Add tool to save information from a process.

Also, modify the ProcessVmRead function to allow arbitrarily large
reads and add a test for it.

Test: Run tool and verify the output can be used to do an offline
Test: unwind.
Test: Ran unit tests.
Change-Id: I0974ddca4f5cf72b4c9fa29b597a0a669e223828

libunwindstack/Android.bp

@@ -215,6 +215,15 @@ cc_binary {
     ],
 }
 
+cc_binary {
+    name: "unwind_for_offline",
+    defaults: ["libunwindstack_tools"],
+
+    srcs: [
+        "tools/unwind_for_offline.cpp",
+    ],
+}
+
 // Generates the elf data for use in the tests for .gnu_debugdata frames.
 // Once these files are generated, use the xz command to compress the data.
 cc_binary_host {

libunwindstack/Memory.cpp

@@ -35,10 +35,6 @@
 namespace unwindstack {
 
 static size_t ProcessVmRead(pid_t pid, uint64_t remote_src, void* dst, size_t len) {
-  struct iovec dst_iov = {
-      .iov_base = dst,
-      .iov_len = len,
-  };
 
   // Split up the remote read across page boundaries.
   // From the manpage:
@@ -49,39 +45,49 @@ static size_t ProcessVmRead(pid_t pid, uint64_t remote_src, void* dst, size_t le
   //   perform a partial transfer that splits a single iovec element.
   constexpr size_t kMaxIovecs = 64;
   struct iovec src_iovs[kMaxIovecs];
-  size_t iovecs_used = 0;
 
   uint64_t cur = remote_src;
+  size_t total_read = 0;
   while (len > 0) {
-    if (iovecs_used == kMaxIovecs) {
-      errno = EINVAL;
-      return 0;
+    struct iovec dst_iov = {
+        .iov_base = &reinterpret_cast<uint8_t*>(dst)[total_read], .iov_len = len,
+    };
+
+    size_t iovecs_used = 0;
+    while (len > 0) {
+      if (iovecs_used == kMaxIovecs) {
+        break;
+      }
+
+      // struct iovec uses void* for iov_base.
+      if (cur >= UINTPTR_MAX) {
+        errno = EFAULT;
+        return total_read;
+      }
+
+      src_iovs[iovecs_used].iov_base = reinterpret_cast<void*>(cur);
+
+      uintptr_t misalignment = cur & (getpagesize() - 1);
+      size_t iov_len = getpagesize() - misalignment;
+      iov_len = std::min(iov_len, len);
+
+      len -= iov_len;
+      if (__builtin_add_overflow(cur, iov_len, &cur)) {
+        errno = EFAULT;
+        return total_read;
+      }
+
+      src_iovs[iovecs_used].iov_len = iov_len;
+      ++iovecs_used;
     }
 
-    // struct iovec uses void* for iov_base.
-    if (cur >= UINTPTR_MAX) {
-      errno = EFAULT;
-      return 0;
+    ssize_t rc = process_vm_readv(pid, &dst_iov, 1, src_iovs, iovecs_used, 0);
+    if (rc == -1) {
+      return total_read;
     }
-
-    src_iovs[iovecs_used].iov_base = reinterpret_cast<void*>(cur);
-
-    uintptr_t misalignment = cur & (getpagesize() - 1);
-    size_t iov_len = getpagesize() - misalignment;
-    iov_len = std::min(iov_len, len);
-
-    len -= iov_len;
-    if (__builtin_add_overflow(cur, iov_len, &cur)) {
-      errno = EFAULT;
-      return 0;
-    }
-
-    src_iovs[iovecs_used].iov_len = iov_len;
-    ++iovecs_used;
+    total_read += rc;
   }
-
-  ssize_t rc = process_vm_readv(pid, &dst_iov, 1, src_iovs, iovecs_used, 0);
-  return rc == -1 ? 0 : rc;
+  return total_read;
 }
 
 static bool PtraceReadLong(pid_t pid, uint64_t addr, long* value) {

libunwindstack/tests/MemoryRemoteTest.cpp

@@ -79,6 +79,35 @@ TEST_F(MemoryRemoteTest, read) {
   ASSERT_TRUE(Detach(pid));
 }
 
