zircon/kernel/lib/instrumentation/profile.cc

// Copyright 2019 The Fuchsia Authors
//
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file or at
// https://opensource.org/licenses/MIT

#include <cstdint>

#include <profile/InstrProfData.inc>

namespace {

using IntPtrT = intptr_t;

enum ValueKind {
#define VALUE_PROF_KIND(Enumerator, Value, Descr) Enumerator = Value,
#include <profile/InstrProfData.inc>
};

struct __llvm_profile_data {
#define INSTR_PROF_DATA(Type, LLVMType, Name, Initializer) Type Name;
#include <profile/InstrProfData.inc>
};

extern "C" {

// This is sometimes emitted by the compiler with a different value.
// The header is expected to use whichever value this had at link time.
// This supplies the default value when the compiler doesn't supply it.
[[gnu::weak]] extern const uint64_t INSTR_PROF_RAW_VERSION_VAR =
    INSTR_PROF_RAW_VERSION;

// The compiler emits phantom references to this as a way to ensure
// that the runtime is linked in.
extern const int INSTR_PROF_PROFILE_RUNTIME_VAR = 0;

}  // extern "C"

// Here _WIN32 really means EFI (Gigaboot).  At link-time, it's Windows/x64
// essentially.  InstrProfData.inc uses #ifdef _WIN32, so match that.
#ifdef _WIN32

// These magic section names don't have macros in InstrProfData.inc,
// though their ".blah$M" counterparts do.

// Merge read-write sections into .data.
#pragma comment(linker, "/MERGE:.lprfc=.data")
#pragma comment(linker, "/MERGE:.lprfd=.data")

// Do not merge .lprfn and .lcovmap into .rdata.
// `llvm-cov` must be able to find them after the fact.

// Allocate read-only section bounds.
#pragma section(".lprfn$A", read)
#pragma section(".lprfn$Z", read)

// Allocate read-write section bounds.
#pragma section(".lprfd$A", read, write)
#pragma section(".lprfd$Z", read, write)
#pragma section(".lprfc$A", read, write)
#pragma section(".lprfc$Z", read, write)

// The ".blah$A" and ".blah$Z" dummy sections get magically sorted
// with ".blah$M" in between them, so these symbols identify the
// bounds of the compiler-emitted data at link time.  The all-zero
// dummy records don't matter to `llvm-profdata`.

// This data is morally `const`, i.e. it's a RELRO case in the ELF world.
// But the compiler complains about a mismatch with the #pragma section
// above if these are declared `const` in the PE-COFF case.
[[gnu::section(".lprfd$A"), gnu::used]] __llvm_profile_data DataStart{};
[[gnu::section(".lprfd$Z"), gnu::used]] __llvm_profile_data DataEnd{};

[[gnu::section(".lprfn$A"), gnu::used]] const char NamesStart{};
[[gnu::section(".lprfn$Z"), gnu::used]] const char NamesEnd{};

[[gnu::section(".lprfc$A"), gnu::used]] uint64_t CountersStart{};
[[gnu::section(".lprfc$Z"), gnu::used]] uint64_t CountersEnd{};

#else  // !_WIN32

extern "C" {

extern const __llvm_profile_data DataStart __asm__(
    INSTR_PROF_QUOTE(INSTR_PROF_SECT_START(INSTR_PROF_DATA_COMMON)));
extern const __llvm_profile_data DataEnd __asm__(
    INSTR_PROF_QUOTE(INSTR_PROF_SECT_STOP(INSTR_PROF_DATA_COMMON)));

extern const char NamesStart __asm__(
    INSTR_PROF_QUOTE(INSTR_PROF_SECT_START(INSTR_PROF_NAME_COMMON)));
extern const char NamesEnd __asm__(
    INSTR_PROF_QUOTE(INSTR_PROF_SECT_STOP(INSTR_PROF_NAME_COMMON)));

extern uint64_t CountersStart __asm__(
    INSTR_PROF_QUOTE(INSTR_PROF_SECT_START(INSTR_PROF_CNTS_COMMON)));
extern uint64_t CountersEnd __asm__(
    INSTR_PROF_QUOTE(INSTR_PROF_SECT_STOP(INSTR_PROF_CNTS_COMMON)));

}  // extern "C"

#endif  // _WIN32

// These are used by the INSTR_PROF_RAW_HEADER initializers.

constexpr uint64_t __llvm_profile_get_magic() {
  return INSTR_PROF_RAW_MAGIC_64;
}

uint64_t __llvm_profile_get_version() { return INSTR_PROF_RAW_VERSION_VAR; }

#define DataSize (&DataEnd - &DataStart)
#define PaddingBytesBeforeCounters 0
#define CountersSize (&CountersEnd - &CountersStart)
#define PaddingBytesAfterCounters 0
#define NamesSize (&NamesEnd - &NamesStart)
#define CountersBegin (reinterpret_cast<uint64_t>(&CountersStart))
#define NamesBegin (reinterpret_cast<uint64_t>(&NamesStart))

// The linker script places this at the start of a page-aligned region
// where it's followed by the compiler-generated sections.
[[gnu::section("__llvm_profile_header"), gnu::used]] struct {
#define INSTR_PROF_RAW_HEADER(Type, Name, Initializer) \
  Type Name##_ = Initializer;
#include <profile/InstrProfData.inc>
} __llvm_profile_header;

}  // namespace