Linux implementation of hat::memory_protector

Author: ZeroMemes

CMakeLists.txt

@@ -47,6 +47,8 @@ set(LIBHAT_SRC
     src/Scanner.cpp
     src/System.cpp
 
+    src/os/linux/MemoryProtector.cpp
+
     src/os/unix/System.cpp
 
     src/os/win32/MemoryProtector.cpp

src/Utils.hpp

@@ -0,0 +1,15 @@
+#pragma once
+
+#include <bit>
+#include <cstdint>
+
+namespace hat::detail {
+
+    constexpr uintptr_t fast_align_down(uintptr_t address, size_t alignment) {
+        return address & ~static_cast<uintptr_t>(alignment - 1);
+    }
+
+    constexpr uintptr_t fast_align_up(uintptr_t address, size_t alignment) {
+        return (address + alignment - 1) & ~static_cast<uintptr_t>(alignment - 1);
+    }
+}

src/os/linux/MemoryProtector.cpp

@@ -0,0 +1,84 @@
+#include <libhat/Defines.hpp>
+#ifdef LIBHAT_LINUX
+
+#include <charconv>
+#include <fstream>
+#include <optional>
+#include <string>
+
+#include <libhat/MemoryProtector.hpp>
+#include <libhat/System.hpp>
+#include "../../Utils.hpp"
+
+#include <sys/mman.h>
+
+namespace hat {
+
+    static int to_system_prot(const protection flags) {
+        int prot = 0;
+        if (static_cast<bool>(flags & protection::Read)) prot |= PROT_READ;
+        if (static_cast<bool>(flags & protection::Write)) prot |= PROT_WRITE;
+        if (static_cast<bool>(flags & protection::Execute)) prot |= PROT_EXEC;
+        return prot;
+    }
+
+    static std::optional<int> get_page_prot(const uintptr_t address) {
+        std::ifstream f("/proc/self/maps");
+        std::string s;
+        while (std::getline(f, s)) {
+            const char* it = s.data();
+            const char* end = s.data() + s.size();
+            std::from_chars_result res{};
+
+            uintptr_t pageBegin;
+            res = std::from_chars(it, end, pageBegin, 16);
+            if (res.ec != std::errc{} || res.ptr == end) {
+                continue;
+            }
+            it = res.ptr + 1; // +1 to skip the hyphen
+
+            uintptr_t pageEnd;
+            res = std::from_chars(it, end, pageEnd, 16);
+            if (res.ec != std::errc{} || res.ptr == end) {
+                continue;
+            }
+            it = res.ptr + 1; // +1 to skip the space
+
+            std::string_view remaining{it, end};
+            if (address >= pageBegin && address < pageEnd && remaining.size() >= 3) {
+                int prot = 0;
+                if (remaining[0] == 'r') prot |= PROT_READ;
+                if (remaining[1] == 'w') prot |= PROT_WRITE;
+                if (remaining[2] == 'x') prot |= PROT_EXEC;
+                return prot;
+            }
+        }
+        return std::nullopt;
+    }
+
+    memory_protector::memory_protector(const uintptr_t address, const size_t size, const protection flags) : address(address), size(size) {
+        const auto pageSize = hat::get_system().page_size;
+
+        const auto oldProt = get_page_prot(address);
+        if (!oldProt) {
+            return; // Failure indicated via is_set()
+        }
+
+        this->oldProtection = static_cast<uint32_t>(*oldProt);
+        this->set = 0 == mprotect(
+            reinterpret_cast<void*>(detail::fast_align_down(address, pageSize)),
+            static_cast<size_t>(detail::fast_align_up(size, pageSize)),
+            to_system_prot(flags)
+        );
+    }
+
+    void memory_protector::restore() {
+        const auto pageSize = hat::get_system().page_size;
+        mprotect(
+            reinterpret_cast<void*>(detail::fast_align_down(address, pageSize)),
+            static_cast<size_t>(detail::fast_align_up(size, pageSize)),
+            this->oldProtection
+        );
+    }
+}
+#endif

src/os/win32/MemoryProtector.cpp

@@ -6,7 +6,8 @@
 #include <Windows.h>
 
 namespace hat {
-    static DWORD ToWinProt(const protection flags) {
+
+    static DWORD to_system_prot(const protection flags) {
         const bool r = static_cast<bool>(flags & protection::Read);
         const bool w = static_cast<bool>(flags & protection::Write);
         const bool x = static_cast<bool>(flags & protection::Execute);
@@ -20,7 +21,12 @@ namespace hat {
     }
 
     memory_protector::memory_protector(const uintptr_t address, const size_t size, const protection flags) : address(address), size(size) {
-        this->set = 0 != VirtualProtect(reinterpret_cast<LPVOID>(this->address), this->size, ToWinProt(flags), reinterpret_cast<PDWORD>(&this->oldProtection));
+        this->set = 0 != VirtualProtect(
+            reinterpret_cast<LPVOID>(this->address),
+            this->size,
+            to_system_prot(flags),
+            reinterpret_cast<PDWORD>(&this->oldProtection)
+        );
     }
 
     void memory_protector::restore() {