Microdumps: refactor out common parts of minidump_writer.cc

This change is a pure refactoring of the common bits of minidump_writer.cc
that will be shared soon with the upcoming microdump_writer.cc.
In particular, this CL is extracting the following classes:
- ThreadInfo: handles the state of the threads in the crashing process.
- RawContextCPU: typedef for arch-specific CPU context structure.
- UContextReader: Fills out a dump RawContextCPU structure from the
  ucontext struct provided by the kernel (arch-dependent).
- SeccompUnwinder: cleans out the stack frames of the Seccomp sandbox
  on the supported architectures.
- MappingInfo: handles information about mappings

BUG=chromium:410294
R=mmandlis@chromium.org

Review URL: https://breakpad.appspot.com/4684002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1388 4c0a9323-5329-0410-9bdc-e9ce6186880e

2 files changed, 17 insertions, 619 deletions

diff --git a/src/client/linux/minidump_writer/linux_dumper.h b/src/client/linux/minidump_writer/linux_dumper.h
index ad2af018..e37ed179 100644
--- a/src/client/linux/minidump_writer/linux_dumper.h
+++ b/src/client/linux/minidump_writer/linux_dumper.h
@@ -44,15 +44,13 @@
 #include <sys/types.h>
 #include <sys/user.h>
 
+#include "client/linux/dump_writer_common/mapping_info.h"
+#include "client/linux/dump_writer_common/thread_info.h"
 #include "common/memory.h"
 #include "google_breakpad/common/minidump_format.h"
 
 namespace google_breakpad {
 
-#if defined(__i386) || defined(__x86_64)
-typedef typeof(((struct user*) 0)->u_debugreg[0]) debugreg_t;
-#endif
-
 // Typedef for our parsing of the auxv variables in /proc/pid/auxv.
 #if defined(__i386) || defined(__ARM_EABI__) || defined(__mips__)
 typedef Elf32_auxv_t elf_aux_entry;
@@ -67,50 +65,6 @@ typedef typeof(((elf_aux_entry*) 0)->a_un.a_val) elf_aux_val_t;
 // This should always be less than NAME_MAX!
 const char kLinuxGateLibraryName[] = "linux-gate.so";
 
-// We produce one of these structures for each thread in the crashed process.
-struct ThreadInfo {
-  pid_t tgid;   // thread group id
-  pid_t ppid;   // parent process
-
-  uintptr_t stack_pointer;  // thread stack pointer
-
-
-#if defined(__i386) || defined(__x86_64)
-  user_regs_struct regs;
-  user_fpregs_struct fpregs;
-  static const unsigned kNumDebugRegisters = 8;
-  debugreg_t dregs[8];
-#if defined(__i386)
-  user_fpxregs_struct fpxregs;
-#endif  // defined(__i386)
-
-#elif defined(__ARM_EABI__)
-  // Mimicking how strace does this(see syscall.c, search for GETREGS)
-  struct user_regs regs;
-  struct user_fpregs fpregs;
-#elif defined(__aarch64__)
-  // Use the structures defined in <asm/ptrace.h>
-  struct user_pt_regs regs;
-  struct user_fpsimd_state fpregs;
-#elif defined(__mips__)
-  user_regs_struct regs;
-  user_fpregs_struct fpregs;
-  uint32_t hi[3];
-  uint32_t lo[3];
-  uint32_t dsp_control;
-#endif
-};
-
-// One of these is produced for each mapping in the process (i.e. line in
-// /proc/$x/maps).
-struct MappingInfo {
-  uintptr_t start_addr;
-  size_t size;
-  size_t offset;  // offset into the backed file.
-  bool exec;  // true if the mapping has the execute bit set.
-  char name[NAME_MAX];
-};
-
 class LinuxDumper {
  public:
   explicit LinuxDumper(pid_t pid);
diff --git a/src/client/linux/minidump_writer/minidump_writer.cc b/src/client/linux/minidump_writer/minidump_writer.cc
index 41b4864b..c65fa9c9 100644
--- a/src/client/linux/minidump_writer/minidump_writer.cc
+++ b/src/client/linux/minidump_writer/minidump_writer.cc
@@ -64,6 +64,9 @@
 
