[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

[Arnaldo Carvalho de Melo <acme@kernel.org>]

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@redhat.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
  ^C contended   total wait     max wait     avg wait         type   caller

           7     53.59 us     10.86 us      7.66 us     rwlock:R   start_this_handle+0xa0
           2     30.35 us     21.99 us     15.17 us      rwsem:R   iterate_dir+0x52
           1      9.04 us      9.04 us      9.04 us     rwlock:W   start_this_handle+0x291
           1      8.73 us      8.73 us      8.73 us     spinlock   raw_spin_rq_lock_nested+0x1e
  #
  # perf lock contention -abl find / > /dev/null
  ^C contended   total wait     max wait     avg wait            address   symbol

           1    262.96 ms    262.96 ms    262.96 ms   ffff8e67502d0170    (mutex)
          12    244.24 us     39.91 us     20.35 us   ffff8e6af56f8070   mmap_lock (rwsem)
           7     30.28 us      6.85 us      4.33 us   ffff8e6c865f1d40   rq_lock (spinlock)
           3      7.42 us      4.03 us      2.47 us   ffff8e6c864b1d40   rq_lock (spinlock)
           2      3.72 us      2.19 us      1.86 us   ffff8e6c86571d40   rq_lock (spinlock)
           1      2.42 us      2.42 us      2.42 us   ffff8e6c86471d40   rq_lock (spinlock)
           4      2.11 us       559 ns       527 ns   ffffffff9a146c80   rcu_state (spinlock)
           3      1.45 us       818 ns       482 ns   ffff8e674ae8384c    (rwlock)
           1       870 ns       870 ns       870 ns   ffff8e68456ee060    (rwlock)
           1       663 ns       663 ns       663 ns   ffff8e6c864f1d40   rq_lock (spinlock)
           1       573 ns       573 ns       573 ns   ffff8e6c86531d40   rq_lock (spinlock)
           1       472 ns       472 ns       472 ns   ffff8e6c86431740    (spinlock)
           1       397 ns       397 ns       397 ns   ffff8e67413a4f04    (spinlock)
  #
  # perf test offcpu
  95: perf record offcpu profiling tests                              : Ok
  #
  # perf kwork latency --use-bpf
  Starting trace, Hit <Ctrl+C> to stop and report
  ^C
    Kwork Name                     | Cpu  | Avg delay     | Count     | Max delay     | Max delay start     | Max delay end       |
   --------------------------------------------------------------------------------------------------------------------------------
    (w)flush_memcg_stats_dwork     | 0000 |   1056.212 ms |         2 |   2112.345 ms |     550113.229573 s |     550115.341919 s |
    (w)toggle_allocation_gate      | 0000 |     10.144 ms |        62 |    416.389 ms |     550113.453518 s |     550113.869907 s |
    (w)0xffff8e6748e28080          | 0002 |      0.623 ms |         1 |      0.623 ms |     550110.989841 s |     550110.990464 s |
    (w)vmstat_shepherd             | 0000 |      0.586 ms |        10 |      2.828 ms |     550111.971536 s |     550111.974364 s |
    (w)vmstat_update               | 0007 |      0.363 ms |         5 |      1.634 ms |     550113.222520 s |     550113.224154 s |
    (w)vmstat_update               | 0000 |      0.324 ms |        10 |      2.827 ms |     550111.971526 s |     550111.974354 s |
    (w)0xffff8e674c5f4a58          | 0002 |      0.102 ms |         5 |      0.134 ms |     550110.989839 s |     550110.989972 s |
    (w)psi_avgs_work               | 0001 |      0.086 ms |         3 |      0.107 ms |     550114.957852 s |     550114.957959 s |
    (w)psi_avgs_work               | 0000 |      0.079 ms |         5 |      0.100 ms |     550118.605668 s |     550118.605768 s |
    (w)kfree_rcu_monitor           | 0006 |      0.079 ms |         1 |      0.079 ms |     550110.925821 s |     550110.925900 s |
    (w)psi_avgs_work               | 0004 |      0.079 ms |         1 |      0.079 ms |     550109.581835 s |     550109.581914 s |
    (w)psi_avgs_work               | 0001 |      0.078 ms |         1 |      0.078 ms |     550109.197809 s |     550109.197887 s |
    (w)psi_avgs_work               | 0002 |      0.077 ms |         5 |      0.086 ms |     550110.669819 s |     550110.669905 s |
  <SNIP>
  # strace -e bpf -o perf-stat-bpf-counters.output perf stat -e cycles --bpf-counters sleep 1

   Performance counter stats for 'sleep 1':

           6,197,983      cycles

         1.003922848 seconds time elapsed

         0.000000000 seconds user
         0.002032000 seconds sys

  # head -7 perf-stat-bpf-counters.output
  bpf(BPF_OBJ_GET, {pathname="/sys/fs/bpf/perf_attr_map", bpf_fd=0, file_flags=0}, 16) = 3
  bpf(BPF_OBJ_GET_INFO_BY_FD, {info={bpf_fd=3, info_len=88, info=0x7ffcead64990}}, 16) = 0
  bpf(BPF_MAP_LOOKUP_ELEM, {map_fd=3, key=0x24129e0, value=0x7ffcead65a48, flags=BPF_ANY}, 32) = 0
  bpf(BPF_LINK_GET_FD_BY_ID, {link_id=1252}, 12) = -1 ENOENT (No such file or directory)
  bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_SOCKET_FILTER, insn_cnt=2, insns=0x7ffcead65780, license="GPL", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=0, func_info_rec_size=0, func_info=NULL, func_info_cnt=0, line_info_rec_size=0, line_info=NULL, line_info_cnt=0, attach_btf_id=0, attach_prog_fd=0}, 116) = 4
  bpf(BPF_PROG_LOAD, {prog_type=BPF_PROG_TYPE_SOCKET_FILTER, insn_cnt=2, insns=0x7ffcead65920, license="GPL", log_level=0, log_size=0, log_buf=NULL, kern_version=KERNEL_VERSION(0, 0, 0), prog_flags=0, prog_name="", prog_ifindex=0, expected_attach_type=BPF_CGROUP_INET_INGRESS, prog_btf_fd=0, func_info_rec_size=0, func_info=NULL, func_info_cnt=0, line_info_rec_size=0, line_info=NULL, line_info_cnt=0, attach_btf_id=0, attach_prog_fd=0, fd_array=NULL}, 128) = 4
  bpf(BPF_BTF_LOAD, {btf="\237\353\1\0\30\0\0\0\0\0\0\0\20\0\0\0\20\0\0\0\5\0\0\0\1\0\0\0\0\0\0\1"..., btf_log_buf=NULL, btf_size=45, btf_log_size=0, btf_log_level=0}, 28) = 4
  #

Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Co-developed-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/Makefile.perf            |  20 +---
 tools/perf/util/bpf_skel/.gitignore |   1 -
 tools/perf/util/bpf_skel/vmlinux.h  | 173 ++++++++++++++++++++++++++++
 3 files changed, 174 insertions(+), 20 deletions(-)
 create mode 100644 tools/perf/util/bpf_skel/vmlinux.h

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 48aba186ceb50792..61c33d100b2bcc90 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -1063,25 +1063,7 @@ $(BPFTOOL): | $(SKEL_TMP_OUT)
 	$(Q)CFLAGS= $(MAKE) -C ../bpf/bpftool \
 		OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
 
-VMLINUX_BTF_PATHS ?= $(if $(O),$(O)/vmlinux)				\
-		     $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)	\
-		     ../../vmlinux					\
-		     /sys/kernel/btf/vmlinux				\
-		     /boot/vmlinux-$(shell uname -r)
-VMLINUX_BTF ?= $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
-
-$(SKEL_OUT)/vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL)
-ifeq ($(VMLINUX_H),)
-	$(QUIET_GEN)$(BPFTOOL) btf dump file $< format c > $@ || \
-	(echo "Failure to generate vmlinux.h needed for the recommended BPF skeleton support." && \
-	echo "To disable this use the build option NO_BPF_SKEL=1." && \
-	echo "Alternatively point at a pre-generated vmlinux.h with VMLINUX_H=<path>." && \
-	false)
-else
-	$(Q)cp "$(VMLINUX_H)" $@
-endif
-
-$(SKEL_TMP_OUT)/%.bpf.o: util/bpf_skel/%.bpf.c $(LIBBPF) $(SKEL_OUT)/vmlinux.h | $(SKEL_TMP_OUT)
+$(SKEL_TMP_OUT)/%.bpf.o: util/bpf_skel/%.bpf.c $(LIBBPF) | $(SKEL_TMP_OUT)
 	$(QUIET_CLANG)$(CLANG) -g -O2 -target bpf -Wall -Werror $(BPF_INCLUDE) \
 	  -c $(filter util/bpf_skel/%.bpf.c,$^) -o $@ && $(LLVM_STRIP) -g $@
 
