summaryrefslogtreecommitdiffstats
path: root/tools/lib/bpf/usdt.c
diff options
context:
space:
mode:
Diffstat (limited to 'tools/lib/bpf/usdt.c')
-rw-r--r--tools/lib/bpf/usdt.c1600
1 files changed, 1600 insertions, 0 deletions
diff --git a/tools/lib/bpf/usdt.c b/tools/lib/bpf/usdt.c
new file mode 100644
index 0000000000..93794f01bb
--- /dev/null
+++ b/tools/lib/bpf/usdt.c
@@ -0,0 +1,1600 @@
+// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
+/* Copyright (c) 2022 Meta Platforms, Inc. and affiliates. */
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <libelf.h>
+#include <gelf.h>
+#include <unistd.h>
+#include <linux/ptrace.h>
+#include <linux/kernel.h>
+
+/* s8 will be marked as poison while it's a reg of riscv */
+#if defined(__riscv)
+#define rv_s8 s8
+#endif
+
+#include "bpf.h"
+#include "libbpf.h"
+#include "libbpf_common.h"
+#include "libbpf_internal.h"
+#include "hashmap.h"
+
+/* libbpf's USDT support consists of BPF-side state/code and user-space
+ * state/code working together in concert. BPF-side parts are defined in
+ * usdt.bpf.h header library. User-space state is encapsulated by struct
+ * usdt_manager and all the supporting code centered around usdt_manager.
+ *
+ * usdt.bpf.h defines two BPF maps that usdt_manager expects: USDT spec map
+ * and IP-to-spec-ID map, which is auxiliary map necessary for kernels that
+ * don't support BPF cookie (see below). These two maps are implicitly
+ * embedded into user's end BPF object file when user's code included
+ * usdt.bpf.h. This means that libbpf doesn't do anything special to create
+ * these USDT support maps. They are created by normal libbpf logic of
+ * instantiating BPF maps when opening and loading BPF object.
+ *
+ * As such, libbpf is basically unaware of the need to do anything
+ * USDT-related until the very first call to bpf_program__attach_usdt(), which
+ * can be called by user explicitly or happen automatically during skeleton
+ * attach (or, equivalently, through generic bpf_program__attach() call). At
+ * this point, libbpf will instantiate and initialize struct usdt_manager and
+ * store it in bpf_object. USDT manager is per-BPF object construct, as each
+ * independent BPF object might or might not have USDT programs, and thus all
+ * the expected USDT-related state. There is no coordination between two
+ * bpf_object in parts of USDT attachment, they are oblivious of each other's
+ * existence and libbpf is just oblivious, dealing with bpf_object-specific
+ * USDT state.
+ *
+ * Quick crash course on USDTs.
+ *
+ * From user-space application's point of view, USDT is essentially just
+ * a slightly special function call that normally has zero overhead, unless it
+ * is being traced by some external entity (e.g, BPF-based tool). Here's how
+ * a typical application can trigger USDT probe:
+ *
+ * #include <sys/sdt.h> // provided by systemtap-sdt-devel package
+ * // folly also provide similar functionality in folly/tracing/StaticTracepoint.h
+ *
+ * STAP_PROBE3(my_usdt_provider, my_usdt_probe_name, 123, x, &y);
+ *
+ * USDT is identified by it's <provider-name>:<probe-name> pair of names. Each
+ * individual USDT has a fixed number of arguments (3 in the above example)
+ * and specifies values of each argument as if it was a function call.
+ *
+ * USDT call is actually not a function call, but is instead replaced by
+ * a single NOP instruction (thus zero overhead, effectively). But in addition
+ * to that, those USDT macros generate special SHT_NOTE ELF records in
+ * .note.stapsdt ELF section. Here's an example USDT definition as emitted by
+ * `readelf -n <binary>`:
+ *
+ * stapsdt 0x00000089 NT_STAPSDT (SystemTap probe descriptors)
+ * Provider: test
+ * Name: usdt12
+ * Location: 0x0000000000549df3, Base: 0x00000000008effa4, Semaphore: 0x0000000000a4606e
+ * Arguments: -4@-1204(%rbp) -4@%edi -8@-1216(%rbp) -8@%r8 -4@$5 -8@%r9 8@%rdx 8@%r10 -4@$-9 -2@%cx -2@%ax -1@%sil
+ *
+ * In this case we have USDT test:usdt12 with 12 arguments.
+ *
+ * Location and base are offsets used to calculate absolute IP address of that
+ * NOP instruction that kernel can replace with an interrupt instruction to
+ * trigger instrumentation code (BPF program for all that we care about).
+ *
+ * Semaphore above is and optional feature. It records an address of a 2-byte
+ * refcount variable (normally in '.probes' ELF section) used for signaling if
+ * there is anything that is attached to USDT. This is useful for user
+ * applications if, for example, they need to prepare some arguments that are
+ * passed only to USDTs and preparation is expensive. By checking if USDT is
+ * "activated", an application can avoid paying those costs unnecessarily.
+ * Recent enough kernel has built-in support for automatically managing this
+ * refcount, which libbpf expects and relies on. If USDT is defined without
+ * associated semaphore, this value will be zero. See selftests for semaphore
+ * examples.
+ *
+ * Arguments is the most interesting part. This USDT specification string is
+ * providing information about all the USDT arguments and their locations. The
+ * part before @ sign defined byte size of the argument (1, 2, 4, or 8) and
+ * whether the argument is signed or unsigned (negative size means signed).
+ * The part after @ sign is assembly-like definition of argument location
+ * (see [0] for more details). Technically, assembler can provide some pretty
+ * advanced definitions, but libbpf is currently supporting three most common
+ * cases:
+ * 1) immediate constant, see 5th and 9th args above (-4@$5 and -4@-9);
+ * 2) register value, e.g., 8@%rdx, which means "unsigned 8-byte integer
+ * whose value is in register %rdx";
+ * 3) memory dereference addressed by register, e.g., -4@-1204(%rbp), which
+ * specifies signed 32-bit integer stored at offset -1204 bytes from
+ * memory address stored in %rbp.
+ *
+ * [0] https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
+ *
+ * During attachment, libbpf parses all the relevant USDT specifications and
+ * prepares `struct usdt_spec` (USDT spec), which is then provided to BPF-side
+ * code through spec map. This allows BPF applications to quickly fetch the
+ * actual value at runtime using a simple BPF-side code.
+ *
+ * With basics out of the way, let's go over less immediately obvious aspects
+ * of supporting USDTs.
+ *
+ * First, there is no special USDT BPF program type. It is actually just
+ * a uprobe BPF program (which for kernel, at least currently, is just a kprobe
+ * program, so BPF_PROG_TYPE_KPROBE program type). With the only difference
+ * that uprobe is usually attached at the function entry, while USDT will
+ * normally will be somewhere inside the function. But it should always be
+ * pointing to NOP instruction, which makes such uprobes the fastest uprobe
+ * kind.
+ *
+ * Second, it's important to realize that such STAP_PROBEn(provider, name, ...)
+ * macro invocations can end up being inlined many-many times, depending on
+ * specifics of each individual user application. So single conceptual USDT
+ * (identified by provider:name pair of identifiers) is, generally speaking,
+ * multiple uprobe locations (USDT call sites) in different places in user
+ * application. Further, again due to inlining, each USDT call site might end
+ * up having the same argument #N be located in a different place. In one call
+ * site it could be a constant, in another will end up in a register, and in
+ * yet another could be some other register or even somewhere on the stack.
+ *
+ * As such, "attaching to USDT" means (in general case) attaching the same
+ * uprobe BPF program to multiple target locations in user application, each
+ * potentially having a completely different USDT spec associated with it.
+ * To wire all this up together libbpf allocates a unique integer spec ID for
+ * each unique USDT spec. Spec IDs are allocated as sequential small integers
+ * so that they can be used as keys in array BPF map (for performance reasons).
+ * Spec ID allocation and accounting is big part of what usdt_manager is
+ * about. This state has to be maintained per-BPF object and coordinate
+ * between different USDT attachments within the same BPF object.