 #include <algorithm>
 
+#include "client/linux/dump_writer_common/seccomp_unwinder.h"
+#include "client/linux/dump_writer_common/thread_info.h"
+#include "client/linux/dump_writer_common/ucontext_reader.h"
 #include "client/linux/handler/exception_handler.h"
 #include "client/linux/minidump_writer/cpu_set.h"
 #include "client/linux/minidump_writer/line_reader.h"
@@ -89,393 +92,14 @@ using google_breakpad::MappingList;
 using google_breakpad::MinidumpFileWriter;
 using google_breakpad::PageAllocator;
 using google_breakpad::ProcCpuInfoReader;
+using google_breakpad::RawContextCPU;
+using google_breakpad::SeccompUnwinder;
 using google_breakpad::ThreadInfo;
 using google_breakpad::TypedMDRVA;
+using google_breakpad::UContextReader;
 using google_breakpad::UntypedMDRVA;
 using google_breakpad::wasteful_vector;
 
-// Minidump defines register structures which are different from the raw
-// structures which we get from the kernel. These are platform specific
-// functions to juggle the ucontext and user structures into minidump format.
-#if defined(__i386__)
-typedef MDRawContextX86 RawContextCPU;
-
-// Write a uint16_t to memory
-//   out: memory location to write to
-//   v: value to write.
-void U16(void* out, uint16_t v) {
-  my_memcpy(out, &v, sizeof(v));
-}
-
-// Write a uint32_t to memory
-//   out: memory location to write to
-//   v: value to write.
-void U32(void* out, uint32_t v) {
-  my_memcpy(out, &v, sizeof(v));
-}
-
-// Juggle an x86 user_(fp|fpx|)regs_struct into minidump format
-//   out: the minidump structure
-//   info: the collection of register structures.
-void CPUFillFromThreadInfo(MDRawContextX86 *out,
-                           const google_breakpad::ThreadInfo &info) {
-  out->context_flags = MD_CONTEXT_X86_ALL;
-
-  out->dr0 = info.dregs[0];
-  out->dr1 = info.dregs[1];
-  out->dr2 = info.dregs[2];
-  out->dr3 = info.dregs[3];
-  // 4 and 5 deliberatly omitted because they aren't included in the minidump
-  // format.
-  out->dr6 = info.dregs[6];
-  out->dr7 = info.dregs[7];
-
-  out->gs = info.regs.xgs;
-  out->fs = info.regs.xfs;
-  out->es = info.regs.xes;
-  out->ds = info.regs.xds;
-
-  out->edi = info.regs.edi;
-  out->esi = info.regs.esi;
-  out->ebx = info.regs.ebx;
-  out->edx = info.regs.edx;
-  out->ecx = info.regs.ecx;
-  out->eax = info.regs.eax;
-
-  out->ebp = info.regs.ebp;
-  out->eip = info.regs.eip;
-  out->cs = info.regs.xcs;
-  out->eflags = info.regs.eflags;
-  out->esp = info.regs.esp;
-  out->ss = info.regs.xss;
-
-  out->float_save.control_word = info.fpregs.cwd;
-  out->float_save.status_word = info.fpregs.swd;
-  out->float_save.tag_word = info.fpregs.twd;
-  out->float_save.error_offset = info.fpregs.fip;
-  out->float_save.error_selector = info.fpregs.fcs;
-  out->float_save.data_offset = info.fpregs.foo;
-  out->float_save.data_selector = info.fpregs.fos;
-
-  // 8 registers * 10 bytes per register.
-  my_memcpy(out->float_save.register_area, info.fpregs.st_space, 10 * 8);
-
-  // This matches the Intel fpsave format.
-  U16(out->extended_registers + 0, info.fpregs.cwd);
-  U16(out->extended_registers + 2, info.fpregs.swd);
-  U16(out->extended_registers + 4, info.fpregs.twd);
-  U16(out->extended_registers + 6, info.fpxregs.fop);
-  U32(out->extended_registers + 8, info.fpxregs.fip);
-  U16(out->extended_registers + 12, info.fpxregs.fcs);
-  U32(out->extended_registers + 16, info.fpregs.foo);
-  U16(out->extended_registers + 20, info.fpregs.fos);
