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//===-- xray_arm.cpp --------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file is a part of XRay, a dynamic runtime instrumentation system.
//
// Implementation of ARM-specific routines (32-bit).
//
//===----------------------------------------------------------------------===//
#include "sanitizer_common/sanitizer_common.h"
#include "xray_defs.h"
#include "xray_interface_internal.h"
#include <atomic>
#include <cassert>
extern "C" void __clear_cache(void *start, void *end);
namespace __xray {
// The machine codes for some instructions used in runtime patching.
enum class PatchOpcodes : uint32_t {
PO_PushR0Lr = 0xE92D4001, // PUSH {r0, lr}
PO_BlxIp = 0xE12FFF3C, // BLX ip
PO_PopR0Lr = 0xE8BD4001, // POP {r0, lr}
PO_B20 = 0xEA000005 // B #20
};
// 0xUUUUWXYZ -> 0x000W0XYZ
inline static uint32_t getMovwMask(const uint32_t Value) XRAY_NEVER_INSTRUMENT {
return (Value & 0xfff) | ((Value & 0xf000) << 4);
}
// 0xWXYZUUUU -> 0x000W0XYZ
inline static uint32_t getMovtMask(const uint32_t Value) XRAY_NEVER_INSTRUMENT {
return getMovwMask(Value >> 16);
}
// Writes the following instructions:
// MOVW R<regNo>, #<lower 16 bits of the |Value|>
// MOVT R<regNo>, #<higher 16 bits of the |Value|>
inline static uint32_t *
write32bitLoadReg(uint8_t regNo, uint32_t *Address,
const uint32_t Value) XRAY_NEVER_INSTRUMENT {
// This is a fatal error: we cannot just report it and continue execution.
assert(regNo <= 15 && "Register number must be 0 to 15.");
// MOVW R, #0xWXYZ in machine code is 0xE30WRXYZ
*Address = (0xE3000000 | (uint32_t(regNo) << 12) | getMovwMask(Value));
Address++;
// MOVT R, #0xWXYZ in machine code is 0xE34WRXYZ
*Address = (0xE3400000 | (uint32_t(regNo) << 12) | getMovtMask(Value));
return Address + 1;
}
// Writes the following instructions:
// MOVW r0, #<lower 16 bits of the |Value|>
// MOVT r0, #<higher 16 bits of the |Value|>
inline static uint32_t *
write32bitLoadR0(uint32_t *Address,
const uint32_t Value) XRAY_NEVER_INSTRUMENT {
return write32bitLoadReg(0, Address, Value);
}
// Writes the following instructions:
// MOVW ip, #<lower 16 bits of the |Value|>
// MOVT ip, #<higher 16 bits of the |Value|>
inline static uint32_t *
write32bitLoadIP(uint32_t *Address,
const uint32_t Value) XRAY_NEVER_INSTRUMENT {
return write32bitLoadReg(12, Address, Value);
}
inline static bool patchSled(const bool Enable, const uint32_t FuncId,
const XRaySledEntry &Sled,
void (*TracingHook)()) XRAY_NEVER_INSTRUMENT {
// When |Enable| == true,
// We replace the following compile-time stub (sled):
//
// xray_sled_n:
// B #20
// 6 NOPs (24 bytes)
//
// With the following runtime patch:
//
// xray_sled_n:
// PUSH {r0, lr}
// MOVW r0, #<lower 16 bits of function ID>
// MOVT r0, #<higher 16 bits of function ID>
// MOVW ip, #<lower 16 bits of address of TracingHook>
// MOVT ip, #<higher 16 bits of address of TracingHook>
// BLX ip
// POP {r0, lr}
//
// Replacement of the first 4-byte instruction should be the last and atomic
// operation, so that the user code which reaches the sled concurrently
// either jumps over the whole sled, or executes the whole sled when the
// latter is ready.
//
// When |Enable|==false, we set back the first instruction in the sled to be
// B #20
uint32_t *FirstAddress = reinterpret_cast<uint32_t *>(Sled.address());
uint32_t *CurAddress = FirstAddress + 1;
if (Enable) {
CurAddress =
write32bitLoadR0(CurAddress, reinterpret_cast<uint32_t>(FuncId));
CurAddress =
write32bitLoadIP(CurAddress, reinterpret_cast<uint32_t>(TracingHook));
*CurAddress = uint32_t(PatchOpcodes::PO_BlxIp);
CurAddress++;
*CurAddress = uint32_t(PatchOpcodes::PO_PopR0Lr);
CurAddress++;
std::atomic_store_explicit(
reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
uint32_t(PatchOpcodes::PO_PushR0Lr), std::memory_order_release);
} else {
std::atomic_store_explicit(
reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
uint32_t(PatchOpcodes::PO_B20), std::memory_order_release);
}
__clear_cache(reinterpret_cast<char *>(FirstAddress),
reinterpret_cast<char *>(CurAddress));
return true;
}
bool patchFunctionEntry(const bool Enable, const uint32_t FuncId,
const XRaySledEntry &Sled,
void (*Trampoline)()) XRAY_NEVER_INSTRUMENT {
return patchSled(Enable, FuncId, Sled, Trampoline);
}
bool patchFunctionExit(const bool Enable, const uint32_t FuncId,
const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
return patchSled(Enable, FuncId, Sled, __xray_FunctionExit);
}
bool patchFunctionTailExit(const bool Enable, const uint32_t FuncId,
const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
return patchSled(Enable, FuncId, Sled, __xray_FunctionTailExit);
}
bool patchCustomEvent(const bool Enable, const uint32_t FuncId,
const XRaySledEntry &Sled)
XRAY_NEVER_INSTRUMENT { // FIXME: Implement in arm?
return false;
}
bool patchTypedEvent(const bool Enable, const uint32_t FuncId,
const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
// FIXME: Implement in arm?
return false;
}
// FIXME: Maybe implement this better?
bool probeRequiredCPUFeatures() XRAY_NEVER_INSTRUMENT { return true; }
} // namespace __xray
extern "C" void __xray_ArgLoggerEntry() XRAY_NEVER_INSTRUMENT {
// FIXME: this will have to be implemented in the trampoline assembly file
}
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