+ *
+ * Spec ID is the key in spec BPF map, value is the actual USDT spec layed out
+ * as struct usdt_spec. Each invocation of BPF program at runtime needs to
+ * know its associated spec ID. It gets it either through BPF cookie, which
+ * libbpf sets to spec ID during attach time, or, if kernel is too old to
+ * support BPF cookie, through IP-to-spec-ID map that libbpf maintains in such
+ * case. The latter means that some modes of operation can't be supported
+ * without BPF cookie. Such mode is attaching to shared library "generically",
+ * without specifying target process. In such case, it's impossible to
+ * calculate absolute IP addresses for IP-to-spec-ID map, and thus such mode
+ * is not supported without BPF cookie support.
+ *
+ * Note that libbpf is using BPF cookie functionality for its own internal
+ * needs, so user itself can't rely on BPF cookie feature. To that end, libbpf
+ * provides conceptually equivalent USDT cookie support. It's still u64
+ * user-provided value that can be associated with USDT attachment. Note that
+ * this will be the same value for all USDT call sites within the same single
+ * *logical* USDT attachment. This makes sense because to user attaching to
+ * USDT is a single BPF program triggered for singular USDT probe. The fact
+ * that this is done at multiple actual locations is a mostly hidden
+ * implementation details. This USDT cookie value can be fetched with
+ * bpf_usdt_cookie(ctx) API provided by usdt.bpf.h
+ *
+ * Lastly, while single USDT can have tons of USDT call sites, it doesn't
+ * necessarily have that many different USDT specs. It very well might be
+ * that 1000 USDT call sites only need 5 different USDT specs, because all the
+ * arguments are typically contained in a small set of registers or stack
+ * locations. As such, it's wasteful to allocate as many USDT spec IDs as
+ * there are USDT call sites. So libbpf tries to be frugal and performs
+ * on-the-fly deduplication during a single USDT attachment to only allocate
+ * the minimal required amount of unique USDT specs (and thus spec IDs). This
+ * is trivially achieved by using USDT spec string (Arguments string from USDT
+ * note) as a lookup key in a hashmap. USDT spec string uniquely defines
+ * everything about how to fetch USDT arguments, so two USDT call sites
+ * sharing USDT spec string can safely share the same USDT spec and spec ID.
+ * Note, this spec string deduplication is happening only during the same USDT
+ * attachment, so each USDT spec shares the same USDT cookie value. This is
+ * not generally true for other USDT attachments within the same BPF object,
+ * as even if USDT spec string is the same, USDT cookie value can be
+ * different. It was deemed excessive to try to deduplicate across independent
+ * USDT attachments by taking into account USDT spec string *and* USDT cookie
+ * value, which would complicated spec ID accounting significantly for little
+ * gain.
+ */
+
+#define USDT_BASE_SEC ".stapsdt.base"
+#define USDT_SEMA_SEC ".probes"
+#define USDT_NOTE_SEC ".note.stapsdt"
+#define USDT_NOTE_TYPE 3
+#define USDT_NOTE_NAME "stapsdt"
+
+/* should match exactly enum __bpf_usdt_arg_type from usdt.bpf.h */
+enum usdt_arg_type {
+ USDT_ARG_CONST,
+ USDT_ARG_REG,
+ USDT_ARG_REG_DEREF,
+};
+
+/* should match exactly struct __bpf_usdt_arg_spec from usdt.bpf.h */
+struct usdt_arg_spec {
+ __u64 val_off;
+ enum usdt_arg_type arg_type;
+ short reg_off;
+ bool arg_signed;
+ char arg_bitshift;
+};
+
+/* should match BPF_USDT_MAX_ARG_CNT in usdt.bpf.h */
+#define USDT_MAX_ARG_CNT 12
+
+/* should match struct __bpf_usdt_spec from usdt.bpf.h */
+struct usdt_spec {
+ struct usdt_arg_spec args[USDT_MAX_ARG_CNT];
+ __u64 usdt_cookie;
+ short arg_cnt;
+};
+
+struct usdt_note {
+ const char *provider;
+ const char *name;
+ /* USDT args specification string, e.g.:
+ * "-4@%esi -4@-24(%rbp) -4@%ecx 2@%ax 8@%rdx"
+ */
+ const char *args;
+ long loc_addr;
+ long base_addr;
+ long sema_addr;
+};
+
+struct usdt_target {
+ long abs_ip;
+ long rel_ip;
+ long sema_off;
+ struct usdt_spec spec;
+ const char *spec_str;
+};
+
+struct usdt_manager {
+ struct bpf_map *specs_map;
+ struct bpf_map *ip_to_spec_id_map;
+
+ int *free_spec_ids;
+ size_t free_spec_cnt;
+ size_t next_free_spec_id;
+
+ bool has_bpf_cookie;
+ bool has_sema_refcnt;
+ bool has_uprobe_multi;
+};
+
+struct usdt_manager *usdt_manager_new(struct bpf_object *obj)
+{
+ static const char *ref_ctr_sysfs_path = "/sys/bus/event_source/devices/uprobe/format/ref_ctr_offset";
+ struct usdt_manager *man;
+ struct bpf_map *specs_map, *ip_to_spec_id_map;
+
+ specs_map = bpf_object__find_map_by_name(obj, "__bpf_usdt_specs");
+ ip_to_spec_id_map = bpf_object__find_map_by_name(obj, "__bpf_usdt_ip_to_spec_id");
+ if (!specs_map || !ip_to_spec_id_map) {
+ pr_warn("usdt: failed to find USDT support BPF maps, did you forget to include bpf/usdt.bpf.h?\n");
+ return ERR_PTR(-ESRCH);
+ }
+
+ man = calloc(1, sizeof(*man));
+ if (!man)
+ return ERR_PTR(-ENOMEM);
+
+ man->specs_map = specs_map;
+ man->ip_to_spec_id_map = ip_to_spec_id_map;
+
+ /* Detect if BPF cookie is supported for kprobes.
+ * We don't need IP-to-ID mapping if we can use BPF cookies.
+ * Added in: 7adfc6c9b315 ("bpf: Add bpf_get_attach_cookie() BPF helper to access bpf_cookie value")
+ */
+ man->has_bpf_cookie = kernel_supports(obj, FEAT_BPF_COOKIE);
+
+ /* Detect kernel support for automatic refcounting of USDT semaphore.
+ * If this is not supported, USDTs with semaphores will not be supported.
+ * Added in: a6ca88b241d5 ("trace_uprobe: support reference counter in fd-based uprobe")
+ */
+ man->has_sema_refcnt = faccessat(AT_FDCWD, ref_ctr_sysfs_path, F_OK, AT_EACCESS) == 0;
+
+ /*
+ * Detect kernel support for uprobe multi link to be used for attaching
+ * usdt probes.
