Fix bug when doing signal handler lookup.

The new lld linker uses all non-zero offset executable maps. There was
a bug when trying to find if the stack is in a signal handler that caused
the code to read the wrong place in the elf. Fixed by not adding the elf
offset to the relative pc.

Also fixed the unwind_for_offline tool to dump multiple stacks if necessary.

Added new offline unit test that would have failed with the old code.

Bug: 79936827

Test: Ran unit tests and libbacktrace unit tests.
Test: Dumped backtraces of system pids.
Test: Ran 137-cfi art test.
Change-Id: Iaca8c18c2a314902e64c3f72831234297e8dcb1b
Merged-In: Iaca8c18c2a314902e64c3f72831234297e8dcb1b
(cherry picked from commit 239425b9fa91ae13d18cf8158b31663876d07acf)

13 files changed, 202 insertions, 62 deletions

diff --git a/libunwindstack/Android.bp b/libunwindstack/Android.bp
index 7b8111c5d..adbacdbcd 100644
--- a/libunwindstack/Android.bp
+++ b/libunwindstack/Android.bp
@@ -261,6 +261,7 @@ cc_test {
         "tests/files/offline/jit_debug_arm/*",
         "tests/files/offline/jit_debug_x86/*",
         "tests/files/offline/gnu_debugdata_arm/*",
+        "tests/files/offline/offset_arm/*",
         "tests/files/offline/straddle_arm/*",
         "tests/files/offline/straddle_arm64/*",
     ],
diff --git a/libunwindstack/Elf.cpp b/libunwindstack/Elf.cpp
index 02f8a9ae0..3762107d6 100644
--- a/libunwindstack/Elf.cpp
+++ b/libunwindstack/Elf.cpp
@@ -160,14 +160,14 @@ uint64_t Elf::GetLastErrorAddress() {
 }
 
 // The relative pc is always relative to the start of the map from which it comes.
-bool Elf::Step(uint64_t rel_pc, uint64_t adjusted_rel_pc, uint64_t elf_offset, Regs* regs,
-               Memory* process_memory, bool* finished) {
+bool Elf::Step(uint64_t rel_pc, uint64_t adjusted_rel_pc, Regs* regs, Memory* process_memory,
+               bool* finished) {
   if (!valid_) {
     return false;
   }
 
   // The relative pc expectd by StepIfSignalHandler is relative to the start of the elf.
-  if (regs->StepIfSignalHandler(rel_pc + elf_offset, this, process_memory)) {
+  if (regs->StepIfSignalHandler(rel_pc, this, process_memory)) {
     *finished = false;
     return true;
   }
diff --git a/libunwindstack/Unwinder.cpp b/libunwindstack/Unwinder.cpp
index 94edb1cc8..98ab30ff3 100644
--- a/libunwindstack/Unwinder.cpp
+++ b/libunwindstack/Unwinder.cpp
@@ -210,8 +210,7 @@ void Unwinder::Unwind(const std::vector<std::string>* initial_map_names_to_skip,
           in_device_map = true;
         } else {
           bool finished;
-          stepped = elf->Step(rel_pc, step_pc, map_info->elf_offset, regs_, process_memory_.get(),
-                              &finished);
+          stepped = elf->Step(rel_pc, step_pc, regs_, process_memory_.get(), &finished);
           elf->GetLastError(&last_error_);
           if (stepped && finished) {
             break;
diff --git a/libunwindstack/include/unwindstack/Elf.h b/libunwindstack/include/unwindstack/Elf.h
index 385973e9f..f4cdbdaf4 100644
--- a/libunwindstack/include/unwindstack/Elf.h
+++ b/libunwindstack/include/unwindstack/Elf.h
@@ -65,8 +65,8 @@ class Elf {
 
   uint64_t GetRelPc(uint64_t pc, const MapInfo* map_info);
 
