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Message-ID: <CAP-5=fWKM09_cgOjEyDjLrs5KgvXv1vLbyBgTFAEV0Sr3f_3YA@mail.gmail.com>
Date: Wed, 20 Jul 2022 08:22:08 -0700
From: Ian Rogers <irogers@...gle.com>
To: Dmitry Vyukov <dvyukov@...gle.com>
Cc: Marco Elver <elver@...gle.com>,
Peter Zijlstra <peterz@...radead.org>,
Frederic Weisbecker <frederic@...nel.org>,
Ingo Molnar <mingo@...nel.org>,
Thomas Gleixner <tglx@...utronix.de>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
Michael Ellerman <mpe@...erman.id.au>,
linuxppc-dev@...ts.ozlabs.org, linux-perf-users@...r.kernel.org,
x86@...nel.org, linux-sh@...r.kernel.org,
kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 01/14] perf/hw_breakpoint: Add KUnit test for
constraints accounting
On Mon, Jul 4, 2022 at 8:11 AM Dmitry Vyukov <dvyukov@...gle.com> wrote:
>
> On Mon, 4 Jul 2022 at 17:06, Marco Elver <elver@...gle.com> wrote:
> >
> > Add KUnit test for hw_breakpoint constraints accounting, with various
> > interesting mixes of breakpoint targets (some care was taken to catch
> > interesting corner cases via bug-injection).
> >
> > The test cannot be built as a module because it requires access to
> > hw_breakpoint_slots(), which is not inlinable or exported on all
> > architectures.
> >
> > Signed-off-by: Marco Elver <elver@...gle.com>
>
> Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>
Acked-by: Ian Rogers <irogers@...gle.com>
Thanks,
Ian
> > ---
> > v3:
> > * Don't use raw_smp_processor_id().
> >
> > v2:
> > * New patch.
> > ---
> > kernel/events/Makefile | 1 +
> > kernel/events/hw_breakpoint_test.c | 323 +++++++++++++++++++++++++++++
> > lib/Kconfig.debug | 10 +
> > 3 files changed, 334 insertions(+)
> > create mode 100644 kernel/events/hw_breakpoint_test.c
> >
> > diff --git a/kernel/events/Makefile b/kernel/events/Makefile
> > index 8591c180b52b..91a62f566743 100644
> > --- a/kernel/events/Makefile
> > +++ b/kernel/events/Makefile
> > @@ -2,4 +2,5 @@
> > obj-y := core.o ring_buffer.o callchain.o
> >
> > obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
> > +obj-$(CONFIG_HW_BREAKPOINT_KUNIT_TEST) += hw_breakpoint_test.o
> > obj-$(CONFIG_UPROBES) += uprobes.o
> > diff --git a/kernel/events/hw_breakpoint_test.c b/kernel/events/hw_breakpoint_test.c
> > new file mode 100644
> > index 000000000000..433c5c45e2a5
> > --- /dev/null
> > +++ b/kernel/events/hw_breakpoint_test.c
> > @@ -0,0 +1,323 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * KUnit test for hw_breakpoint constraints accounting logic.
> > + *
> > + * Copyright (C) 2022, Google LLC.