-  U32(out->extended_registers + 24, info.fpxregs.mxcsr);
-
-  my_memcpy(out->extended_registers + 32, &info.fpxregs.st_space, 128);
-  my_memcpy(out->extended_registers + 160, &info.fpxregs.xmm_space, 128);
-}
-
-// Juggle an x86 ucontext into minidump format
-//   out: the minidump structure
-//   info: the collection of register structures.
-void CPUFillFromUContext(MDRawContextX86 *out, const ucontext *uc,
-                         const struct _libc_fpstate* fp) {
-  const greg_t* regs = uc->uc_mcontext.gregs;
-
-  out->context_flags = MD_CONTEXT_X86_FULL |
-                       MD_CONTEXT_X86_FLOATING_POINT;
-
-  out->gs = regs[REG_GS];
-  out->fs = regs[REG_FS];
-  out->es = regs[REG_ES];
-  out->ds = regs[REG_DS];
-
-  out->edi = regs[REG_EDI];
-  out->esi = regs[REG_ESI];
-  out->ebx = regs[REG_EBX];
-  out->edx = regs[REG_EDX];
-  out->ecx = regs[REG_ECX];
-  out->eax = regs[REG_EAX];
-
-  out->ebp = regs[REG_EBP];
-  out->eip = regs[REG_EIP];
-  out->cs = regs[REG_CS];
-  out->eflags = regs[REG_EFL];
-  out->esp = regs[REG_UESP];
-  out->ss = regs[REG_SS];
-
-  out->float_save.control_word = fp->cw;
-  out->float_save.status_word = fp->sw;
-  out->float_save.tag_word = fp->tag;
-  out->float_save.error_offset = fp->ipoff;
-  out->float_save.error_selector = fp->cssel;
-  out->float_save.data_offset = fp->dataoff;
-  out->float_save.data_selector = fp->datasel;
-
-  // 8 registers * 10 bytes per register.
-  my_memcpy(out->float_save.register_area, fp->_st, 10 * 8);
-}
-
-#elif defined(__x86_64)
-typedef MDRawContextAMD64 RawContextCPU;
-
-void CPUFillFromThreadInfo(MDRawContextAMD64 *out,
-                           const google_breakpad::ThreadInfo &info) {
-  out->context_flags = MD_CONTEXT_AMD64_FULL |
-                       MD_CONTEXT_AMD64_SEGMENTS;
-
-  out->cs = info.regs.cs;
-
-  out->ds = info.regs.ds;
-  out->es = info.regs.es;
-  out->fs = info.regs.fs;
-  out->gs = info.regs.gs;
-
-  out->ss = info.regs.ss;
-  out->eflags = info.regs.eflags;
-
-  out->dr0 = info.dregs[0];
-  out->dr1 = info.dregs[1];
-  out->dr2 = info.dregs[2];
-  out->dr3 = info.dregs[3];
-  // 4 and 5 deliberatly omitted because they aren't included in the minidump
-  // format.
-  out->dr6 = info.dregs[6];
-  out->dr7 = info.dregs[7];
-
-  out->rax = info.regs.rax;
-  out->rcx = info.regs.rcx;
-  out->rdx = info.regs.rdx;
-  out->rbx = info.regs.rbx;
-
-  out->rsp = info.regs.rsp;
-
-  out->rbp = info.regs.rbp;
-  out->rsi = info.regs.rsi;
-  out->rdi = info.regs.rdi;
-  out->r8 = info.regs.r8;
-  out->r9 = info.regs.r9;
-  out->r10 = info.regs.r10;
-  out->r11 = info.regs.r11;
-  out->r12 = info.regs.r12;
-  out->r13 = info.regs.r13;
-  out->r14 = info.regs.r14;
-  out->r15 = info.regs.r15;
-
-  out->rip = info.regs.rip;
-
-  out->flt_save.control_word = info.fpregs.cwd;
-  out->flt_save.status_word = info.fpregs.swd;
-  out->flt_save.tag_word = info.fpregs.ftw;
-  out->flt_save.error_opcode = info.fpregs.fop;
-  out->flt_save.error_offset = info.fpregs.rip;
-  out->flt_save.error_selector = 0;  // We don't have this.
-  out->flt_save.data_offset = info.fpregs.rdp;
-  out->flt_save.data_selector = 0;   // We don't have this.
-  out->flt_save.mx_csr = info.fpregs.mxcsr;
-  out->flt_save.mx_csr_mask = info.fpregs.mxcr_mask;
-  my_memcpy(&out->flt_save.float_registers, &info.fpregs.st_space, 8 * 16);
-  my_memcpy(&out->flt_save.xmm_registers, &info.fpregs.xmm_space, 16 * 16);