-  bool Step(uint64_t rel_pc, uint64_t adjusted_rel_pc, uint64_t elf_offset, Regs* regs,
-            Memory* process_memory, bool* finished);
+  bool Step(uint64_t rel_pc, uint64_t adjusted_rel_pc, Regs* regs, Memory* process_memory,
+            bool* finished);
 
   ElfInterface* CreateInterfaceFromMemory(Memory* memory);
 
diff --git a/libunwindstack/tests/ElfTest.cpp b/libunwindstack/tests/ElfTest.cpp
index f9028c4a5..aecbf6dcb 100644
--- a/libunwindstack/tests/ElfTest.cpp
+++ b/libunwindstack/tests/ElfTest.cpp
@@ -133,7 +133,7 @@ TEST_F(ElfTest, elf_invalid) {
   ASSERT_FALSE(elf.GetFunctionName(0, &name, &func_offset));
 
   bool finished;
-  ASSERT_FALSE(elf.Step(0, 0, 0, nullptr, nullptr, &finished));
+  ASSERT_FALSE(elf.Step(0, 0, nullptr, nullptr, &finished));
 }
 
 TEST_F(ElfTest, elf32_invalid_machine) {
@@ -330,7 +330,7 @@ TEST_F(ElfTest, step_in_signal_map) {
   elf.FakeSetValid(true);
   elf.FakeSetLoadBias(0);
   bool finished;
-  ASSERT_TRUE(elf.Step(0x1000, 0x1000, 0x2000, &regs, &process_memory, &finished));
+  ASSERT_TRUE(elf.Step(0x3000, 0x1000, &regs, &process_memory, &finished));
   EXPECT_FALSE(finished);
   EXPECT_EQ(15U, regs.pc());
   EXPECT_EQ(13U, regs.sp());
@@ -370,7 +370,7 @@ TEST_F(ElfTest, step_in_interface) {
   EXPECT_CALL(*interface, Step(0x1000, 0, &regs, &process_memory, &finished))
       .WillOnce(::testing::Return(true));
 
-  ASSERT_TRUE(elf.Step(0x1004, 0x1000, 0x2000, &regs, &process_memory, &finished));
+  ASSERT_TRUE(elf.Step(0x1004, 0x1000, &regs, &process_memory, &finished));
 }
 
 TEST_F(ElfTest, step_in_interface_non_zero_load_bias) {
@@ -388,7 +388,7 @@ TEST_F(ElfTest, step_in_interface_non_zero_load_bias) {
   EXPECT_CALL(*interface, Step(0x7300, 0x4000, &regs, &process_memory, &finished))
       .WillOnce(::testing::Return(true));
 
-  ASSERT_TRUE(elf.Step(0x7304, 0x7300, 0x2000, &regs, &process_memory, &finished));
+  ASSERT_TRUE(elf.Step(0x7304, 0x7300, &regs, &process_memory, &finished));
 }
 
 TEST_F(ElfTest, get_global_invalid_elf) {
diff --git a/libunwindstack/tests/UnwindOfflineTest.cpp b/libunwindstack/tests/UnwindOfflineTest.cpp
index 8cb640f54..a187dc379 100644
--- a/libunwindstack/tests/UnwindOfflineTest.cpp
+++ b/libunwindstack/tests/UnwindOfflineTest.cpp
@@ -45,6 +45,12 @@
 
 namespace unwindstack {
 
+static void AddMemory(std::string file_name, MemoryOfflineParts* parts) {
+  MemoryOffline* memory = new MemoryOffline;
+  ASSERT_TRUE(memory->Init(file_name.c_str(), 0));
+  parts->Add(memory);
+}
+
 class UnwindOfflineTest : public ::testing::Test {
  protected:
   void TearDown() override {
@@ -63,9 +69,24 @@ class UnwindOfflineTest : public ::testing::Test {
     maps_.reset(new BufferMaps(data.c_str()));
     ASSERT_TRUE(maps_->Parse());
 
