bpf_program__attach_kprobe_opts() currently attaches a single kprobe only by func_name, with an optional offset. This covers only the symbol- based form, not the raw-address form that the kernel already supports for both kprobe PMU events and legacy tracefs/debugfs kprobes. Callers that already have a target IP still have to drop down to perf_event_open() or direct tracefs writes.
libbpf already exposes address-based attach for kprobe_multi through bpf_kprobe_multi_opts.addrs. This commit adds bpf_kprobe_opts.addr so that single kprobes can be attached either by func_name + offset or by raw address. Signed-off-by: Hoyeon Lee <[email protected]> --- tools/lib/bpf/libbpf.c | 77 +++++++++++++++++++++++++++++------------- tools/lib/bpf/libbpf.h | 5 ++- 2 files changed, 57 insertions(+), 25 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 9ea41f40dc82..a49ea01288ad 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -11523,7 +11523,7 @@ static int determine_uprobe_retprobe_bit(void) #define PERF_UPROBE_REF_CTR_OFFSET_SHIFT 32 static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name, - uint64_t offset, int pid, size_t ref_ctr_off) + uint64_t offset_or_addr, int pid, size_t ref_ctr_off) { const size_t attr_sz = sizeof(struct perf_event_attr); struct perf_event_attr attr; @@ -11558,7 +11558,7 @@ static int perf_event_open_probe(bool uprobe, bool retprobe, const char *name, attr.type = type; attr.config |= (__u64)ref_ctr_off << PERF_UPROBE_REF_CTR_OFFSET_SHIFT; attr.config1 = ptr_to_u64(name); /* kprobe_func or uprobe_path */ - attr.config2 = offset; /* kprobe_addr or probe_offset */ + attr.config2 = offset_or_addr; /* kprobe_addr or probe_offset */ /* pid filter is meaningful only for uprobes */ pfd = syscall(__NR_perf_event_open, &attr, @@ -11633,13 +11633,14 @@ static const char *tracefs_available_filter_functions_addrs(void) } static void gen_probe_legacy_event_name(char *buf, size_t buf_sz, - const char *name, size_t offset) + const char *name, uint64_t offset_or_addr) { static int index = 0; int i; - snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%zx", getpid(), - __sync_fetch_and_add(&index, 1), name, offset); + snprintf(buf, buf_sz, "libbpf_%u_%d_%s_0x%" PRIx64, getpid(), + __sync_fetch_and_add(&index, 1), name ?: "addr", + offset_or_addr); /* sanitize name in the probe name */ for (i = 0; buf[i]; i++) { @@ -11648,13 +11649,27 @@ static void gen_probe_legacy_event_name(char *buf, size_t buf_sz, } } +static void gen_kprobe_target(char *buf, size_t buf_sz, const char *name, + uint64_t offset_or_addr) +{ + if (name) + snprintf(buf, buf_sz, "%s+0x%" PRIx64, name, offset_or_addr); + else + snprintf(buf, buf_sz, "0x%" PRIx64, offset_or_addr); +} + static int add_kprobe_event_legacy(const char *probe_name, bool retprobe, - const char *kfunc_name, size_t offset) + const char *kfunc_name, uint64_t offset_or_addr) { - return append_to_file(tracefs_kprobe_events(), "%c:%s/%s %s+0x%zx", + char probe_target[128]; + + gen_kprobe_target(probe_target, sizeof(probe_target), kfunc_name, + offset_or_addr); + + return append_to_file(tracefs_kprobe_events(), "%c:%s/%s %s", retprobe ? 'r' : 'p', retprobe ? "kretprobes" : "kprobes", - probe_name, kfunc_name, offset); + probe_name, probe_target); } static int remove_kprobe_event_legacy(const char *probe_name, bool retprobe) @@ -11674,24 +11689,27 @@ static int determine_kprobe_perf_type_legacy(const char *probe_name, bool retpro } static int perf_event_kprobe_open_legacy(const char *probe_name, bool retprobe, - const char *kfunc_name, size_t offset, int pid) + const char *kfunc_name, uint64_t offset_or_addr, int pid) { const size_t attr_sz = sizeof(struct perf_event_attr); struct perf_event_attr attr; int