feat(libkernel): implement getppid

core/libs/prx/libkernel/CMakeLists.txt

@@ -485,6 +485,15 @@ if(BUILD_TESTING)
         set_tests_properties(guest_signals PROPERTIES ENVIRONMENT_MODIFICATION
             "PATH=path_list_prepend:$<TARGET_FILE_DIR:libkernel>")
     endif()
+    add_test_executable(guest_parent_process_tests ${LIBS_INCLUDE_DIR}/tests/GuestParentProcess.cpp)
+    target_include_directories(guest_parent_process_tests PRIVATE ${LIBS_INCLUDE_DIR})
+    target_link_libraries(guest_parent_process_tests PRIVATE libkernel libc)
+    configure_windows_unwind(guest_parent_process_tests)
+    add_test(NAME guest_parent_process COMMAND guest_parent_process_tests)
+    if(WIN32)
+        set_tests_properties(guest_parent_process PROPERTIES ENVIRONMENT_MODIFICATION
+            "PATH=path_list_prepend:$<TARGET_FILE_DIR:libkernel>")
+    endif()
     add_test_executable(guest_kill_tests ${LIBS_INCLUDE_DIR}/tests/GuestKill.cpp)
     target_include_directories(guest_kill_tests PRIVATE ${LIBS_INCLUDE_DIR})
     target_link_libraries(guest_kill_tests PRIVATE libkernel libc)

core/libs/prx/libkernel/System/src/Process.cpp

@@ -4,6 +4,7 @@
 #endif
 #include <windows.h>
 #include <shellapi.h>
+#include <tlhelp32.h>
 #else
 #include <sched.h>
 #include <unistd.h>
@@ -199,6 +200,32 @@ int APS5_VABI getpid_nid_postfix(void) {
     return static_cast<int>(pid);
 }
 
+int APS5_VABI getppid_nid_postfix(void) {
+#ifdef _WIN32
+    const DWORD self = GetCurrentProcessId();
+    const HANDLE snapshot = CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0);
+    if (snapshot == INVALID_HANDLE_VALUE)
+        throw std::system_error(static_cast<int>(GetLastError()), std::system_category(), "getppid: CreateToolhelp32Snapshot");
+    PROCESSENTRY32W entry{};
+    entry.dwSize = sizeof(entry);
+    bool found = false;
+    DWORD pid = 0;
+    for (BOOL more = Process32FirstW(snapshot, &entry); more && !found; more = Process32NextW(snapshot, &entry)) {
+        if (entry.th32ProcessID == self) {
+            pid = entry.th32ParentProcessID;
+            found = true;
+        }
+    }
+    CloseHandle(snapshot);
+    if (!found) throw std::runtime_error("getppid: the process is missing from the process snapshot");
+#else
+    const auto pid = ::getppid();
+#endif
+    if (static_cast<std::uint64_t>(pid) > static_cast<std::uint64_t>(std::numeric_limits<int>::max()))
+        throw std::runtime_error("Parent process identifier is outside the guest range");
+    return static_cast<int>(pid);
+}
+
 int APS5_VABI sceKernelGetAppInfo(int pid, void* info) {
     if (pid != getpid_nid_postfix()) return SCE_KERNEL_ERROR_EPERM;
     if (info == nullptr) return 0;

core/libs/tests/GuestParentProcess.cpp

@@ -0,0 +1,25 @@
+#include "prx/libc/include/general/VabiMacros.hpp"
+#include <cstdlib>
+#ifdef _WIN32
+#include <windows.h>
+#else
+#include <unistd.h>
+#endif
+extern "C" {
+int APS5_VABI getpid_nid_postfix(void);
+int APS5_VABI getppid_nid_postfix(void);
+}
+static void Require(bool value) { if (!value) std::abort(); }
+int main() {
+    const int parent = getppid_nid_postfix();
+    Require(parent > 0 && parent != getpid_nid_postfix());
+    Require(getppid_nid_postfix() == parent);
+#ifdef _WIN32
+    const HANDLE process = OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, FALSE, static_cast<DWORD>(parent));
+    Require(process != nullptr);
+    CloseHandle(process);
+#else
+    Require(parent == static_cast<int>(::getppid()));
+#endif
+    return 0;
+}