| Message ID | 20210830214106.4142056-4-songliubraving@fb.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | bpf: introduce bpf_get_branch_snapshot | expand |
On Mon, Aug 30, 2021 at 2:44 PM Song Liu <songliubraving@fb.com> wrote: > > This test uses bpf_get_branch_snapshot from a fexit program. The test uses > a target kernel function (bpf_fexit_loop_test1) and compares the record > against kallsyms. If there isn't enough record matching kallsyms, the > test fails. > > Signed-off-by: Song Liu <songliubraving@fb.com> > --- > net/bpf/test_run.c | 15 ++- > .../bpf/prog_tests/get_branch_snapshot.c | 106 ++++++++++++++++++ > .../selftests/bpf/progs/get_branch_snapshot.c | 41 +++++++ > tools/testing/selftests/bpf/trace_helpers.c | 30 +++++ > tools/testing/selftests/bpf/trace_helpers.h | 5 + > 5 files changed, 196 insertions(+), 1 deletion(-) > create mode 100644 tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c > create mode 100644 tools/testing/selftests/bpf/progs/get_branch_snapshot.c > > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c > index 2eb0e55ef54d2..6cc179a532c9c 100644 > --- a/net/bpf/test_run.c > +++ b/net/bpf/test_run.c > @@ -231,6 +231,18 @@ struct sock * noinline bpf_kfunc_call_test3(struct sock *sk) > return sk; > } > > +noinline int bpf_fexit_loop_test1(int n) We have bpf_testmod as part of selftests now, which allows us to add whatever in-kernel functionality we need, without polluting the kernel itself. fentry/fexit attach to kernel functions works as well, so do you think we can use that here for testing? > +{ > + int i, sum = 0; > + > + /* the primary goal of this test is to test LBR. Create a lot of > + * branches in the function, so we can catch it easily. > + */ > + for (i = 0; i < n; i++) > + sum += i; > + return sum; > +} > + > __diag_pop(); > > ALLOW_ERROR_INJECTION(bpf_modify_return_test, ERRNO); > @@ -293,7 +305,8 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog, > bpf_fentry_test5(11, (void *)12, 13, 14, 15) != 65 || > bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111 || > bpf_fentry_test7((struct bpf_fentry_test_t *)0) != 0 || > - bpf_fentry_test8(&arg) != 0) > + bpf_fentry_test8(&arg) != 0 || > + bpf_fexit_loop_test1(101) != 5050) > goto out; > break; > case BPF_MODIFY_RETURN: > diff --git a/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c > new file mode 100644 > index 0000000000000..9bb16826418fb > --- /dev/null > +++ b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c > @@ -0,0 +1,106 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2021 Facebook */ > +#include <test_progs.h> > +#include "get_branch_snapshot.skel.h" > + > +static int *pfd_array; > +static int cpu_cnt; > + > +static int create_perf_events(void) > +{ > + struct perf_event_attr attr = {0}; > + int cpu; > + > + /* create perf event */ > + attr.size = sizeof(attr); > + attr.type = PERF_TYPE_RAW; > + attr.config = 0x1b00; > + attr.sample_type = PERF_SAMPLE_BRANCH_STACK; > + attr.branch_sample_type = PERF_SAMPLE_BRANCH_KERNEL | > + PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY; > + > + cpu_cnt = libbpf_num_possible_cpus(); > + pfd_array = malloc(sizeof(int) * cpu_cnt); > + if (!pfd_array) { > + cpu_cnt = 0; > + return 1; > + } > + > + for (cpu = 0; cpu < libbpf_num_possible_cpus(); cpu++) { nit: use cpu_cnt from above? > + pfd_array[cpu] = syscall(__NR_perf_event_open, &attr, > + -1, cpu, -1, PERF_FLAG_FD_CLOEXEC); > + if (pfd_array[cpu] < 0) > + break; > + } > + > + return cpu == 0; > +} > + > +static void close_perf_events(void) > +{ > + int cpu = 0; > + int fd; > + > + while (cpu++ < cpu_cnt) { > + fd = pfd_array[cpu]; > + if (fd < 0) > + break; > + close(fd); > + } > + free(pfd_array); > +} > + > +void test_get_branch_snapshot(void) > +{ > + struct get_branch_snapshot *skel; > + int err, prog_fd; > + __u32 retval; > + > + if (create_perf_events()) { > + test__skip(); /* system doesn't support LBR */ > + goto cleanup; Cleanup inside create_perf_events() and just return here. Or at least initialize skel to NULL above, otherwise __destroy() below will cause SIGSEGV, most probably. > + } > + > + skel = get_branch_snapshot__open_and_load(); > + if (!ASSERT_OK_PTR(skel, "get_branch_snapshot__open_and_load")) > + goto cleanup; > + > + err = kallsyms_find("bpf_fexit_loop_test1", &skel->bss->address_low); > + if (!ASSERT_OK(err, "kallsyms_find")) > + goto cleanup; > + > + err = kallsyms_find_next("bpf_fexit_loop_test1", &skel->bss->address_high); > + if (!ASSERT_OK(err, "kallsyms_find_next")) > + goto cleanup; > + > + err = get_branch_snapshot__attach(skel); > + if (!ASSERT_OK(err, "get_branch_snapshot__attach")) > + goto cleanup; > + > + prog_fd = bpf_program__fd(skel->progs.test1); > + err = bpf_prog_test_run(prog_fd, 1, NULL, 0, > + NULL, 0, &retval, NULL); > + > + if (!ASSERT_OK(err, "bpf_prog_test_run")) > + goto cleanup; > + > + if (skel->bss->total_entries < 16) { > + /* too few entries for the hit/waste test */ > + test__skip(); > + goto cleanup; > + } > + > + ASSERT_GT(skel->bss->test1_hits, 5, "find_test1_in_lbr"); > + > + /* Given we stop LBR in software, we will waste a few entries. > + * But we should try to waste as few as possibleentries. We are at s/possibleentries/possible entries/ > + * about 7 on x86_64 systems. > + * Add a check for < 10 so that we get heads-up when something > + * changes and wastes too many entries. > + */ > + ASSERT_LT(skel->bss->wasted_entries, 10, "check_wasted_entries"); > + > +cleanup: > + get_branch_snapshot__destroy(skel); > + close_perf_events(); > +} > diff --git a/tools/testing/selftests/bpf/progs/get_branch_snapshot.c b/tools/testing/selftests/bpf/progs/get_branch_snapshot.c > new file mode 100644 > index 0000000000000..9c944e7480b95 > --- /dev/null > +++ b/tools/testing/selftests/bpf/progs/get_branch_snapshot.c > @@ -0,0 +1,41 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* Copyright (c) 2021 Facebook */ > +#include "vmlinux.h" > +#include <bpf/bpf_helpers.h> > +#include <bpf/bpf_tracing.h> > + > +char _license[] SEC("license") = "GPL"; > + > +__u64 test1_hits = 0; > +__u64 address_low = 0; > +__u64 address_high = 0; > +int wasted_entries = 0; > +long total_entries = 0; > + > +#define MAX_LBR_ENTRIES 32 see my comment on another patch, if kernel defines this constant as enum, we'll automatically get it from vmlinux.h. > + > +struct perf_branch_entry entries[MAX_LBR_ENTRIES] = {}; > + > + > +static inline bool in_range(__u64 val) > +{ > + return (val >= address_low) && (val < address_high); > +} > + [...]
