diff options
Diffstat (limited to 'lib/xray/xray_x86_64.cc')
| -rw-r--r-- | lib/xray/xray_x86_64.cc | 36 |
1 files changed, 36 insertions, 0 deletions
diff --git a/lib/xray/xray_x86_64.cc b/lib/xray/xray_x86_64.cc index 2e9a8d270..e34806fa1 100644 --- a/lib/xray/xray_x86_64.cc +++ b/lib/xray/xray_x86_64.cc @@ -75,8 +75,10 @@ uint64_t getTSCFrequency() XRAY_NEVER_INSTRUMENT { static constexpr uint8_t CallOpCode = 0xe8; static constexpr uint16_t MovR10Seq = 0xba41; static constexpr uint16_t Jmp9Seq = 0x09eb; +static constexpr uint16_t Jmp20Seq = 0x14eb; static constexpr uint8_t JmpOpCode = 0xe9; static constexpr uint8_t RetOpCode = 0xc3; +static constexpr uint16_t NopwSeq = 0x9066; static constexpr int64_t MinOffset{std::numeric_limits<int32_t>::min()}; static constexpr int64_t MaxOffset{std::numeric_limits<int32_t>::max()}; @@ -201,6 +203,40 @@ bool patchFunctionTailExit(const bool Enable, const uint32_t FuncId, return true; } +bool patchCustomEvent(const bool Enable, const uint32_t FuncId, + const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT { + // Here we do the dance of replacing the following sled: + // + // xray_sled_n: + // jmp +19 // 2 bytes + // ... + // + // With the following: + // + // nopw // 2 bytes* + // ... + // + // We need to do this in the following order: + // + // 1. Overwrite the 5-byte nop with the call (relative), where (relative) is + // the relative offset to the __xray_CustomEvent trampoline. + // 2. Do a two-byte atomic write over the 'jmp +24' to turn it into a 'nopw'. + // This allows us to "enable" this code once the changes have committed. + // + // The "unpatch" should just turn the 'nopw' back to a 'jmp +24'. + // + if (Enable) { + std::atomic_store_explicit( + reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), NopwSeq, + std::memory_order_release); + } else { + std::atomic_store_explicit( + reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), Jmp20Seq, + std::memory_order_release); + } + return false; +} + // We determine whether the CPU we're running on has the correct features we // need. In x86_64 this will be rdtscp support. bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT { |