unwindstack: add Memory::ReadPartially.

Add a way to read while allowing for partial reads.

Test: new tests added to libunwindstack_test, ran 32/64 on hikey960, sailfish
Test: ran unwind on hikey960/sailfish
Change-Id: I8b11d9230fcd3122148ef3f980863ac1404ad70a

1 files changed, 41 insertions, 0 deletions

diff --git a/libunwindstack/tests/MemoryLocalTest.cpp b/libunwindstack/tests/MemoryLocalTest.cpp
index 73eebdd8c..957b239a6 100644
--- a/libunwindstack/tests/MemoryLocalTest.cpp
+++ b/libunwindstack/tests/MemoryLocalTest.cpp
@@ -16,6 +16,7 @@
 
 #include <stdint.h>
 #include <string.h>
+#include <sys/mman.h>
 
 #include <vector>
 
@@ -67,4 +68,44 @@ TEST(MemoryLocalTest, read_overflow) {
   ASSERT_FALSE(local.Read(reinterpret_cast<uint64_t>(&value), dst.data(), SIZE_MAX));
 }
 
+TEST(MemoryLocalTest, ReadPartially) {
+  char* mapping = static_cast<char*>(
+      mmap(nullptr, 2 * getpagesize(), PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
+
+  ASSERT_NE(MAP_FAILED, mapping);
+
+  mprotect(mapping + getpagesize(), getpagesize(), PROT_NONE);
+  memset(mapping + getpagesize() - 1024, 0x4c, 1024);
+
+  MemoryLocal local;
+
+  std::vector<uint8_t> dst(4096);
+  ASSERT_EQ(1024U, local.ReadPartially(reinterpret_cast<uint64_t>(mapping + getpagesize() - 1024),
+                                       dst.data(), 4096));
+  for (size_t i = 0; i < 1024; i++) {
+    ASSERT_EQ(0x4cU, dst[i]) << "Failed at byte " << i;
+  }
+
+  ASSERT_EQ(0, munmap(mapping, 2 * getpagesize()));
+}
+
+TEST(MemoryLocalTest, read_hole) {
+  void* mapping =
+      mmap(nullptr, 3 * 4096, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  ASSERT_NE(MAP_FAILED, mapping);
+  memset(mapping, 0xFF, 3 * 4096);
+  mprotect(static_cast<char*>(mapping) + 4096, 4096, PROT_NONE);
+
+  MemoryLocal local;
+  std::vector<uint8_t> dst(4096 * 3, 0xCC);
+  ASSERT_EQ(4096U, local.ReadPartially(reinterpret_cast<uintptr_t>(mapping), dst.data(), 4096 * 3));
+  for (size_t i = 0; i < 4096; ++i) {
+    ASSERT_EQ(0xFF, dst[i]);
+  }
+  for (size_t i = 4096; i < 4096 * 3; ++i) {
+    ASSERT_EQ(0xCC, dst[i]);
+  }
+  ASSERT_EQ(0, munmap(mapping, 3 * 4096));
+}
+
 }  // namespace unwindstack