+ */
+ man->has_uprobe_multi = kernel_supports(obj, FEAT_UPROBE_MULTI_LINK);
+ return man;
+}
+
+void usdt_manager_free(struct usdt_manager *man)
+{
+ if (IS_ERR_OR_NULL(man))
+ return;
+
+ free(man->free_spec_ids);
+ free(man);
+}
+
+static int sanity_check_usdt_elf(Elf *elf, const char *path)
+{
+ GElf_Ehdr ehdr;
+ int endianness;
+
+ if (elf_kind(elf) != ELF_K_ELF) {
+ pr_warn("usdt: unrecognized ELF kind %d for '%s'\n", elf_kind(elf), path);
+ return -EBADF;
+ }
+
+ switch (gelf_getclass(elf)) {
+ case ELFCLASS64:
+ if (sizeof(void *) != 8) {
+ pr_warn("usdt: attaching to 64-bit ELF binary '%s' is not supported\n", path);
+ return -EBADF;
+ }
+ break;
+ case ELFCLASS32:
+ if (sizeof(void *) != 4) {
+ pr_warn("usdt: attaching to 32-bit ELF binary '%s' is not supported\n", path);
+ return -EBADF;
+ }
+ break;
+ default:
+ pr_warn("usdt: unsupported ELF class for '%s'\n", path);
+ return -EBADF;
+ }
+
+ if (!gelf_getehdr(elf, &ehdr))
+ return -EINVAL;
+
+ if (ehdr.e_type != ET_EXEC && ehdr.e_type != ET_DYN) {
+ pr_warn("usdt: unsupported type of ELF binary '%s' (%d), only ET_EXEC and ET_DYN are supported\n",
+ path, ehdr.e_type);
+ return -EBADF;
+ }
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+ endianness = ELFDATA2LSB;
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+ endianness = ELFDATA2MSB;
+#else
+# error "Unrecognized __BYTE_ORDER__"
+#endif
+ if (endianness != ehdr.e_ident[EI_DATA]) {
+ pr_warn("usdt: ELF endianness mismatch for '%s'\n", path);
+ return -EBADF;
+ }
+
+ return 0;
+}
+
+static int find_elf_sec_by_name(Elf *elf, const char *sec_name, GElf_Shdr *shdr, Elf_Scn **scn)
+{
+ Elf_Scn *sec = NULL;
+ size_t shstrndx;
+
+ if (elf_getshdrstrndx(elf, &shstrndx))
+ return -EINVAL;
+
+ /* check if ELF is corrupted and avoid calling elf_strptr if yes */
+ if (!elf_rawdata(elf_getscn(elf, shstrndx), NULL))
+ return -EINVAL;
+
+ while ((sec = elf_nextscn(elf, sec)) != NULL) {
+ char *name;
+
+ if (!gelf_getshdr(sec, shdr))
+ return -EINVAL;
+
+ name = elf_strptr(elf, shstrndx, shdr->sh_name);
+ if (name && strcmp(sec_name, name) == 0) {
+ *scn = sec;
+ return 0;
+ }
+ }
+
+ return -ENOENT;
+}
+
+struct elf_seg {
+ long start;
+ long end;
+ long offset;
+ bool is_exec;
+};
+
+static int cmp_elf_segs(const void *_a, const void *_b)
+{
+ const struct elf_seg *a = _a;
+ const struct elf_seg *b = _b;
+
+ return a->start < b->start ? -1 : 1;
+}
+
+static int parse_elf_segs(Elf *elf, const char *path, struct elf_seg **segs, size_t *seg_cnt)
+{
+ GElf_Phdr phdr;
+ size_t n;
+ int i, err;
+ struct elf_seg *seg;
+ void *tmp;
+
+ *seg_cnt = 0;
+
+ if (elf_getphdrnum(elf, &n)) {
+ err = -errno;
+ return err;
+ }
+
+ for (i = 0; i < n; i++) {
+ if (!gelf_getphdr(elf, i, &phdr)) {
+ err = -errno;
+ return err;
+ }
+
+ pr_debug("usdt: discovered PHDR #%d in '%s': vaddr 0x%lx memsz 0x%lx offset 0x%lx type 0x%lx flags 0x%lx\n",
+ i, path, (long)phdr.p_vaddr, (long)phdr.p_memsz, (long)phdr.p_offset,
+ (long)phdr.p_type, (long)phdr.p_flags);
+ if (phdr.p_type != PT_LOAD)
+ continue;
+
+ tmp = libbpf_reallocarray(*segs, *seg_cnt + 1, sizeof(**segs));
+ if (!tmp)
+ return -ENOMEM;
+
+ *segs = tmp;
+ seg = *segs + *seg_cnt;
+ (*seg_cnt)++;
+
+ seg->start = phdr.p_vaddr;
+ seg->end = phdr.p_vaddr + phdr.p_memsz;
+ seg->offset = phdr.p_offset;
+ seg->is_exec = phdr.p_flags & PF_X;
+ }
+
+ if (*seg_cnt == 0) {
+ pr_warn("usdt: failed to find PT_LOAD program headers in '%s'\n", path);
+ return -ESRCH;
+ }
+
+ qsort(*segs, *seg_cnt, sizeof(**segs), cmp_elf_segs);
+ return 0;
+}
+
+static int parse_vma_segs(int pid, const char *lib_path, struct elf_seg **segs, size_t *seg_cnt)
+{
+ char path[PATH_MAX], line[PATH_MAX], mode[16];
+ size_t seg_start, seg_end, seg_off;
+ struct elf_seg *seg;
+ int tmp_pid, i, err;
+ FILE *f;
+
+ *seg_cnt = 0;
+
+ /* Handle containerized binaries only accessible from
+ * /proc/<pid>/root/<path>. They will be reported as just /<path> in
+ * /proc/<pid>/maps.
+ */
+ if (sscanf(lib_path, "/proc/%d/root%s", &tmp_pid, path) == 2 && pid == tmp_pid)
+ goto proceed;
+
+ if (!realpath(lib_path, path)) {
+ pr_warn("usdt: failed to get absolute path of '%s' (err %d), using path as is...\n",
+ lib_path, -errno);
+ libbpf_strlcpy(path, lib_path, sizeof(path));
+ }
+
+proceed:
+ sprintf(line, "/proc/%d/maps", pid);
+ f = fopen(line, "re");
+ if (!f) {
+ err = -errno;
+ pr_warn("usdt: failed to open '%s' to get base addr of '%s': %d\n",
+ line, lib_path, err);
+ return err;
+ }
+
+ /* We need to handle lines with no path at the end:
+ *
+ * 7f5c6f5d1000-7f5c6f5d3000 rw-p 001c7000 08:04 21238613 /usr/lib64/libc-2.17.so
+ * 7f5c6f5d3000-7f5c6f5d8000 rw-p 00000000 00:00 0
+ * 7f5c6f5d8000-7f5c6f5d9000 r-xp 00000000 103:01 362990598 /data/users/andriin/linux/tools/bpf/usdt/libhello_usdt.so
+ */
+ while (fscanf(f, "%zx-%zx %s %zx %*s %*d%[^\n]\n",
+ &seg_start, &seg_end, mode, &seg_off, line) == 5) {
+ void *tmp;
+
+ /* to handle no path case (see above) we need to capture line
+ * without skipping any whitespaces. So we need to strip
+ * leading whitespaces manually here
+ */
+ i = 0;
+ while (isblank(line[i]))
+ i++;
+ if (strcmp(line + i, path) != 0)
+ continue;
+
+ pr_debug("usdt: discovered segment for lib '%s': addrs %zx-%zx mode %s offset %zx\n",
+ path, seg_start, seg_end, mode, seg_off);
+
+ /* ignore non-executable sections for shared libs */
+ if (mode[2] != 'x')
+ continue;
+
+ tmp = libbpf_reallocarray(*segs, *seg_cnt + 1, sizeof(**segs));
+ if (!tmp) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+
+ *segs = tmp;
+ seg = *segs + *seg_cnt;
+ *seg_cnt += 1;
+
+ seg->start = seg_start;
+ seg->end = seg_end;
+ seg->offset = seg_off;
+ seg->is_exec = true;
+ }
+
+ if (*seg_cnt == 0) {
+ pr_warn("usdt: failed to find '%s' (resolved to '%s') within PID %d memory mappings\n",
+ lib_path, path, pid);
+ err = -ESRCH;
+ goto err_out;
+ }
+
+ qsort(*segs, *seg_cnt, sizeof(**segs), cmp_elf_segs);
+ err = 0;
+err_out:
+ fclose(f);
+ return err;
+}
+
+static struct elf_seg *find_elf_seg(struct elf_seg *segs, size_t seg_cnt, long virtaddr)
