kfunc_btf_fds.map = hashmap__new(bpf_core_hash_fn, bpf_core_equal_fn, + NULL); + if (!obj->kfunc_btf_fds.map) + return -ENOMEM; + + obj->kfunc_btf_fds.fds = calloc(8, sizeof(*obj->kfunc_btf_fds.fds)); + if (!obj->kfunc_btf_fds.fds) { + hashmap__free(obj->kfunc_btf_fds.map); + return -ENOMEM; + } + obj->kfunc_btf_fds.cap_cnt = 8; + } + + if (!hashmap__find(obj->kfunc_btf_fds.map, kern_btf, &value)) { + size_t *cap_cnt = &obj->kfunc_btf_fds.cap_cnt; + /* Not found, insert BTF fd into slot, and grab next + * index from the fd array. + */ + ret = libbpf_ensure_mem((void **)&obj->kfunc_btf_fds.fds, + cap_cnt, sizeof(int), obj->kfunc_btf_fds.n_fds + 1); + if (ret) + return ret; + index = obj->kfunc_btf_fds.n_fds++; + obj->kfunc_btf_fds.fds[index] = kern_btf_fd; + value = (void *)index; + ret = hashmap__add(obj->kfunc_btf_fds.map, kern_btf, &value); + if (ret) + return ret; + + } else { + index = (size_t)value; + } + /* index starts from 0, so shift offset by 1 as offset == 0 is reserved + * for btf_vmlinux in the kernel + */ + ext->ksym.offset = index + 1; + } else { + ext->ksym.offset = 0; } kern_func = btf__type_by_id(kern_btf, kfunc_id); @@ -6901,6 +6960,12 @@ int bpf_object__load_xattr(struct bpf_object_load_attr *attr) err = bpf_gen__finish(obj->gen_loader); } + /* clean up kfunc_btf */ + hashmap__free(obj->kfunc_btf_fds.map); + obj->kfunc_btf_fds.map = NULL; + zfree(&obj->kfunc_btf_fds.fds); + obj->kfunc_btf_fds.cap_cnt = obj->kfunc_btf_fds.n_fds = 0; + /* clean up module BTFs */ for (i = 0; i < obj->btf_module_cnt; i++) { close(obj->btf_modules[i].fd); diff --git a/tools/lib/bpf/libbpf_internal.h b/tools/lib/bpf/libbpf_internal.h index 533b0211f40a..701719d9caaf 100644 --- a/tools/lib/bpf/libbpf_internal.h +++ b/tools/lib/bpf/libbpf_internal.h @@ -276,6 +276,8 @@ struct bpf_prog_load_params { __u32 log_level; char *log_buf; size_t log_buf_sz; + int *kfunc_btf_fds; + __u32 kfunc_btf_fds_cnt; }; int libbpf__bpf_prog_load(const struct bpf_prog_load_params *load_attr);
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com> --- tools/lib/bpf/bpf.c | 3 ++ tools/lib/bpf/libbpf.c | 71 +++++++++++++++++++++++++++++++-- tools/lib/bpf/libbpf_internal.h | 2 + 3 files changed, 73 insertions(+), 3 deletions(-)