bpf_program__attach_kprobe_opts() documents single-kprobe attach through func_name, with an optional offset. For the PMU-based non-legacy path, func_name = NULL with an absolute address in offset already works as well, but that is not described in the API.
This commit clarifies this existing non-legacy behavior. For PMU-based attach, callers can use func_name = NULL with an absolute address in offset as the raw-address form. For legacy tracefs/debugfs kprobes, reject this form explicitly. Signed-off-by: Hoyeon Lee <[email protected]> --- tools/lib/bpf/libbpf.c | 33 ++++++++++++++++++++++++--------- tools/lib/bpf/libbpf.h | 3 ++- 2 files changed, 26 insertions(+), 10 deletions(-) diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index 9ea41f40dc82..8cf90a073455 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -28,6 +28,7 @@ #include <asm/unistd.h> #include <linux/err.h> #include <linux/kernel.h> +#include <linux/kallsyms.h> #include <linux/bpf.h> #include <linux/btf.h> #include <linux/filter.h> @@ -11523,7 +11524,8 @@ 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 +11560,7 @@ 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, @@ -11648,6 +11650,15 @@ 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) { @@ -11781,6 +11792,7 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, const struct bpf_kprobe_opts *opts) { DECLARE_LIBBPF_OPTS(bpf_perf_event_opts, pe_opts); + char probe_target[KSYM_NAME_LEN + 32]; enum probe_attach_mode attach_mode; char *legacy_probe = NULL; struct bpf_link *link; @@ -11816,6 +11828,11 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, default: return libbpf_err_ptr(-EINVAL); } + if (!func_name && legacy) + return libbpf_err_ptr(-ENOTSUP); + + gen_kprobe_target(probe_target, sizeof(probe_target), + func_name, offset); if (!legacy) { pfd = perf_event_open_probe(false /* uprobe */, retprobe, @@ -11835,21 +11852,19 @@ bpf_program__attach_kprobe_opts(const struct bpf_program *prog, offset, -1 /* pid */); } if (pfd < 0) { - err = -errno; - pr_warn("prog '%s': failed to create %s '%s+0x%zx' perf event: %s\n", + err = pfd; + pr_warn("prog '%s': failed to create %s '%s' perf event: %s\n", prog->name, retprobe ? "kretprobe" : "kprobe", - func_name, offset, - errstr(err)); + probe_target, errstr(err)); goto err_out; } link = bpf_program__attach_perf_event_opts(prog, pfd, &pe_opts); err = libbpf_get_error(link); if (err) { close(pfd); - pr_warn("prog '%s': failed to attach to %s '%s+0x%zx': %s\n", + pr_warn("prog '%s': failed to attach to %s '%s': %s\n", prog->name, retprobe ? "kretprobe" : "kprobe", - func_name, offset, - errstr(err)); + probe_target, errstr(err)); goto err_clean_legacy; } if (legacy) { diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h index 0be34852350f..f75f3ab0f20c 100644 --- a/tools/lib/bpf/libbpf.h +++ b/tools/lib/bpf/libbpf.h @@ -557,7 +557,7 @@ struct bpf_kprobe_opts { size_t sz; /* custom user-provided value fetchable through bpf_get_attach_cookie() */ __u64 bpf_cookie; - /* function's offset to install kprobe to */ + /* function offset, or raw address if func_name == NULL (non-legacy) */ size_t offset; /* kprobe is return probe */ bool retprobe; @@ -565,6 +565,7 @@ struct bpf_kprobe_opts { enum probe_attach_mode attach_mode; size_t :0; }; + #define bpf_kprobe_opts__last_field attach_mode LIBBPF_API struct bpf_link * -- 2.52.0
