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338 lines (277 loc) · 8.49 KB
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/*
* Copyright (c) 2016 GitHub, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <cstring>
#include <sstream>
#include <fcntl.h>
#include <sys/types.h>
#include <unistd.h>
#include "bcc_elf.h"
#include "bcc_proc.h"
#include "usdt.h"
#include "vendor/tinyformat.hpp"
namespace USDT {
Probe::Location::Location(uint64_t addr, const char *arg_fmt) : address_(addr) {
ArgumentParser_x64 parser(arg_fmt);
while (!parser.done()) {
Argument arg;
if (!parser.parse(&arg))
continue;
arguments_.push_back(std::move(arg));
}
}
Probe::Probe(const char *bin_path, const char *provider, const char *name,
uint64_t semaphore, const optional<int> &pid)
: bin_path_(bin_path),
provider_(provider),
name_(name),
semaphore_(semaphore),
pid_(pid) {}
bool Probe::in_shared_object() {
if (!in_shared_object_)
in_shared_object_ = (bcc_elf_is_shared_obj(bin_path_.c_str()) == 1);
return in_shared_object_.value();
}
bool Probe::resolve_global_address(uint64_t *global, const uint64_t addr) {
if (in_shared_object()) {
return (pid_ &&
!bcc_resolve_global_addr(*pid_, bin_path_.c_str(), addr, global));
}
*global = addr;
return true;
}
bool Probe::add_to_semaphore(int16_t val) {
assert(pid_ && attached_semaphore_);
if (!attached_semaphore_) {
uint64_t addr;
if (!resolve_global_address(&addr, semaphore_))
return false;
attached_semaphore_ = addr;
}
off_t address = static_cast<off_t>(attached_semaphore_.value());
std::string procmem = tfm::format("/proc/%d/mem", pid_.value());
int memfd = ::open(procmem.c_str(), O_RDWR);
if (memfd < 0)
return false;
int16_t original;
if (::lseek(memfd, address, SEEK_SET) < 0 ||
::read(memfd, &original, 2) != 2) {
::close(memfd);
return false;
}
original = original + val;
if (::lseek(memfd, address, SEEK_SET) < 0 ||
::write(memfd, &original, 2) != 2) {
::close(memfd);
return false;
}
::close(memfd);
return true;
}
bool Probe::enable(const std::string &fn_name) {
if (attached_to_)
return false;
if (need_enable()) {
if (!pid_)
return false;
if (!add_to_semaphore(+1))
return false;
}
attached_to_ = fn_name;
return true;
}
bool Probe::disable() {
if (!attached_to_)
return false;
attached_to_ = nullopt;
if (need_enable()) {
assert(pid_);
return add_to_semaphore(-1);
}
return true;
}
std::string Probe::largest_arg_type(size_t arg_n) {
Argument *largest = nullptr;
for (Location &location : locations_) {
Argument *candidate = &location.arguments_[arg_n];
if (!largest ||
std::abs(candidate->arg_size()) > std::abs(largest->arg_size()))
largest = candidate;
}
assert(largest);
return largest->ctype();
}
bool Probe::usdt_getarg(std::ostream &stream) {
const size_t arg_count = locations_[0].arguments_.size();
if (!attached_to_)
return false;
if (arg_count == 0)
return true;
for (size_t arg_n = 0; arg_n < arg_count; ++arg_n) {
std::string ctype = largest_arg_type(arg_n);
std::string cptr = tfm::format("*((%s *)dest)", ctype);
tfm::format(stream,
"static inline int _bpf_readarg_%s_%d("
"struct pt_regs *ctx, void *dest, size_t len) {\n"
" if (len != sizeof(%s)) return -1;\n",
attached_to_.value(), arg_n + 1, ctype);
if (locations_.size() == 1) {
Location &location = locations_.front();
stream << " ";
if (!location.arguments_[arg_n].assign_to_local(stream, cptr, bin_path_,
pid_))
return false;
stream << "\n return 0;\n}\n";
} else {
stream << " switch(ctx->ip) {\n";
for (Location &location : locations_) {
uint64_t global_address;
if (!resolve_global_address(&global_address, location.address_))
return false;
tfm::format(stream, " case 0x%xULL: ", global_address);
