263 lines
9.2 KiB
C++
263 lines
9.2 KiB
C++
#include "cpuid.h"
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#include "sanitizer_common/sanitizer_common.h"
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#include "xray_defs.h"
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#include "xray_interface_internal.h"
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#include <atomic>
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#include <cstdint>
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#include <errno.h>
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#include <fcntl.h>
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#include <iterator>
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#include <limits>
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#include <tuple>
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#include <unistd.h>
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namespace __xray {
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static std::pair<ssize_t, bool>
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retryingReadSome(int Fd, char *Begin, char *End) XRAY_NEVER_INSTRUMENT {
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auto BytesToRead = std::distance(Begin, End);
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ssize_t BytesRead;
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ssize_t TotalBytesRead = 0;
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while (BytesToRead && (BytesRead = read(Fd, Begin, BytesToRead))) {
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if (BytesRead == -1) {
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if (errno == EINTR)
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continue;
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Report("Read error; errno = %d\n", errno);
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return std::make_pair(TotalBytesRead, false);
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}
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TotalBytesRead += BytesRead;
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BytesToRead -= BytesRead;
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Begin += BytesRead;
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}
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return std::make_pair(TotalBytesRead, true);
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}
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static bool readValueFromFile(const char *Filename,
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long long *Value) XRAY_NEVER_INSTRUMENT {
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int Fd = open(Filename, O_RDONLY | O_CLOEXEC);
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if (Fd == -1)
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return false;
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static constexpr size_t BufSize = 256;
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char Line[BufSize] = {};
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ssize_t BytesRead;
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bool Success;
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std::tie(BytesRead, Success) = retryingReadSome(Fd, Line, Line + BufSize);
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close(Fd);
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if (!Success)
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return false;
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char *End = nullptr;
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long long Tmp = internal_simple_strtoll(Line, &End, 10);
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bool Result = false;
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if (Line[0] != '\0' && (*End == '\n' || *End == '\0')) {
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*Value = Tmp;
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Result = true;
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}
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return Result;
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}
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uint64_t getTSCFrequency() XRAY_NEVER_INSTRUMENT {
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long long TSCFrequency = -1;
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if (readValueFromFile("/sys/devices/system/cpu/cpu0/tsc_freq_khz",
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&TSCFrequency)) {
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TSCFrequency *= 1000;
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} else if (readValueFromFile(
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"/sys/devices/system/cpu/cpu0/cpufreq/cpuinfo_max_freq",
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&TSCFrequency)) {
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TSCFrequency *= 1000;
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} else {
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Report("Unable to determine CPU frequency for TSC accounting.\n");
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}
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return TSCFrequency == -1 ? 0 : static_cast<uint64_t>(TSCFrequency);
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}
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static constexpr uint8_t CallOpCode = 0xe8;
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static constexpr uint16_t MovR10Seq = 0xba41;
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static constexpr uint16_t Jmp9Seq = 0x09eb;
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static constexpr uint16_t Jmp20Seq = 0x14eb;
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static constexpr uint8_t JmpOpCode = 0xe9;
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static constexpr uint8_t RetOpCode = 0xc3;
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static constexpr uint16_t NopwSeq = 0x9066;
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static constexpr int64_t MinOffset{std::numeric_limits<int32_t>::min()};
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static constexpr int64_t MaxOffset{std::numeric_limits<int32_t>::max()};
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bool patchFunctionEntry(const bool Enable, const uint32_t FuncId,
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const XRaySledEntry &Sled,
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void (*Trampoline)()) XRAY_NEVER_INSTRUMENT {
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// Here we do the dance of replacing the following sled:
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//
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// xray_sled_n:
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// jmp +9
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// <9 byte nop>
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//
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// With the following:
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//
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// mov r10d, <function id>
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// call <relative 32bit offset to entry trampoline>
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//
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// We need to do this in the following order:
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//
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// 1. Put the function id first, 2 bytes from the start of the sled (just
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// after the 2-byte jmp instruction).
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// 2. Put the call opcode 6 bytes from the start of the sled.
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// 3. Put the relative offset 7 bytes from the start of the sled.
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// 4. Do an atomic write over the jmp instruction for the "mov r10d"
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// opcode and first operand.
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//
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// Prerequisite is to compute the relative offset to the trampoline's address.
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int64_t TrampolineOffset = reinterpret_cast<int64_t>(Trampoline) -
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(static_cast<int64_t>(Sled.Address) + 11);
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if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) {
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Report("XRay Entry trampoline (%p) too far from sled (%p)\n",
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Trampoline, reinterpret_cast<void *>(Sled.Address));
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return false;
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}
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if (Enable) {
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*reinterpret_cast<uint32_t *>(Sled.Address + 2) = FuncId;
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*reinterpret_cast<uint8_t *>(Sled.Address + 6) = CallOpCode;
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*reinterpret_cast<uint32_t *>(Sled.Address + 7) = TrampolineOffset;
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std::atomic_store_explicit(
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reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), MovR10Seq,
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std::memory_order_release);
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} else {
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std::atomic_store_explicit(
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reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), Jmp9Seq,
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std::memory_order_release);
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// FIXME: Write out the nops still?