diff --git a/tools/perf/util/bpf_skel/.gitignore b/tools/perf/util/bpf_skel/.gitignore
index cd01455e1b53c3d9..7a1c832825de8445 100644
--- a/tools/perf/util/bpf_skel/.gitignore
+++ b/tools/perf/util/bpf_skel/.gitignore
@@ -1,4 +1,3 @@
 # SPDX-License-Identifier: GPL-2.0-only
 .tmp
 *.skel.h
-vmlinux.h
diff --git a/tools/perf/util/bpf_skel/vmlinux.h b/tools/perf/util/bpf_skel/vmlinux.h
new file mode 100644
index 0000000000000000..449b1ea91fc48143
--- /dev/null
+++ b/tools/perf/util/bpf_skel/vmlinux.h
@@ -0,0 +1,173 @@
+#ifndef __VMLINUX_H
+#define __VMLINUX_H
+
+#include <linux/bpf.h>
+#include <linux/types.h>
+#include <linux/perf_event.h>
+#include <stdbool.h>
+
+// non-UAPI kernel data structures, used in the .bpf.c BPF tool component.
+
+// Just the fields used in these tools preserving the access index so that
+// libbpf can fixup offsets with the ones used in the kernel when loading the
+// BPF bytecode, if they differ from what is used here.
+
+typedef __u8 u8;
+typedef __u32 u32;
+typedef __u64 u64;
+typedef __s64 s64;
+
+typedef int pid_t;
+
+enum cgroup_subsys_id {
+	perf_event_cgrp_id  = 8,
+};
+
+enum {
+	HI_SOFTIRQ = 0,
+	TIMER_SOFTIRQ,
+	NET_TX_SOFTIRQ,
+	NET_RX_SOFTIRQ,
+	BLOCK_SOFTIRQ,
+	IRQ_POLL_SOFTIRQ,
+	TASKLET_SOFTIRQ,
+	SCHED_SOFTIRQ,
+	HRTIMER_SOFTIRQ,
+	RCU_SOFTIRQ,    /* Preferable RCU should always be the last softirq */
+
+	NR_SOFTIRQS
+};
+
+typedef struct {
+	s64	counter;
+} __attribute__((preserve_access_index)) atomic64_t;
+
+typedef atomic64_t atomic_long_t;
+
+struct raw_spinlock {
+	int rawlock;
+} __attribute__((preserve_access_index));
+
+typedef struct raw_spinlock raw_spinlock_t;
+
+typedef struct {
+	struct raw_spinlock rlock;
+} __attribute__((preserve_access_index)) spinlock_t;
+
+struct sighand_struct {
+	spinlock_t siglock;
+} __attribute__((preserve_access_index));
+
+struct rw_semaphore {
+	atomic_long_t owner;
+} __attribute__((preserve_access_index));
+
+struct mutex {
+	atomic_long_t owner;
+} __attribute__((preserve_access_index));
+
+struct kernfs_node {
+	u64 id;
+} __attribute__((preserve_access_index));
+
+struct cgroup {
+	struct kernfs_node *kn;
+	int                level;
+}  __attribute__((preserve_access_index));
+
+struct cgroup_subsys_state {
+	struct cgroup *cgroup;
+} __attribute__((preserve_access_index));
+
+struct css_set {
+	struct cgroup_subsys_state *subsys[13];
+	struct cgroup *dfl_cgrp;
+} __attribute__((preserve_access_index));
+
+struct mm_struct {
+	struct rw_semaphore mmap_lock;
+} __attribute__((preserve_access_index));
+
+struct task_struct {
+	unsigned int	      flags;
+	struct mm_struct      *mm;
+	pid_t		      pid;
+	pid_t		      tgid;
+	char		      comm[16];
+	struct sighand_struct *sighand;
+	struct css_set	      *cgroups;
+} __attribute__((preserve_access_index));
+
+struct trace_entry {
+	short unsigned int type;
+	unsigned char	   flags;
+	unsigned char	   preempt_count;
+	int		   pid;
+} __attribute__((preserve_access_index));
+
+struct trace_event_raw_irq_handler_entry {
+	struct trace_entry ent;
+	int		   irq;
+	u32		   __data_loc_name;
+	char		   __data[];
+} __attribute__((preserve_access_index));
+
+struct trace_event_raw_irq_handler_exit {
+	struct trace_entry ent;
+	int		   irq;
+	int		   ret;
+	char		   __data[];
+} __attribute__((preserve_access_index));
+
+struct trace_event_raw_softirq {
+	struct trace_entry ent;
+	unsigned int	   vec;
+	char		   __data[];
+} __attribute__((preserve_access_index));
+
+struct trace_event_raw_workqueue_execute_start {
+	struct trace_entry ent;
+	void		   *work;
+	void		   *function;
+	char		   __data[];
+} __attribute__((preserve_access_index));
+
+struct trace_event_raw_workqueue_execute_end {
+	struct trace_entry ent;
+	void		   *work;
+	void		   *function;
+	char		  __data[];
+} __attribute__((preserve_access_index));
+
+struct trace_event_raw_workqueue_activate_work {
+	struct trace_entry ent;
+	void		   *work;
+	char		   __data[];
+} __attribute__((preserve_access_index));
+
+struct perf_sample_data {
+	u64			 addr;
+	u64			 period;
+	union perf_sample_weight weight;
+	u64			 txn;
+	union perf_mem_data_src	 data_src;
+	u64			 ip;
+	struct {
+		u32		 pid;
+		u32		 tid;
+	} tid_entry;
+	u64			 time;
+	u64			 id;
+	struct {
+		u32		 cpu;
+	} cpu_entry;
+	u64			 phys_addr;
+	u64			 data_page_size;
+	u64			 code_page_size;
+} __attribute__((__aligned__(64))) __attribute__((preserve_access_index));
+
+struct bpf_perf_event_data_kern {
+	struct perf_sample_data *data;
+	struct perf_event	*event;
+} __attribute__((preserve_access_index));
+#endif // __VMLINUX_H
-- 
2.39.2