if (!location.arguments_[arg_n].assign_to_local(stream, cptr, bin_path_,
pid_))
return false;
stream << " return 0;\n";
}
stream << " }\n";
stream << " return -1;\n}\n";
}
}
return true;
}
void Probe::add_location(uint64_t addr, const char *fmt) {
locations_.emplace_back(addr, fmt);
}
void Context::_each_probe(const char *binpath, const struct bcc_elf_usdt *probe,
void *p) {
Context *ctx = static_cast<Context *>(p);
ctx->add_probe(binpath, probe);
}
int Context::_each_module(const char *modpath, uint64_t, uint64_t, void *p) {
bcc_elf_foreach_usdt(modpath, _each_probe, p);
return 0;
}
void Context::add_probe(const char *binpath, const struct bcc_elf_usdt *probe) {
for (auto &p : probes_) {
if (p->provider_ == probe->provider && p->name_ == probe->name) {
p->add_location(probe->pc, probe->arg_fmt);
return;
}
}
probes_.emplace_back(
new Probe(binpath, probe->provider, probe->name, probe->semaphore, pid_));
probes_.back()->add_location(probe->pc, probe->arg_fmt);
}
std::string Context::resolve_bin_path(const std::string &bin_path) {
std::string result;
if (char *which = bcc_procutils_which(bin_path.c_str())) {
result = which;
::free(which);
} else if (const char *which_so = bcc_procutils_which_so(bin_path.c_str())) {
result = which_so;
}
return result;
}
Probe *Context::get(const std::string &probe_name) {
for (auto &p : probes_) {
if (p->name_ == probe_name)
return p.get();
}
return nullptr;
}
bool Context::generate_usdt_args(std::ostream &stream) {
stream << "#include <uapi/linux/ptrace.h>\n";
for (auto &p : probes_) {
if (p->enabled() && !p->usdt_getarg(stream))
return false;
}
return true;
}
bool Context::enable_probe(const std::string &probe_name,
const std::string &fn_name) {
if (pid_stat_ && pid_stat_->is_stale())
return false;
auto p = get(probe_name);
return p && p->enable(fn_name);
}
void Context::each_uprobe(each_uprobe_cb callback) {
for (auto &p : probes_) {
if (!p->enabled())
continue;
for (Probe::Location &loc : p->locations_) {
callback(p->bin_path_.c_str(), p->attached_to_->c_str(), loc.address_,
pid_.value_or(-1));
}
}
}
Context::Context(const std::string &bin_path) : loaded_(false) {
std::string full_path = resolve_bin_path(bin_path);
if (!full_path.empty()) {
if (bcc_elf_foreach_usdt(full_path.c_str(), _each_probe, this) == 0)
loaded_ = true;
}
}
Context::Context(int pid) : pid_(pid), pid_stat_(pid), loaded_(false) {
if (bcc_procutils_each_module(pid, _each_module, this) == 0)
loaded_ = true;
}
Context::~Context() {
if (pid_stat_ && !pid_stat_->is_stale()) {
for (auto &p : probes_) p->disable();
}
}
}
extern "C" {
#include "bcc_usdt.h"
void *bcc_usdt_new_frompid(int pid) {
USDT::Context *ctx = new USDT::Context(pid);
if (!ctx->loaded()) {
delete ctx;
return nullptr;
}
return static_cast<void *>(ctx);
}
void *bcc_usdt_new_frompath(const char *path) {
USDT::Context *ctx = new USDT::Context(path);
if (!ctx->loaded()) {
delete ctx;
return nullptr;
}
return static_cast<void *>(ctx);
}
void bcc_usdt_close(void *usdt) {
USDT::Context *ctx = static_cast<USDT::Context *>(usdt);
delete ctx;
}
int bcc_usdt_enable_probe(void *usdt, const char *probe_name,
const char *fn_name) {
USDT::Context *ctx = static_cast<USDT::Context *>(usdt);
return ctx->enable_probe(probe_name, fn_name) ? 0 : -1;
}
const char *bcc_usdt_genargs(void *usdt) {
static std::string storage_;
USDT::Context *ctx = static_cast<USDT::Context *>(usdt);
std::ostringstream stream;
if (!ctx->generate_usdt_args(stream))
return nullptr;
storage_ = stream.str();
return storage_.c_str();
}
void bcc_usdt_foreach_uprobe(void *usdt, bcc_usdt_uprobe_cb callback) {
USDT::Context *ctx = static_cast<USDT::Context *>(usdt);
ctx->each_uprobe(callback);
}
}