linux-kernel - Re: [PATCH RFC/RFT] perf bpf skels: Stop using vmlinux.h generated from BTF, use subset of used structs + CO-RE. was Re: BPF skels in perf .Re: [GIT PULL] perf tools changes for v6.4

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 5 May 2023 22:43:36 +0200
From:   Jiri Olsa <olsajiri@...il.com>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <olsajiri@...il.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>,
        Namhyung Kim <namhyung@...nel.org>, Song Liu <song@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Clark Williams <williams@...hat.com>,
        Kate Carcia <kcarcia@...hat.com>, linux-kernel@...r.kernel.org,
        linux-perf-users@...r.kernel.org,
        Adrian Hunter <adrian.hunter@...el.com>,
        Changbin Du <changbin.du@...wei.com>,
        Hao Luo <haoluo@...gle.com>, James Clark <james.clark@....com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Roman Lozko <lozko.roma@...il.com>,
        Stephane Eranian <eranian@...gle.com>,
        Thomas Richter <tmricht@...ux.ibm.com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        bpf <bpf@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>,
        Yang Jihong <yangjihong1@...wei.com>,
        Mark Rutland <mark.rutland@....com>,
        Paul Clarke <pc@...ibm.com>
Subject: Re: [PATCH RFC/RFT] perf bpf skels: Stop using vmlinux.h generated
 from BTF, use subset of used structs + CO-RE. was Re: BPF skels in perf .Re:
 [GIT PULL] perf tools changes for v6.4

On Fri, May 05, 2023 at 10:04:47AM -0700, Ian Rogers wrote:
> On Fri, May 5, 2023 at 9:56 AM Arnaldo Carvalho de Melo <acme@...nel.org> wrote:
> >
> > Em Fri, May 05, 2023 at 10:33:15AM -0300, Arnaldo Carvalho de Melo escreveu:
> > > Em Fri, May 05, 2023 at 01:03:14AM +0200, Jiri Olsa escreveu:
> > > That with the preserve_access_index isn't needed, we need just the
> > > fields that we access in the tools, right?
> >
> > I'm now doing build test this in many distro containers, without the two
> > reverts, i.e. BPF skels continue as opt-out as in my pull request, to
> > test build and also for the functionality tests on the tools using such
> > bpf skels, see below, no touching of vmlinux nor BTF data during the
> > build.
> >
> > - Arnaldo
> >
> > From 882adaee50bc27f85374aeb2fbaa5b76bef60d05 Mon Sep 17 00:00:00 2001
> > From: Arnaldo Carvalho de Melo <acme@...hat.com>
> > Date: Thu, 4 May 2023 19:03:51 -0300
> > Subject: [PATCH 1/1] perf bpf skels: Stop using vmlinux.h generated from BTF,
> >  use subset of used structs + CO-RE
> >
> > Linus reported a build break due to using a vmlinux without a BTF elf
> > section to generate the vmlinux.h header with bpftool for use in the BPF
> > tools in tools/perf/util/bpf_skel/*.bpf.c.
> >
> > Instead add a vmlinux.h file with the structs needed with the fields the
> > tools need, marking the structs with __attribute__((preserve_access_index)),
> > so that libbpf's CO-RE code can fixup the struct field offsets.
> >
> > In some cases the vmlinux.h file that was being generated by bpftool
> > from the kernel BTF information was not needed at all, just including
> > linux/bpf.h, sometimes linux/perf_event.h was enough as non-UAPI
> > types were not being used.
> >
> > To keep te patch small, include those UAPI headers from the trimmed down
> > vmlinux.h file, that then provides the tools with just the structs and
> > the subset of its fields needed for them.
> >
> > Testing it:
> >
> >   # perf lock contention -b find / > /dev/null

I tested perf lock con -abv -L rcu_state sleep 1
and needed fix below

jirka


---
>From b12aea55f1171dc09cde2957f9019c84bda7adbb Mon Sep 17 00:00:00 2001
From: Jiri Olsa <jolsa@...nel.org>
Date: Fri, 5 May 2023 13:28:46 +0200
Subject: [PATCH] perf tools: Fix lock_contention bpf program

We need to define empty 'struct rq' so the runqueues gets
resolved properly:

  # ./perf lock con -b
  libbpf: extern (var ksym) 'runqueues': incompatible types, expected [99] fwd rq, but kernel has [19783] struct rq
  libbpf: failed to load object 'lock_contention_bpf'
  libbpf: failed to load BPF skeleton 'lock_contention_bpf': -22
  Failed to load lock-contention BPF skeleton

Also rq__old/rq__new need additional '_' so the suffix is ignored
properly.

Signed-off-by: Jiri Olsa <jolsa@...nel.org>
---
 tools/perf/util/bpf_skel/lock_contention.bpf.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/tools/perf/util/bpf_skel/lock_contention.bpf.c b/tools/perf/util/bpf_skel/lock_contention.bpf.c
index 8911e2a077d8..c2bf24c68c14 100644
--- a/tools/perf/util/bpf_skel/lock_contention.bpf.c
+++ b/tools/perf/util/bpf_skel/lock_contention.bpf.c
@@ -416,13 +416,15 @@ int contention_end(u64 *ctx)
 	return 0;
 }
 
+struct rq {};
+
 extern struct rq runqueues __ksym;
 
-struct rq__old {
+struct rq___old {
 	raw_spinlock_t lock;
 } __attribute__((preserve_access_index));
 
-struct rq__new {
+struct rq___new {
 	raw_spinlock_t __lock;
 } __attribute__((preserve_access_index));
 
@@ -434,8 +436,8 @@ int BPF_PROG(collect_lock_syms)
 
 	for (int i = 0; i < MAX_CPUS; i++) {
 		struct rq *rq = bpf_per_cpu_ptr(&runqueues, i);
-		struct rq__new *rq_new = (void *)rq;
-		struct rq__old *rq_old = (void *)rq;
+		struct rq___new *rq_new = (void *)rq;
+		struct rq___old *rq_old = (void *)rq;
 
 		if (rq == NULL)
 			break;
-- 
2.40.1