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c index 2eb0e55ef54d2..6cc179a532c9c 100644 --- a/net/bpf/test_run.c +++ b/net/bpf/test_run.c @@ -231,6 +231,18 @@ struct sock * noinline bpf_kfunc_call_test3(struct sock *sk) return sk; } +noinline int bpf_fexit_loop_test1(int n) +{ + int i, sum = 0; + + /* the primary goal of this test is to test LBR. Create a lot of + * branches in the function, so we can catch it easily. + */ + for (i = 0; i < n; i++) + sum += i; + return sum; +} + __diag_pop(); ALLOW_ERROR_INJECTION(bpf_modify_return_test, ERRNO); @@ -293,7 +305,8 @@ int bpf_prog_test_run_tracing(struct bpf_prog *prog, bpf_fentry_test5(11, (void *)12, 13, 14, 15) != 65 || bpf_fentry_test6(16, (void *)17, 18, 19, (void *)20, 21) != 111 || bpf_fentry_test7((struct bpf_fentry_test_t *)0) != 0 || - bpf_fentry_test8(&arg) != 0) + bpf_fentry_test8(&arg) != 0 || + bpf_fexit_loop_test1(101) != 5050) goto out; break; case BPF_MODIFY_RETURN: diff --git a/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c new file mode 100644 index 0000000000000..9bb16826418fb --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c @@ -0,0 +1,106 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2021 Facebook */ +#include <test_progs.h> +#include "get_branch_snapshot.skel.h" + +static int *pfd_array; +static int cpu_cnt; + +static int create_perf_events(void) +{ + struct perf_event_attr attr = {0}; + int cpu; + + /* create perf event */ + attr.size = sizeof(attr); + attr.type = PERF_TYPE_RAW; + attr.config = 0x1b00; + attr.sample_type = PERF_SAMPLE_BRANCH_STACK; + attr.branch_sample_type = PERF_SAMPLE_BRANCH_KERNEL | + PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY; + + cpu_cnt = libbpf_num_possible_cpus(); + pfd_array = malloc(sizeof(int) * cpu_cnt); + if (!pfd_array) { + cpu_cnt = 0; + return 1; + } + + for (cpu = 0; cpu < libbpf_num_possible_cpus(); cpu++) { + pfd_array[cpu] = syscall(__NR_perf_event_open, &attr, + -1, cpu, -1, PERF_FLAG_FD_CLOEXEC); + if (pfd_array[cpu] < 0) + break; + } + + return cpu == 0; +} + +static void close_perf_events(void) +{ + int cpu = 0; + int fd; + + while (cpu++ < cpu_cnt) { + fd = pfd_array[cpu]; + if (fd < 0) + break; + close(fd); + } + free(pfd_array); +} + +void test_get_branch_snapshot(void) +{ + struct get_branch_snapshot *skel; + int err, prog_fd; + __u32 retval; + + if (create_perf_events()) { + test__skip(); /* system doesn't support LBR */ + goto cleanup; + } + + skel = get_branch_snapshot__open_and_load(); + if (!ASSERT_OK_PTR(skel, "get_branch_snapshot__open_and_load")) + goto cleanup; + + err = kallsyms_find("bpf_fexit_loop_test1", &skel->bss->address_low); + if (!ASSERT_OK(err, "kallsyms_find")) + goto cleanup; + + err = kallsyms_find_next("bpf_fexit_loop_test1", &skel->bss->address_high); + if (!ASSERT_OK(err, "kallsyms_find_next")) + goto cleanup; + + err = get_branch_snapshot__attach(skel); + if (!ASSERT_OK(err, "get_branch_snapshot__attach")) + goto cleanup; + + prog_fd = bpf_program__fd(skel->progs.test1); + err = bpf_prog_test_run(prog_fd, 1, NULL, 0, + NULL, 0, &retval, NULL); + + if (!ASSERT_OK(err, "bpf_prog_test_run")) + goto cleanup; + + if (skel->bss->total_entries < 16) { + /* too few entries for the hit/waste test */ + test__skip(); + goto cleanup; + } + + ASSERT_GT(skel->bss->test1_hits, 5, "find_test1_in_lbr"); + + /* Given we stop LBR in software, we will waste a few entries. + * But we should try to waste as few as possibleentries. We are at + * about 7 on x86_64 systems. + * Add a check for < 10 so that we get heads-up when something + * changes and wastes too many