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//===-- xray_AArch64.cc -----------------------------------------*- 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 AArch64-specific routines (64-bit).
//
//===----------------------------------------------------------------------===//
#include "sanitizer_common/sanitizer_common.h"
#include "xray_defs.h"
#include "xray_emulate_tsc.h"
#include "xray_interface_internal.h"
#include <atomic>
#include <cassert>
namespace __xray {
uint64_t cycleFrequency() XRAY_NEVER_INSTRUMENT {
// There is no instruction like RDTSCP in user mode on ARM. ARM's CP15 does
// not have a constant frequency like TSC on x86[_64]; it may go faster or
// slower depending on CPU's turbo or power saving modes. Furthermore, to
// read from CP15 on ARM a kernel modification or a driver is needed.
// We can not require this from users of compiler-rt.
// So on ARM we use clock_gettime(2) which gives the result in nanoseconds.
// To get the measurements per second, we scale this by the number of
// nanoseconds per second, pretending that the TSC frequency is 1GHz and
// one TSC tick is 1 nanosecond.
return NanosecondsPerSecond;
}
// The machine codes for some instructions used in runtime patching.
enum class PatchOpcodes : uint32_t {
PO_StpX0X30SP_m16e = 0xA9BF7BE0, // STP X0, X30, [SP, #-16]!
PO_LdrW0_12 = 0x18000060, // LDR W0, #12
PO_LdrX16_12 = 0x58000070, // LDR X16, #12
PO_BlrX16 = 0xD63F0200, // BLR X16
PO_LdpX0X30SP_16 = 0xA8C17BE0, // LDP X0, X30, [SP], #16
PO_B32 = 0x14000008 // B #32
};
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 #32
// 7 NOPs (24 bytes)
//
// With the following runtime patch:
//
// xray_sled_n:
// STP X0, X30, [SP, #-16]! ; PUSH {r0, lr}
// LDR W0, #12 ; W0 := function ID
// LDR X16,#12 ; X16 := address of the trampoline
// BLR X16
// ;DATA: 32 bits of function ID
// ;DATA: lower 32 bits of the address of the trampoline
// ;DATA: higher 32 bits of the address of the trampoline
// LDP X0, X30, [SP], #16 ; 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 #32
uint32_t *FirstAddress = reinterpret_cast<uint32_t *>(Sled.Address);
if (Enable) {
uint32_t *CurAddress = FirstAddress + 1;
*CurAddress = uint32_t(PatchOpcodes::PO_LdrW0_12);
CurAddress++;
*CurAddress = uint32_t(PatchOpcodes::PO_LdrX16_12);
CurAddress++;
*CurAddress = uint32_t(PatchOpcodes::PO_BlrX16);
CurAddress++;
*CurAddress = FuncId;
CurAddress++;
*reinterpret_cast<void (**)()>(CurAddress) = TracingHook;
CurAddress += 2;
*CurAddress = uint32_t(PatchOpcodes::PO_LdpX0X30SP_16);
std::atomic_store_explicit(
reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
uint32_t(PatchOpcodes::PO_StpX0X30SP_m16e), std::memory_order_release);
} else {
std::atomic_store_explicit(
reinterpret_cast<std::atomic<uint32_t> *>(FirstAddress),
uint32_t(PatchOpcodes::PO_B32), std::memory_order_release);
}
return true;
}
bool patchFunctionEntry(const bool Enable, const uint32_t FuncId,
const XRaySledEntry &Sled) XRAY_NEVER_INSTRUMENT {
return patchSled(Enable, FuncId, Sled, __xray_FunctionEntry);
}
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 {
// FIXME: In the future we'd need to distinguish between non-tail exits and
// tail exits for better information preservation.
return patchSled(Enable, FuncId, Sled, __xray_FunctionExit);
}
} // namespace __xray
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