Refactor backtrace cursors

8 files changed, 133 insertions, 0 deletions

diff --git a/library/cpp/yt/memory/CMakeLists.darwin-x86_64.txt b/library/cpp/yt/memory/CMakeLists.darwin-x86_64.txt
index 30fdfbef100..fff3bb860b4 100644
--- a/library/cpp/yt/memory/CMakeLists.darwin-x86_64.txt
+++ b/library/cpp/yt/memory/CMakeLists.darwin-x86_64.txt
@@ -27,5 +27,6 @@ target_sources(cpp-yt-memory PRIVATE
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/chunked_output_stream.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/ref.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/ref_tracked.cpp
+  ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/safe_memory_reader.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/shared_range.cpp
 )
diff --git a/library/cpp/yt/memory/CMakeLists.linux-aarch64.txt b/library/cpp/yt/memory/CMakeLists.linux-aarch64.txt
index 7325ab2c740..899e0b4d0dd 100644
--- a/library/cpp/yt/memory/CMakeLists.linux-aarch64.txt
+++ b/library/cpp/yt/memory/CMakeLists.linux-aarch64.txt
@@ -28,5 +28,6 @@ target_sources(cpp-yt-memory PRIVATE
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/chunked_output_stream.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/ref.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/ref_tracked.cpp
+  ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/safe_memory_reader.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/shared_range.cpp
 )
diff --git a/library/cpp/yt/memory/CMakeLists.linux-x86_64.txt b/library/cpp/yt/memory/CMakeLists.linux-x86_64.txt
index 7325ab2c740..899e0b4d0dd 100644
--- a/library/cpp/yt/memory/CMakeLists.linux-x86_64.txt
+++ b/library/cpp/yt/memory/CMakeLists.linux-x86_64.txt
@@ -28,5 +28,6 @@ target_sources(cpp-yt-memory PRIVATE
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/chunked_output_stream.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/ref.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/ref_tracked.cpp
+  ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/safe_memory_reader.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/shared_range.cpp
 )
diff --git a/library/cpp/yt/memory/CMakeLists.windows-x86_64.txt b/library/cpp/yt/memory/CMakeLists.windows-x86_64.txt
index da62073cb8c..c0ecdaaeb89 100644
--- a/library/cpp/yt/memory/CMakeLists.windows-x86_64.txt
+++ b/library/cpp/yt/memory/CMakeLists.windows-x86_64.txt
@@ -24,5 +24,6 @@ target_sources(cpp-yt-memory PRIVATE
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/chunked_output_stream.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/ref.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/ref_tracked.cpp
+  ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/safe_memory_reader.cpp
   ${CMAKE_SOURCE_DIR}/library/cpp/yt/memory/shared_range.cpp
 )
diff --git a/library/cpp/yt/memory/safe_memory_reader-inl.h b/library/cpp/yt/memory/safe_memory_reader-inl.h
new file mode 100644
index 00000000000..69d8c1c9184
--- /dev/null
+++ b/library/cpp/yt/memory/safe_memory_reader-inl.h
@@ -0,0 +1,19 @@
+#ifndef SAFE_MEMORY_READER_INL_H_
+#error "Direct inclusion of this file is not allowed, include safe_memory_reader.h"
+// For the sake of sane code completion.
+#include "safe_memory_reader.h"
+#endif
+
+namespace NYT {
+
+////////////////////////////////////////////////////////////////////////////////
+
+template <class T>
+bool TSafeMemoryReader::Read(const void* addr, T* value)
+{
+    return ReadRaw(addr, value, sizeof(*value));
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace NYT
diff --git a/library/cpp/yt/memory/safe_memory_reader.cpp b/library/cpp/yt/memory/safe_memory_reader.cpp
new file mode 100644
index 00000000000..49d88b3ba1b
--- /dev/null
+++ b/library/cpp/yt/memory/safe_memory_reader.cpp
@@ -0,0 +1,45 @@
+#include "safe_memory_reader.h"
+
+#ifdef _linux_
+#include <fcntl.h>
+#include <unistd.h>
+#endif
+
+#include <library/cpp/yt/assert/assert.h>
+
+namespace NYT {
+
+////////////////////////////////////////////////////////////////////////////////
+
+TSafeMemoryReader::TSafeMemoryReader()
+{
+#ifdef _linux_
+    FD_ = ::open("/proc/self/mem", O_RDONLY);
+    YT_VERIFY(FD_ >= 0);
+#endif
+}
+
+TSafeMemoryReader::~TSafeMemoryReader()
+{
+#ifdef _linux_
+    ::close(FD_);
+#endif
+}
+
+bool TSafeMemoryReader::ReadRaw(const void* addr, void* ptr, size_t size)
+{
+#ifdef _linux_
+    int ret;
+    do {
+        ret = ::pread64(FD_, ptr, size, reinterpret_cast<uintptr_t>(addr));
+    } while (ret < 0 && errno == EINTR);
+    return ret == static_cast<int>(size);
+#else
+    Y_UNUSED(FD_, addr, ptr, size);
+    return false;
+#endif
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace NYT
diff --git a/library/cpp/yt/memory/safe_memory_reader.h b/library/cpp/yt/memory/safe_memory_reader.h
new file mode 100644
index 00000000000..0ea87d32903
--- /dev/null
+++ b/library/cpp/yt/memory/safe_memory_reader.h
@@ -0,0 +1,38 @@
+#pragma once
+
+#include "public.h"
+
+namespace NYT {
+
+////////////////////////////////////////////////////////////////////////////////
+
+//! Enables safe read-only access to the address space of the current process.
+/*!
+ *   Inaccessible memory locations will not cause any traps but rather report
+ *   failure via return value.
+ */
+class TSafeMemoryReader
+{
+public:
+    TSafeMemoryReader();
+    TSafeMemoryReader(const TSafeMemoryReader&) = delete;
+    ~TSafeMemoryReader();
+
+    //! Attempts to read #value at address #addr.
+    //! Returns |true| on success, |false| on failure.
+    template <class T>
+    bool Read(const void* addr, T* value);
+
+private:
+    int FD_ = -1;
+
+    bool ReadRaw(const void* addr, void* ptr, size_t size);
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace NYT
+
+#define SAFE_MEMORY_READER_INL_H_
+#include "safe_memory_reader-inl.h"
+#undef SAFE_MEMORY_READER_INL_H_
diff --git a/library/cpp/yt/memory/unittests/safe_memory_reader_ut.cpp b/library/cpp/yt/memory/unittests/safe_memory_reader_ut.cpp
new file mode 100644
index 00000000000..9873dd80bea
--- /dev/null
+++ b/library/cpp/yt/memory/unittests/safe_memory_reader_ut.cpp
@@ -0,0 +1,27 @@
+
+#include <library/cpp/testing/gtest/gtest.h>
+
+#include <library/cpp/yt/memory/safe_memory_reader.h>
+
+namespace NYT {
+namespace {
+
+////////////////////////////////////////////////////////////////////////////////
+
+TEST(TSafeMemoryReaderTest, Simple)
+{
+    TSafeMemoryReader reader;
+
+    int i = 1;
+
+    int value;
+    ASSERT_TRUE(reader.Read(&i, &value));
+    ASSERT_EQ(value, 1);
+
+    ASSERT_FALSE(reader.Read(reinterpret_cast<void*>(0x1ee3beef), &value));
+}
+
+////////////////////////////////////////////////////////////////////////////////
+
+} // namespace
+} // namespace NYT