From 025bd7c753aab18cd594924a46ab46ac47209df9 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Fri, 10 Sep 2021 11:33:52 -0700 Subject: [PATCH] selftests/bpf: Add test for bpf_get_branch_snapshot This test uses bpf_get_branch_snapshot from a fexit program. The test uses a target function (bpf_testmod_loop_test) and compares the record against kallsyms. If there isn't enough record matching kallsyms, the test fails. Signed-off-by: Song Liu Signed-off-by: Alexei Starovoitov Acked-by: Andrii Nakryiko Acked-by: John Fastabend Link: https://lore.kernel.org/bpf/20210910183352.3151445-4-songliubraving@fb.com --- .../selftests/bpf/bpf_testmod/bpf_testmod.c | 19 +++- .../selftests/bpf/prog_tests/core_reloc.c | 14 +-- .../bpf/prog_tests/get_branch_snapshot.c | 100 ++++++++++++++++++ .../selftests/bpf/prog_tests/module_attach.c | 39 ------- .../selftests/bpf/progs/get_branch_snapshot.c | 40 +++++++ tools/testing/selftests/bpf/test_progs.c | 39 +++++++ tools/testing/selftests/bpf/test_progs.h | 2 + tools/testing/selftests/bpf/trace_helpers.c | 37 +++++++ tools/testing/selftests/bpf/trace_helpers.h | 5 + 9 files changed, 243 insertions(+), 52 deletions(-) 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/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c index 141d8da687d2..50fc5561110a 100644 --- a/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c +++ b/tools/testing/selftests/bpf/bpf_testmod/bpf_testmod.c @@ -13,6 +13,18 @@ DEFINE_PER_CPU(int, bpf_testmod_ksym_percpu) = 123; +noinline int bpf_testmod_loop_test(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; +} + noinline ssize_t bpf_testmod_test_read(struct file *file, struct kobject *kobj, struct bin_attribute *bin_attr, @@ -24,7 +36,11 @@ bpf_testmod_test_read(struct file *file, struct kobject *kobj, .len = len, }; - trace_bpf_testmod_test_read(current, &ctx); + /* This is always true. Use the check to make sure the compiler + * doesn't remove bpf_testmod_loop_test. + */ + if (bpf_testmod_loop_test(101) > 100) + trace_bpf_testmod_test_read(current, &ctx); return -EIO; /* always fail */ } @@ -71,4 +87,3 @@ module_exit(bpf_testmod_exit); MODULE_AUTHOR("Andrii Nakryiko"); MODULE_DESCRIPTION("BPF selftests module"); MODULE_LICENSE("Dual BSD/GPL"); - diff --git a/tools/testing/selftests/bpf/prog_tests/core_reloc.c b/tools/testing/selftests/bpf/prog_tests/core_reloc.c index 4739b15b2a97..15d355af8d1d 100644 --- a/tools/testing/selftests/bpf/prog_tests/core_reloc.c +++ b/tools/testing/selftests/bpf/prog_tests/core_reloc.c @@ -30,7 +30,7 @@ static int duration = 0; .output_len = sizeof(struct core_reloc_module_output), \ .prog_sec_name = sec_name, \ .raw_tp_name = tp_name, \ - .trigger = trigger_module_test_read, \ + .trigger = __trigger_module_test_read, \ .needs_testmod = true, \ } @@ -475,19 +475,11 @@ static int setup_type_id_case_failure(struct core_reloc_test_case *test) return 0; } -static int trigger_module_test_read(const struct core_reloc_test_case *test) +static int __trigger_module_test_read(const struct core_reloc_test_case *test) { struct core_reloc_module_output *exp = (void *)test->output; - int fd, err; - - fd = open("/sys/kernel/bpf_testmod", O_RDONLY); - err = -errno; - if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err)) - return err; - - read(fd, NULL, exp->len); /* request expected number of bytes */ - close(fd); + trigger_module_test_read(exp->len); return 0; } 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 000000000000..f81db9135ae4 --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/get_branch_snapshot.c @@ -0,0 +1,100 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2021 Facebook */ +#include +#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 < cpu_cnt; 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 = NULL; + int err; + + 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_testmod_loop_test", &skel->bss->address_low); + if (!ASSERT_OK(err, "kallsyms_find")) + goto cleanup; + + err = kallsyms_find_next("bpf_testmod_loop_test", &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; + + trigger_module_test_read(100); + + if (skel->bss->total_entries < 16) { + /* too few entries for the hit/waste test */ + test__skip(); + goto cleanup; + } + + ASSERT_GT(skel->bss->test1_hits, 6, "find_looptest_in_lbr"); + + /* Given we stop LBR in software, we will waste a few entries. + * But we should try to waste as few as possible entries. 