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Diffstat (limited to 'compiler-rt/lib/xray/xray_interface.cc')
| -rw-r--r-- | compiler-rt/lib/xray/xray_interface.cc | 179 |
1 files changed, 179 insertions, 0 deletions
diff --git a/compiler-rt/lib/xray/xray_interface.cc b/compiler-rt/lib/xray/xray_interface.cc new file mode 100644 index 00000000000..997829e9358 --- /dev/null +++ b/compiler-rt/lib/xray/xray_interface.cc @@ -0,0 +1,179 @@ +//===-- xray_interface.cpp --------------------------------------*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This file is a part of XRay, a dynamic runtime instrumentation system. +// +// Implementation of the API functions. +// +//===----------------------------------------------------------------------===// + +#include "xray_interface_internal.h" +#include <atomic> +#include <cstdint> +#include <cstdio> +#include <errno.h> +#include <limits> +#include <sys/mman.h> + +namespace __xray { + +// This is the function to call when we encounter the entry or exit sleds. +std::atomic<void (*)(int32_t, XRayEntryType)> XRayPatchedFunction{nullptr}; + +} // namespace __xray + +extern "C" { +// The following functions have to be defined in assembler, on a per-platform +// basis. See xray_trampoline_*.s files for implementations. +extern void __xray_FunctionEntry(); +extern void __xray_FunctionExit(); +} + +extern std::atomic<bool> XRayInitialized; +extern std::atomic<__xray::XRaySledMap> XRayInstrMap; + +int __xray_set_handler(void (*entry)(int32_t, XRayEntryType)) { + if (XRayInitialized.load(std::memory_order_acquire)) { + __xray::XRayPatchedFunction.store(entry, std::memory_order_release); + return 1; + } + return 0; +} + +std::atomic<bool> XRayPatching{false}; + +XRayPatchingStatus __xray_patch() { + // FIXME: Make this happen asynchronously. For now just do this sequentially. + if (!XRayInitialized.load(std::memory_order_acquire)) + return XRayPatchingStatus::NOT_INITIALIZED; // Not initialized. + + static bool NotPatching = false; + if (!XRayPatching.compare_exchange_strong(NotPatching, true, + std::memory_order_acq_rel, + std::memory_order_acquire)) { + return XRayPatchingStatus::ONGOING; // Already patching. + } + + // Step 1: Compute the function id, as a unique identifier per function in the + // instrumentation map. + __xray::XRaySledMap InstrMap = XRayInstrMap.load(std::memory_order_acquire); + if (InstrMap.Entries == 0) + return XRayPatchingStatus::NOT_INITIALIZED; + + int32_t FuncId = 1; + static constexpr uint8_t CallOpCode = 0xe8; + static constexpr uint16_t MovR10Seq = 0xba41; + static constexpr uint8_t JmpOpCode = 0xe9; + uint64_t CurFun = 0; + for (std::size_t I = 0; I < InstrMap.Entries; I++) { + auto Sled = InstrMap.Sleds[I]; + auto F = Sled.Function; + if (CurFun == 0) + CurFun = F; + if (F != CurFun) { + ++FuncId; + CurFun = F; + } + + // While we're here, we should patch the nop sled. To do that we mprotect + // the page containing the function to be writeable. + void *PageAlignedAddr = + reinterpret_cast<void *>(Sled.Address & ~((2 << 16) - 1)); + std::size_t MProtectLen = + (Sled.Address + 12) - reinterpret_cast<uint64_t>(PageAlignedAddr); + if (mprotect(PageAlignedAddr, MProtectLen, + PROT_READ | PROT_WRITE | PROT_EXEC) == -1) { + printf("Failed mprotect: %d\n", errno); + return XRayPatchingStatus::FAILED; + } + + static constexpr int64_t MinOffset{std::numeric_limits<int32_t>::min()}; + static constexpr int64_t MaxOffset{std::numeric_limits<int32_t>::max()}; + if (Sled.Kind == XRayEntryType::ENTRY) { + // Here we do the dance of replacing the following sled: + // + // xray_sled_n: + // jmp +9 + // <9 byte nop> + // + // With the following: + // + // mov r10d, <function id> + // call <relative 32bit offset to entry trampoline> + // + // We need to do this in the following order: + // + // 1. Put the function id first, 2 bytes from the start of the sled (just + // after the 2-byte jmp instruction). + // 2. Put the call opcode 6 bytes from the start of the sled. + // 3. Put the relative offset 7 bytes from the start of the sled. + // 4. Do an atomic write over the jmp instruction for the "mov r10d" + // opcode and first operand. + // + // Prerequisite is to compute the relative offset to the + // __xray_FunctionEntry function's address. + int64_t TrampolineOffset = + reinterpret_cast<int64_t>(__xray_FunctionEntry) - + (static_cast<int64_t>(Sled.Address) + 11); + if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) { + // FIXME: Print out an error here. + continue; + } + *reinterpret_cast<uint32_t *>(Sled.Address + 2) = FuncId; + *reinterpret_cast<uint8_t *>(Sled.Address + 6) = CallOpCode; + *reinterpret_cast<uint32_t *>(Sled.Address + 7) = TrampolineOffset; + std::atomic_store_explicit( + reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), MovR10Seq, + std::memory_order_release); + } + + if (Sled.Kind == XRayEntryType::EXIT) { + // Here we do the dance of replacing the following sled: + // + // xray_sled_n: + // ret + // <10 byte nop> + // + // With the following: + // + // mov r10d, <function id> + // jmp <relative 32bit offset to exit trampoline> + // + // 1. Put the function id first, 2 bytes from the start of the sled (just + // after the 1-byte ret instruction). + // 2. Put the jmp opcode 6 bytes from the start of the sled. + // 3. Put the relative offset 7 bytes from the start of the sled. + // 4. Do an atomic write over the jmp instruction for the "mov r10d" + // opcode and first operand. + // + // Prerequisite is to compute the relative offset fo the + // __xray_FunctionExit function's address. + int64_t TrampolineOffset = + reinterpret_cast<int64_t>(__xray_FunctionExit) - + (static_cast<int64_t>(Sled.Address) + 11); + if (TrampolineOffset < MinOffset || TrampolineOffset > MaxOffset) { + // FIXME: Print out an error here. + continue; + } + *reinterpret_cast<uint32_t *>(Sled.Address + 2) = FuncId; + *reinterpret_cast<uint8_t *>(Sled.Address + 6) = JmpOpCode; + *reinterpret_cast<uint32_t *>(Sled.Address + 7) = TrampolineOffset; + std::atomic_store_explicit( + reinterpret_cast<std::atomic<uint16_t> *>(Sled.Address), MovR10Seq, + std::memory_order_release); + } + + if (mprotect(PageAlignedAddr, MProtectLen, PROT_READ | PROT_EXEC) == -1) { + printf("Failed mprotect: %d\n", errno); + return XRayPatchingStatus::FAILED; + } + } + XRayPatching.store(false, std::memory_order_release); + return XRayPatchingStatus::NOTIFIED; +} |