+{
+ struct elf_seg *seg;
+ int i;
+
+ /* for ELF binaries (both executables and shared libraries), we are
+ * given virtual address (absolute for executables, relative for
+ * libraries) which should match address range of [seg_start, seg_end)
+ */
+ for (i = 0, seg = segs; i < seg_cnt; i++, seg++) {
+ if (seg->start <= virtaddr && virtaddr < seg->end)
+ return seg;
+ }
+ return NULL;
+}
+
+static struct elf_seg *find_vma_seg(struct elf_seg *segs, size_t seg_cnt, long offset)
+{
+ struct elf_seg *seg;
+ int i;
+
+ /* for VMA segments from /proc/<pid>/maps file, provided "address" is
+ * actually a file offset, so should be fall within logical
+ * offset-based range of [offset_start, offset_end)
+ */
+ for (i = 0, seg = segs; i < seg_cnt; i++, seg++) {
+ if (seg->offset <= offset && offset < seg->offset + (seg->end - seg->start))
+ return seg;
+ }
+ return NULL;
+}
+
+static int parse_usdt_note(Elf *elf, const char *path, GElf_Nhdr *nhdr,
+ const char *data, size_t name_off, size_t desc_off,
+ struct usdt_note *usdt_note);
+
+static int parse_usdt_spec(struct usdt_spec *spec, const struct usdt_note *note, __u64 usdt_cookie);
+
+static int collect_usdt_targets(struct usdt_manager *man, Elf *elf, const char *path, pid_t pid,
+ const char *usdt_provider, const char *usdt_name, __u64 usdt_cookie,
+ struct usdt_target **out_targets, size_t *out_target_cnt)
+{
+ size_t off, name_off, desc_off, seg_cnt = 0, vma_seg_cnt = 0, target_cnt = 0;
+ struct elf_seg *segs = NULL, *vma_segs = NULL;
+ struct usdt_target *targets = NULL, *target;
+ long base_addr = 0;
+ Elf_Scn *notes_scn, *base_scn;
+ GElf_Shdr base_shdr, notes_shdr;
+ GElf_Ehdr ehdr;
+ GElf_Nhdr nhdr;
+ Elf_Data *data;
+ int err;
+
+ *out_targets = NULL;
+ *out_target_cnt = 0;
+
+ err = find_elf_sec_by_name(elf, USDT_NOTE_SEC, &notes_shdr, &notes_scn);
+ if (err) {
+ pr_warn("usdt: no USDT notes section (%s) found in '%s'\n", USDT_NOTE_SEC, path);
+ return err;
+ }
+
+ if (notes_shdr.sh_type != SHT_NOTE || !gelf_getehdr(elf, &ehdr)) {
+ pr_warn("usdt: invalid USDT notes section (%s) in '%s'\n", USDT_NOTE_SEC, path);
+ return -EINVAL;
+ }
+
+ err = parse_elf_segs(elf, path, &segs, &seg_cnt);
+ if (err) {
+ pr_warn("usdt: failed to process ELF program segments for '%s': %d\n", path, err);
+ goto err_out;
+ }
+
+ /* .stapsdt.base ELF section is optional, but is used for prelink
+ * offset compensation (see a big comment further below)
+ */
+ if (find_elf_sec_by_name(elf, USDT_BASE_SEC, &base_shdr, &base_scn) == 0)
+ base_addr = base_shdr.sh_addr;
+
+ data = elf_getdata(notes_scn, 0);
+ off = 0;
+ while ((off = gelf_getnote(data, off, &nhdr, &name_off, &desc_off)) > 0) {
+ long usdt_abs_ip, usdt_rel_ip, usdt_sema_off = 0;
+ struct usdt_note note;
+ struct elf_seg *seg = NULL;
+ void *tmp;
+
+ err = parse_usdt_note(elf, path, &nhdr, data->d_buf, name_off, desc_off, &note);
+ if (err)
+ goto err_out;
+
+ if (strcmp(note.provider, usdt_provider) != 0 || strcmp(note.name, usdt_name) != 0)
+ continue;
+
+ /* We need to compensate "prelink effect". See [0] for details,
+ * relevant parts quoted here:
+ *
+ * Each SDT probe also expands into a non-allocated ELF note. You can
+ * find this by looking at SHT_NOTE sections and decoding the format;
+ * see below for details. Because the note is non-allocated, it means
+ * there is no runtime cost, and also preserved in both stripped files
+ * and .debug files.
+ *
+ * However, this means that prelink won't adjust the note's contents
+ * for address offsets. Instead, this is done via the .stapsdt.base
+ * section. This is a special section that is added to the text. We
+ * will only ever have one of these sections in a final link and it
+ * will only ever be one byte long. Nothing about this section itself
+ * matters, we just use it as a marker to detect prelink address
+ * adjustments.
+ *
+ * Each probe note records the link-time address of the .stapsdt.base
+ * section alongside the probe PC address. The decoder compares the
+ * base address stored in the note with the .stapsdt.base section's
+ * sh_addr. Initially these are the same, but the section header will
+ * be adjusted by prelink. So the decoder applies the difference to
+ * the probe PC address to get the correct prelinked PC address; the
+ * same adjustment is applied to the semaphore address, if any.
+ *
+ * [0] https://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation
+ */
+ usdt_abs_ip = note.loc_addr;
+ if (base_addr)
+ usdt_abs_ip += base_addr - note.base_addr;
+
+ /* When attaching uprobes (which is what USDTs basically are)
+ * kernel expects file offset to be specified, not a relative
+ * virtual address, so we need to translate virtual address to
+ * file offset, for both ET_EXEC and ET_DYN binaries.
+ */
+ seg = find_elf_seg(segs, seg_cnt, usdt_abs_ip);
+ if (!seg) {
+ err = -ESRCH;
+ pr_warn("usdt: failed to find ELF program segment for '%s:%s' in '%s' at IP 0x%lx\n",
+ usdt_provider, usdt_name, path, usdt_abs_ip);
+ goto err_out;
+ }
+ if (!seg->is_exec) {
+ err = -ESRCH;
+ pr_warn("usdt: matched ELF binary '%s' segment [0x%lx, 0x%lx) for '%s:%s' at IP 0x%lx is not executable\n",
+ path, seg->start, seg->end, usdt_provider, usdt_name,
+ usdt_abs_ip);
+ goto err_out;
+ }
+ /* translate from virtual address to file offset */
+ usdt_rel_ip = usdt_abs_ip - seg->start + seg->offset;
+
+ if (ehdr.e_type == ET_DYN && !man->has_bpf_cookie) {
+ /* If we don't have BPF cookie support but need to
+ * attach to a shared library, we'll need to know and
+ * record absolute addresses of attach points due to
+ * the need to lookup USDT spec by absolute IP of
+ * triggered uprobe. Doing this resolution is only
+ * possible when we have a specific PID of the process
+ * that's using specified shared library. BPF cookie
+ * removes the absolute address limitation as we don't
+ * need to do this lookup (we just use BPF cookie as
+ * an index of USDT spec), so for newer kernels with
+ * BPF cookie support libbpf supports USDT attachment
+ * to shared libraries with no PID filter.
