> Sorry about a little pedantic. In d_path() function comments, we have: > * Convert a dentry into an ASCII path name. If the entry has been deleted > * the string " (deleted)" is appended. Note that this is ambiguous. > Note that there is a space before "(deleted)". I would like to the above > changed to > - a regular full path with " (deleted)" is appended. Ah, so sorry about this, I should be more preciseness and thanks again for your preciseness and patience.I'll submit another revision to fix this. Yonghong Song <yhs@xxxxxx> 于2019年12月18日周三 上午12:29写道： > > > > On 12/17/19 1:47 AM, Wenbo Zhang 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 > > > > v12->v13: addressed Gregg and Yonghong's feedback > > - rename to get_fd_path > > - refactor code & comment to be clearer and more compliant > > > > v11->v12: addressed Alexei's feedback > > - only allow tracepoints to make sure it won't dead lock > > > > v10->v11: addressed Al and Alexei's feedback > > - fix missing fput() > > > > v9->v10: addressed Andrii's feedback > > - send this patch together with the patch selftests as one patch series > > > > v8->v9: > > - format helper description > > > > v7->v8: addressed Alexei's feedback > > - use fget_raw instead of fdget_raw, as fdget_raw is only used inside fs/ > > - ensure we're in user context which is safe fot the help to run > > - filter unmountable pseudo filesystem, because they don't have real path > > - supplement the description of this helper function > > > > v6->v7: > > - fix missing signed-off-by line > > > > v5->v6: addressed Andrii's feedback > > - avoid unnecessary goto end by having two explicit returns > > > > 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 length > > 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 > > > > Signed-off-by: Wenbo Zhang <ethercflow@xxxxxxxxx> > > Ack with still the minor issue below, not sure whether another revision > will be needed or not or the maintainer can just fix up before merging. > > Acked-by: Yonghong Song <yhs@xxxxxx> > > > > --- > > include/uapi/linux/bpf.h | 29 +++++++++++++- > > kernel/trace/bpf_trace.c | 69 ++++++++++++++++++++++++++++++++++ > > tools/include/uapi/linux/bpf.h | 29 +++++++++++++- > > 3 files changed, 125 insertions(+), 2 deletions(-) > > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > > index dbbcf0b02970..c1e4fd286614 100644 > > --- a/include/uapi/linux/bpf.h > > +++ b/include/uapi/linux/bpf.h > > @@ -2821,6 +2821,32 @@ union bpf_attr { > > * Return > > * On success, the strictly positive length of the string, including > > * the trailing NUL character. On error, a negative value. > > + * > > + * int bpf_get_fd_path(char *path, u32 size, int fd) > > + * Description > > + * Get **file** atrribute from the current task by *fd*, then call > > + * **d_path** to get it's absolute path and copy it as string into > > + * *path* of *size*. Notice the **path** don't support unmountable > > + * pseudo filesystems as they don't have path (eg: SOCKFS, PIPEFS). > > + * The *size* must be strictly positive. On success, the helper > > + * makes sure that the *path* is NUL-terminated, and the buffer > > + * could be: > > + * - a regular full path (include mountable fs eg: /proc, /sys) > > + * - a regular full path with "(deleted)" is appended. > > Sorry about a little pedantic. In d_path() function comments, we have: > * Convert a dentry into an ASCII path name. If the entry has been deleted > * the string " (deleted)" is appended. Note that this is ambiguous. > > Note that there is a space before "(deleted)". I would like to the above > changed to > - a regular full path with " (deleted)" is appended. > > > + * On failure, it is filled with zeroes. > > + * Return > > + * On success, returns the length of the copied string INCLUDING > > + * the trailing '\0'. > > + * > > + * On failure, the returned value is one of the following: > > + * > > + * **-EPERM** if no permission to get the path (eg: in irq ctx). > > + * > > + * **-EBADF** if *fd* is invalid. > > + * > > + * **-EINVAL** if *fd* corresponds to a unmountable pseudo fs > > + * > > + * **-ENAMETOOLONG** if full path is longer than *size* > > */ > > #define __BPF_FUNC_MAPPER(FN) \ > > FN(unspec), \ > > @@ -2938,7 +2964,8 @@ union bpf_attr { > > FN(probe_read_user), \ > > FN(probe_read_kernel), \ > > FN(probe_read_user_str), \ > > - FN(probe_read_kernel_str), > > + FN(probe_read_kernel_str), \ > > + FN(get_fd_path), > > > > /* 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 e5ef4ae9edb5..43a6aa6ad967 100644 > > --- a/kernel/trace/bpf_trace.c > > +++ b/kernel/trace/bpf_trace.c > > @@ -762,6 +762,71 @@ static const struct bpf_func_proto bpf_send_signal_proto = { > > .arg1_type = ARG_ANYTHING, > > }; > > > > +BPF_CALL_3(bpf_get_fd_path, char *, dst, u32, size, int, fd) > > +{ > > + int ret = -EBADF; > > + struct file *f; > > + char *p; > > + > > + /* Ensure we're in user context which is safe for the helper to > > + * run. This helper has no business in a kthread. > > + */ > > + if (unlikely(in_interrupt() || > > + current->flags & (PF_KTHREAD | PF_EXITING))) { > > + ret = -EPERM; > > + goto error; > > + } > > + > > + /* Use fget_raw instead of fget to support O_PATH, and it doesn't > > + * have any sleepable code, so it's ok to be here. > > + */ > > + f = fget_raw(fd); > > + if (!f) > > + goto error; > > + > > + /* For unmountable pseudo filesystem, it seems to have no meaning > > + * to get their fake paths as they don't have path, and to be no > > + * way to validate this function pointer can be always safe to call > > + * in the current context. > > + */ > > + if (f->f_path.dentry->d_op && f->f_path.dentry->d_op->d_dname) { > > + ret = -EINVAL; > > + fput(f); > > + goto error; > > + } > > + > > + /* After filter unmountable pseudo filesytem, d_path won't call > > + * dentry->d_op->d_name(), the normally path doesn't have any > > + * sleepable code, and despite it uses the current macro to get > > + * fs_struct (current->fs), we've already ensured we're in user > > + * context, so it's ok to be here. > > + */ > > + p = d_path(&f->f_path, dst, size); > > + if (IS_ERR(p)) { > > + ret = PTR_ERR(p); > > + fput(f); > > + goto error; > > + } > > + > > + ret = strlen(p) + 1; > > + memmove(dst, p, ret); > > + fput(f); > > + return ret; > > + > > +error: > > + memset(dst, '0', size); > > + return ret; > > +} > > + > > +static const struct bpf_func_proto bpf_get_fd_path_proto = { > > + .func = bpf_get_fd_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) > > { > > @@ -953,6 +1018,8 @@ tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > > return &bpf_get_stackid_proto_tp; > > case BPF_FUNC_get_stack: > > return &bpf_get_stack_proto_tp; > > + case BPF_FUNC_get_fd_path: > > + return &bpf_get_fd_path_proto; > > default: > > return tracing_func_proto(func_id, prog); > > } > > @@ -1146,6 +1213,8 @@ raw_tp_prog_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) > > return &bpf_get_stackid_proto_raw_tp; > > case BPF_FUNC_get_stack: > > return &bpf_get_stack_proto_raw_tp; > > + case BPF_FUNC_get_fd_path: > > + return &bpf_get_fd_path_proto; > > default: > > return tracing_func_proto(func_id, prog); > > } > > diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h > > index dbbcf0b02970..c1e4fd286614 100644 > > --- a/tools/include/uapi/linux/bpf.h > > +++ b/tools/include/uapi/linux/bpf.h > > @@ -2821,6 +2821,32 @@ union bpf_attr { > > * Return > > * On success, the strictly positive length of the string, including > > * the trailing NUL character. On error, a negative value. > > + * > > + * int bpf_get_fd_path(char *path, u32 size, int fd) > > + * Description > > + * Get **file** atrribute from the current task by *fd*, then call > > + * **d_path** to get it's absolute path and copy it as string into > > + * *path* of *size*. Notice the **path** don't support unmountable > > + * pseudo filesystems as they don't have path (eg: SOCKFS, PIPEFS). > > + * The *size* must be strictly positive. On success, the helper > > + * makes sure that the *path* is NUL-terminated, and the buffer > > + * could be: > > + * - a regular full path (include mountable fs eg: /proc, /sys) > > + * - a regular full path with "(deleted)" is appended. > > + * On failure, it is filled with zeroes. > > + * Return > > + * On success, returns the length of the copied string INCLUDING > > + * the trailing '\0'. > > + * > > + * On failure, the returned value is one of the following: > > + * > > + * **-EPERM** if no permission to get the path (eg: in irq ctx). > > + * > > + * **-EBADF** if *fd* is invalid. > > + * > > + * **-EINVAL** if *fd* corresponds to a unmountable pseudo fs > > + * > > + * **-ENAMETOOLONG** if full path is longer than *size* > > */ > > #define __BPF_FUNC_MAPPER(FN) \ > > FN(unspec), \ > > @@ -2938,7 +2964,8 @@ union bpf_attr { > > FN(probe_read_user), \ > > FN(probe_read_kernel), \ > > FN(probe_read_user_str), \ > > - FN(probe_read_kernel_str), > > + FN(probe_read_kernel_str), \ > > + FN(get_fd_path), > > > > /* integer value in 'imm' field of BPF_CALL instruction selects which helper > > * function eBPF program intends to call > >