-}
-
-void CPUFillFromUContext(MDRawContextAMD64 *out, const ucontext *uc,
-                         const struct _libc_fpstate* fpregs) {
-  const greg_t* regs = uc->uc_mcontext.gregs;
-
-  out->context_flags = MD_CONTEXT_AMD64_FULL;
-
-  out->cs = regs[REG_CSGSFS] & 0xffff;
-
-  out->fs = (regs[REG_CSGSFS] >> 32) & 0xffff;
-  out->gs = (regs[REG_CSGSFS] >> 16) & 0xffff;
-
-  out->eflags = regs[REG_EFL];
-
-  out->rax = regs[REG_RAX];
-  out->rcx = regs[REG_RCX];
-  out->rdx = regs[REG_RDX];
-  out->rbx = regs[REG_RBX];
-
-  out->rsp = regs[REG_RSP];
-  out->rbp = regs[REG_RBP];
-  out->rsi = regs[REG_RSI];
-  out->rdi = regs[REG_RDI];
-  out->r8 = regs[REG_R8];
-  out->r9 = regs[REG_R9];
-  out->r10 = regs[REG_R10];
-  out->r11 = regs[REG_R11];
-  out->r12 = regs[REG_R12];
-  out->r13 = regs[REG_R13];
-  out->r14 = regs[REG_R14];
-  out->r15 = regs[REG_R15];
-
-  out->rip = regs[REG_RIP];
-
-  out->flt_save.control_word = fpregs->cwd;
-  out->flt_save.status_word = fpregs->swd;
-  out->flt_save.tag_word = fpregs->ftw;
-  out->flt_save.error_opcode = fpregs->fop;
-  out->flt_save.error_offset = fpregs->rip;
-  out->flt_save.data_offset = fpregs->rdp;
-  out->flt_save.error_selector = 0;  // We don't have this.
-  out->flt_save.data_selector = 0;  // We don't have this.
-  out->flt_save.mx_csr = fpregs->mxcsr;
-  out->flt_save.mx_csr_mask = fpregs->mxcr_mask;
-  my_memcpy(&out->flt_save.float_registers, &fpregs->_st, 8 * 16);
-  my_memcpy(&out->flt_save.xmm_registers, &fpregs->_xmm, 16 * 16);
-}
-
-#elif defined(__ARMEL__)
-typedef MDRawContextARM RawContextCPU;
-
-void CPUFillFromThreadInfo(MDRawContextARM* out,
-                           const google_breakpad::ThreadInfo& info) {
-  out->context_flags = MD_CONTEXT_ARM_FULL;
-
-  for (int i = 0; i < MD_CONTEXT_ARM_GPR_COUNT; ++i)
-    out->iregs[i] = info.regs.uregs[i];
-  // No CPSR register in ThreadInfo(it's not accessible via ptrace)
-  out->cpsr = 0;
-#if !defined(__ANDROID__)
-  out->float_save.fpscr = info.fpregs.fpsr |
-    (static_cast<uint64_t>(info.fpregs.fpcr) << 32);
-  // TODO: sort this out, actually collect floating point registers
-  my_memset(&out->float_save.regs, 0, sizeof(out->float_save.regs));
-  my_memset(&out->float_save.extra, 0, sizeof(out->float_save.extra));
-#endif
-}
-
-void CPUFillFromUContext(MDRawContextARM* out, const ucontext* uc) {
-  out->context_flags = MD_CONTEXT_ARM_FULL;
-
-  out->iregs[0] = uc->uc_mcontext.arm_r0;
-  out->iregs[1] = uc->uc_mcontext.arm_r1;
-  out->iregs[2] = uc->uc_mcontext.arm_r2;
-  out->iregs[3] = uc->uc_mcontext.arm_r3;
-  out->iregs[4] = uc->uc_mcontext.arm_r4;
-  out->iregs[5] = uc->uc_mcontext.arm_r5;
-  out->iregs[6] = uc->uc_mcontext.arm_r6;
-  out->iregs[7] = uc->uc_mcontext.arm_r7;
-  out->iregs[8] = uc->uc_mcontext.arm_r8;
-  out->iregs[9] = uc->uc_mcontext.arm_r9;
-  out->iregs[10] = uc->uc_mcontext.arm_r10;
-
-  out->iregs[11] = uc->uc_mcontext.arm_fp;
-  out->iregs[12] = uc->uc_mcontext.arm_ip;
-  out->iregs[13] = uc->uc_mcontext.arm_sp;
-  out->iregs[14] = uc->uc_mcontext.arm_lr;
-  out->iregs[15] = uc->uc_mcontext.arm_pc;
-
-  out->cpsr = uc->uc_mcontext.arm_cpsr;
-
-  // TODO: fix this after fixing ExceptionHandler
-  out->float_save.fpscr = 0;
-  my_memset(&out->float_save.regs, 0, sizeof(out->float_save.regs));
-  my_memset(&out->float_save.extra, 0, sizeof(out->float_save.extra));
-}
-
-#elif defined(__aarch64__)
-typedef MDRawContextARM64 RawContextCPU;