+ */
+ if (pid < 0) {
+ pr_warn("usdt: attaching to shared libraries without specific PID is not supported on current kernel\n");
+ err = -ENOTSUP;
+ goto err_out;
+ }
+
+ /* vma_segs are lazily initialized only if necessary */
+ if (vma_seg_cnt == 0) {
+ err = parse_vma_segs(pid, path, &vma_segs, &vma_seg_cnt);
+ if (err) {
+ pr_warn("usdt: failed to get memory segments in PID %d for shared library '%s': %d\n",
+ pid, path, err);
+ goto err_out;
+ }
+ }
+
+ seg = find_vma_seg(vma_segs, vma_seg_cnt, usdt_rel_ip);
+ if (!seg) {
+ err = -ESRCH;
+ pr_warn("usdt: failed to find shared lib memory segment for '%s:%s' in '%s' at relative IP 0x%lx\n",
+ usdt_provider, usdt_name, path, usdt_rel_ip);
+ goto err_out;
+ }
+
+ usdt_abs_ip = seg->start - seg->offset + usdt_rel_ip;
+ }
+
+ pr_debug("usdt: probe for '%s:%s' in %s '%s': addr 0x%lx base 0x%lx (resolved abs_ip 0x%lx rel_ip 0x%lx) args '%s' in segment [0x%lx, 0x%lx) at offset 0x%lx\n",
+ usdt_provider, usdt_name, ehdr.e_type == ET_EXEC ? "exec" : "lib ", path,
+ note.loc_addr, note.base_addr, usdt_abs_ip, usdt_rel_ip, note.args,
+ seg ? seg->start : 0, seg ? seg->end : 0, seg ? seg->offset : 0);
+
+ /* Adjust semaphore address to be a file offset */
+ if (note.sema_addr) {
+ if (!man->has_sema_refcnt) {
+ pr_warn("usdt: kernel doesn't support USDT semaphore refcounting for '%s:%s' in '%s'\n",
+ usdt_provider, usdt_name, path);
+ err = -ENOTSUP;
+ goto err_out;
+ }
+
+ seg = find_elf_seg(segs, seg_cnt, note.sema_addr);
+ if (!seg) {
+ err = -ESRCH;
+ pr_warn("usdt: failed to find ELF loadable segment with semaphore of '%s:%s' in '%s' at 0x%lx\n",
+ usdt_provider, usdt_name, path, note.sema_addr);
+ goto err_out;
+ }
+ if (seg->is_exec) {
+ err = -ESRCH;
+ pr_warn("usdt: matched ELF binary '%s' segment [0x%lx, 0x%lx] for semaphore of '%s:%s' at 0x%lx is executable\n",
+ path, seg->start, seg->end, usdt_provider, usdt_name,
+ note.sema_addr);
+ goto err_out;
+ }
+
+ usdt_sema_off = note.sema_addr - seg->start + seg->offset;
+
+ pr_debug("usdt: sema for '%s:%s' in %s '%s': addr 0x%lx base 0x%lx (resolved 0x%lx) in segment [0x%lx, 0x%lx] at offset 0x%lx\n",
+ usdt_provider, usdt_name, ehdr.e_type == ET_EXEC ? "exec" : "lib ",
+ path, note.sema_addr, note.base_addr, usdt_sema_off,
+ seg->start, seg->end, seg->offset);
+ }
+
+ /* Record adjusted addresses and offsets and parse USDT spec */
+ tmp = libbpf_reallocarray(targets, target_cnt + 1, sizeof(*targets));
+ if (!tmp) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ targets = tmp;
+
+ target = &targets[target_cnt];
+ memset(target, 0, sizeof(*target));
+
+ target->abs_ip = usdt_abs_ip;
+ target->rel_ip = usdt_rel_ip;
+ target->sema_off = usdt_sema_off;
+
+ /* notes.args references strings from ELF itself, so they can
+ * be referenced safely until elf_end() call
+ */
+ target->spec_str = note.args;
+
+ err = parse_usdt_spec(&target->spec, &note, usdt_cookie);
+ if (err)
+ goto err_out;
+
+ target_cnt++;
+ }
+
+ *out_targets = targets;
+ *out_target_cnt = target_cnt;
+ err = target_cnt;
+
+err_out:
+ free(segs);
+ free(vma_segs);
+ if (err < 0)
+ free(targets);
+ return err;
+}
+
+struct bpf_link_usdt {
+ struct bpf_link link;
+
+ struct usdt_manager *usdt_man;
+
+ size_t spec_cnt;
+ int *spec_ids;
+
+ size_t uprobe_cnt;
+ struct {
+ long abs_ip;
+ struct bpf_link *link;
+ } *uprobes;
+
+ struct bpf_link *multi_link;
+};
+
+static int bpf_link_usdt_detach(struct bpf_link *link)
+{
+ struct bpf_link_usdt *usdt_link = container_of(link, struct bpf_link_usdt, link);
+ struct usdt_manager *man = usdt_link->usdt_man;
+ int i;
+
+ bpf_link__destroy(usdt_link->multi_link);
+
+ /* When having multi_link, uprobe_cnt is 0 */
+ for (i = 0; i < usdt_link->uprobe_cnt; i++) {
+ /* detach underlying uprobe link */
+ bpf_link__destroy(usdt_link->uprobes[i].link);
+ /* there is no need to update specs map because it will be
+ * unconditionally overwritten on subsequent USDT attaches,
+ * but if BPF cookies are not used we need to remove entry
+ * from ip_to_spec_id map, otherwise we'll run into false
+ * conflicting IP errors
+ */
+ if (!man->has_bpf_cookie) {
+ /* not much we can do about errors here */
+ (void)bpf_map_delete_elem(bpf_map__fd(man->ip_to_spec_id_map),
+ &usdt_link->uprobes[i].abs_ip);
+ }
+ }
+
+ /* try to return the list of previously used spec IDs to usdt_manager
+ * for future reuse for subsequent USDT attaches
+ */
+ if (!man->free_spec_ids) {
+ /* if there were no free spec IDs yet, just transfer our IDs */
+ man->free_spec_ids = usdt_link->spec_ids;
+ man->free_spec_cnt = usdt_link->spec_cnt;
+ usdt_link->spec_ids = NULL;
+ } else {
+ /* otherwise concat IDs */
+ size_t new_cnt = man->free_spec_cnt + usdt_link->spec_cnt;
+ int *new_free_ids;
+
+ new_free_ids = libbpf_reallocarray(man->free_spec_ids, new_cnt,
+ sizeof(*new_free_ids));
+ /* If we couldn't resize free_spec_ids, we'll just leak
+ * a bunch of free IDs; this is very unlikely to happen and if
+ * system is so exhausted on memory, it's the least of user's
+ * concerns, probably.
+ * So just do our best here to return those IDs to usdt_manager.
+ * Another edge case when we can legitimately get NULL is when
+ * new_cnt is zero, which can happen in some edge cases, so we
+ * need to be careful about that.
+ */
+ if (new_free_ids || new_cnt == 0) {
+ memcpy(new_free_ids + man->free_spec_cnt, usdt_link->spec_ids,
+ usdt_link->spec_cnt * sizeof(*usdt_link->spec_ids));
+ man->free_spec_ids = new_free_ids;
+ man->free_spec_cnt = new_cnt;
+ }
+ }
+
+ return 0;
+}
+
+static void bpf_link_usdt_dealloc(struct bpf_link *link)
+{
+ struct bpf_link_usdt *usdt_link = container_of(link, struct bpf_link_usdt, link);
+
+ free(usdt_link->spec_ids);
+ free(usdt_link->uprobes);
+ free(usdt_link);
+}
+
+static size_t specs_hash_fn(long key, void *ctx)
+{
+ return str_hash((char *)key);
+}
+
+static bool specs_equal_fn(long key1, long key2, void *ctx)
+{
+ return strcmp((char *)key1, (char *)key2) == 0;
+}
+
+static int allocate_spec_id(struct usdt_manager *man, struct hashmap *specs_hash,
+ struct bpf_link_usdt *link, struct usdt_target *target,
+ int *spec_id, bool *is_new)
+{
+ long tmp;
+ void *new_ids;
+ int err;
+
+ /* check if we already allocated spec ID for this spec string */