-    std::unique_ptr<MemoryOffline> stack_memory(new MemoryOffline);
-    ASSERT_TRUE(stack_memory->Init((dir_ + "stack.data").c_str(), 0));
-    process_memory_.reset(stack_memory.release());
+    std::string stack_name(dir_ + "stack.data");
+    struct stat st;
+    if (stat(stack_name.c_str(), &st) == 0 && S_ISREG(st.st_mode)) {
+      std::unique_ptr<MemoryOffline> stack_memory(new MemoryOffline);
+      ASSERT_TRUE(stack_memory->Init((dir_ + "stack.data").c_str(), 0));
+      process_memory_.reset(stack_memory.release());
+    } else {
+      std::unique_ptr<MemoryOfflineParts> stack_memory(new MemoryOfflineParts);
+      for (size_t i = 0;; i++) {
+        stack_name = dir_ + "stack" + std::to_string(i) + ".data";
+        if (stat(stack_name.c_str(), &st) == -1 || !S_ISREG(st.st_mode)) {
+          ASSERT_TRUE(i != 0) << "No stack data files found.";
+          break;
+        }
+        AddMemory(stack_name, stack_memory.get());
+      }
+      process_memory_.reset(stack_memory.release());
+    }
 
     switch (arch) {
       case ARCH_ARM: {
@@ -179,7 +200,7 @@ static std::string DumpFrames(Unwinder& unwinder) {
 }
 
 TEST_F(UnwindOfflineTest, pc_straddle_arm) {
-  Init("straddle_arm/", ARCH_ARM);
+  ASSERT_NO_FATAL_FAILURE(Init("straddle_arm/", ARCH_ARM));
 
   Unwinder unwinder(128, maps_.get(), regs_.get(), process_memory_);
   unwinder.Unwind();
@@ -203,7 +224,7 @@ TEST_F(UnwindOfflineTest, pc_straddle_arm) {
 }
 
 TEST_F(UnwindOfflineTest, pc_in_gnu_debugdata_arm) {
-  Init("gnu_debugdata_arm/", ARCH_ARM);
+  ASSERT_NO_FATAL_FAILURE(Init("gnu_debugdata_arm/", ARCH_ARM));
 
   Unwinder unwinder(128, maps_.get(), regs_.get(), process_memory_);
   unwinder.Unwind();
@@ -223,7 +244,7 @@ TEST_F(UnwindOfflineTest, pc_in_gnu_debugdata_arm) {
 }
 
 TEST_F(UnwindOfflineTest, pc_straddle_arm64) {
-  Init("straddle_arm64/", ARCH_ARM64);
+  ASSERT_NO_FATAL_FAILURE(Init("straddle_arm64/", ARCH_ARM64));
 
   Unwinder unwinder(128, maps_.get(), regs_.get(), process_memory_);
   unwinder.Unwind();
@@ -254,14 +275,8 @@ TEST_F(UnwindOfflineTest, pc_straddle_arm64) {
   EXPECT_EQ(0x7fe0d84110U, unwinder.frames()[5].sp);
 }
 
-static void AddMemory(std::string file_name, MemoryOfflineParts* parts) {
-  MemoryOffline* memory = new MemoryOffline;
-  ASSERT_TRUE(memory->Init(file_name.c_str(), 0));
-  parts->Add(memory);
-}
-
 TEST_F(UnwindOfflineTest, jit_debug_x86) {
-  Init("jit_debug_x86/", ARCH_X86);
+  ASSERT_NO_FATAL_FAILURE(Init("jit_debug_x86/", ARCH_X86));
 
   MemoryOfflineParts* memory = new MemoryOfflineParts;
   AddMemory(dir_ + "descriptor.data", memory);
@@ -554,7 +569,7 @@ TEST_F(UnwindOfflineTest, jit_debug_x86) {
 }
 
 TEST_F(UnwindOfflineTest, jit_debug_arm) {
-  Init("jit_debug_arm/", ARCH_ARM);
+  ASSERT_NO_FATAL_FAILURE(Init("jit_debug_arm/", ARCH_ARM));
 