> > + */
> > +
> > +#include <kunit/test.h>
> > +#include <linux/cpumask.h>
> > +#include <linux/hw_breakpoint.h>
> > +#include <linux/kthread.h>
> > +#include <linux/perf_event.h>
> > +#include <asm/hw_breakpoint.h>
> > +
> > +#define TEST_REQUIRES_BP_SLOTS(test, slots) \
> > + do { \
> > + if ((slots) > get_test_bp_slots()) { \
> > + kunit_skip((test), "Requires breakpoint slots: %d > %d", slots, \
> > + get_test_bp_slots()); \
> > + } \
> > + } while (0)
> > +
> > +#define TEST_EXPECT_NOSPC(expr) KUNIT_EXPECT_EQ(test, -ENOSPC, PTR_ERR(expr))
> > +
> > +#define MAX_TEST_BREAKPOINTS 512
> > +
> > +static char break_vars[MAX_TEST_BREAKPOINTS];
> > +static struct perf_event *test_bps[MAX_TEST_BREAKPOINTS];
> > +static struct task_struct *__other_task;
> > +
> > +static struct perf_event *register_test_bp(int cpu, struct task_struct *tsk, int idx)
> > +{
> > + struct perf_event_attr attr = {};
> > +
> > + if (WARN_ON(idx < 0 || idx >= MAX_TEST_BREAKPOINTS))
> > + return NULL;
> > +
> > + hw_breakpoint_init(&attr);
> > + attr.bp_addr = (unsigned long)&break_vars[idx];
> > + attr.bp_len = HW_BREAKPOINT_LEN_1;
> > + attr.bp_type = HW_BREAKPOINT_RW;
> > + return perf_event_create_kernel_counter(&attr, cpu, tsk, NULL, NULL);
> > +}
> > +
> > +static void unregister_test_bp(struct perf_event **bp)
> > +{
> > + if (WARN_ON(IS_ERR(*bp)))
> > + return;
> > + if (WARN_ON(!*bp))
> > + return;
> > + unregister_hw_breakpoint(*bp);
> > + *bp = NULL;
> > +}
> > +
> > +static int get_test_bp_slots(void)
> > +{
> > + static int slots;
> > +
> > + if (!slots)
> > + slots = hw_breakpoint_slots(TYPE_DATA);
> > +
> > + return slots;
> > +}
> > +
> > +static void fill_one_bp_slot(struct kunit *test, int *id, int cpu, struct task_struct *tsk)
> > +{
> > + struct perf_event *bp = register_test_bp(cpu, tsk, *id);
> > +
> > + KUNIT_ASSERT_NOT_NULL(test, bp);
> > + KUNIT_ASSERT_FALSE(test, IS_ERR(bp));
> > + KUNIT_ASSERT_NULL(test, test_bps[*id]);
> > + test_bps[(*id)++] = bp;
> > +}
> > +
> > +/*
> > + * Fills up the given @cpu/@tsk with breakpoints, only leaving @skip slots free.
> > + *
> > + * Returns true if this can be called again, continuing at @id.
> > + */
> > +static bool fill_bp_slots(struct kunit *test, int *id, int cpu, struct task_struct *tsk, int skip)
> > +{
> > + for (int i = 0; i < get_test_bp_slots() - skip; ++i)
> > + fill_one_bp_slot(test, id, cpu, tsk);
> > +
> > + return *id + get_test_bp_slots() <= MAX_TEST_BREAKPOINTS;
> > +}
> > +
> > +static int dummy_kthread(void *arg)
> > +{
> > + return 0;
> > +}
> > +
> > +static struct task_struct *get_other_task(struct kunit *test)
> > +{
> > + struct task_struct *tsk;
> > +
> > + if (__other_task)
> > + return __other_task;
> > +
> > + tsk = kthread_create(dummy_kthread, NULL, "hw_breakpoint_dummy_task");
> > + KUNIT_ASSERT_FALSE(test, IS_ERR(tsk));
> > + __other_task = tsk;
> > + return __other_task;
> > +}
> > +
> > +static int get_test_cpu(int num)
> > +{
> > + int cpu;
> > +
> > + WARN_ON(num < 0);
> > +
> > + for_each_online_cpu(cpu) {
> > + if (num-- <= 0)
> > + break;
> > + }
> > +
> > + return cpu;
> > +}
> > +
> > +/* ===== Test cases ===== */
> > +
> > +static void test_one_cpu(struct kunit *test)
> > +{
> > + int idx = 0;
> > +
> > + fill_bp_slots(test, &idx, get_test_cpu(0), NULL, 0);
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > +}
> > +
> > +static void test_many_cpus(struct kunit *test)
> > +{
> > + int idx = 0;
> > + int cpu;
> > +
> > + /* Test that CPUs are independent. */