+ if (hashmap__find(specs_hash, target->spec_str, &tmp)) {
+ *spec_id = tmp;
+ *is_new = false;
+ return 0;
+ }
+
+ /* otherwise it's a new ID that needs to be set up in specs map and
+ * returned back to usdt_manager when USDT link is detached
+ */
+ new_ids = libbpf_reallocarray(link->spec_ids, link->spec_cnt + 1, sizeof(*link->spec_ids));
+ if (!new_ids)
+ return -ENOMEM;
+ link->spec_ids = new_ids;
+
+ /* get next free spec ID, giving preference to free list, if not empty */
+ if (man->free_spec_cnt) {
+ *spec_id = man->free_spec_ids[man->free_spec_cnt - 1];
+
+ /* cache spec ID for current spec string for future lookups */
+ err = hashmap__add(specs_hash, target->spec_str, *spec_id);
+ if (err)
+ return err;
+
+ man->free_spec_cnt--;
+ } else {
+ /* don't allocate spec ID bigger than what fits in specs map */
+ if (man->next_free_spec_id >= bpf_map__max_entries(man->specs_map))
+ return -E2BIG;
+
+ *spec_id = man->next_free_spec_id;
+
+ /* cache spec ID for current spec string for future lookups */
+ err = hashmap__add(specs_hash, target->spec_str, *spec_id);
+ if (err)
+ return err;
+
+ man->next_free_spec_id++;
+ }
+
+ /* remember new spec ID in the link for later return back to free list on detach */
+ link->spec_ids[link->spec_cnt] = *spec_id;
+ link->spec_cnt++;
+ *is_new = true;
+ return 0;
+}
+
+struct bpf_link *usdt_manager_attach_usdt(struct usdt_manager *man, const struct bpf_program *prog,
+ pid_t pid, const char *path,
+ const char *usdt_provider, const char *usdt_name,
+ __u64 usdt_cookie)
+{
+ unsigned long *offsets = NULL, *ref_ctr_offsets = NULL;
+ int i, err, spec_map_fd, ip_map_fd;
+ LIBBPF_OPTS(bpf_uprobe_opts, opts);
+ struct hashmap *specs_hash = NULL;
+ struct bpf_link_usdt *link = NULL;
+ struct usdt_target *targets = NULL;
+ __u64 *cookies = NULL;
+ struct elf_fd elf_fd;
+ size_t target_cnt;
+
+ spec_map_fd = bpf_map__fd(man->specs_map);
+ ip_map_fd = bpf_map__fd(man->ip_to_spec_id_map);
+
+ err = elf_open(path, &elf_fd);
+ if (err)
+ return libbpf_err_ptr(err);
+
+ err = sanity_check_usdt_elf(elf_fd.elf, path);
+ if (err)
+ goto err_out;
+
+ /* normalize PID filter */
+ if (pid < 0)
+ pid = -1;
+ else if (pid == 0)
+ pid = getpid();
+
+ /* discover USDT in given binary, optionally limiting
+ * activations to a given PID, if pid > 0
+ */
+ err = collect_usdt_targets(man, elf_fd.elf, path, pid, usdt_provider, usdt_name,
+ usdt_cookie, &targets, &target_cnt);
+ if (err <= 0) {
+ err = (err == 0) ? -ENOENT : err;
+ goto err_out;
+ }
+
+ specs_hash = hashmap__new(specs_hash_fn, specs_equal_fn, NULL);
+ if (IS_ERR(specs_hash)) {
+ err = PTR_ERR(specs_hash);
+ goto err_out;
+ }
+
+ link = calloc(1, sizeof(*link));
+ if (!link) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+
+ link->usdt_man = man;
+ link->link.detach = &bpf_link_usdt_detach;
+ link->link.dealloc = &bpf_link_usdt_dealloc;
+
+ if (man->has_uprobe_multi) {
+ offsets = calloc(target_cnt, sizeof(*offsets));
+ cookies = calloc(target_cnt, sizeof(*cookies));
+ ref_ctr_offsets = calloc(target_cnt, sizeof(*ref_ctr_offsets));
+
+ if (!offsets || !ref_ctr_offsets || !cookies) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ } else {
+ link->uprobes = calloc(target_cnt, sizeof(*link->uprobes));
+ if (!link->uprobes) {
+ err = -ENOMEM;
+ goto err_out;
+ }
+ }
+
+ for (i = 0; i < target_cnt; i++) {
+ struct usdt_target *target = &targets[i];
+ struct bpf_link *uprobe_link;
+ bool is_new;
+ int spec_id;
+
+ /* Spec ID can be either reused or newly allocated. If it is
+ * newly allocated, we'll need to fill out spec map, otherwise
+ * entire spec should be valid and can be just used by a new
+ * uprobe. We reuse spec when USDT arg spec is identical. We
+ * also never share specs between two different USDT
+ * attachments ("links"), so all the reused specs already
+ * share USDT cookie value implicitly.
+ */
+ err = allocate_spec_id(man, specs_hash, link, target, &spec_id, &is_new);
+ if (err)
+ goto err_out;
+
+ if (is_new && bpf_map_update_elem(spec_map_fd, &spec_id, &target->spec, BPF_ANY)) {
+ err = -errno;
+ pr_warn("usdt: failed to set USDT spec #%d for '%s:%s' in '%s': %d\n",
+ spec_id, usdt_provider, usdt_name, path, err);
+ goto err_out;
+ }
+ if (!man->has_bpf_cookie &&
+ bpf_map_update_elem(ip_map_fd, &target->abs_ip, &spec_id, BPF_NOEXIST)) {
+ err = -errno;
+ if (err == -EEXIST) {
+ pr_warn("usdt: IP collision detected for spec #%d for '%s:%s' in '%s'\n",
+ spec_id, usdt_provider, usdt_name, path);
+ } else {
+ pr_warn("usdt: failed to map IP 0x%lx to spec #%d for '%s:%s' in '%s': %d\n",
+ target->abs_ip, spec_id, usdt_provider, usdt_name,
+ path, err);
+ }
+ goto err_out;
+ }
+
+ if (man->has_uprobe_multi) {
+ offsets[i] = target->rel_ip;
+ ref_ctr_offsets[i] = target->sema_off;
+ cookies[i] = spec_id;
+ } else {
+ opts.ref_ctr_offset = target->sema_off;
+ opts.bpf_cookie = man->has_bpf_cookie ? spec_id : 0;
+ uprobe_link = bpf_program__attach_uprobe_opts(prog, pid, path,
+ target->rel_ip, &opts);
+ err = libbpf_get_error(uprobe_link);
+ if (err) {
+ pr_warn("usdt: failed to attach uprobe #%d for '%s:%s' in '%s': %d\n",
+ i, usdt_provider, usdt_name, path, err);
+ goto err_out;
+ }
+
+ link->uprobes[i].link = uprobe_link;
+ link->uprobes[i].abs_ip = target->abs_ip;
+ link->uprobe_cnt++;
+ }
+ }
+
+ if (man->has_uprobe_multi) {
+ LIBBPF_OPTS(bpf_uprobe_multi_opts, opts_multi,
+ .ref_ctr_offsets = ref_ctr_offsets,
+ .offsets = offsets,
+ .cookies = cookies,
+ .cnt = target_cnt,
+ );
+
+ link->multi_link = bpf_program__attach_uprobe_multi(prog, pid, path,
+ NULL, &opts_multi);
+ if (!link->multi_link) {
+ err = -errno;
+ pr_warn("usdt: failed to attach uprobe multi for '%s:%s' in '%s': %d\n",
+ usdt_provider, usdt_name, path, err);
+ goto err_out;
+ }
+
+ free(offsets);
+ free(ref_ctr_offsets);
+ free(cookies);
+ }
+
+ free(targets);
+ hashmap__free(specs_hash);
+ elf_close(&elf_fd);
+ return &link->link;
+
+err_out:
+ free(offsets);
+ free(ref_ctr_offsets);
+ free(cookies);
+
+ if (link)
+ bpf_link__destroy(&link->link);
+ free(targets);
+ hashmap__free(specs_hash);
+ elf_close(&elf_fd);
+ return libbpf_err_ptr(err);
+}
+
+/* Parse out USDT ELF note from '.note.stapsdt' section.
+ * Logic inspired by perf's code.