type, pfd, err; + char probe_target[128]; - err = add_kprobe_event_legacy(probe_name, retprobe, kfunc_name, offset); + gen_kprobe_target(probe_target, sizeof(probe_target), kfunc_name, + offset_or_addr); + + err = add_kprobe_event_legacy(probe_name, retprobe, kfunc_name, + offset_or_addr); if (err < 0) { - pr_warn("failed to add legacy kprobe event for '%s+0x%zx': %s\n", - kfunc_name, offset, + pr_warn("failed to add legacy kprobe event for '%s': %s\n", probe_target, errstr(err)); return err; } type = determine_kprobe_perf_type_legacy(probe_name, retprobe); if (type < 0) { err = type; - pr_warn("failed to determine legacy kprobe event id for '%s+0x%zx': %s\n", - kfunc_name, offset, + pr_warn("failed to determine legacy kprobe event id for '%s': %s\n", probe_target, errstr(err)); goto err_clean_legacy; } @@ -11784,6 +11802,9 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, enum probe_attach_mode attach_mode; char *legacy_probe = NULL; struct bpf_link *link; + uint64_t offset_or_addr; + char probe_target[128]; + unsigned long addr; size_t offset; bool retprobe, legacy; int pfd, err; @@ -11794,8 +11815,18 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, attach_mode = OPTS_GET(opts, attach_mode, PROBE_ATTACH_MODE_DEFAULT); retprobe = OPTS_GET(opts, retprobe, false); offset = OPTS_GET(opts, offset, 0); + addr = OPTS_GET(opts, addr, 0); + offset_or_addr = func_name ? offset : addr; pe_opts.bpf_cookie = OPTS_GET(opts, bpf_cookie, 0); + if (!!func_name == !!addr) + return libbpf_err_ptr(-EINVAL); + if (addr && offset) + return libbpf_err_ptr(-EINVAL); + + gen_kprobe_target(probe_target, sizeof(probe_target), func_name, + offset_or_addr); + legacy = determine_kprobe_perf_type() < 0; switch (attach_mode) { case PROBE_ATTACH_MODE_LEGACY: @@ -11819,26 +11850,25 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, if (!legacy) { pfd = perf_event_open_probe(false /* uprobe */, retprobe, - func_name, offset, + func_name, offset_or_addr, -1 /* pid */, 0 /* ref_ctr_off */); } else { char probe_name[MAX_EVENT_NAME_LEN]; gen_probe_legacy_event_name(probe_name, sizeof(probe_name), - func_name, offset); + func_name, offset_or_addr); legacy_probe = strdup(probe_name); if (!legacy_probe) return libbpf_err_ptr(-ENOMEM); pfd = perf_event_kprobe_open_legacy(legacy_probe, retprobe, func_name, - offset, -1 /* pid */); + offset_or_addr, -1 /* pid */); } if (pfd < 0) { - err = -errno; - pr_warn("prog '%s': failed to create %s '%s+0x%zx' perf event: %s\n", - prog->name, retprobe ? "kretprobe" : "kprobe", - func_name, offset, + err = pfd; + pr_warn("prog '%s': failed to create %s '%s' perf event: %s\n", + prog->name, retprobe ? "kretprobe" : "kprobe", probe_target, errstr(err)); goto err_out; } @@ -11846,9 +11876,8 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, err = libbpf_get_error(link); if (err) { close(pfd); - pr_warn("prog '%s': failed to attach to %s '%s+0x%zx': %s\n", - prog->name, retprobe ? "kretprobe" : "kprobe", - func_name, offset, + pr_warn("prog '%s': failed to attach to %s '%s': %s\n", + prog->name, retprobe ? "kretprobe" : "kprobe", probe_target, errstr(err)); goto err_clean_legacy; } diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 0be34852350f..526d44111e81 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -563,9 +563,12 @@ struct bpf_kprobe_opts { bool retprobe; /* kprobe attach mode */ enum probe_attach_mode attach_mode; + /* kernel address to install kprobe to; mutually exclusive with func_name */ + unsigned long addr; size_t :0; }; -#define bpf_kprobe_opts__last_field attach_mode + +#define bpf_kprobe_opts__last_field addr LIBBPF_API struct bpf_link * bpf_program__attach_kprobe(const struct bpf_program *prog, bool retprobe, -- 2.52.0
