From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 856E1C43603 for ; Tue, 17 Dec 2019 04:06:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3296521775 for ; Tue, 17 Dec 2019 04:06:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="rNjt5GfR" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726907AbfLQEGK (ORCPT ); Mon, 16 Dec 2019 23:06:10 -0500 Received: from mail-ua1-f66.google.com ([209.85.222.66]:38564 "EHLO mail-ua1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726296AbfLQEGK (ORCPT ); Mon, 16 Dec 2019 23:06:10 -0500 Received: by mail-ua1-f66.google.com with SMTP id z17so2950295uac.5; Mon, 16 Dec 2019 20:06:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=rZR4WxfTXLuZhywVifXRiInVzhtxjrgCpN59zPaZHeo=; b=rNjt5GfRgReG+Nc4mKj4f4clWHMEGLEyTlaDb3vm8H+bEgZFSfQJULvvQvcEhPexRi Sb5KCoWBgxYfxkIs5bol6e4zB/PUbZEk/J8TUTaVoumu/2/MFvLogX9WAcy/OdahYGrn XrpiGMDBCqyACGemUl0Jv/uYScu/X0sMgQmRRPopSOLBM4aQ5+qL+wLbsVtu7eSLzQKr EWN0axJGHB6o6LNpHTMrBTdjlzI+eKviRbYPhmHXbHkluabX2D7Gya03hjLh9i9V14jA fBBxVXA1CPBQXrPsAND2WJwc+K78roFdqYJnXfk/UyZHBsxPo4phdtdKLTjNZJbqt45d k8xw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=rZR4WxfTXLuZhywVifXRiInVzhtxjrgCpN59zPaZHeo=; b=m2rFziPK9haDnSoc5S8VpvlgMINnwbShm6jiiqz/YP9H8FWuSbvn/Tn/rMlMH1z1Nr u/xyD6cpc8nBfYGnH6QvlHsDeA7eF6vPXiuhdcOmxGeybKuXvV6lCNklJpksiVIbBOFE Qp57OzT56ohu59/Ma2s6NaAWdU50/W0vLF2FCbiMUIhNb4SdaH9fZQNX3ZJwIg+8xMEh CnrpzKcKJ0DEqlUXrh1l70FFvGpAAtu3L+AbrCqMGas0ufrM+yTM+Q1tqKdWFO3IfexP ElPvIUBNXhhT3/dcU0PuSt6I0f1D+qV2VRhuGc5DyIyyq1/ahAdljC6zB5NrSqyBwU0q DvZw== X-Gm-Message-State: APjAAAUKDrEMyt7pOgFeUUhmfkyhhvw4SdXny6uYsQn5uUSVCpufc64W LGUUz96jFLUgS944Y9ZEj1QPO+uYABV+qztxK4E= X-Google-Smtp-Source: APXvYqxNoTQnB5p5K+Yx3oEfF3F/hDOhk/vV0pzSaGL83oQsOSkOB0y6/SVSt6bPfUiw22zNLD140zYjFxyDA3BrejY= X-Received: by 2002:ab0:b12:: with SMTP id b18mr1883895uak.90.1576555568966; Mon, 16 Dec 2019 20:06:08 -0800 (PST) MIME-Version: 1.0 References: <0117d6e17ba8b3b1273e5a964f87a71c1b2d8741.1576381512.git.ethercflow@gmail.com> In-Reply-To: From: Wenbo Zhang Date: Tue, 17 Dec 2019 12:05:58 +0800 Message-ID: Subject: Re: [PATCH bpf-next v12 1/2] bpf: add new helper get_file_path for mapping a file descriptor to a pathname To: Brendan Gregg Cc: bpf , Alexei Starovoitov , Daniel Borkmann , Yonghong Song , Andrii Nakryiko , Networking Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org > I just realized that among my tools that want the path, the input is eith= er: > A) syscall tracepoints: int fd > B) kprobes: struct file * > This serves (A). If we ever add a different helper for (B), we might > think that this helper was misnamed. Should it be called get_fd_path > instead? That leaves get_file_path available for a later "struct file > *" -> pathname helper. +1, I'll rename it in the next version. Brendan Gregg =E4=BA=8E2019=E5=B9=B412=E6=9C=8817=E6= =97=A5=E5=91=A8=E4=BA=8C =E4=B8=8A=E5=8D=886:09=E5=86=99=E9=81=93=EF=BC=9A > > On Sat, Dec 14, 2019 at 8:01 PM 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 > > > > 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 f= s/ > > - ensure we're in user context which is safe fot the help to run > > - filter unmountable pseudo filesystem, because they don't have real pa= th > > - 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 pointe= r > > 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 > > --- > > include/uapi/linux/bpf.h | 29 +++++++++++++- > > kernel/trace/bpf_trace.c | 70 ++++++++++++++++++++++++++++++++++ > > tools/include/uapi/linux/bpf.h | 29 +++++++++++++- > > 3 files changed, 126 insertions(+), 2 deletions(-) > > > > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h > > index dbbcf0b02970..71d9705df120 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_file_path(char *path, u32 size, int fd) > > + * Description > > + * Get **file** atrribute from the current task by *fd*, t= hen call > > + * **d_path** to get it's absolute path and copy it as str= ing into > > + * *path* of *size*. Notice the **path** don't