+TEST_F(MemoryRemoteTest, read_large) {
+  static constexpr size_t kTotalPages = 245;
+  std::vector<uint8_t> src(kTotalPages * getpagesize());
+  for (size_t i = 0; i < kTotalPages; i++) {
+    memset(&src[i * getpagesize()], i, getpagesize());
+  }
+
+  pid_t pid;
+  if ((pid = fork()) == 0) {
+    while (true)
+      ;
+    exit(1);
+  }
+  ASSERT_LT(0, pid);
+  TestScopedPidReaper reap(pid);
+
+  ASSERT_TRUE(Attach(pid));
+
+  MemoryRemote remote(pid);
+
+  std::vector<uint8_t> dst(kTotalPages * getpagesize());
+  ASSERT_TRUE(remote.ReadFully(reinterpret_cast<uint64_t>(src.data()), dst.data(), src.size()));
+  for (size_t i = 0; i < kTotalPages * getpagesize(); i++) {
+    ASSERT_EQ(i / getpagesize(), dst[i]) << "Failed at byte " << i;
+  }
+
+  ASSERT_TRUE(Detach(pid));
+}
+
 TEST_F(MemoryRemoteTest, read_partial) {
   char* mapping = static_cast<char*>(
       mmap(nullptr, 4 * getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));

