diff options
author | Alexei Starovoitov <ast@kernel.org> | 2022-05-10 14:42:06 -0700 |
---|---|---|
committer | Alexei Starovoitov <ast@kernel.org> | 2022-05-10 14:42:06 -0700 |
commit | cb411545309e69753bfa4805060c17faaa25500d (patch) | |
tree | b3668dbe0d94016081c7e48f29d1bc0febf1f471 | |
parent | 9376d3898b2da50e6a6e7c0c1a0d7a3bbf0b8f44 (diff) | |
parent | 5b6c7e5c44349b29c614e1b61f80c6849fc72ccf (diff) | |
download | linux-cb411545309e69753bfa4805060c17faaa25500d.tar.bz2 |
Merge branch 'bpf: Speed up symbol resolving in kprobe multi link'
Jiri Olsa says:
====================
hi,
sending additional fix for symbol resolving in kprobe multi link
requested by Alexei and Andrii [1].
This speeds up bpftrace kprobe attachment, when using pure symbols
(3344 symbols) to attach:
Before:
# perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
...
6.5681 +- 0.0225 seconds time elapsed ( +- 0.34% )
After:
# perf stat -r 5 -e cycles ./src/bpftrace -e 'kprobe:x* { } i:ms:1 { exit(); }'
...
0.5661 +- 0.0275 seconds time elapsed ( +- 4.85% )
v6 changes:
- rewrote patch 1 changelog and fixed the line length [Christoph]
v5 changes:
- added acks [Masami]
- workaround in selftest for RCU warning by filtering out several
functions to attach
v4 changes:
- fix compile issue [kernel test robot]
- added acks [Andrii]
v3 changes:
- renamed kallsyms_lookup_names to ftrace_lookup_symbols
and moved it to ftrace.c [Masami]
- added ack [Andrii]
- couple small test fixes [Andrii]
v2 changes (first version [2]):
- removed the 2 seconds check [Alexei]
- moving/forcing symbols sorting out of kallsyms_lookup_names function [Alexei]
- skipping one array allocation and copy_from_user [Andrii]
- several small fixes [Masami,Andrii]
- build fix [kernel test robot]
thanks,
jirka
[1] https://lore.kernel.org/bpf/CAEf4BzZtQaiUxQ-sm_hH2qKPRaqGHyOfEsW96DxtBHRaKLoL3Q@mail.gmail.com/
[2] https://lore.kernel.org/bpf/20220407125224.310255-1-jolsa@kernel.org/
====================
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
-rw-r--r-- | include/linux/ftrace.h | 6 | ||||
-rw-r--r-- | include/linux/kallsyms.h | 7 | ||||
-rw-r--r-- | kernel/kallsyms.c | 3 | ||||
-rw-r--r-- | kernel/trace/bpf_trace.c | 112 | ||||
-rw-r--r-- | kernel/trace/fprobe.c | 32 | ||||
-rw-r--r-- | kernel/trace/ftrace.c | 62 | ||||
-rw-r--r-- | tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c | 143 | ||||
-rw-r--r-- | tools/testing/selftests/bpf/progs/kprobe_multi_empty.c | 12 |
8 files changed, 308 insertions, 69 deletions
diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 4816b7e11047..820500430eae 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -303,6 +303,8 @@ int unregister_ftrace_function(struct ftrace_ops *ops); extern void ftrace_stub(unsigned long a0, unsigned long a1, struct ftrace_ops *op, struct ftrace_regs *fregs); + +int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs); #else /* !CONFIG_FUNCTION_TRACER */ /* * (un)register_ftrace_function must be a macro since the ops parameter @@ -313,6 +315,10 @@ extern void ftrace_stub(unsigned long a0, unsigned long a1, static inline void ftrace_kill(void) { } static inline void ftrace_free_init_mem(void) { } static inline void ftrace_free_mem(struct module *mod, void *start, void *end) { } +static inline int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs) +{ + return -EOPNOTSUPP; +} #endif /* CONFIG_FUNCTION_TRACER */ struct ftrace_func_entry { diff --git a/include/linux/kallsyms.h b/include/linux/kallsyms.h index ce1bd2fbf23e..ad39636e0c3f 100644 --- a/include/linux/kallsyms.h +++ b/include/linux/kallsyms.h @@ -65,11 +65,11 @@ static inline void *dereference_symbol_descriptor(void *ptr) return ptr; } +#ifdef CONFIG_KALLSYMS int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, unsigned long), void *data); -#ifdef CONFIG_KALLSYMS /* Lookup the address for a symbol. Returns 0 if not found. */ unsigned long kallsyms_lookup_name(const char *name); @@ -163,6 +163,11 @@ static inline bool kallsyms_show_value(const struct cred *cred) return false; } +static inline int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, + unsigned long), void *data) +{ + return -EOPNOTSUPP; +} #endif /*CONFIG_KALLSYMS*/ static inline void print_ip_sym(const char *loglvl, unsigned long ip) diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c index 79f2eb617a62..fbdf8d3279ac 100644 --- a/kernel/kallsyms.c +++ b/kernel/kallsyms.c @@ -29,6 +29,7 @@ #include <linux/compiler.h> #include <linux/module.h> #include <linux/kernel.h> +#include <linux/bsearch.h> /* * These will be re-linked against their real values @@ -228,7 +229,6 @@ unsigned long kallsyms_lookup_name(const char *name) return module_kallsyms_lookup_name(name); } -#ifdef CONFIG_LIVEPATCH /* * Iterate over all symbols in vmlinux. For symbols from modules use * module_kallsyms_on_each_symbol instead. @@ -251,7 +251,6 @@ int kallsyms_on_each_symbol(int (*fn)(void *, const char *, struct module *, } return 0; } -#endif /* CONFIG_LIVEPATCH */ static unsigned long get_symbol_pos(unsigned long addr, unsigned long *symbolsize, diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index f15b826f9899..7fd11c17558d 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2229,6 +2229,59 @@ struct bpf_kprobe_multi_run_ctx { unsigned long entry_ip; }; +struct user_syms { + const char **syms; + char *buf; +}; + +static int copy_user_syms(struct user_syms *us, unsigned long __user *usyms, u32 cnt) +{ + unsigned long __user usymbol; + const char **syms = NULL; + char *buf = NULL, *p; + int err = -ENOMEM; + unsigned int i; + + syms = kvmalloc(cnt * sizeof(*syms), GFP_KERNEL); + if (!syms) + goto error; + + buf = kvmalloc(cnt * KSYM_NAME_LEN, GFP_KERNEL); + if (!buf) + goto error; + + for (p = buf, i = 0; i < cnt; i++) { + if (__get_user(usymbol, usyms + i)) { + err = -EFAULT; + goto error; + } + err = strncpy_from_user(p, (const char __user *) usymbol, KSYM_NAME_LEN); + if (err == KSYM_NAME_LEN) + err = -E2BIG; + if (err < 0) + goto error; + syms[i] = p; + p += err + 1; + } + + us->syms = syms; + us->buf = buf; + return 0; + +error: + if (err) { + kvfree(syms); + kvfree(buf); + } + return err; +} + +static void free_user_syms(struct user_syms *us) +{ + kvfree(us->syms); + kvfree(us->buf); +} + static void bpf_kprobe_multi_link_release(struct bpf_link *link) { struct bpf_kprobe_multi_link *kmulti_link; @@ -2349,53 +2402,12 @@ kprobe_multi_link_handler(struct fprobe *fp, unsigned long entry_ip, kprobe_multi_link_prog_run(link, entry_ip, regs); } -static int -kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt, - unsigned long *addrs) +static int symbols_cmp(const void *a, const void *b) { - unsigned long addr, size; - const char __user **syms; - int err = -ENOMEM; - unsigned int i; - char *func; - - size = cnt * sizeof(*syms); - syms = kvzalloc(size, GFP_KERNEL); - if (!syms) - return -ENOMEM; + const char **str_a = (const char **) a; + const char **str_b = (const char **) b; - func = kmalloc(KSYM_NAME_LEN, GFP_KERNEL); - if (!func) - goto error; - - if (copy_from_user(syms, usyms, size)) { - err = -EFAULT; - goto error; - } - - for (i = 0; i < cnt; i++) { - err = strncpy_from_user(func, syms[i], KSYM_NAME_LEN); - if (err == KSYM_NAME_LEN) - err = -E2BIG; - if (err < 0) - goto error; - err = -EINVAL; - addr = kallsyms_lookup_name(func); - if (!addr) - goto error; - if (!kallsyms_lookup_size_offset(addr, &size, NULL)) - goto error; - addr = ftrace_location_range(addr, addr + size - 1); - if (!addr) - goto error; - addrs[i] = addr; - } - - err = 0; -error: - kvfree(syms); - kfree(func); - return err; + return strcmp(*str_a, *str_b); } int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) @@ -2441,7 +2453,15 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr goto error; } } else { - err = kprobe_multi_resolve_syms(usyms, cnt, addrs); + struct user_syms us; + + err = copy_user_syms(&us, usyms, cnt); + if (err) + goto error; + + sort(us.syms, cnt, sizeof(*us.syms), symbols_cmp, NULL); + err = ftrace_lookup_symbols(us.syms, cnt, addrs); + free_user_syms(&us); if (err) goto error; } diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c index 89d9f994ebb0..aac63ca9c3d1 100644 --- a/kernel/trace/fprobe.c +++ b/kernel/trace/fprobe.c @@ -85,39 +85,31 @@ static void fprobe_exit_handler(struct rethook_node *rh, void *data, } NOKPROBE_SYMBOL(fprobe_exit_handler); +static int symbols_cmp(const void *a, const void *b) +{ + const char **str_a = (const char **) a; + const char **str_b = (const char **) b; + + return strcmp(*str_a, *str_b); +} + /* Convert ftrace location address from symbols */ static unsigned long *get_ftrace_locations(const char **syms, int num) { - unsigned long addr, size; unsigned long *addrs; - int i; /* Convert symbols to symbol address */ addrs = kcalloc(num, sizeof(*addrs), GFP_KERNEL); if (!addrs) return ERR_PTR(-ENOMEM); - for (i = 0; i < num; i++) { - addr = kallsyms_lookup_name(syms[i]); - if (!addr) /* Maybe wrong symbol */ - goto error; - - /* Convert symbol address to ftrace location. */ - if (!kallsyms_lookup_size_offset(addr, &size, NULL) || !size) - goto error; + /* ftrace_lookup_symbols expects sorted symbols */ + sort(syms, num, sizeof(*syms), symbols_cmp, NULL); - addr = ftrace_location_range(addr, addr + size - 1); - if (!addr) /* No dynamic ftrace there. */ - goto error; + if (!ftrace_lookup_symbols(syms, num, addrs)) + return addrs; - addrs[i] = addr; - } - - return addrs; - -error: kfree(addrs); - return ERR_PTR(-ENOENT); } diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 4f1d2f5e7263..07d87c7a525d 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -7964,3 +7964,65 @@ ftrace_enable_sysctl(struct ctl_table *table, int write, mutex_unlock(&ftrace_lock); return ret; } + +static int symbols_cmp(const void *a, const void *b) +{ + const char **str_a = (const char **) a; + const char **str_b = (const char **) b; + + return strcmp(*str_a, *str_b); +} + +struct kallsyms_data { + unsigned long *addrs; + const char **syms; + size_t cnt; + size_t found; +}; + +static int kallsyms_callback(void *data, const char *name, + struct module *mod, unsigned long addr) +{ + struct kallsyms_data *args = data; + + if (!bsearch(&name, args->syms, args->cnt, sizeof(*args->syms), symbols_cmp)) + return 0; + + addr = ftrace_location(addr); + if (!addr) + return 0; + + args->addrs[args->found++] = addr; + return args->found == args->cnt ? 1 : 0; +} + +/** + * ftrace_lookup_symbols - Lookup addresses for array of symbols + * + * @sorted_syms: array of symbols pointers symbols to resolve, + * must be alphabetically sorted + * @cnt: number of symbols/addresses in @syms/@addrs arrays + * @addrs: array for storing resulting addresses + * + * This function looks up addresses for array of symbols provided in + * @syms array (must be alphabetically sorted) and stores them in + * @addrs array, which needs to be big enough to store at least @cnt + * addresses. + * + * This function returns 0 if all provided symbols are found, + * -ESRCH otherwise. + */ +int ftrace_lookup_symbols(const char **sorted_syms, size_t cnt, unsigned long *addrs) +{ + struct kallsyms_data args; + int err; + + args.addrs = addrs; + args.syms = sorted_syms; + args.cnt = cnt; + args.found = 0; + err = kallsyms_on_each_symbol(kallsyms_callback, &args); + if (err < 0) + return err; + return args.found == args.cnt ? 0 : -ESRCH; +} diff --git a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c index c56db65d4c15..816eacededd1 100644 --- a/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c +++ b/tools/testing/selftests/bpf/prog_tests/kprobe_multi_test.c @@ -2,6 +2,9 @@ #include <test_progs.h> #include "kprobe_multi.skel.h" #include "trace_helpers.h" +#include "kprobe_multi_empty.skel.h" +#include "bpf/libbpf_internal.h" +#include "bpf/hashmap.h" static void kprobe_multi_test_run(struct kprobe_multi *skel, bool test_return) { @@ -301,6 +304,144 @@ cleanup: kprobe_multi__destroy(skel); } +static inline __u64 get_time_ns(void) +{ + struct timespec t; + + clock_gettime(CLOCK_MONOTONIC, &t); + return (__u64) t.tv_sec * 1000000000 + t.tv_nsec; +} + +static size_t symbol_hash(const void *key, void *ctx __maybe_unused) +{ + return str_hash((const char *) key); +} + +static bool symbol_equal(const void *key1, const void *key2, void *ctx __maybe_unused) +{ + return strcmp((const char *) key1, (const char *) key2) == 0; +} + +static int get_syms(char ***symsp, size_t *cntp) +{ + size_t cap = 0, cnt = 0, i; + char *name, **syms = NULL; + struct hashmap *map; + char buf[256]; + FILE *f; + int err; + + /* + * The available_filter_functions contains many duplicates, + * but other than that all symbols are usable in kprobe multi + * interface. + * Filtering out duplicates by using hashmap__add, which won't + * add existing entry. + */ + f = fopen("/sys/kernel/debug/tracing/available_filter_functions", "r"); + if (!f) + return -EINVAL; + + map = hashmap__new(symbol_hash, symbol_equal, NULL); + if (IS_ERR(map)) + goto error; + + while (fgets(buf, sizeof(buf), f)) { + /* skip modules */ + if (strchr(buf, '[')) + continue; + if (sscanf(buf, "%ms$*[^\n]\n", &name) != 1) + continue; + /* + * We attach to almost all kernel functions and some of them + * will cause 'suspicious RCU usage' when fprobe is attached + * to them. Filter out the current culprits - arch_cpu_idle + * and rcu_* functions. + */ + if (!strcmp(name, "arch_cpu_idle")) + continue; + if (!strncmp(name, "rcu_", 4)) + continue; + err = hashmap__add(map, name, NULL); + if (err) { + free(name); + if (err == -EEXIST) + continue; + goto error; + } + err = libbpf_ensure_mem((void **) &syms, &cap, + sizeof(*syms), cnt + 1); + if (err) { + free(name); + goto error; + } + syms[cnt] = name; + cnt++; + } + + *symsp = syms; + *cntp = cnt; + +error: + fclose(f); + hashmap__free(map); + if (err) { + for (i = 0; i < cnt; i++) + free(syms[cnt]); + free(syms); + } + return err; +} + +static void test_bench_attach(void) +{ + LIBBPF_OPTS(bpf_kprobe_multi_opts, opts); + struct kprobe_multi_empty *skel = NULL; + long attach_start_ns, attach_end_ns; + long detach_start_ns, detach_end_ns; + double attach_delta, detach_delta; + struct bpf_link *link = NULL; + char **syms = NULL; + size_t cnt, i; + + if (!ASSERT_OK(get_syms(&syms, &cnt), "get_syms")) + return; + + skel = kprobe_multi_empty__open_and_load(); + if (!ASSERT_OK_PTR(skel, "kprobe_multi_empty__open_and_load")) + goto cleanup; + + opts.syms = (const char **) syms; + opts.cnt = cnt; + + attach_start_ns = get_time_ns(); + link = bpf_program__attach_kprobe_multi_opts(skel->progs.test_kprobe_empty, + NULL, &opts); + attach_end_ns = get_time_ns(); + + if (!ASSERT_OK_PTR(link, "bpf_program__attach_kprobe_multi_opts")) + goto cleanup; + + detach_start_ns = get_time_ns(); + bpf_link__destroy(link); + detach_end_ns = get_time_ns(); + + attach_delta = (attach_end_ns - attach_start_ns) / 1000000000.0; + detach_delta = (detach_end_ns - detach_start_ns) / 1000000000.0; + + printf("%s: found %lu functions\n", __func__, cnt); + printf("%s: attached in %7.3lfs\n", __func__, attach_delta); + printf("%s: detached in %7.3lfs\n", __func__, detach_delta); + +cleanup: + kprobe_multi_empty__destroy(skel); + if (syms) { + for (i = 0; i < cnt; i++) + free(syms[i]); + free(syms); + } +} + void test_kprobe_multi_test(void) { if (!ASSERT_OK(load_kallsyms(), "load_kallsyms")) @@ -320,4 +461,6 @@ void test_kprobe_multi_test(void) test_attach_api_syms(); if (test__start_subtest("attach_api_fails")) test_attach_api_fails(); + if (test__start_subtest("bench_attach")) + test_bench_attach(); } diff --git a/tools/testing/selftests/bpf/progs/kprobe_multi_empty.c b/tools/testing/selftests/bpf/progs/kprobe_multi_empty.c new file mode 100644 index 000000000000..e76e499aca39 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/kprobe_multi_empty.c @@ -0,0 +1,12 @@ +// SPDX-License-Identifier: GPL-2.0 +#include <linux/bpf.h> +#include <bpf/bpf_helpers.h> +#include <bpf/bpf_tracing.h> + +char _license[] SEC("license") = "GPL"; + +SEC("kprobe.multi/") +int test_kprobe_empty(struct pt_regs *ctx) +{ + return 0; +} |