From mboxrd@z Thu Jan 1 00:00:00 1970 From: Y Song Subject: Re: [PATCH] [RFC] bpf: tracing: new helper bpf_get_current_cgroup_ino Date: Tue, 22 May 2018 20:33:24 -0700 Message-ID: References: <20180513173318.21680-1-alban@kinvolk.io> <20180521162609.lpdrnozowmzdn57m@ast-mbp.dhcp.thefacebook.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Alexei Starovoitov Cc: netdev , containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Alban Crequy , Alban Crequy , tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: containers.vger.kernel.org I did a quick prototyping and the above interface seems working fine. The kernel change: =============== [yhs@localhost bpf-next]$ git diff diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index 97446bbe2ca5..669b7383fddb 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -1976,7 +1976,8 @@ union bpf_attr { FN(fib_lookup), \ FN(sock_hash_update), \ FN(msg_redirect_hash), \ - FN(sk_redirect_hash), + FN(sk_redirect_hash), \ + FN(get_current_cgroup_id), /* 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 ce2cbbff27e4..e11e3298f911 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -493,6 +493,21 @@ static const struct bpf_func_proto bpf_current_task_under_cgroup_proto = { .arg2_type = ARG_ANYTHING, }; +BPF_CALL_0(bpf_get_current_cgroup_id) +{ + struct cgroup *cgrp = task_dfl_cgroup(current); + if (!cgrp) + return -EINVAL; + + return cgrp->kn->id.id; +} + +static const struct bpf_func_proto bpf_get_current_cgroup_id_proto = { + .func = bpf_get_current_cgroup_id, + .gpl_only = false, + .ret_type = RET_INTEGER, +}; + BPF_CALL_3(bpf_probe_read_str, void *, dst, u32, size, const void *, unsafe_ptr) { @@ -563,6 +578,8 @@ tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog) return &bpf_get_prandom_u32_proto; case BPF_FUNC_probe_read_str: return &bpf_probe_read_str_proto; + case BPF_FUNC_get_current_cgroup_id: + return &bpf_get_current_cgroup_id_proto; default: return NULL; } The following program can be used to print out a cgroup id given a cgroup path. [yhs@localhost cg]$ cat get_cgroup_id.c #define _GNU_SOURCE #include #include #include #include #include int main(int argc, char **argv) { int dirfd, err, flags, mount_id, fhsize; struct file_handle *fhp; char *pathname; if (argc != 2) { printf("usage: %s \n", argv[0]); return 1; } pathname = argv[1]; dirfd = AT_FDCWD; flags = 0; fhsize = sizeof(*fhp); fhp = malloc(fhsize); if (!fhp) return 1; err = name_to_handle_at(dirfd, pathname, fhp, &mount_id, flags); if (err >= 0) { printf("error\n"); return 1; } fhsize = sizeof(struct file_handle) + fhp->handle_bytes; fhp = realloc(fhp, fhsize); if (!fhp) return 1; err = name_to_handle_at(dirfd, pathname, fhp, &mount_id, flags); if (err < 0) perror("name_to_handle_at"); else { int i; printf("dir = %s, mount_id = %d\n", pathname, mount_id); printf("handle_bytes = %d, handle_type = %d\n", fhp->handle_bytes, fhp->handle_type); if (fhp->handle_bytes != 8) return 1; printf("cgroup_id = 0x%llx\n", *(unsigned long long *)fhp->f_handle); } return 0; } [yhs@localhost cg]$ Given a cgroup path, the user can get cgroup_id and use it in their bpf program for filtering purpose. I run a simple program t.c int main() { while(1) sleep(1); return 0; } in the cgroup v2 directory /home/yhs/tmp/yhs none on /home/yhs/tmp type cgroup2 (rw,relatime,seclabel) $ ./get_cgroup_id /home/yhs/tmp/yhs dir = /home/yhs/tmp/yhs, mount_id = 124 handle_bytes = 8, handle_type = 1 cgroup_id = 0x1000006b2 // the below command to get cgroup_id from the kernel for the // process compiled with t.c and ran under /home/yhs/tmp/yhs: $ sudo ./trace.py -p 4067 '__x64_sys_nanosleep "cgid = %llx", $cgid' PID TID COMM FUNC - 4067 4067 a.out __x64_sys_nanosleep cgid = 1000006b2 4067 4067 a.out __x64_sys_nanosleep cgid = 1000006b2 4067 4067 a.out __x64_sys_nanosleep cgid = 1000006b2 ^C[yhs@localhost tools]$ The kernel and user space cgid matches. Will provide a formal patch later. On Mon, May 21, 2018 at 5:24 PM, Y Song wrote: > On Mon, May 21, 2018 at 9:26 AM, Alexei Starovoitov > wrote: >> On Sun, May 13, 2018 at 07:33:18PM +0200, Alban Crequy wrote: >>> >>> +BPF_CALL_2(bpf_get_current_cgroup_ino, u32, hierarchy, u64, flags) >>> +{ >>> + // TODO: pick the correct hierarchy instead of the mem controller >>> + struct cgroup *cgrp = task_cgroup(current, memory_cgrp_id); >>> + >>> + if (unlikely(!cgrp)) >>> + return -EINVAL; >>> + if (unlikely(hierarchy)) >>> + return -EINVAL; >>> + if (unlikely(flags)) >>> + return -EINVAL; >>> + >>> + return cgrp->kn->id.ino; >> >> ino only is not enough to identify cgroup. It needs generation number too. >> I don't quite see how hierarchy and flags can be used in the future. >> Also why limit it to memcg? >> >> How about something like this instead: >> >> BPF_CALL_2(bpf_get_current_cgroup_id) >> { >> struct cgroup *cgrp = task_dfl_cgroup(current); >> >> return cgrp->kn->id.id; >> } >> The user space can use fhandle api to get the same 64-bit id. > > I think this should work. This will also be useful to bcc as user > space can encode desired id > in the bpf program and compared that id to the current cgroup id, so we can have > cgroup level tracing (esp. stat collection) support. To cope with > cgroup hierarchy, user can use > cgroup-array based approach or explicitly compare against multiple cgroup id's.