> nit: I'd avoid unnecessary goto end (and end label itself) by having > two explicit returns: > return 0; > error: > memset(...); Agree, I'll send a new patch with explicit returns. BTW Yonghong has pointed this on v1 too, but I didn't get the whole point at that time, just made a part of change. Thank you both. > This seems like a rather useful helper not just in tracing context. So > if maintainers are ok with that, maybe you can follow up with patch > that adds it in more BPF program types. Glad to hear this, I'll keep following up with it. Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx> 于2019年11月2日周六 下午1:37写道： > > On Fri, Nov 1, 2019 at 5:57 AM Wenbo Zhang <ethercflow@xxxxxxxxx> wrote: > > > > When people want to identify which file system files are being opened, > > read, and written to, they can use this helper with file descriptor as > > input to achieve this goal. Other pseudo filesystems are also supported. > > > > This requirement is mainly discussed here: > > > > https://github.com/iovisor/bcc/issues/237 > > > > v4->v5: addressed Andrii and Daniel's feedback > > - rename bpf_fd2path to bpf_get_file_path to be consistent with other > > helper's names > > - when fdget_raw fails, set ret to -EBADF instead of -EINVAL > > - remove fdput from fdget_raw's error path > > - use IS_ERR instead of IS_ERR_OR_NULL as d_path ether returns a pointer > > into the buffer or an error code if the path was too long > > - modify the normal path's return value to return copied string lengh > > including NUL > > - update this helper description's Return bits. > > > > v3->v4: addressed Daniel's feedback > > - fix missing fdput() > > - move fd2path from kernel/bpf/trace.c to kernel/trace/bpf_trace.c > > - move fd2path's test code to another patch > > - add comment to explain why use fdget_raw instead of fdget > > > > v2->v3: addressed Yonghong's feedback > > - remove unnecessary LOCKDOWN_BPF_READ > > - refactor error handling section for enhanced readability > > - provide a test case in tools/testing/selftests/bpf > > > > v1->v2: addressed Daniel's feedback > > - fix backward compatibility > > - add this helper description > > - fix signed-off name > > --- > > See nit below, but I'm fine with the current state as well. > > Acked-by: Andrii Nakryiko <andriin@xxxxxx> > > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper > > * function eBPF program intends to call > > diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c > > index f50bf19f7a05..fc9f577e65f5 100644 > > --- a/kernel/trace/bpf_trace.c > > +++ b/kernel/trace/bpf_trace.c > > @@ -683,6 +683,53 @@ static const struct bpf_func_proto bpf_send_signal_proto = { > > .arg1_type = ARG_ANYTHING, > > }; > > > > +BPF_CALL_3(bpf_get_file_path, char *, dst, u32, size, int, fd) > > +{ > > + struct fd f; > > + char *p; > > + int ret = -EBADF; > > + > > + /* Use fdget_raw instead of fdget to support O_PATH, and > > + * fdget_raw doesn't have any sleepable code, so it's ok > > + * to be here. > > + */ > > + f = fdget_raw(fd); > > + if (!f.file) > > + goto error; > > + > > + /* d_path doesn't have any sleepable code, so it's ok to > > + * be here. But it uses the current macro to get fs_struct > > + * (current->fs). So this helper shouldn't be called in > > + * interrupt context. > > + */ > > + p = d_path(&f.file->f_path, dst, size); > > + if (IS_ERR(p)) { > > + ret = PTR_ERR(p); > > + fdput(f); > > + goto error; > > + } > > + > > + ret = strlen(p); > > + memmove(dst, p, ret); > > + dst[ret++] = '\0'; > > + fdput(f); > > + goto end; > > + > > +error: > > + memset(dst, '0', size); > > +end: > > + return ret; > > nit: I'd avoid unnecessary goto end (and end label itself) by having > two explicit returns: > > return 0; > error: > memset(...); > return ret; > > > +} > > + > > +static const struct bpf_func_proto bpf_get_file_path_proto = { > > + .func = bpf_get_file_path, > > + .gpl_only = true, > > + .ret_type = RET_INTEGER, > > + .arg1_type = ARG_PTR_TO_UNINIT_MEM, > > + .arg2_type = ARG_CONST_SIZE, > > + .arg3_type = ARG_ANYTHING, > > +}; > > + > > static const struct bpf_func_proto * > > tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > > { > > @@ -735,6 +782,8 @@ tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > > #endif > > case BPF_FUNC_send_signal: > > return &bpf_send_signal_proto; > > + case BPF_FUNC_get_file_path: > > + return &bpf_get_file_path_proto; > > This seems like a rather useful helper not just in tracing context. So > if maintainers are ok with that, maybe you can follow up with patch > that adds it in more BPF program types. > > > default: > > return NULL; > > } > > [...]