> > + for_each_online_cpu(cpu) {
> > + bool do_continue = fill_bp_slots(test, &idx, cpu, NULL, 0);
> > +
> > + TEST_EXPECT_NOSPC(register_test_bp(cpu, NULL, idx));
> > + if (!do_continue)
> > + break;
> > + }
> > +}
> > +
> > +static void test_one_task_on_all_cpus(struct kunit *test)
> > +{
> > + int idx = 0;
> > +
> > + fill_bp_slots(test, &idx, -1, current, 0);
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > + /* Remove one and adding back CPU-target should work. */
> > + unregister_test_bp(&test_bps[0]);
> > + fill_one_bp_slot(test, &idx, get_test_cpu(0), NULL);
> > +}
> > +
> > +static void test_two_tasks_on_all_cpus(struct kunit *test)
> > +{
> > + int idx = 0;
> > +
> > + /* Test that tasks are independent. */
> > + fill_bp_slots(test, &idx, -1, current, 0);
> > + fill_bp_slots(test, &idx, -1, get_other_task(test), 0);
> > +
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, get_other_task(test), idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), get_other_task(test), idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > + /* Remove one from first task and adding back CPU-target should not work. */
> > + unregister_test_bp(&test_bps[0]);
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > +}
> > +
> > +static void test_one_task_on_one_cpu(struct kunit *test)
> > +{
> > + int idx = 0;
> > +
> > + fill_bp_slots(test, &idx, get_test_cpu(0), current, 0);
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > + /*
> > + * Remove one and adding back CPU-target should work; this case is
> > + * special vs. above because the task's constraints are CPU-dependent.
> > + */
> > + unregister_test_bp(&test_bps[0]);
> > + fill_one_bp_slot(test, &idx, get_test_cpu(0), NULL);
> > +}
> > +
> > +static void test_one_task_mixed(struct kunit *test)
> > +{
> > + int idx = 0;
> > +
> > + TEST_REQUIRES_BP_SLOTS(test, 3);
> > +
> > + fill_one_bp_slot(test, &idx, get_test_cpu(0), current);
> > + fill_bp_slots(test, &idx, -1, current, 1);
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > +
> > + /* Transition from CPU-dependent pinned count to CPU-independent. */
> > + unregister_test_bp(&test_bps[0]);
> > + unregister_test_bp(&test_bps[1]);
> > + fill_one_bp_slot(test, &idx, get_test_cpu(0), NULL);
> > + fill_one_bp_slot(test, &idx, get_test_cpu(0), NULL);
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > +}
> > +
> > +static void test_two_tasks_on_one_cpu(struct kunit *test)
> > +{
> > + int idx = 0;
> > +
> > + fill_bp_slots(test, &idx, get_test_cpu(0), current, 0);
> > + fill_bp_slots(test, &idx, get_test_cpu(0), get_other_task(test), 0);
> > +
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, get_other_task(test), idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), get_other_task(test), idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > + /* Can still create breakpoints on some other CPU. */
> > + fill_bp_slots(test, &idx, get_test_cpu(1), NULL, 0);
> > +}
> > +
> > +static void test_two_tasks_on_one_all_cpus(struct kunit *test)
> > +{
> > + int idx = 0;
> > +
> > + fill_bp_slots(test, &idx, get_test_cpu(0), current, 0);
> > + fill_bp_slots(test, &idx, -1, get_other_task(test), 0);
> > +
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, get_other_task(test), idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), get_other_task(test), idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > + /* Cannot create breakpoints on some other CPU either. */