   MemoryOfflineParts* memory = new MemoryOfflineParts;
   AddMemory(dir_ + "descriptor.data", memory);
@@ -872,7 +887,7 @@ TEST_F(UnwindOfflineTest, jit_debug_arm) {
 // fallback to iterating over the cies/fdes and ignore the eh_frame_hdr.
 // No .gnu_debugdata section in the elf file, so no symbols.
 TEST_F(UnwindOfflineTest, bad_eh_frame_hdr_arm64) {
-  Init("bad_eh_frame_hdr_arm64/", ARCH_ARM64);
+  ASSERT_NO_FATAL_FAILURE(Init("bad_eh_frame_hdr_arm64/", ARCH_ARM64));
 
   Unwinder unwinder(128, maps_.get(), regs_.get(), process_memory_);
   unwinder.Unwind();
@@ -901,7 +916,7 @@ TEST_F(UnwindOfflineTest, bad_eh_frame_hdr_arm64) {
 // The elf has bad eh_frame unwind information for the pcs. If eh_frame
 // is used first, the unwind will not match the expected output.
 TEST_F(UnwindOfflineTest, debug_frame_first_x86) {
-  Init("debug_frame_first_x86/", ARCH_X86);
+  ASSERT_NO_FATAL_FAILURE(Init("debug_frame_first_x86/", ARCH_X86));
 
   Unwinder unwinder(128, maps_.get(), regs_.get(), process_memory_);
   unwinder.Unwind();
@@ -929,7 +944,7 @@ TEST_F(UnwindOfflineTest, debug_frame_first_x86) {
 
 // Make sure that a pc that is at the beginning of an fde unwinds correctly.
 TEST_F(UnwindOfflineTest, eh_frame_hdr_begin_x86_64) {
-  Init("eh_frame_hdr_begin_x86_64/", ARCH_X86_64);
+  ASSERT_NO_FATAL_FAILURE(Init("eh_frame_hdr_begin_x86_64/", ARCH_X86_64));
 
   Unwinder unwinder(128, maps_.get(), regs_.get(), process_memory_);
   unwinder.Unwind();
@@ -956,7 +971,7 @@ TEST_F(UnwindOfflineTest, eh_frame_hdr_begin_x86_64) {
 }
 
 TEST_F(UnwindOfflineTest, art_quick_osr_stub_arm) {
-  Init("art_quick_osr_stub_arm/", ARCH_ARM);
+  ASSERT_NO_FATAL_FAILURE(Init("art_quick_osr_stub_arm/", ARCH_ARM));
 
   MemoryOfflineParts* memory = new MemoryOfflineParts;
   AddMemory(dir_ + "descriptor.data", memory);
@@ -1070,4 +1085,78 @@ TEST_F(UnwindOfflineTest, art_quick_osr_stub_arm) {
   EXPECT_EQ(0xcd4ff960U, unwinder.frames()[24].sp);
 }
 
