Add libunwindstack support for Mips and Mips64

This patch requires v3.18 kernel or above, because v3.10 kernel
has a bug (as of 8/1/2017) in the ptrace(GETREGSET) function for mips
and mips64.

Change-Id: I004c1fa190193eebe1c84440b366289122a6bd8a
Signed-off-by: Douglas Leung <douglas.leung@mips.com>
Signed-off-by: Dejan Jovicevic <dejan.jovicevic@mips.com>
diff --git a/libunwindstack/RegsMips64.cpp b/libunwindstack/RegsMips64.cpp
new file mode 100644
index 0000000..b4e5246
--- /dev/null
+++ b/libunwindstack/RegsMips64.cpp
@@ -0,0 +1,161 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <stdint.h>
+
+#include <functional>
+
+#include <unwindstack/Elf.h>
+#include <unwindstack/MapInfo.h>
+#include <unwindstack/Memory.h>
+#include <unwindstack/RegsMips64.h>
+
+#include "MachineMips64.h"
+#include "UcontextMips64.h"
+#include "UserMips64.h"
+
+namespace unwindstack {
+
+RegsMips64::RegsMips64()
+    : RegsImpl<uint64_t>(MIPS64_REG_LAST, MIPS64_REG_SP,
+                         Location(LOCATION_REGISTER, MIPS64_REG_RA)) {}
+
+ArchEnum RegsMips64::Arch() {
+  return ARCH_MIPS64;
+}
+
+uint64_t RegsMips64::GetAdjustedPc(uint64_t rel_pc, Elf* elf) {
+  if (!elf->valid()) {
+    return rel_pc;
+  }
+
+  // For now, just assuming no compact branches
+  if (rel_pc < 8) {
+    return rel_pc;
+  }
+  return rel_pc - 8;
+}
+
+void RegsMips64::SetFromRaw() {
+  set_pc(regs_[MIPS64_REG_PC]);
+  set_sp(regs_[MIPS64_REG_SP]);
+}
+
+bool RegsMips64::SetPcFromReturnAddress(Memory*) {
+  if (pc() == regs_[MIPS64_REG_RA]) {
+    return false;
+  }
+
+  set_pc(regs_[MIPS64_REG_RA]);
+  return true;
+}
+
+void RegsMips64::IterateRegisters(std::function<void(const char*, uint64_t)> fn) {
+  fn("r0", regs_[MIPS64_REG_R0]);
+  fn("r1", regs_[MIPS64_REG_R1]);
+  fn("r2", regs_[MIPS64_REG_R2]);
+  fn("r3", regs_[MIPS64_REG_R3]);
+  fn("r4", regs_[MIPS64_REG_R4]);
+  fn("r5", regs_[MIPS64_REG_R5]);
+  fn("r6", regs_[MIPS64_REG_R6]);
+  fn("r7", regs_[MIPS64_REG_R7]);
+  fn("r8", regs_[MIPS64_REG_R8]);
+  fn("r9", regs_[MIPS64_REG_R9]);
+  fn("r10", regs_[MIPS64_REG_R10]);
+  fn("r11", regs_[MIPS64_REG_R11]);
+  fn("r12", regs_[MIPS64_REG_R12]);
+  fn("r13", regs_[MIPS64_REG_R13]);
+  fn("r14", regs_[MIPS64_REG_R14]);
+  fn("r15", regs_[MIPS64_REG_R15]);
+  fn("r16", regs_[MIPS64_REG_R16]);
+  fn("r17", regs_[MIPS64_REG_R17]);
+  fn("r18", regs_[MIPS64_REG_R18]);
+  fn("r19", regs_[MIPS64_REG_R19]);
+  fn("r20", regs_[MIPS64_REG_R20]);
+  fn("r21", regs_[MIPS64_REG_R21]);
+  fn("r22", regs_[MIPS64_REG_R22]);
+  fn("r23", regs_[MIPS64_REG_R23]);
+  fn("r24", regs_[MIPS64_REG_R24]);
+  fn("r25", regs_[MIPS64_REG_R25]);
+  fn("r26", regs_[MIPS64_REG_R26]);
+  fn("r27", regs_[MIPS64_REG_R27]);
+  fn("r28", regs_[MIPS64_REG_R28]);
+  fn("sp", regs_[MIPS64_REG_SP]);
+  fn("r30", regs_[MIPS64_REG_R30]);
+  fn("ra", regs_[MIPS64_REG_RA]);
+  fn("pc", regs_[MIPS64_REG_PC]);
+}
+
+Regs* RegsMips64::Read(void* remote_data) {
+  mips64_user_regs* user = reinterpret_cast<mips64_user_regs*>(remote_data);
+  RegsMips64* regs = new RegsMips64();
+  uint64_t* reg_data = reinterpret_cast<uint64_t*>(regs->RawData());
+
+  memcpy(regs->RawData(), &user->regs[MIPS64_EF_R0], (MIPS64_REG_R31 + 1) * sizeof(uint64_t));
+
+  reg_data[MIPS64_REG_PC] = user->regs[MIPS64_EF_CP0_EPC];
+  regs->SetFromRaw();
+  return regs;
+}
+
+Regs* RegsMips64::CreateFromUcontext(void* ucontext) {
+  mips64_ucontext_t* mips64_ucontext = reinterpret_cast<mips64_ucontext_t*>(ucontext);
+
+  RegsMips64* regs = new RegsMips64();
+  // Copy 64 bit sc_regs over to 64 bit regs
+  memcpy(regs->RawData(), &mips64_ucontext->uc_mcontext.sc_regs[0], 32 * sizeof(uint64_t));
+  (*regs)[MIPS64_REG_PC] = mips64_ucontext->uc_mcontext.sc_pc;
+  regs->SetFromRaw();
+  return regs;
+}
+
+bool RegsMips64::StepIfSignalHandler(uint64_t rel_pc, Elf* elf, Memory* process_memory) {
+  uint64_t data;
+  Memory* elf_memory = elf->memory();
+  // Read from elf memory since it is usually more expensive to read from
+  // process memory.
+  if (!elf_memory->Read(rel_pc, &data, sizeof(data))) {
+    return false;
+  }
+
+  // Look for the kernel sigreturn function.
+  // __vdso_rt_sigreturn:
+  // 0x2402145b     li  v0, 0x145b
+  // 0x0000000c     syscall
+  if (data != 0x0000000c2402145bULL) {
+    return false;
+  }
+
+  // vdso_rt_sigreturn => read rt_sigframe
+  // offset = siginfo offset + sizeof(siginfo) + uc_mcontext offset
+  // read 64 bit sc_regs[32] from stack into 64 bit regs_
+  if (!process_memory->Read(sp() + 24 + 128 + 40, regs_.data(),
+                            sizeof(uint64_t) * (MIPS64_REG_LAST - 1))) {
+    return false;
+  }
+
+  // offset = siginfo offset + sizeof(siginfo) + uc_mcontext offset + sc_pc offset
+  // read 64 bit sc_pc from stack into 64 bit regs_[MIPS64_REG_PC]
+  if (!process_memory->Read(sp() + 24 + 128 + 40 + 576, &regs_[MIPS64_REG_PC],
+                            sizeof(uint64_t))) {
+    return false;
+  }
+
+  SetFromRaw();
+  return true;
+}
+
+}  // namespace unwindstack