On 4/10/20 3:36 PM, Andrii Nakryiko wrote:
On Wed, Apr 8, 2020 at 4:25 PM Yonghong Song <yhs@xxxxxx> wrote:A dumper bpf program is a tracing program with attach type BPF_TRACE_DUMP. During bpf program load, the load attribute attach_prog_fd carries the target directory fd. The program will be verified against btf_id of the target_proto. If the program is loaded successfully, the dump target, as represented as a relative path to /sys/kernel/bpfdump, will be remembered in prog->aux->dump_target, which will be used later to create dumpers. Signed-off-by: Yonghong Song <yhs@xxxxxx> --- include/linux/bpf.h | 2 ++ include/uapi/linux/bpf.h | 1 + kernel/bpf/dump.c | 40 ++++++++++++++++++++++++++++++++++ kernel/bpf/syscall.c | 8 ++++++- kernel/bpf/verifier.c | 15 +++++++++++++ tools/include/uapi/linux/bpf.h | 1 + 6 files changed, 66 insertions(+), 1 deletion(-)[...]+int bpf_dump_set_target_info(u32 target_fd, struct bpf_prog *prog) +{ + struct bpfdump_target_info *tinfo; + const char *target_proto; + struct file *target_file; + struct fd tfd; + int err = 0, btf_id; + + if (!btf_vmlinux) + return -EINVAL; + + tfd = fdget(target_fd); + target_file = tfd.file; + if (!target_file) + return -EBADF;fdput is missing (or rather err = -BADF; goto done; ?)
No need to do fdput if tfd.file is NULL.
+ + if (target_file->f_inode->i_op != &bpf_dir_iops) { + err = -EINVAL; + goto done; + } + + tinfo = target_file->f_inode->i_private; + target_proto = tinfo->target_proto; + btf_id = btf_find_by_name_kind(btf_vmlinux, target_proto, + BTF_KIND_FUNC); + + if (btf_id > 0) { + prog->aux->dump_target = tinfo->target; + prog->aux->attach_btf_id = btf_id; + } + + err = min(btf_id, 0);this min trick looks too clever... why not more straightforward and composable: if (btf_id < 0) { err = btf_id; goto done; } prog->aux->dump_target = tinfo->target; prog->aux->attach_btf_id = btf_id; ?
this can be done.
+done: + fdput(tfd); + return err; +} + int bpf_dump_reg_target(const char *target, const char *target_proto, const struct seq_operations *seq_ops, diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index 64783da34202..41005dee8957 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -2060,7 +2060,12 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr) prog->expected_attach_type = attr->expected_attach_type; prog->aux->attach_btf_id = attr->attach_btf_id; - if (attr->attach_prog_fd) { + if (type == BPF_PROG_TYPE_TRACING && + attr->expected_attach_type == BPF_TRACE_DUMP) { + err = bpf_dump_set_target_info(attr->attach_prog_fd, prog);looking at bpf_attr, it's not clear why attach_prog_fd and prog_ifindex were not combined into a single union field... this probably got missed? But in this case I'd say let's create a union { __u32 attach_prog_fd; __u32 attach_target_fd; (similar to terminology for BPF_PROG_ATTACH) }; instead of reusing not-exactly-matching field names?
I thought about this, but thinking to avoid uapi change (although compatible). Maybe we should. Let me think about this.
+ if (err) + goto free_prog_nouncharge; + } else if (attr->attach_prog_fd) { struct bpf_prog *tgt_prog; tgt_prog = bpf_prog_get(attr->attach_prog_fd); @@ -2145,6 +2150,7 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr) err = bpf_prog_new_fd(prog); if (err < 0) bpf_prog_put(prog); + return err;[...]