+ */
+static int parse_usdt_note(Elf *elf, const char *path, GElf_Nhdr *nhdr,
+ const char *data, size_t name_off, size_t desc_off,
+ struct usdt_note *note)
+{
+ const char *provider, *name, *args;
+ long addrs[3];
+ size_t len;
+
+ /* sanity check USDT note name and type first */
+ if (strncmp(data + name_off, USDT_NOTE_NAME, nhdr->n_namesz) != 0)
+ return -EINVAL;
+ if (nhdr->n_type != USDT_NOTE_TYPE)
+ return -EINVAL;
+
+ /* sanity check USDT note contents ("description" in ELF terminology) */
+ len = nhdr->n_descsz;
+ data = data + desc_off;
+
+ /* +3 is the very minimum required to store three empty strings */
+ if (len < sizeof(addrs) + 3)
+ return -EINVAL;
+
+ /* get location, base, and semaphore addrs */
+ memcpy(&addrs, data, sizeof(addrs));
+
+ /* parse string fields: provider, name, args */
+ provider = data + sizeof(addrs);
+
+ name = (const char *)memchr(provider, '\0', data + len - provider);
+ if (!name) /* non-zero-terminated provider */
+ return -EINVAL;
+ name++;
+ if (name >= data + len || *name == '\0') /* missing or empty name */
+ return -EINVAL;
+
+ args = memchr(name, '\0', data + len - name);
+ if (!args) /* non-zero-terminated name */
+ return -EINVAL;
+ ++args;
+ if (args >= data + len) /* missing arguments spec */
+ return -EINVAL;
+
+ note->provider = provider;
+ note->name = name;
+ if (*args == '\0' || *args == ':')
+ note->args = "";
+ else
+ note->args = args;
+ note->loc_addr = addrs[0];
+ note->base_addr = addrs[1];
+ note->sema_addr = addrs[2];
+
+ return 0;
+}
+
+static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz);
+
+static int parse_usdt_spec(struct usdt_spec *spec, const struct usdt_note *note, __u64 usdt_cookie)
+{
+ struct usdt_arg_spec *arg;
+ const char *s;
+ int arg_sz, len;
+
+ spec->usdt_cookie = usdt_cookie;
+ spec->arg_cnt = 0;
+
+ s = note->args;
+ while (s[0]) {
+ if (spec->arg_cnt >= USDT_MAX_ARG_CNT) {
+ pr_warn("usdt: too many USDT arguments (> %d) for '%s:%s' with args spec '%s'\n",
+ USDT_MAX_ARG_CNT, note->provider, note->name, note->args);
+ return -E2BIG;
+ }
+
+ arg = &spec->args[spec->arg_cnt];
+ len = parse_usdt_arg(s, spec->arg_cnt, arg, &arg_sz);
+ if (len < 0)
+ return len;
+
+ arg->arg_signed = arg_sz < 0;
+ if (arg_sz < 0)
+ arg_sz = -arg_sz;
+
+ switch (arg_sz) {
+ case 1: case 2: case 4: case 8:
+ arg->arg_bitshift = 64 - arg_sz * 8;
+ break;
+ default:
+ pr_warn("usdt: unsupported arg #%d (spec '%s') size: %d\n",
+ spec->arg_cnt, s, arg_sz);
+ return -EINVAL;
+ }
+
+ s += len;
+ spec->arg_cnt++;
+ }
+
+ return 0;
+}
+
+/* Architecture-specific logic for parsing USDT argument location specs */
+
+#if defined(__x86_64__) || defined(__i386__)
+
+static int calc_pt_regs_off(const char *reg_name)
+{
+ static struct {
+ const char *names[4];
+ size_t pt_regs_off;
+ } reg_map[] = {
+#ifdef __x86_64__
+#define reg_off(reg64, reg32) offsetof(struct pt_regs, reg64)
+#else
+#define reg_off(reg64, reg32) offsetof(struct pt_regs, reg32)
+#endif
+ { {"rip", "eip", "", ""}, reg_off(rip, eip) },
+ { {"rax", "eax", "ax", "al"}, reg_off(rax, eax) },
+ { {"rbx", "ebx", "bx", "bl"}, reg_off(rbx, ebx) },
+ { {"rcx", "ecx", "cx", "cl"}, reg_off(rcx, ecx) },
+ { {"rdx", "edx", "dx", "dl"}, reg_off(rdx, edx) },
+ { {"rsi", "esi", "si", "sil"}, reg_off(rsi, esi) },
+ { {"rdi", "edi", "di", "dil"}, reg_off(rdi, edi) },
+ { {"rbp", "ebp", "bp", "bpl"}, reg_off(rbp, ebp) },
+ { {"rsp", "esp", "sp", "spl"}, reg_off(rsp, esp) },
+#undef reg_off
+#ifdef __x86_64__
+ { {"r8", "r8d", "r8w", "r8b"}, offsetof(struct pt_regs, r8) },
+ { {"r9", "r9d", "r9w", "r9b"}, offsetof(struct pt_regs, r9) },
+ { {"r10", "r10d", "r10w", "r10b"}, offsetof(struct pt_regs, r10) },
+ { {"r11", "r11d", "r11w", "r11b"}, offsetof(struct pt_regs, r11) },
+ { {"r12", "r12d", "r12w", "r12b"}, offsetof(struct pt_regs, r12) },
+ { {"r13", "r13d", "r13w", "r13b"}, offsetof(struct pt_regs, r13) },
+ { {"r14", "r14d", "r14w", "r14b"}, offsetof(struct pt_regs, r14) },
+ { {"r15", "r15d", "r15w", "r15b"}, offsetof(struct pt_regs, r15) },
+#endif
+ };
+ int i, j;
+
+ for (i = 0; i < ARRAY_SIZE(reg_map); i++) {
+ for (j = 0; j < ARRAY_SIZE(reg_map[i].names); j++) {
+ if (strcmp(reg_name, reg_map[i].names[j]) == 0)
+ return reg_map[i].pt_regs_off;
+ }
+ }
+
+ pr_warn("usdt: unrecognized register '%s'\n", reg_name);
+ return -ENOENT;
+}
+
+static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
+{
+ char reg_name[16];
+ int len, reg_off;
+ long off;
+
+ if (sscanf(arg_str, " %d @ %ld ( %%%15[^)] ) %n", arg_sz, &off, reg_name, &len) == 3) {
+ /* Memory dereference case, e.g., -4@-20(%rbp) */
+ arg->arg_type = USDT_ARG_REG_DEREF;
+ arg->val_off = off;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else if (sscanf(arg_str, " %d @ ( %%%15[^)] ) %n", arg_sz, reg_name, &len) == 2) {
+ /* Memory dereference case without offset, e.g., 8@(%rsp) */
+ arg->arg_type = USDT_ARG_REG_DEREF;
+ arg->val_off = 0;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else if (sscanf(arg_str, " %d @ %%%15s %n", arg_sz, reg_name, &len) == 2) {
+ /* Register read case, e.g., -4@%eax */
+ arg->arg_type = USDT_ARG_REG;
+ arg->val_off = 0;
+
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else if (sscanf(arg_str, " %d @ $%ld %n", arg_sz, &off, &len) == 2) {
+ /* Constant value case, e.g., 4@$71 */
+ arg->arg_type = USDT_ARG_CONST;
+ arg->val_off = off;
+ arg->reg_off = 0;
+ } else {
+ pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
+ return -EINVAL;
+ }
+
+ return len;
+}
+
+#elif defined(__s390x__)
+
+/* Do not support __s390__ for now, since user_pt_regs is broken with -m31. */
+
+static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
+{
+ unsigned int reg;
+ int len;
+ long off;
+
+ if (sscanf(arg_str, " %d @ %ld ( %%r%u ) %n", arg_sz, &off, &reg, &len) == 3) {
+ /* Memory dereference case, e.g., -2@-28(%r15) */
+ arg->arg_type = USDT_ARG_REG_DEREF;
+ arg->val_off = off;
+ if (reg > 15) {
+ pr_warn("usdt: unrecognized register '%%r%u'\n", reg);
+ return -EINVAL;
+ }
+ arg->reg_off = offsetof(user_pt_regs, gprs[reg]);
+ } else if (sscanf(arg_str, " %d @ %%r%u %n", arg_sz, &reg, &len) == 2) {
+ /* Register read case, e.g., -8@%r0 */
+ arg->arg_type = USDT_ARG_REG;
+ arg->val_off = 0;
+ if (reg > 15) {
+ pr_warn("usdt: unrecognized register '%%r%u'\n", reg);
+ return -EINVAL;
+ }
+ arg->reg_off = offsetof(user_pt_regs, gprs[reg]);
+ } else if (sscanf(arg_str, " %d @ %ld %n", arg_sz, &off, &len) == 2) {
+ /* Constant value case, e.g., 4@71 */
+ arg->arg_type = USDT_ARG_CONST;
+ arg->val_off = off;
+ arg->reg_off = 0;
+ } else {
+ pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
+ return -EINVAL;
+ }
+
+ return len;
+}
+
+#elif defined(__aarch64__)
+
+static int calc_pt_regs_off(const char *reg_name)
+{
+ int reg_num;
+
+ if (sscanf(reg_name, "x%d", &reg_num) == 1) {
+ if (reg_num >= 0 && reg_num < 31)