entries. + */ + ASSERT_LT(skel->bss->wasted_entries, 10, "check_wasted_entries"); + +cleanup: + get_branch_snapshot__destroy(skel); + close_perf_events(); +} diff --git a/tools/testing/selftests/bpf/progs/get_branch_snapshot.c b/tools/testing/selftests/bpf/progs/get_branch_snapshot.c new file mode 100644 index 0000000000000..9c944e7480b95 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/get_branch_snapshot.c @@ -0,0 +1,41 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2021 Facebook */ +#include "vmlinux.h" +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +char _license[] SEC("license") = "GPL"; + +__u64 test1_hits = 0; +__u64 address_low = 0; +__u64 address_high = 0; +int wasted_entries = 0; +long total_entries = 0; + +#define MAX_LBR_ENTRIES 32 + +struct perf_branch_entry entries[MAX_LBR_ENTRIES] = {}; + + +static inline bool in_range(__u64 val) +{ + return (val >= address_low) && (val < address_high); +} + +SEC("fexit/bpf_fexit_loop_test1") +int BPF_PROG(test1, int n, int ret) +{ + long i; + + total_entries = bpf_get_branch_snapshot(entries, sizeof(entries)); + + for (i = 0; i < MAX_LBR_ENTRIES; i++) { + if (i >= total_entries) + break; + if (in_range(entries[i].from) && in_range(entries[i].to)) + test1_hits++; + else if (!test1_hits) + wasted_entries++; + } + return 0; +} diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c index e7a19b04d4eaf..2926a3b626821 100644 --- a/tools/testing/selftests/bpf/trace_helpers.c +++ b/tools/testing/selftests/bpf/trace_helpers.c @@ -117,6 +117,36 @@ int kallsyms_find(const char *sym, unsigned long long *addr) return err; } +/* find the address of the next symbol, this can be used to determine the + * end of a function + */ +int kallsyms_find_next(const char *sym, unsigned long long *addr) +{ + char type, name[500]; + unsigned long long value; + bool found = false; + int err = 0; + FILE *f; + + f = fopen("/proc/kallsyms", "r"); + if (!f) + return -EINVAL; + + while (fscanf(f, "%llx %c %499s%*[^\n]\n", &value, &type, name) > 0) { + if (found) { + *addr = value; + goto out; + } + if (strcmp(name, sym) == 0) + found = true; + } + err = -ENOENT; + +out: + fclose(f); + return err; +} + void read_trace_pipe(void) { int trace_fd; diff --git a/tools/testing/selftests/bpf/trace_helpers.h b/tools/testing/selftests/bpf/trace_helpers.h index d907b445524d5..bc8ed86105d94 100644 --- a/tools/testing/selftests/bpf/trace_helpers.h +++ b/tools/testing/selftests/bpf/trace_helpers.h @@ -16,6 +16,11 @@ long ksym_get_addr(const char *name); /* open kallsyms and find addresses on the fly, faster than load + search. */ int kallsyms_find(const char *sym, unsigned long long *addr); +/* find the address of the next symbol, this can be used to determine the + * end of a function + */ +int kallsyms_find_next(const char *sym, unsigned long long *addr); + void read_trace_pipe(void); ssize_t get_uprobe_offset(const void *addr, ssize_t base);
This test uses bpf_get_branch_snapshot from a fexit program. The test uses a target kernel function (bpf_fexit_loop_test1) and compares the record against kallsyms. If there isn't enough record matching kallsyms, the test fails. Signed-off-by: Song Liu <songliubraving@fb.com> --- net/bpf/test_run.c | 15 ++- .../bpf/prog_tests/get_branch_snapshot.c | 106 ++++++++++++++++++ .../selftests/bpf/progs/get_branch_snapshot.c | 41 +++++++ tools/testing/selftests/bpf/trace_helpers.c | 30 +++++ tools/testing/selftests/bpf/trace_helpers.h | 5 + 5 files changed, 196 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c create mode 100644 tools/testing/selftests/bpf/progs/get_branch_snapshot.c