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/prog_tests/module_attach.c b/tools/testing/selftests/bpf/prog_tests/module_attach.c index d85a69b7ce44..1797a6e4d6d8 100644 --- a/tools/testing/selftests/bpf/prog_tests/module_attach.c +++ b/tools/testing/selftests/bpf/prog_tests/module_attach.c @@ -6,45 +6,6 @@ static int duration; -static int trigger_module_test_read(int read_sz) -{ - int fd, err; - - fd = open("/sys/kernel/bpf_testmod", O_RDONLY); - err = -errno; - if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err)) - return err; - - read(fd, NULL, read_sz); - close(fd); - - return 0; -} - -static int trigger_module_test_write(int write_sz) -{ - int fd, err; - char *buf = malloc(write_sz); - - if (!buf) - return -ENOMEM; - - memset(buf, 'a', write_sz); - buf[write_sz-1] = '\0'; - - fd = open("/sys/kernel/bpf_testmod", O_WRONLY); - err = -errno; - if (CHECK(fd < 0, "testmod_file_open", "failed: %d\n", err)) { - free(buf); - return err; - } - - write(fd, buf, write_sz); - close(fd); - free(buf); - return 0; -} - static int delete_module(const char *name, int flags) { return syscall(__NR_delete_module, name, flags); 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 000000000000..a1b139888048 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/get_branch_snapshot.c @@ -0,0 +1,40 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2021 Facebook */ +#include "vmlinux.h" +#include +#include + +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 ENTRY_CNT 32 +struct perf_branch_entry entries[ENTRY_CNT] = {}; + +static inline bool in_range(__u64 val) +{ + return (val >= address_low) && (val < address_high); +} + +SEC("fexit/bpf_testmod_loop_test") +int BPF_PROG(test1, int n, int ret) +{ + long i; + + total_entries = bpf_get_branch_snapshot(entries, sizeof(entries), 0); + total_entries /= sizeof(struct perf_branch_entry); + + for (i = 0; i < ENTRY_CNT; 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/test_progs.c b/tools/testing/selftests/bpf/test_progs.c index cc1cd240445d..2ed01f615d20 100644 --- a/tools/testing/selftests/bpf/test_progs.c +++ b/tools/testing/selftests/bpf/test_progs.c @@ -743,6 +743,45 @@ int cd_flavor_subdir(const char *exec_name) return chdir(flavor); } +int trigger_module_test_read(int read_sz) +{ + int fd, err; + + fd = open("/sys/kernel/bpf_testmod", O_RDONLY); + err = -errno; + if (!ASSERT_GE(fd, 0, "testmod_file_open")) + return err; + + read(fd, NULL, read_sz); + close(fd); + + return 0; +} + +int trigger_module_test_write(int write_sz) +{ + int fd, err; + char *buf = malloc(write_sz); + + if (!buf) + return -ENOMEM; + + memset(buf, 'a', write_sz); + buf[write_sz-1] = '\0'; + + fd = open("/sys/kernel/bpf_testmod", O_WRONLY); + err = -errno; + if (!ASSERT_GE(fd, 0, "testmod_file_open")) { + free(buf); + return err; + } + + write(fd, buf, write_sz); + close(fd); + free(buf); + return 0; +} + #define MAX_BACKTRACE_SZ 128 void crash_handler(int signum) { diff --git a/tools/testing/selftests/bpf/test_progs.h b/tools/testing/selftests/bpf/test_progs.h index c8c2bf878f67..94bef0aa74cf 100644 --- a/tools/testing/selftests/bpf/test_progs.h +++ b/tools/testing/selftests/bpf/test_progs.h @@ -291,6 +291,8 @@ int compare_map_keys(int map1_fd, int map2_fd); int compare_stack_ips(int smap_fd, int amap_fd, int stack_trace_len); int extract_build_id(char *build_id, size_t size); int kern_sync_rcu(void); +int trigger_module_test_read(int read_sz); +int trigger_module_test_write(int write_sz); #ifdef __x86_64__ #define SYS_NANOSLEEP_KPROBE_NAME "__x64_sys_nanosleep" diff --git a/tools/testing/selftests/bpf/trace_helpers.c b/tools/testing/selftests/bpf/trace_helpers.c index e7a19b04d4ea..5100a169b72b 100644 --- a/tools/testing/selftests/bpf/trace_helpers.c +++ b/tools/testing/selftests/bpf/trace_helpers.c @@ -1,4 +1,5 @@ // SPDX-License-Identifier: GPL-2.0 +#include #include #include #include @@ -117,6 +118,42 @@ out: return err; } +/* find the address of the next symbol of the same type, this can be used + * to determine the end of a function. + */ +int kallsyms_find_next(const char *sym, unsigned long long *addr) +{ + char type, found_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) { + /* Different types of symbols in kernel modules are mixed + * in /proc/kallsyms. Only return the next matching type. + * Use tolower() for type so that 'T' matches 't'. + */ + if (found && found_type == tolower(type)) { + *addr = value; + goto out; + } + if (strcmp(name, sym) == 0) { + found = true; + found_type = tolower(type); + } + } + 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 d907b445524d..bc8ed86105d9 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);