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cc: Implement symbol resolution for USDT
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@vmg
vmg committed Apr 28, 2016
1 parent 4850155 commit dd0a606
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Showing 3 changed files with 55 additions and 42 deletions.
27 changes: 8 additions & 19 deletions src/cc/usdt.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -40,28 +40,18 @@ Probe::Probe(const char *bin_path, const char *provider, const char *name,
name_(name),
semaphore_(semaphore) {}

const std::string &Probe::usdt_thunks(const std::string &prefix) {
if (!gen_thunks_.empty())
return gen_thunks_;

std::ostringstream stream;
bool Probe::usdt_thunks(std::ostream &stream, const std::string &prefix) {
for (size_t i = 0; i < locations_.size(); ++i) {
tfm::format(
stream,
"int %s_thunk_%d(struct pt_regs *ctx) { return %s(ctx, %d); }\n",
prefix, i, prefix, i);
}

gen_thunks_ = stream.str();
return gen_thunks_;
return true;
}

const std::string &Probe::usdt_cases(const optional<int> &pid) {
if (!gen_cases_.empty())
return gen_cases_;

std::ostringstream stream;
size_t arg_count = locations_[0].arguments_.size();
bool Probe::usdt_cases(std::ostream &stream, const optional<int> &pid) {
const size_t arg_count = locations_[0].arguments_.size();

for (size_t arg_n = 0; arg_n < arg_count; ++arg_n) {
Argument *largest = nullptr;
Expand All @@ -80,14 +70,13 @@ const std::string &Probe::usdt_cases(const optional<int> &pid) {

for (size_t arg_n = 0; arg_n < location.arguments_.size(); ++arg_n) {
Argument *arg = location.arguments_[arg_n];
arg->assign_to_local(stream, tfm::format("arg%d", arg_n + 1), bin_path_,
pid);
if (!arg->assign_to_local(stream, tfm::format("arg%d", arg_n + 1),
bin_path_, pid))
return false;
}
stream << "}\n";
}

gen_cases_ = stream.str();
return gen_cases_;
return true;
}

void Probe::add_location(uint64_t addr, const char *fmt) {
Expand Down
17 changes: 8 additions & 9 deletions src/cc/usdt.h
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Original file line number Diff line number Diff line change
Expand Up @@ -35,15 +35,15 @@ class Argument {
optional<std::string> deref_ident_;
optional<std::string> register_name_;

uint64_t get_global_address(const std::string &binpath,
const optional<int> &pid) const;
bool get_global_address(uint64_t *address, const std::string &binpath,
const optional<int> &pid) const;
static const std::unordered_map<std::string, std::string> translations_;

public:
Argument();
~Argument();

void assign_to_local(std::ostream &stream, const std::string &local_name,
bool assign_to_local(std::ostream &stream, const std::string &local_name,
const std::string &binpath,
const optional<int> &pid = nullopt) const;

Expand Down Expand Up @@ -103,19 +103,16 @@ class Probe {

std::vector<Location> locations_;

std::string gen_thunks_;
std::string gen_cases_;

public:
Probe(const char *bin_path, const char *provider, const char *name,
uint64_t semaphore);

void add_location(uint64_t addr, const char *fmt);
bool need_enable() const { return semaphore_ != 0x0; }
size_t location_count() const { return locations_.size(); }
size_t num_locations() const { return locations_.size(); }

const std::string &usdt_thunks(const std::string &prefix);
const std::string &usdt_cases(const optional<int> &pid);
bool usdt_thunks(std::ostream &stream, const std::string &prefix);
bool usdt_cases(std::ostream &stream, const optional<int> &pid = nullopt);

friend class Context;
};
Expand All @@ -131,5 +128,7 @@ class Context {
public:
Context(const std::string &bin_path);
Context(int pid);

size_t num_probes() const { return probes_.size(); }
};
}
53 changes: 39 additions & 14 deletions src/cc/usdt_args.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,9 +15,13 @@
*/
#include <unordered_map>

#include "syms.h"
#include "usdt.h"
#include "vendor/tinyformat.hpp"

#include "bcc_elf.h"
#include "bcc_syms.h"

namespace USDT {

Argument::Argument() {}
Expand Down Expand Up @@ -49,12 +53,25 @@ void Argument::normalize_register_name(std::string *normalized) const {
normalized->assign(it->second);
}

uint64_t Argument::get_global_address(const std::string &binpath,
const optional<int> &pid) const {
return 0x0;
bool Argument::get_global_address(uint64_t *address, const std::string &binpath,
const optional<int> &pid) const {
if (pid) {
return ProcSyms(*pid).resolve_name(binpath.c_str(), deref_ident_->c_str(),
address);
}

if (bcc_elf_is_shared_obj(binpath.c_str()) == 0) {
struct bcc_symbol sym = {deref_ident_->c_str(), binpath.c_str(), 0x0};
if (!bcc_find_symbol_addr(&sym) && sym.offset) {
*address = sym.offset;
return true;
}
}

return false;
}

void Argument::assign_to_local(std::ostream &stream,
bool Argument::assign_to_local(std::ostream &stream,
const std::string &local_name,
const std::string &binpath,
const optional<int> &pid) const {
Expand All @@ -63,12 +80,12 @@ void Argument::assign_to_local(std::ostream &stream,

if (constant_) {
tfm::format(stream, "%s = %d;\n", local_name, *constant_);
return;
return true;
}

if (!deref_offset_) {
tfm::format(stream, "%s = (%s)ctx->%s;\n", local_name, ctype(), regname);
return;
return true;
}

if (deref_offset_ && !deref_ident_) {
Expand All @@ -78,16 +95,24 @@ void Argument::assign_to_local(std::ostream &stream,
" bpf_probe_read(&%s, sizeof(%s), (void *)__temp);\n"
"}\n",
regname, *deref_offset_, local_name, local_name);
return;
return true;
}

if (deref_offset_ && deref_ident_) {
uint64_t global_address;
if (!get_global_address(&global_address, binpath, pid))
return false;

tfm::format(stream,
"{\n"
" u64 __temp = 0x%xull + %d;\n"
" bpf_probe_read(&%s, sizeof(%s), (void *)__temp);\n"
"}\n",
global_address, *deref_offset_, local_name, local_name);
return true;
}

tfm::format(stream,
"{\n"
" u64 __temp = 0x%xull + %d;\n"
" bpf_probe_read(&%s, sizeof(%s), (void *)__temp);\n"
"}\n",
get_global_address(binpath, pid), *deref_offset_, local_name,
local_name);
return false;
}

ssize_t ArgumentParser::parse_number(ssize_t pos, optional<int> *result) {
Expand Down

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