support unm= ountable > > + * pseudo filesystems as they don't have path (eg: SOCKFS,= PIPEFS). > > + * The *size* must be strictly positive. On success, the h= elper > > + * makes sure that the *path* is NUL-terminated, and the b= uffer > > + * could be: > > + * - a regular full path (include mountable fs eg: /proc, = /sys) > > + * - a regular full path with "(deleted)" at the end. > > + * On failure, it is filled with zeroes. > > + * Return > > + * On success, returns the length of the copied string INC= LUDING > > + * the trailing NUL. > > + * > > + * 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_file_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..db9c0ec46a5d 100644 > > --- a/kernel/trace/bpf_trace.c > > +++ b/kernel/trace/bpf_trace.c > > @@ -762,6 +762,72 @@ static const struct bpf_func_proto bpf_send_signal= _proto =3D { > > .arg1_type =3D ARG_ANYTHING, > > }; > > > > +BPF_CALL_3(bpf_get_file_path, char *, dst, u32, size, int, fd) > > +{ > > + struct file *f; > > + char *p; > > + int ret =3D -EBADF; > > + > > + /* 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 =3D -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 =3D fget_raw(fd); > > + if (!f) > > + goto error; > > + > > + /* For unmountable pseudo filesystem, it seems to have no meani= ng > > + * to get their fake paths as they don't have path, and to be n= o > > + * 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 =3D -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 =3D d_path(&f->f_path, dst, size); > > + if (IS_ERR(p)) { > > + ret =3D PTR_ERR(p); > > + fput(f); > > + goto error; > > + } > > + > > + ret =3D strlen(p); > > + memmove(dst, p, ret); > > + dst[ret++] =3D '\0'; > > + fput(f); > > + return ret; > > + > > +error: > > + memset(dst, '0', size); > > + return ret; > > +} > > + > > +static const struct bpf_func_proto bpf_get_file_path_proto =3D { > > + .func =3D bpf_get_file_path, > > + .gpl_only =3D true, > > + .ret_type =3D RET_INTEGER, > > + .arg1_type =3D ARG_PTR_TO_UNINIT_MEM, > > + .arg2_type =3D ARG_CONST_SIZE, > > + .arg3_type =3D ARG_ANYTHING, > > +}; > > + > > static const struct bpf_func_proto * > > tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *pr= og) > > { > > @@ -953,6 +1019,8 @@ 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_file_path: > > + return &bpf_get_file_path_proto; > > default: > > return tracing_func_proto(func_id, prog); > > } > > @@ -1146,6 +1214,8 @@ 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_file_path: > > + return &bpf_get_file_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..71d9705df120 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_file_path(char *path, u32 size, int fd) > > + * Description > > + * Get **file** atrribute from the current task by *fd*, t= hen call > > + * **d_path** to get it's absolute path and copy it as str= ing into > > + * *path* of *size*. Notice the **path** don't support unm= ountable > > + * pseudo filesystems as they don't have path (eg: SOCKFS,= PIPEFS). > > + * The *size* must be strictly positive. On success, the h= elper > > + * makes sure that the *path* is NUL-terminated, and the b= uffer > > + * could be: > > + * - a regular full path (include mountable fs eg: /proc, = /sys) > > + * - a regular full path with "(deleted)" at the end. > > + * On failure, it is filled with zeroes. > > + * Return > > + * On success, returns the length of the copied string INC= LUDING > > + * the trailing NUL. > > + * > > + * 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_file_path), > > > I just realized that among my tools that want the path, the input is eith= er: > > A) syscall tracepoints: int fd > B) kprobes: struct file * > > This serves (A). If we ever add a different helper for (B), we might > think that this helper was misnamed. Should it be called get_fd_path > instead? That leaves get_file_path available for a later "struct file > *" -> pathname helper. > > Brendan > > -- > Brendan Gregg, Senior Performance Architect, Netflix