-
-void CPUFillFromThreadInfo(MDRawContextARM64* out,
-                           const google_breakpad::ThreadInfo& info) {
-  out->context_flags = MD_CONTEXT_ARM64_FULL;
-
-  out->cpsr = static_cast<uint32_t>(info.regs.pstate);
-  for (int i = 0; i < MD_CONTEXT_ARM64_REG_SP; ++i)
-    out->iregs[i] = info.regs.regs[i];
-  out->iregs[MD_CONTEXT_ARM64_REG_SP] = info.regs.sp;
-  out->iregs[MD_CONTEXT_ARM64_REG_PC] = info.regs.pc;
-
-  out->float_save.fpsr = info.fpregs.fpsr;
-  out->float_save.fpcr = info.fpregs.fpcr;
-  my_memcpy(&out->float_save.regs, &info.fpregs.vregs,
-      MD_FLOATINGSAVEAREA_ARM64_FPR_COUNT * 16);
-}
-
-void CPUFillFromUContext(MDRawContextARM64* out, const ucontext* uc,
-                         const struct fpsimd_context* fpregs) {
-  out->context_flags = MD_CONTEXT_ARM64_FULL;
-
-  out->cpsr = static_cast<uint32_t>(uc->uc_mcontext.pstate);
-  for (int i = 0; i < MD_CONTEXT_ARM64_REG_SP; ++i)
-    out->iregs[i] = uc->uc_mcontext.regs[i];
-  out->iregs[MD_CONTEXT_ARM64_REG_SP] = uc->uc_mcontext.sp;
-  out->iregs[MD_CONTEXT_ARM64_REG_PC] = uc->uc_mcontext.pc;
-
-  out->float_save.fpsr = fpregs->fpsr;
-  out->float_save.fpcr = fpregs->fpcr;
-  my_memcpy(&out->float_save.regs, &fpregs->vregs,
-      MD_FLOATINGSAVEAREA_ARM64_FPR_COUNT * 16);
-}
-
-#elif defined(__mips__)
-typedef MDRawContextMIPS RawContextCPU;
-
-static void CPUFillFromThreadInfo(MDRawContextMIPS* out,
-                                  const google_breakpad::ThreadInfo& info) {
-  out->context_flags = MD_CONTEXT_MIPS_FULL;
-
-  for (int i = 0; i < MD_CONTEXT_MIPS_GPR_COUNT; ++i)
-    out->iregs[i] = info.regs.regs[i];
-
-  out->mdhi = info.regs.hi;
-  out->mdlo = info.regs.lo;
-
-  for (int i = 0; i < MD_CONTEXT_MIPS_DSP_COUNT; ++i) {
-    out->hi[i] = info.hi[i];
-    out->lo[i] = info.lo[i];
-  }
-  out->dsp_control = info.dsp_control;
-
-  out->epc = info.regs.epc;
-  out->badvaddr = info.regs.badvaddr;
-  out->status = info.regs.status;
-  out->cause = info.regs.cause;
-
-  for (int i = 0; i < MD_FLOATINGSAVEAREA_MIPS_FPR_COUNT; ++i)
-    out->float_save.regs[i] = info.fpregs.regs[i];
-
-  out->float_save.fpcsr = info.fpregs.fpcsr;
-  out->float_save.fir = info.fpregs.fir;
-}
-
-static void CPUFillFromUContext(MDRawContextMIPS* out, const ucontext* uc) {
-  out->context_flags = MD_CONTEXT_MIPS_FULL;
-
-  for (int i = 0; i < MD_CONTEXT_MIPS_GPR_COUNT; ++i)
-    out->iregs[i] = uc->uc_mcontext.gregs[i];
-
-  out->mdhi = uc->uc_mcontext.mdhi;
-  out->mdlo = uc->uc_mcontext.mdlo;
-
-  out->hi[0] = uc->uc_mcontext.hi1;
-  out->hi[1] = uc->uc_mcontext.hi2;
-  out->hi[2] = uc->uc_mcontext.hi3;
-  out->lo[0] = uc->uc_mcontext.lo1;
-  out->lo[1] = uc->uc_mcontext.lo2;
-  out->lo[2] = uc->uc_mcontext.lo3;
-  out->dsp_control = uc->uc_mcontext.dsp;
-
-  out->epc = uc->uc_mcontext.pc;
-  out->badvaddr = 0;  // Not reported in signal context.
-  out->status = 0;  // Not reported in signal context.
-  out->cause = 0;  // Not reported in signal context.
-
-  for (int i = 0; i < MD_FLOATINGSAVEAREA_MIPS_FPR_COUNT; ++i)
-#if defined (__ANDROID__)
-    out->float_save.regs[i] = uc->uc_mcontext.fpregs[i];
-#else
-    out->float_save.regs[i] = uc->uc_mcontext.fpregs.fp_r.fp_dregs[i];
-#endif
-
-  out->float_save.fpcsr = uc->uc_mcontext.fpc_csr;
-  out->float_save.fir = uc->uc_mcontext.fpc_eir;  // Unused.
-}
-
-#else
-#error "This code has not been ported to your platform yet."
-#endif
 
