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Date: Fri, 26 Jun 2020 17:42:34 -0700 From: Yonghong Song <yhs@...com> To: Song Liu <songliubraving@...com>, <bpf@...r.kernel.org>, <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org> CC: <peterz@...radead.org>, <ast@...nel.org>, <daniel@...earbox.net>, <kernel-team@...com>, <john.fastabend@...il.com>, <kpsingh@...omium.org> Subject: Re: [PATCH v3 bpf-next 4/4] selftests/bpf: add bpf_iter test with bpf_get_task_stack() On 6/26/20 5:26 PM, Song Liu wrote: > The new test is similar to other bpf_iter tests. It would be great if you can show some results from bpf_iter_task_stack.c dump. > > Signed-off-by: Song Liu <songliubraving@...com> > --- > .../selftests/bpf/prog_tests/bpf_iter.c | 17 ++++++ > .../selftests/bpf/progs/bpf_iter_task_stack.c | 53 +++++++++++++++++++ > 2 files changed, 70 insertions(+) > create mode 100644 tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > > diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c > index 1e2e0fced6e81..fed42755416db 100644 > --- a/tools/testing/selftests/bpf/prog_tests/bpf_iter.c > +++ b/tools/testing/selftests/bpf/prog_tests/bpf_iter.c > @@ -5,6 +5,7 @@ > #include "bpf_iter_netlink.skel.h" > #include "bpf_iter_bpf_map.skel.h" > #include "bpf_iter_task.skel.h" > +#include "bpf_iter_task_stack.skel.h" > #include "bpf_iter_task_file.skel.h" > #include "bpf_iter_tcp4.skel.h" > #include "bpf_iter_tcp6.skel.h" > @@ -110,6 +111,20 @@ static void test_task(void) > bpf_iter_task__destroy(skel); > } > > +static void test_task_stack(void) > +{ > + struct bpf_iter_task_stack *skel; > + > + skel = bpf_iter_task_stack__open_and_load(); > + if (CHECK(!skel, "bpf_iter_task_stack__open_and_load", > + "skeleton open_and_load failed\n")) > + return; > + > + do_dummy_read(skel->progs.dump_task_stack); > + > + bpf_iter_task_stack__destroy(skel); > +} > + > static void test_task_file(void) > { > struct bpf_iter_task_file *skel; > @@ -452,6 +467,8 @@ void test_bpf_iter(void) > test_bpf_map(); > if (test__start_subtest("task")) > test_task(); > + if (test__start_subtest("task_stack")) > + test_task_stack(); > if (test__start_subtest("task_file")) > test_task_file(); > if (test__start_subtest("tcp4")) > diff --git a/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > new file mode 100644 > index 0000000000000..39b21df17c3ee > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/bpf_iter_task_stack.c > @@ -0,0 +1,53 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2020 Facebook */ > +/* "undefine" structs in vmlinux.h, because we "override" them below */ > +#define bpf_iter_meta bpf_iter_meta___not_used > +#define bpf_iter__task bpf_iter__task___not_used > +#include "vmlinux.h" > +#undef bpf_iter_meta > +#undef bpf_iter__task > +#include <bpf/bpf_helpers.h> > +#include <bpf/bpf_tracing.h> > + > +char _license[] SEC("license") = "GPL"; > + > +struct bpf_iter_meta { > + struct seq_file *seq; > + __u64 session_id; > + __u64 seq_num; > +} __attribute__((preserve_access_index)); > + > +struct bpf_iter__task { > + struct bpf_iter_meta *meta; > + struct task_struct *task; > +} __attribute__((preserve_access_index)); Please take a look at bpf_iter_task.c. The above code can be simplified as #include "bpf_iter.h" #include <bpf/bpf_helpers.h> #include <bpf/bpf_tracing.h> > + > +#define MAX_STACK_TRACE_DEPTH 64 > +unsigned long entries[MAX_STACK_TRACE_DEPTH]; > +#define SIZE_OF_ULONG (sizeof(unsigned long)) > + > +SEC("iter/task") > +int dump_task_stack(struct bpf_iter__task *ctx) > +{ > + struct seq_file *seq = ctx->meta->seq; > + struct task_struct *task = ctx->task; > + long i, retlen; > + > + if (task == (void *)0) > + return 0; > + > + retlen = bpf_get_task_stack(task, entries, > + MAX_STACK_TRACE_DEPTH * SIZE_OF_ULONG, 0); > + if (retlen < 0) > + return 0; > + > + BPF_SEQ_PRINTF(seq, "pid: %8u num_entries: %8u\n", task->pid, > + retlen / SIZE_OF_ULONG); > + for (i = 0; i < MAX_STACK_TRACE_DEPTH; i++) { > + if (retlen > i * SIZE_OF_ULONG) > + BPF_SEQ_PRINTF(seq, "[<0>] %pB\n", (void *)entries[i]); > + } > + BPF_SEQ_PRINTF(seq, "\n"); > + > + return 0; > +} >
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