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}
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return true;
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}
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bool patchFunctionExit(const bool Enable, const uint32_t FuncId,
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const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
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// Here we do the dance of replacing the following sled:
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//
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// xray_sled_n:
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// ret
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// <10 byte nop>
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//
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// With the following:
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//
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// mov r10d, <function id>
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// jmp <relative 32bit offset to exit trampoline>
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//
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// 1. Put the function id first, 2 bytes from the start of the sled (just
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// after the 1-byte ret instruction).
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// 2. Put the jmp opcode 6 bytes from the start of the sled.
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// 3. Put the relative offset 7 bytes from the start of the sled.
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// 4. Do an atomic write over the jmp instruction for the "mov r10d"
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// opcode and first operand.
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//
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// Prerequisite is to compute the relative offset fo the
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// __xray_FunctionExit function's address.
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int64_t TrampolineOffset = reinterpret_cast<int64_t>(__xray_FunctionExit) -
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(static_cast<int64_t>(Sled.Address) + 11);
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if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) {
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Report("XRay Exit trampoline (%p) too far from sled (%p)\n",
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__xray_FunctionExit, reinterpret_cast<void *>(Sled.Address));
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return false;
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}
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if (Enable) {
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*reinterpret_cast<uint32_t *>(Sled.Address + 2) = FuncId;
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*reinterpret_cast<uint8_t *>(Sled.Address + 6) = JmpOpCode;
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*reinterpret_cast<uint32_t *>(Sled.Address + 7) = TrampolineOffset;
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std::atomic_store_explicit(
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reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), MovR10Seq,
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std::memory_order_release);
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} else {
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std::atomic_store_explicit(
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reinterpret_cast<std::atomic<uint8_t> *>(Sled.Address), RetOpCode,
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std::memory_order_release);
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// FIXME: Write out the nops still?
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}
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return true;
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}
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bool patchFunctionTailExit(const bool Enable, const uint32_t FuncId,
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const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
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// Here we do the dance of replacing the tail call sled with a similar
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// sequence as the entry sled, but calls the tail exit sled instead.
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int64_t TrampolineOffset =
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reinterpret_cast<int64_t>(__xray_FunctionTailExit) -
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(static_cast<int64_t>(Sled.Address) + 11);
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if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) {
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Report("XRay Exit trampoline (%p) too far from sled (%p)\n",
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__xray_FunctionExit, reinterpret_cast<void *>(Sled.Address));
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return false;
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}
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if (Enable) {
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*reinterpret_cast<uint32_t *>(Sled.Address + 2) = FuncId;
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*reinterpret_cast<uint8_t *>(Sled.Address + 6) = CallOpCode;
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*reinterpret_cast<uint32_t *>(Sled.Address + 7) = TrampolineOffset;
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std::atomic_store_explicit(
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reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), MovR10Seq,
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std::memory_order_release);
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} else {
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std::atomic_store_explicit(
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reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), Jmp9Seq,
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std::memory_order_release);
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// FIXME: Write out the nops still?
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}
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return true;
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}
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bool patchCustomEvent(const bool Enable, const uint32_t FuncId,
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const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
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// Here we do the dance of replacing the following sled:
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//
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// xray_sled_n:
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// jmp +19 // 2 bytes
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// ...
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//
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// With the following:
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//
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// nopw // 2 bytes*
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// ...
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//
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// We need to do this in the following order:
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//
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// 1. Overwrite the 5-byte nop with the call (relative), where (relative) is
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// the relative offset to the __xray_CustomEvent trampoline.
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// 2. Do a two-byte atomic write over the 'jmp +24' to turn it into a 'nopw'.
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// This allows us to "enable" this code once the changes have committed.
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//
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// The "unpatch" should just turn the 'nopw' back to a 'jmp +24'.
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//
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if (Enable) {
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std::atomic_store_explicit(
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reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), NopwSeq,
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std::memory_order_release);
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} else {
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std::atomic_store_explicit(
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reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), Jmp20Seq,
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std::memory_order_release);
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}
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return false;
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}
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// We determine whether the CPU we're running on has the correct features we
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// need. In x86_64 this will be rdtscp support.
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bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT {
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unsigned int EAX, EBX, ECX, EDX;
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// We check whether rdtscp support is enabled. According to the x86_64 manual,
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// level should be set at 0x80000001, and we should have a look at bit 27 in
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// EDX. That's 0x8000000 (or 1u << 26).
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__get_cpuid(0x80000001, &EAX, &EBX, &ECX, &EDX);
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if (!(EDX & (1u << 26))) {
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Report("Missing rdtscp support.\n");
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return false;
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}
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// Also check whether we can determine the CPU frequency, since if we cannot,
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// we should use the emulated TSC instead.
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if (!getTSCFrequency()) {
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Report("Unable to determine CPU frequency.\n");
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return false;
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}
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return true;
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}
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} // namespace __xray
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