 class MinidumpWriter {
  public:
@@ -629,123 +253,6 @@ class MinidumpWriter {
     return true;
   }
 
-  // Check if the top of the stack is part of a system call that has been
-  // redirected by the seccomp sandbox. If so, try to pop the stack frames
-  // all the way back to the point where the interception happened.
-  void PopSeccompStackFrame(RawContextCPU* cpu, const MDRawThread& thread,
-                            uint8_t* stack_copy) {
-#if defined(__x86_64)
-    uint64_t bp = cpu->rbp;
-    uint64_t top = thread.stack.start_of_memory_range;
-    for (int i = 4; i--; ) {
-      if (bp < top ||
-          bp + sizeof(bp) > thread.stack.start_of_memory_range +
-          thread.stack.memory.data_size ||
-          bp & 1) {
-        break;
-      }
-      uint64_t old_top = top;
-      top = bp;
-      uint8_t* bp_addr = stack_copy + bp - thread.stack.start_of_memory_range;
-      my_memcpy(&bp, bp_addr, sizeof(bp));
-      if (bp == 0xDEADBEEFDEADBEEFull) {
-        struct {
-          uint64_t r15;
-          uint64_t r14;
-          uint64_t r13;
-          uint64_t r12;
-          uint64_t r11;
-          uint64_t r10;
-          uint64_t r9;
-          uint64_t r8;
-          uint64_t rdi;
-          uint64_t rsi;
-          uint64_t rdx;
-          uint64_t rcx;
-          uint64_t rbx;
-          uint64_t deadbeef;
-          uint64_t rbp;
-          uint64_t fakeret;
-          uint64_t ret;
-          /* char redzone[128]; */
-        } seccomp_stackframe;
-        if (top - offsetof(typeof(seccomp_stackframe), deadbeef) < old_top ||
-            top - offsetof(typeof(seccomp_stackframe), deadbeef) +
-            sizeof(seccomp_stackframe) >
-            thread.stack.start_of_memory_range+thread.stack.memory.data_size) {
-          break;
-        }
-        my_memcpy(&seccomp_stackframe,
-                  bp_addr - offsetof(typeof(seccomp_stackframe), deadbeef),
-                  sizeof(seccomp_stackframe));
-        cpu->rbx = seccomp_stackframe.rbx;
-        cpu->rcx = seccomp_stackframe.rcx;
-        cpu->rdx = seccomp_stackframe.rdx;
-        cpu->rsi = seccomp_stackframe.rsi;
-        cpu->rdi = seccomp_stackframe.rdi;
-        cpu->rbp = seccomp_stackframe.rbp;
-        cpu->rsp = top + 4*sizeof(uint64_t) + 128;
-        cpu->r8  = seccomp_stackframe.r8;
-        cpu->r9  = seccomp_stackframe.r9;
-        cpu->r10 = seccomp_stackframe.r10;
-        cpu->r11 = seccomp_stackframe.r11;
-        cpu->r12 = seccomp_stackframe.r12;
-        cpu->r13 = seccomp_stackframe.r13;
-        cpu->r14 = seccomp_stackframe.r14;
-        cpu->r15 = seccomp_stackframe.r15;
-        cpu->rip = seccomp_stackframe.fakeret;
-        return;
-      }
-    }
-#elif defined(__i386__)
-    uint32_t bp = cpu->ebp;
-    uint32_t top = thread.stack.start_of_memory_range;
-    for (int i = 4; i--; ) {
-      if (bp < top ||
-          bp + sizeof(bp) > thread.stack.start_of_memory_range +
-          thread.stack.memory.data_size ||
-          bp & 1) {
-        break;
-      }
-      uint32_t old_top = top;
-      top = bp;
-      uint8_t* bp_addr = stack_copy + bp - thread.stack.start_of_memory_range;
-      my_memcpy(&bp, bp_addr, sizeof(bp));
-      if (bp == 0xDEADBEEFu) {
-        struct {
-          uint32_t edi;
-          uint32_t esi;
-          uint32_t edx;
-          uint32_t ecx;
-          uint32_t ebx;
-          uint32_t deadbeef;
-          uint32_t ebp;
-          uint32_t fakeret;
-          uint32_t ret;
-        } seccomp_stackframe;
-        if (top - offsetof(typeof(seccomp_stackframe), deadbeef) < old_top ||
-            top - offsetof(typeof(seccomp_stackframe), deadbeef) +
-            sizeof(seccomp_stackframe) >
-            thread.stack.start_of_memory_range+thread.stack.memory.data_size) {
-          break;
-        }
-        my_memcpy(&seccomp_stackframe,
-                  bp_addr - offsetof(typeof(seccomp_stackframe), deadbeef),
-                  sizeof(seccomp_stackframe));
-        cpu->ebx = seccomp_stackframe.ebx;
-        cpu->ecx = seccomp_stackframe.ecx;
-        cpu->edx = seccomp_stackframe.edx;
-        cpu->esi = seccomp_stackframe.esi;
-        cpu->edi = seccomp_stackframe.edi;
-        cpu->ebp = seccomp_stackframe.ebp;
-        cpu->esp = top + 4*sizeof(void*);
-        cpu->eip = seccomp_stackframe.fakeret;
-        return;
-      }
-    }
-#endif
-  }
-
   bool FillThreadStack(MDRawThread* thread, uintptr_t stack_pointer,
                        int max_stack_len, uint8_t** stack_copy) {
     *stack_copy = NULL;
@@ -816,12 +323,13 @@ class MinidumpWriter {
           ucontext_ &&
           !dumper_->IsPostMortem()) {
         uint8_t* stack_copy;
-        if (!FillThreadStack(&thread, GetStackPointer(), -1, &stack_copy))
+        const uintptr_t stack_ptr = UContextReader::GetStackPointer(ucontext_);
+        if (!FillThreadStack(&thread, stack_ptr, -1, &stack_copy))
           return false;
 