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(1), NULL, idx));
> > +}
> > +
> > +static void test_task_on_all_and_one_cpu(struct kunit *test)
> > +{
> > + int tsk_on_cpu_idx, cpu_idx;
> > + int idx = 0;
> > +
> > + TEST_REQUIRES_BP_SLOTS(test, 3);
> > +
> > + fill_bp_slots(test, &idx, -1, current, 2);
> > + /* Transitioning from only all CPU breakpoints to mixed. */
> > + tsk_on_cpu_idx = idx;
> > + fill_one_bp_slot(test, &idx, get_test_cpu(0), current);
> > + fill_one_bp_slot(test, &idx, -1, current);
> > +
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > +
> > + /* We should still be able to use up another CPU's slots. */
> > + cpu_idx = idx;
> > + fill_one_bp_slot(test, &idx, get_test_cpu(1), NULL);
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(1), NULL, idx));
> > +
> > + /* Transitioning back to task target on all CPUs. */
> > + unregister_test_bp(&test_bps[tsk_on_cpu_idx]);
> > + /* Still have a CPU target breakpoint in get_test_cpu(1). */
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + /* Remove it and try again. */
> > + unregister_test_bp(&test_bps[cpu_idx]);
> > + fill_one_bp_slot(test, &idx, -1, current);
> > +
> > + TEST_EXPECT_NOSPC(register_test_bp(-1, current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), current, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(0), NULL, idx));
> > + TEST_EXPECT_NOSPC(register_test_bp(get_test_cpu(1), NULL, idx));
> > +}
> > +
> > +static struct kunit_case hw_breakpoint_test_cases[] = {
> > + KUNIT_CASE(test_one_cpu),
> > + KUNIT_CASE(test_many_cpus),
> > + KUNIT_CASE(test_one_task_on_all_cpus),
> > + KUNIT_CASE(test_two_tasks_on_all_cpus),
> > + KUNIT_CASE(test_one_task_on_one_cpu),
> > + KUNIT_CASE(test_one_task_mixed),
> > + KUNIT_CASE(test_two_tasks_on_one_cpu),
> > + KUNIT_CASE(test_two_tasks_on_one_all_cpus),
> > + KUNIT_CASE(test_task_on_all_and_one_cpu),
> > + {},
> > +};
> > +
> > +static int test_init(struct kunit *test)
> > +{
> > + /* Most test cases want 2 distinct CPUs. */
> > + return num_online_cpus() < 2 ? -EINVAL : 0;
> > +}
> > +
> > +static void test_exit(struct kunit *test)
> > +{
> > + for (int i = 0; i < MAX_TEST_BREAKPOINTS; ++i) {
> > + if (test_bps[i])
> > + unregister_test_bp(&test_bps[i]);
> > + }
> > +
> > + if (__other_task) {
> > + kthread_stop(__other_task);
> > + __other_task = NULL;
> > + }
> > +}
> > +
> > +static struct kunit_suite hw_breakpoint_test_suite = {
> > + .name = "hw_breakpoint",
> > + .test_cases = hw_breakpoint_test_cases,
> > + .init = test_init,
> > + .exit = test_exit,
> > +};
> > +
> > +kunit_test_suites(&hw_breakpoint_test_suite);
> > +
> > +MODULE_LICENSE("GPL");
> > +MODULE_AUTHOR("Marco Elver <elver@...gle.com>");
> > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> > index 2e24db4bff19..4c87a6edf046 100644
> > --- a/lib/Kconfig.debug
> > +++ b/lib/Kconfig.debug
> > @@ -2513,6 +2513,16 @@ config STACKINIT_KUNIT_TEST
> > CONFIG_GCC_PLUGIN_STRUCTLEAK, CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF,
> > or CONFIG_GCC_PLUGIN_STRUCTLEAK_BYREF_ALL.
> >
> > +config HW_BREAKPOINT_KUNIT_TEST
> > + bool "Test hw_breakpoint constraints accounting" if !KUNIT_ALL_TESTS
> > + depends on HAVE_HW_BREAKPOINT
> > + depends on KUNIT=y
> > + default KUNIT_ALL_TESTS
> > + help
> > + Tests for hw_breakpoint constraints accounting.
> > +
> > + If unsure, say N.
> > +
> > config TEST_UDELAY
> > tristate "udelay test driver"
> > help
> > --
> > 2.37.0.rc0.161.g10f37bed90-goog
> >
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