+TEST_F(UnwindOfflineTest, offset_arm) {
+  ASSERT_NO_FATAL_FAILURE(Init("offset_arm/", ARCH_ARM));
+
+  Unwinder unwinder(128, maps_.get(), regs_.get(), process_memory_);
+  unwinder.Unwind();
+
+  std::string frame_info(DumpFrames(unwinder));
+  ASSERT_EQ(19U, unwinder.NumFrames()) << "Unwind:\n" << frame_info;
+  EXPECT_EQ(
+      "  #00 pc 0032bfa0 (offset 0x42000)  libunwindstack_test (SignalInnerFunction+40)\n"
+      "  #01 pc 0032bfeb (offset 0x42000)  libunwindstack_test (SignalMiddleFunction+2)\n"
+      "  #02 pc 0032bff3 (offset 0x42000)  libunwindstack_test (SignalOuterFunction+2)\n"
+      "  #03 pc 0032fed3 (offset 0x42000)  libunwindstack_test "
+      "(_ZN11unwindstackL19SignalCallerHandlerEiP7siginfoPv+26)\n"
+      "  #04 pc 00026528 (offset 0x25000)  libc.so\n"
+      "  #05 pc 00000000  <unknown>\n"
+      "  #06 pc 0032c2d9 (offset 0x42000)  libunwindstack_test (InnerFunction+736)\n"
+      "  #07 pc 0032cc4f (offset 0x42000)  libunwindstack_test (MiddleFunction+42)\n"
+      "  #08 pc 0032cc81 (offset 0x42000)  libunwindstack_test (OuterFunction+42)\n"
+      "  #09 pc 0032e547 (offset 0x42000)  libunwindstack_test "
+      "(_ZN11unwindstackL19RemoteThroughSignalEij+270)\n"
+      "  #10 pc 0032ed99 (offset 0x42000)  libunwindstack_test "
+      "(_ZN11unwindstack55UnwindTest_remote_through_signal_with_invalid_func_Test8TestBodyEv+16)\n"
+      "  #11 pc 00354453 (offset 0x42000)  libunwindstack_test (_ZN7testing4Test3RunEv+154)\n"
+      "  #12 pc 00354de7 (offset 0x42000)  libunwindstack_test (_ZN7testing8TestInfo3RunEv+194)\n"
+      "  #13 pc 00355105 (offset 0x42000)  libunwindstack_test (_ZN7testing8TestCase3RunEv+180)\n"
+      "  #14 pc 0035a215 (offset 0x42000)  libunwindstack_test "
+      "(_ZN7testing8internal12UnitTestImpl11RunAllTestsEv+664)\n"
+      "  #15 pc 00359f4f (offset 0x42000)  libunwindstack_test (_ZN7testing8UnitTest3RunEv+110)\n"
+      "  #16 pc 0034d3db (offset 0x42000)  libunwindstack_test (main+38)\n"
+      "  #17 pc 00092c0d (offset 0x25000)  libc.so (__libc_init+48)\n"
+      "  #18 pc 0004202f (offset 0x42000)  libunwindstack_test (_start_main+38)\n",
+      frame_info);
+
+  EXPECT_EQ(0x2e55fa0U, unwinder.frames()[0].pc);
+  EXPECT_EQ(0xf43d2cccU, unwinder.frames()[0].sp);
+  EXPECT_EQ(0x2e55febU, unwinder.frames()[1].pc);
+  EXPECT_EQ(0xf43d2ce0U, unwinder.frames()[1].sp);
+  EXPECT_EQ(0x2e55ff3U, unwinder.frames()[2].pc);
+  EXPECT_EQ(0xf43d2ce8U, unwinder.frames()[2].sp);
+  EXPECT_EQ(0x2e59ed3U, unwinder.frames()[3].pc);
+  EXPECT_EQ(0xf43d2cf0U, unwinder.frames()[3].sp);
+  EXPECT_EQ(0xf4136528U, unwinder.frames()[4].pc);
+  EXPECT_EQ(0xf43d2d10U, unwinder.frames()[4].sp);
+  EXPECT_EQ(0U, unwinder.frames()[5].pc);
+  EXPECT_EQ(0xffcc0ee0U, unwinder.frames()[5].sp);
+  EXPECT_EQ(0x2e562d9U, unwinder.frames()[6].pc);
+  EXPECT_EQ(0xffcc0ee0U, unwinder.frames()[6].sp);
+  EXPECT_EQ(0x2e56c4fU, unwinder.frames()[7].pc);
+  EXPECT_EQ(0xffcc1060U, unwinder.frames()[7].sp);
+  EXPECT_EQ(0x2e56c81U, unwinder.frames()[8].pc);
+  EXPECT_EQ(0xffcc1078U, unwinder.frames()[8].sp);
+  EXPECT_EQ(0x2e58547U, unwinder.frames()[9].pc);
+  EXPECT_EQ(0xffcc1090U, unwinder.frames()[9].sp);
+  EXPECT_EQ(0x2e58d99U, unwinder.frames()[10].pc);
+  EXPECT_EQ(0xffcc1438U, unwinder.frames()[10].sp);
+  EXPECT_EQ(0x2e7e453U, unwinder.frames()[11].pc);
+  EXPECT_EQ(0xffcc1448U, unwinder.frames()[11].sp);
+  EXPECT_EQ(0x2e7ede7U, unwinder.frames()[12].pc);
+  EXPECT_EQ(0xffcc1458U, unwinder.frames()[12].sp);
+  EXPECT_EQ(0x2e7f105U, unwinder.frames()[13].pc);
+  EXPECT_EQ(0xffcc1490U, unwinder.frames()[13].sp);
+  EXPECT_EQ(0x2e84215U, unwinder.frames()[14].pc);
+  EXPECT_EQ(0xffcc14c0U, unwinder.frames()[14].sp);
+  EXPECT_EQ(0x2e83f4fU, unwinder.frames()[15].pc);
+  EXPECT_EQ(0xffcc1510U, unwinder.frames()[15].sp);
+  EXPECT_EQ(0x2e773dbU, unwinder.frames()[16].pc);
+  EXPECT_EQ(0xffcc1528U, unwinder.frames()[16].sp);
+  EXPECT_EQ(0xf41a2c0dU, unwinder.frames()[17].pc);
+  EXPECT_EQ(0xffcc1540U, unwinder.frames()[17].sp);
+  EXPECT_EQ(0x2b6c02fU, unwinder.frames()[18].pc);
+  EXPECT_EQ(0xffcc1558U, unwinder.frames()[18].sp);
+}
+
 }  // namespace unwindstack
diff --git a/libunwindstack/tests/files/offline/offset_arm/libc.so b/libunwindstack/tests/files/offline/offset_arm/libc.so
new file mode 100644
index 000000000..9f5c8ca44
--- /dev/null
+++ b/libunwindstack/tests/files/offline/offset_arm/libc.so
diff --git a/libunwindstack/tests/files/offline/offset_arm/libunwindstack_test b/libunwindstack/tests/files/offline/offset_arm/libunwindstack_test
new file mode 100644
index 000000000..7a30bfa44
--- /dev/null
+++ b/libunwindstack/tests/files/offline/offset_arm/libunwindstack_test
diff --git a/libunwindstack/tests/files/offline/offset_arm/maps.txt b/libunwindstack/tests/files/offline/offset_arm/maps.txt
new file mode 100644
index 000000000..62244645e
--- /dev/null
+++ b/libunwindstack/tests/files/offline/offset_arm/maps.txt
@@ -0,0 +1,2 @@
+2b6c000-2e92000 r-xp 42000 00:00 0   libunwindstack_test
+f4135000-f41a9000 r-xp 25000 00:00 0   libc.so
diff --git a/libunwindstack/tests/files/offline/offset_arm/regs.txt b/libunwindstack/tests/files/offline/offset_arm/regs.txt
new file mode 100644
index 000000000..1f4ac8f7b
--- /dev/null
+++ b/libunwindstack/tests/files/offline/offset_arm/regs.txt
@@ -0,0 +1,16 @@
+r0: 5
+r1: 5
+r2: 4
+r3: 1
+r4: 73804b6b
+r5: f3c9c000
+r6: 2ea09ac
+r7: 10624dd3
+r8: f41b5d8c
+r9: f3c9c000
+r10: 6f17
+r11: f3c94048
+ip: 2ea0807
+sp: f43d2ccc
+lr: 2e55fef
+pc: 2e55fa0
diff --git a/libunwindstack/tests/files/offline/offset_arm/stack0.data b/libunwindstack/tests/files/offline/offset_arm/stack0.data
new file mode 100644
index 000000000..23a987415
--- /dev/null
+++ b/libunwindstack/tests/files/offline/offset_arm/stack0.data
diff --git a/libunwindstack/tests/files/offline/offset_arm/stack1.data b/libunwindstack/tests/files/offline/offset_arm/stack1.data
new file mode 100644
index 000000000..49bdd1e26
--- /dev/null
+++ b/libunwindstack/tests/files/offline/offset_arm/stack1.data
diff --git a/libunwindstack/tools/unwind_for_offline.cpp b/libunwindstack/tools/unwind_for_offline.cpp
index 74868d43d..589731d0e 100644
--- a/libunwindstack/tools/unwind_for_offline.cpp
+++ b/libunwindstack/tools/unwind_for_offline.cpp
@@ -30,6 +30,7 @@
 #include <memory>
 #include <string>
 #include <unordered_map>
+#include <utility>
 #include <vector>
 