         // Copy 256 bytes around crashing instruction pointer to minidump.
         const size_t kIPMemorySize = 256;
-        uint64_t ip = GetInstructionPointer();
+        uint64_t ip = UContextReader::GetInstructionPointer(ucontext_);
         // Bound it to the upper and lower bounds of the memory map
         // it's contained within. If it's not in mapped memory,
         // don't bother trying to write it.
@@ -867,12 +375,12 @@ class MinidumpWriter {
           return false;
         my_memset(cpu.get(), 0, sizeof(RawContextCPU));
 #if !defined(__ARM_EABI__) && !defined(__mips__)
-        CPUFillFromUContext(cpu.get(), ucontext_, float_state_);
+        UContextReader::FillCPUContext(cpu.get(), ucontext_, float_state_);
 #else
-        CPUFillFromUContext(cpu.get(), ucontext_);
+        UContextReader::FillCPUContext(cpu.get(), ucontext_);
 #endif
         if (stack_copy)
-          PopSeccompStackFrame(cpu.get(), thread, stack_copy);
+          SeccompUnwinder::PopSeccompStackFrame(cpu.get(), thread, stack_copy);
         thread.thread_context = cpu.location();
         crashing_thread_context_ = cpu.location();
       } else {
@@ -892,9 +400,9 @@ class MinidumpWriter {
         if (!cpu.Allocate())
           return false;
         my_memset(cpu.get(), 0, sizeof(RawContextCPU));
-        CPUFillFromThreadInfo(cpu.get(), info);
+        info.FillCPUContext(cpu.get());
         if (stack_copy)
-          PopSeccompStackFrame(cpu.get(), thread, stack_copy);
+          SeccompUnwinder::PopSeccompStackFrame(cpu.get(), thread, stack_copy);
         thread.thread_context = cpu.location();
         if (dumper_->threads()[i] == GetCrashThread()) {
           crashing_thread_context_ = cpu.location();
@@ -902,7 +410,7 @@ class MinidumpWriter {
             // This is the crashing thread of a live process, but
             // no context was provided, so set the crash address
             // while the instruction pointer is already here.
-            dumper_->set_crash_address(GetInstructionPointer(info));
+            dumper_->set_crash_address(info.GetInstructionPointer());
           }
         }
       }
@@ -1297,70 +805,6 @@ class MinidumpWriter {
     return dumper_->crash_thread();
   }
 
