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Diffstat (limited to 'lib/libbpf/src/usdt.c')
| -rw-r--r-- | lib/libbpf/src/usdt.c | 1519 |
1 files changed, 1519 insertions, 0 deletions
diff --git a/lib/libbpf/src/usdt.c b/lib/libbpf/src/usdt.c new file mode 100644 index 0000000..d18e379 --- /dev/null +++ b/lib/libbpf/src/usdt.c @@ -0,0 +1,1519 @@ +// 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; +}; + +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 = access(ref_ctr_sysfs_path, F_OK) == 0; + + 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, "r"); + 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, ¬es_shdr, ¬es_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, ¬e); + 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, ¬e, 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; +}; + +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; + + 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. + */ + if (new_free_ids) { + 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(const void *key, void *ctx) +{ + const char *s = key; + + return str_hash(s); +} + +static bool specs_equal_fn(const void *key1, const void *key2, void *ctx) +{ + const char *s1 = key1; + const char *s2 = key2; + + return strcmp(s1, s2) == 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) +{ + void *tmp; + int err; + + /* check if we already allocated spec ID for this spec string */ + if (hashmap__find(specs_hash, target->spec_str, &tmp)) { + *spec_id = (long)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 + */ + tmp = libbpf_reallocarray(link->spec_ids, link->spec_cnt + 1, sizeof(*link->spec_ids)); + if (!tmp) + return -ENOMEM; + link->spec_ids = tmp; + + /* 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, (void *)(long)*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, (void *)(long)*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) +{ + int i, fd, 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; + size_t target_cnt; + Elf *elf; + + spec_map_fd = bpf_map__fd(man->specs_map); + ip_map_fd = bpf_map__fd(man->ip_to_spec_id_map); + + /* TODO: perform path resolution similar to uprobe's */ + fd = open(path, O_RDONLY); + if (fd < 0) { + err = -errno; + pr_warn("usdt: failed to open ELF binary '%s': %d\n", path, err); + return libbpf_err_ptr(err); + } + + elf = elf_begin(fd, ELF_C_READ_MMAP, NULL); + if (!elf) { + err = -EBADF; + pr_warn("usdt: failed to parse ELF binary '%s': %s\n", path, elf_errmsg(-1)); + goto err_out; + } + + err = sanity_check_usdt_elf(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, 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; + + 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; + } + + 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++; + } + + free(targets); + hashmap__free(specs_hash); + elf_end(elf); + close(fd); + + return &link->link; + +err_out: + if (link) + bpf_link__destroy(&link->link); + free(targets); + hashmap__free(specs_hash); + if (elf) + elf_end(elf); + close(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); + +static int parse_usdt_spec(struct usdt_spec *spec, const struct usdt_note *note, __u64 usdt_cookie) +{ + const char *s; + int 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; + } + + len = parse_usdt_arg(s, spec->arg_cnt, &spec->args[spec->arg_cnt]); + if (len < 0) + return len; + + 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) +{ + char *reg_name = NULL; + int arg_sz, len, reg_off; + long off; + + if (sscanf(arg_str, " %d @ %ld ( %%%m[^)] ) %n", &arg_sz, &off, ®_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); + free(reg_name); + if (reg_off < 0) + return reg_off; + arg->reg_off = reg_off; + } else if (sscanf(arg_str, " %d @ %%%ms %n", &arg_sz, ®_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); + free(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; + } + + 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", + arg_num, arg_str, arg_sz); + 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) +{ + unsigned int reg; + int arg_sz, len; + long off; + + if (sscanf(arg_str, " %d @ %ld ( %%r%u ) %n", &arg_sz, &off, ®, &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, ®, &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; + } + + 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", + arg_num, arg_str, arg_sz); + 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", ®_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) +{ + char *reg_name = NULL; + int arg_sz, len, reg_off; + long off; + + if (sscanf(arg_str, " %d @ \[ %m[a-z0-9], %ld ] %n", &arg_sz, ®_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); + free(reg_name); + if (reg_off < 0) + return reg_off; + arg->reg_off = reg_off; + } else if (sscanf(arg_str, " %d @ \[ %m[a-z0-9] ] %n", &arg_sz, ®_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); + free(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 @ %m[a-z0-9] %n", &arg_sz, ®_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); + free(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; + } + + 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", + arg_num, arg_str, arg_sz); + 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) +{ + char *reg_name = NULL; + int arg_sz, len, reg_off; + long off; + + if (sscanf(arg_str, " %d @ %ld ( %m[a-z0-9] ) %n", &arg_sz, &off, ®_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); + free(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 @ %m[a-z0-9] %n", &arg_sz, ®_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); + free(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; + } + + 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", + arg_num, arg_str, arg_sz); + return -EINVAL; + } + + return len; +} + +#else + +static int parse_usdt_arg(const char *arg_str, int arg_num, struct usdt_arg_spec *arg) +{ + pr_warn("usdt: libbpf doesn't support USDTs on current architecture\n"); + return -ENOTSUP; +} + +#endif |