 #include <unwindstack/Elf.h>
@@ -78,30 +79,44 @@ bool SaveRegs(unwindstack::Regs* regs) {
   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;
-  }
+bool SaveStack(pid_t pid, const std::vector<std::pair<uint64_t, uint64_t>>& stacks) {
+  for (size_t i = 0; i < stacks.size(); i++) {
+    std::string file_name;
+    if (stacks.size() != 1) {
+      file_name = "stack" + std::to_string(i) + ".data";
+    } else {
+      file_name = "stack.data";
+    }
 
-  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;
-  }
+    // Do this first, so if it fails, we don't create the file.
+    uint64_t sp_start = stacks[i].first;
+    uint64_t sp_end = stacks[i].second;
+    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;
+    }
 
-  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;
-  }
+    printf("Saving the stack 0x%" PRIx64 "-0x%" PRIx64 "\n", sp_start, sp_end);
 
-  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;
+    std::unique_ptr<FILE, decltype(&fclose)> fp(fopen(file_name.c_str(), "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;
+    }
+
+    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 false;
+    }
   }
 
   return true;
@@ -110,17 +125,11 @@ bool SaveStack(pid_t pid, uint64_t sp_start, uint64_t sp_end) {
 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);
+    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);
+    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.
@@ -129,6 +138,13 @@ bool CreateElfFromMemory(std::shared_ptr<unwindstack::Memory>& memory, map_info_
     printf("Cannot read data from address %" PRIx64 " length %zu\n", info->start, buffer.size());
     return false;
   }
+
+  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;
+  }
+
   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);
@@ -198,9 +214,21 @@ int SaveData(pid_t pid) {
   unwinder.Unwind();
 
   std::unordered_map<uint64_t, map_info_t> maps_by_start;
-  uint64_t last_sp;
+  std::vector<std::pair<uint64_t, uint64_t>> stacks;
+  uint64_t sp_map_start = 0;
+  unwindstack::MapInfo* map_info = maps.Find(sp);
+  if (map_info != nullptr) {
+    stacks.emplace_back(std::make_pair(sp, map_info->end));
+    sp_map_start = map_info->start;
+  }
+
   for (auto frame : unwinder.frames()) {
-    last_sp = frame.sp;
+    map_info = maps.Find(frame.sp);
+    if (map_info != nullptr && sp_map_start != map_info->start) {
+      stacks.emplace_back(std::make_pair(frame.sp, map_info->end));
+      sp_map_start = map_info->start;
+    }
+
     if (maps_by_start.count(frame.map_start) == 0) {
       auto info = &maps_by_start[frame.map_start];
       info->start = frame.map_start;
@@ -211,7 +239,12 @@ int SaveData(pid_t pid) {
         // 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;
+          printf("Ignoring map ");
+          if (!info->name.empty()) {
+            printf("%s\n", info->name.c_str());
+          } else {
+            printf("anonymous:%" PRIx64 "\n", info->start);
+          }
         }
       }
     }
@@ -221,7 +254,7 @@ int SaveData(pid_t pid) {
     printf("%s\n", unwinder.FormatFrame(i).c_str());
   }
 
-  if (!SaveStack(pid, sp, last_sp)) {
+  if (!SaveStack(pid, stacks)) {
     return 1;
   }