-#if defined(__i386__)
-  uintptr_t GetStackPointer() {
-    return ucontext_->uc_mcontext.gregs[REG_ESP];
-  }
-
-  uintptr_t GetInstructionPointer() {
-    return ucontext_->uc_mcontext.gregs[REG_EIP];
-  }
-
-  uintptr_t GetInstructionPointer(const ThreadInfo& info) {
-    return info.regs.eip;
-  }
-#elif defined(__x86_64)
-  uintptr_t GetStackPointer() {
-    return ucontext_->uc_mcontext.gregs[REG_RSP];
-  }
-
-  uintptr_t GetInstructionPointer() {
-    return ucontext_->uc_mcontext.gregs[REG_RIP];
-  }
-
-  uintptr_t GetInstructionPointer(const ThreadInfo& info) {
-    return info.regs.rip;
-  }
-#elif defined(__ARM_EABI__)
-  uintptr_t GetStackPointer() {
-    return ucontext_->uc_mcontext.arm_sp;
-  }
-
-  uintptr_t GetInstructionPointer() {
-    return ucontext_->uc_mcontext.arm_pc;
-  }
-
-  uintptr_t GetInstructionPointer(const ThreadInfo& info) {
-    return info.regs.uregs[15];
-  }
-#elif defined(__aarch64__)
-  uintptr_t GetStackPointer() {
-    return ucontext_->uc_mcontext.sp;
-  }
-
-  uintptr_t GetInstructionPointer() {
-    return ucontext_->uc_mcontext.pc;
-  }
-
-  uintptr_t GetInstructionPointer(const ThreadInfo& info) {
-    return info.regs.pc;
-  }
-#elif defined(__mips__)
-  uintptr_t GetStackPointer() {
-    return ucontext_->uc_mcontext.gregs[MD_CONTEXT_MIPS_REG_SP];
-  }
-
-  uintptr_t GetInstructionPointer() {
-    return ucontext_->uc_mcontext.pc;
-  }
-
-  uintptr_t GetInstructionPointer(const ThreadInfo& info) {
-    return info.regs.epc;
-  }
-#else
-#error "This code has not been ported to your platform yet."
-#endif
-
   void NullifyDirectoryEntry(MDRawDirectory* dirent) {
     dirent->stream_type = 0;
     dirent->location.data_size = 0;