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7158005b4e
BPF filtering tests can sometime fail. Running the test in verbose mode shows the following: $ sudo perf test 42 42: BPF filter : 42.1: Basic BPF filtering : FAILED! 42.2: BPF pinning : Skip 42.3: BPF prologue generation : Skip $ perf --version perf version 4.18.0-425.3.1.el8.ppc64le $ sudo perf test -v 42 42: BPF filter : 42.1: Basic BPF filtering : --- start --- test child forked, pid 711060 ... bpf: config 'func=do_epoll_wait' is ok Looking at the vmlinux_path (8 entries long) Using /usr/lib/debug/lib/modules/4.18.0-425.3.1.el8.ppc64le/vmlinux for symbols Open Debuginfo file: /usr/lib/debug/.build-id/81/56f5a07f92ccb62c5600ba0e4aacfb5f3a7534.debug Try to find probe point from debuginfo. Matched function: do_epoll_wait [4ef8cb0] found inline addr: 0xc00000000061dbe4 Probe point found: __se_compat_sys_epoll_pwait+196 found inline addr: 0xc00000000061d9f4 Probe point found: __se_sys_epoll_pwait+196 found inline addr: 0xc00000000061d824 Probe point found: __se_sys_epoll_wait+36 Found 3 probe_trace_events. Opening /sys/kernel/tracing//kprobe_events write=1 ... BPF filter result incorrect, expected 56, got 56 samples test child finished with -1 ---- end ---- BPF filter subtest 1: FAILED! The statement above about the result being incorrect looks weird, and it is due to that particular perf build missing commit3e11300cdf("perf test: Fix bpf test sample mismatch reporting"). In reality, due to commit4b04e0decd("perf test: Fix basic bpf filtering test"), perf expects there to be 56*3 samples. However, the number of samples we receive is going to be dependent on where the probes are installed, which is dependent on where do_epoll_wait gets inlined. On s390x, it looks like probes at all the inlined locations are hit. But, that is not the case on ppc64le. Fix this by switching the test to instead use the syscall tracepoint. This ensures that we will only ever install a single event enabling us to reliably determine the sample count. Reported-by: Disha Goel <disgoel@linux.vnet.ibm.com> Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Cc: Kajol Jain <kjain@linux.ibm.com> Cc: bpf@vger.kernel.org Link: http://lore.kernel.org/lkml/20230123083224.276404-1-naveen.n.rao@linux.vnet.ibm.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
60 lines
1.8 KiB
C
60 lines
1.8 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* bpf-script-example.c
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* Test basic LLVM building
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*/
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#ifndef LINUX_VERSION_CODE
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# error Need LINUX_VERSION_CODE
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# error Example: for 4.2 kernel, put 'clang-opt="-DLINUX_VERSION_CODE=0x40200" into llvm section of ~/.perfconfig'
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#endif
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#define BPF_ANY 0
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#define BPF_MAP_TYPE_ARRAY 2
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#define BPF_FUNC_map_lookup_elem 1
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#define BPF_FUNC_map_update_elem 2
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static void *(*bpf_map_lookup_elem)(void *map, void *key) =
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(void *) BPF_FUNC_map_lookup_elem;
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static void *(*bpf_map_update_elem)(void *map, void *key, void *value, int flags) =
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(void *) BPF_FUNC_map_update_elem;
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/*
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* Following macros are taken from tools/lib/bpf/bpf_helpers.h,
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* and are used to create BTF defined maps. It is easier to take
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* 2 simple macros, than being able to include above header in
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* runtime.
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*
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* __uint - defines integer attribute of BTF map definition,
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* Such attributes are represented using a pointer to an array,
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* in which dimensionality of array encodes specified integer
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* value.
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*
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* __type - defines pointer variable with typeof(val) type for
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* attributes like key or value, which will be defined by the
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* size of the type.
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*/
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#define __uint(name, val) int (*name)[val]
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#define __type(name, val) typeof(val) *name
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#define SEC(NAME) __attribute__((section(NAME), used))
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struct {
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__uint(type, BPF_MAP_TYPE_ARRAY);
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__uint(max_entries, 1);
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__type(key, int);
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__type(value, int);
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} flip_table SEC(".maps");
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SEC("syscalls:sys_enter_epoll_pwait")
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int bpf_func__SyS_epoll_pwait(void *ctx)
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{
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int ind =0;
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int *flag = bpf_map_lookup_elem(&flip_table, &ind);
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int new_flag;
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if (!flag)
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return 0;
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/* flip flag and store back */
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new_flag = !*flag;
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bpf_map_update_elem(&flip_table, &ind, &new_flag, BPF_ANY);
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return new_flag;
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}
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char _license[] SEC("license") = "GPL";
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int _version SEC("version") = LINUX_VERSION_CODE;
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