+ return offsetof(struct user_pt_regs, regs[reg_num]);
+ } else if (strcmp(reg_name, "sp") == 0) {
+ return offsetof(struct user_pt_regs, sp);
+ }
+ pr_warn("usdt: unrecognized register '%s'\n", reg_name);
+ return -ENOENT;
+}
+
+static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
+{
+ char reg_name[16];
+ int len, reg_off;
+ long off;
+
+ if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] , %ld ] %n", arg_sz, reg_name, &off, &len) == 3) {
+ /* Memory dereference case, e.g., -4@[sp, 96] */
+ arg->arg_type = USDT_ARG_REG_DEREF;
+ arg->val_off = off;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] ] %n", arg_sz, reg_name, &len) == 2) {
+ /* Memory dereference case, e.g., -4@[sp] */
+ arg->arg_type = USDT_ARG_REG_DEREF;
+ arg->val_off = 0;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else if (sscanf(arg_str, " %d @ %ld %n", arg_sz, &off, &len) == 2) {
+ /* Constant value case, e.g., 4@5 */
+ arg->arg_type = USDT_ARG_CONST;
+ arg->val_off = off;
+ arg->reg_off = 0;
+ } else if (sscanf(arg_str, " %d @ %15[a-z0-9] %n", arg_sz, reg_name, &len) == 2) {
+ /* Register read case, e.g., -8@x4 */
+ arg->arg_type = USDT_ARG_REG;
+ arg->val_off = 0;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else {
+ pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
+ return -EINVAL;
+ }
+
+ return len;
+}
+
+#elif defined(__riscv)
+
+static int calc_pt_regs_off(const char *reg_name)
+{
+ static struct {
+ const char *name;
+ size_t pt_regs_off;
+ } reg_map[] = {
+ { "ra", offsetof(struct user_regs_struct, ra) },
+ { "sp", offsetof(struct user_regs_struct, sp) },
+ { "gp", offsetof(struct user_regs_struct, gp) },
+ { "tp", offsetof(struct user_regs_struct, tp) },
+ { "a0", offsetof(struct user_regs_struct, a0) },
+ { "a1", offsetof(struct user_regs_struct, a1) },
+ { "a2", offsetof(struct user_regs_struct, a2) },
+ { "a3", offsetof(struct user_regs_struct, a3) },
+ { "a4", offsetof(struct user_regs_struct, a4) },
+ { "a5", offsetof(struct user_regs_struct, a5) },
+ { "a6", offsetof(struct user_regs_struct, a6) },
+ { "a7", offsetof(struct user_regs_struct, a7) },
+ { "s0", offsetof(struct user_regs_struct, s0) },
+ { "s1", offsetof(struct user_regs_struct, s1) },
+ { "s2", offsetof(struct user_regs_struct, s2) },
+ { "s3", offsetof(struct user_regs_struct, s3) },
+ { "s4", offsetof(struct user_regs_struct, s4) },
+ { "s5", offsetof(struct user_regs_struct, s5) },
+ { "s6", offsetof(struct user_regs_struct, s6) },
+ { "s7", offsetof(struct user_regs_struct, s7) },
+ { "s8", offsetof(struct user_regs_struct, rv_s8) },
+ { "s9", offsetof(struct user_regs_struct, s9) },
+ { "s10", offsetof(struct user_regs_struct, s10) },
+ { "s11", offsetof(struct user_regs_struct, s11) },
+ { "t0", offsetof(struct user_regs_struct, t0) },
+ { "t1", offsetof(struct user_regs_struct, t1) },
+ { "t2", offsetof(struct user_regs_struct, t2) },
+ { "t3", offsetof(struct user_regs_struct, t3) },
+ { "t4", offsetof(struct user_regs_struct, t4) },
+ { "t5", offsetof(struct user_regs_struct, t5) },
+ { "t6", offsetof(struct user_regs_struct, t6) },
+ };
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(reg_map); i++) {
+ if (strcmp(reg_name, reg_map[i].name) == 0)
+ return reg_map[i].pt_regs_off;
+ }
+
+ pr_warn("usdt: unrecognized register '%s'\n", reg_name);
+ return -ENOENT;
+}
+
+static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
+{
+ char reg_name[16];
+ int len, reg_off;
+ long off;
+
+ if (sscanf(arg_str, " %d @ %ld ( %15[a-z0-9] ) %n", arg_sz, &off, reg_name, &len) == 3) {
+ /* Memory dereference case, e.g., -8@-88(s0) */
+ arg->arg_type = USDT_ARG_REG_DEREF;
+ arg->val_off = off;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else if (sscanf(arg_str, " %d @ %ld %n", arg_sz, &off, &len) == 2) {
+ /* Constant value case, e.g., 4@5 */
+ arg->arg_type = USDT_ARG_CONST;
+ arg->val_off = off;
+ arg->reg_off = 0;
+ } else if (sscanf(arg_str, " %d @ %15[a-z0-9] %n", arg_sz, reg_name, &len) == 2) {
+ /* Register read case, e.g., -8@a1 */
+ arg->arg_type = USDT_ARG_REG;
+ arg->val_off = 0;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else {
+ pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
+ return -EINVAL;
+ }
+
+ return len;
+}
+
+#elif defined(__arm__)
+
+static int calc_pt_regs_off(const char *reg_name)
+{
+ static struct {
+ const char *name;
+ size_t pt_regs_off;
+ } reg_map[] = {
+ { "r0", offsetof(struct pt_regs, uregs[0]) },
+ { "r1", offsetof(struct pt_regs, uregs[1]) },
+ { "r2", offsetof(struct pt_regs, uregs[2]) },
+ { "r3", offsetof(struct pt_regs, uregs[3]) },
+ { "r4", offsetof(struct pt_regs, uregs[4]) },
+ { "r5", offsetof(struct pt_regs, uregs[5]) },
+ { "r6", offsetof(struct pt_regs, uregs[6]) },
+ { "r7", offsetof(struct pt_regs, uregs[7]) },
+ { "r8", offsetof(struct pt_regs, uregs[8]) },
+ { "r9", offsetof(struct pt_regs, uregs[9]) },
+ { "r10", offsetof(struct pt_regs, uregs[10]) },
+ { "fp", offsetof(struct pt_regs, uregs[11]) },
+ { "ip", offsetof(struct pt_regs, uregs[12]) },
+ { "sp", offsetof(struct pt_regs, uregs[13]) },
+ { "lr", offsetof(struct pt_regs, uregs[14]) },
+ { "pc", offsetof(struct pt_regs, uregs[15]) },
+ };
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(reg_map); i++) {
+ if (strcmp(reg_name, reg_map[i].name) == 0)
+ return reg_map[i].pt_regs_off;
+ }
+
+ pr_warn("usdt: unrecognized register '%s'\n", reg_name);
+ return -ENOENT;
+}
+
+static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
+{
+ char reg_name[16];
+ int len, reg_off;
+ long off;
+
+ if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] , #%ld ] %n",
+ arg_sz, reg_name, &off, &len) == 3) {
+ /* Memory dereference case, e.g., -4@[fp, #96] */
+ arg->arg_type = USDT_ARG_REG_DEREF;
+ arg->val_off = off;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else if (sscanf(arg_str, " %d @ \[ %15[a-z0-9] ] %n", arg_sz, reg_name, &len) == 2) {
+ /* Memory dereference case, e.g., -4@[sp] */
+ arg->arg_type = USDT_ARG_REG_DEREF;
+ arg->val_off = 0;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else if (sscanf(arg_str, " %d @ #%ld %n", arg_sz, &off, &len) == 2) {
+ /* Constant value case, e.g., 4@#5 */
+ arg->arg_type = USDT_ARG_CONST;
+ arg->val_off = off;
+ arg->reg_off = 0;
+ } else if (sscanf(arg_str, " %d @ %15[a-z0-9] %n", arg_sz, reg_name, &len) == 2) {
+ /* Register read case, e.g., -8@r4 */
+ arg->arg_type = USDT_ARG_REG;
+ arg->val_off = 0;
+ reg_off = calc_pt_regs_off(reg_name);
+ if (reg_off < 0)
+ return reg_off;
+ arg->reg_off = reg_off;
+ } else {
+ pr_warn("usdt: unrecognized arg #%d spec '%s'\n", arg_num, arg_str);
+ return -EINVAL;
+ }
+
+ return len;
+}
+
+#else
+
+static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg, int *arg_sz)
+{
+ pr_warn("usdt: libbpf doesn't support USDTs on current architecture\n");
+ return -ENOTSUP;
+}
+
+#endif