libunwindstack/tools/unwind_for_offline.cpp

@@ -0,0 +1,262 @@
+/*
+ * 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.
+ */
+
+#define _GNU_SOURCE 1
+#include <errno.h>
+#include <inttypes.h>
+#include <signal.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ptrace.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <memory>
+#include <string>
+#include <unordered_map>
+#include <vector>
+
+#include <unwindstack/Elf.h>
+#include <unwindstack/Maps.h>
+#include <unwindstack/Memory.h>
+#include <unwindstack/Regs.h>
+#include <unwindstack/Unwinder.h>
+
+#include <android-base/stringprintf.h>
+
+struct map_info_t {
+  uint64_t start;
+  uint64_t end;
+  uint64_t offset;
+  std::string name;
+};
+
+static bool Attach(pid_t pid) {
+  if (ptrace(PTRACE_ATTACH, pid, 0, 0) == -1) {
+    return false;
+  }
+
+  // Allow at least 1 second to attach properly.
+  for (size_t i = 0; i < 1000; i++) {
+    siginfo_t si;
+    if (ptrace(PTRACE_GETSIGINFO, pid, 0, &si) == 0) {
+      return true;
+    }
+    usleep(1000);
+  }
+  printf("%d: Failed to stop.\n", pid);
+  return false;
+}
+
+bool SaveRegs(unwindstack::Regs* regs) {
+  std::unique_ptr<FILE, decltype(&fclose)> fp(fopen("regs.txt", "w+"), &fclose);
+  if (fp == nullptr) {
+    printf("Failed to create file regs.txt.\n");
+    return false;
+  }
+  regs->IterateRegisters([&fp](const char* name, uint64_t value) {
+    fprintf(fp.get(), "%s: %" PRIx64 "\n", name, value);
+  });
+
+  return true;
+}
+
+bool SaveStack(pid_t pid, uint64_t sp_start, uint64_t sp_end) {
+  std::unique_ptr<FILE, decltype(&fclose)> fp(fopen("stack.data", "w+"), &fclose);
+  if (fp == nullptr) {
+    printf("Failed to create stack.data.\n");
+    return false;
+  }
+
+  size_t bytes = fwrite(&sp_start, 1, sizeof(sp_start), fp.get());
+  if (bytes != sizeof(sp_start)) {
+    perror("Failed to write all data.");
+    return false;
+  }
+
+  std::vector<uint8_t> buffer(sp_end - sp_start);
+  auto process_memory = unwindstack::Memory::CreateProcessMemory(pid);
+  if (!process_memory->Read(sp_start, buffer.data(), buffer.size())) {
+    printf("Unable to read stack data.\n");
+    return false;
+  }
+
+  bytes = fwrite(buffer.data(), 1, buffer.size(), fp.get());
+  if (bytes != buffer.size()) {
+    printf("Failed to write all stack data: stack size %zu, written %zu\n", buffer.size(), bytes);
+    return 1;
+  }
+
+  return true;
+}
+
+bool CreateElfFromMemory(std::shared_ptr<unwindstack::Memory>& memory, map_info_t* info) {
+  std::string cur_name;
+  if (info->name.empty()) {
+    cur_name = android::base::StringPrintf("anonymous:%" PRIx64, info->start);
+  } else {
+    cur_name = basename(info->name.c_str());
+    cur_name = android::base::StringPrintf("%s:%" PRIx64, basename(info->name.c_str()), info->start);
+  }
+
+  std::unique_ptr<FILE, decltype(&fclose)> output(fopen(cur_name.c_str(), "w+"), &fclose);
+  if (output == nullptr) {
+    printf("Cannot create %s\n", cur_name.c_str());
+    return false;
+  }
+  std::vector<uint8_t> buffer(info->end - info->start);
+  // If this is a mapped in file, it might not be possible to read the entire
+  // map, so read all that is readable.
+  size_t bytes = memory->Read(info->start, buffer.data(), buffer.size());
+  if (bytes == 0) {
+    printf("Cannot read data from address %" PRIx64 " length %zu\n", info->start, buffer.size());
+    return false;
+  }
+  size_t bytes_written = fwrite(buffer.data(), 1, bytes, output.get());
+  if (bytes_written != bytes) {
+    printf("Failed to write all data to file: bytes read %zu, written %zu\n", bytes, bytes_written);
+    return false;
+  }
+
+  // Replace the name with the new name.
+  info->name = cur_name;
+
+  return true;
+}
+
+bool CopyElfFromFile(map_info_t* info) {
+  std::unique_ptr<FILE, decltype(&fclose)> fp(fopen(info->name.c_str(), "r"), &fclose);
+  if (fp == nullptr) {
+    return false;
+  }
+
+  std::string cur_name = basename(info->name.c_str());
+  std::unique_ptr<FILE, decltype(&fclose)> output(fopen(cur_name.c_str(), "w+"), &fclose);
+  if (output == nullptr) {
+    printf("Cannot create file %s\n", cur_name.c_str());
+    return false;
+  }
+  std::vector<uint8_t> buffer(10000);
+  size_t bytes;
+  while ((bytes = fread(buffer.data(), 1, buffer.size(), fp.get())) > 0) {
+    size_t bytes_written = fwrite(buffer.data(), 1, bytes, output.get());
+    if (bytes_written != bytes) {
+      printf("Bytes written doesn't match bytes read: read %zu, written %zu\n", bytes,
+             bytes_written);
+      return false;
+    }
+  }
+
+  // Replace the name with the new name.
+  info->name = cur_name;
+
+  return true;
+}
+
+int SaveData(pid_t pid) {
+  unwindstack::Regs* regs = unwindstack::Regs::RemoteGet(pid);
+  if (regs == nullptr) {
+    printf("Unable to get remote reg data.\n");
+    return 1;
+  }
+
+  unwindstack::RemoteMaps maps(pid);
+  if (!maps.Parse()) {
+    printf("Unable to parse maps.\n");
+    return 1;
+  }
+
+  // Save the current state of the registers.
+  if (!SaveRegs(regs)) {
+    return 1;
+  }
+
+  // Do an unwind so we know how much of the stack to save, and what
+  // elf files are involved.
+  uint64_t sp = regs->sp();
+  auto process_memory = unwindstack::Memory::CreateProcessMemory(pid);
+  unwindstack::Unwinder unwinder(1024, &maps, regs, process_memory);
+  unwinder.Unwind();
+
+  std::unordered_map<uint64_t, map_info_t> maps_by_start;
+  uint64_t last_sp;
+  for (auto frame : unwinder.frames()) {
+    last_sp = frame.sp;
+    if (maps_by_start.count(frame.map_start) == 0) {
+      auto info = &maps_by_start[frame.map_start];
+      info->start = frame.map_start;
+      info->end = frame.map_end;
+      info->offset = frame.map_offset;
+      info->name = frame.map_name;
+      if (!CopyElfFromFile(info)) {
+        // Try to create the elf from memory, this will handle cases where
+        // the data only exists in memory such as vdso data on x86.
+        if (!CreateElfFromMemory(process_memory, info)) {
+          return 1;
+        }
+      }
+    }
+  }
+
+  if (!SaveStack(pid, sp, last_sp)) {
+    return 1;
+  }
+
+  std::vector<std::pair<uint64_t, map_info_t>> sorted_maps(maps_by_start.begin(),
+                                                           maps_by_start.end());
+  std::sort(sorted_maps.begin(), sorted_maps.end(),
+            [](auto& a, auto& b) { return a.first < b.first; });
+
+  std::unique_ptr<FILE, decltype(&fclose)> fp(fopen("maps.txt", "w+"), &fclose);
+  if (fp == nullptr) {
+    printf("Failed to create maps.txt.\n");
+    return false;
+  }
+
+  for (auto& element : sorted_maps) {
+    map_info_t& map = element.second;
+    fprintf(fp.get(), "%" PRIx64 "-%" PRIx64 " r-xp %" PRIx64 " 00:00 0", map.start, map.end,
+            map.offset);
+    if (!map.name.empty()) {
+      fprintf(fp.get(), "   %s", map.name.c_str());
+    }
+    fprintf(fp.get(), "\n");
+  }
+
+  return 0;
+}
+
+int main(int argc, char** argv) {
+  if (argc != 2) {
+    printf("Usage: unwind_for_offline <PID>\n");
+    return 1;
+  }
+
+  pid_t pid = atoi(argv[1]);
+  if (!Attach(pid)) {
+    printf("Failed to attach to pid %d: %s\n", pid, strerror(errno));
+    return 1;
+  }
+
+  int return_code = SaveData(pid);
+
+  ptrace(PTRACE_DETACH, pid, 0, 0);
+
+  return return_code;
+}