Kernel: Consolidate finding the ELF stack size with validation

Previously, we started parsing the ELF file again in a completely
different place, and without the partial mapping that we do while
validating.

Instead of doing manual parsing in two places, just capture the
requested stack size right after we validated it.

Kernel/Syscalls/execve.cpp

@@ -286,6 +286,9 @@ static ErrorOr<LoadResult> load_elf_object(Memory::AddressSpace& new_space, Open
     FlatPtr load_base_address = 0;
     size_t stack_size = Thread::default_userspace_stack_size;
 
+    if (minimum_stack_size.has_value() && minimum_stack_size.value() > stack_size)
+        stack_size = minimum_stack_size.value();
+
     auto elf_name = TRY(object_description.pseudo_path());
     VERIFY(!Processor::in_critical());
 
@@ -380,13 +383,6 @@ static ErrorOr<LoadResult> load_elf_object(Memory::AddressSpace& new_space, Open
         if (program_header.type() == PT_LOAD)
             return load_section(program_header);
 
-        if (program_header.type() == PT_GNU_STACK) {
-            auto new_stack_size = program_header.size_in_memory();
-
-            if (new_stack_size > stack_size)
-                stack_size = new_stack_size;
-        }
-
         // NOTE: We ignore other program header types.
         return {};
     };
@@ -405,9 +401,6 @@ static ErrorOr<LoadResult> load_elf_object(Memory::AddressSpace& new_space, Open
         return ENOEXEC;
     }
 
-    if (minimum_stack_size.has_value() && minimum_stack_size.value() > stack_size)
-        stack_size = minimum_stack_size.value();
-
     auto* stack_region = TRY(new_space.allocate_region(Memory::RandomizeVirtualAddress::Yes, {}, stack_size, PAGE_SIZE, "Stack (Main thread)"sv, PROT_READ | PROT_WRITE, AllocationStrategy::Reserve));
     stack_region->set_stack(true);
 
@@ -424,42 +417,19 @@ static ErrorOr<LoadResult> load_elf_object(Memory::AddressSpace& new_space, Open
 
 ErrorOr<LoadResult>
 Process::load(Memory::AddressSpace& new_space, NonnullRefPtr<OpenFileDescription> main_program_description,
-    RefPtr<OpenFileDescription> interpreter_description, const ElfW(Ehdr) & main_program_header)
+    RefPtr<OpenFileDescription> interpreter_description, const ElfW(Ehdr) & main_program_header, Optional<size_t> minimum_stack_size)
 {
     auto load_offset = TRY(get_load_offset(main_program_header, main_program_description, interpreter_description));
 
     if (interpreter_description.is_null()) {
-        auto load_result = TRY(load_elf_object(new_space, main_program_description, load_offset, ShouldAllocateTls::Yes, ShouldAllowSyscalls::No));
+        auto load_result = TRY(load_elf_object(new_space, main_program_description, load_offset, ShouldAllocateTls::Yes, ShouldAllowSyscalls::No, minimum_stack_size));
         m_master_tls_region = load_result.tls_region;
         m_master_tls_size = load_result.tls_size;
         m_master_tls_alignment = load_result.tls_alignment;
         return load_result;
     }
 
-    Optional<size_t> requested_main_program_stack_size;
-    {
-        auto main_program_size = main_program_description->inode()->size();
-        auto main_program_rounded_size = TRY(Memory::page_round_up(main_program_size));
-
-        auto main_program_vmobject = TRY(Memory::SharedInodeVMObject::try_create_with_inode(*main_program_description->inode()));
-        auto main_program_region = TRY(MM.allocate_kernel_region_with_vmobject(*main_program_vmobject, main_program_rounded_size, "Loaded Main Program ELF"sv, Memory::Region::Access::Read));
-
-        auto main_program_image = ELF::Image(main_program_region->vaddr().as_ptr(), main_program_size);
-        if (!main_program_image.is_valid())
-            return EINVAL;
-
-        main_program_image.for_each_program_header([&requested_main_program_stack_size](ELF::Image::ProgramHeader const& program_header) {
-            if (program_header.type() != PT_GNU_STACK)
-                return;
-
-            if (program_header.size_in_memory() == 0)
-                return;
-
-            requested_main_program_stack_size = program_header.size_in_memory();
-        });
-    }
-
-    auto interpreter_load_result = TRY(load_elf_object(new_space, *interpreter_description, load_offset, ShouldAllocateTls::No, ShouldAllowSyscalls::Yes, requested_main_program_stack_size));
+    auto interpreter_load_result = TRY(load_elf_object(new_space, *interpreter_description, load_offset, ShouldAllocateTls::No, ShouldAllowSyscalls::Yes, minimum_stack_size));
 
     // TLS allocation will be done in userspace by the loader
     VERIFY(!interpreter_load_result.tls_region);
@@ -489,7 +459,7 @@ void Process::clear_signal_handlers_for_exec()
 }
 
 ErrorOr<void> Process::do_exec(NonnullRefPtr<OpenFileDescription> main_program_description, Vector<NonnullOwnPtr<KString>> arguments, Vector<NonnullOwnPtr<KString>> environment,
-    RefPtr<OpenFileDescription> interpreter_description, Thread*& new_main_thread, InterruptsState& previous_interrupts_state, const ElfW(Ehdr) & main_program_header)
+    RefPtr<OpenFileDescription> interpreter_description, Thread*& new_main_thread, InterruptsState& previous_interrupts_state, const ElfW(Ehdr) & main_program_header, Optional<size_t> minimum_stack_size)
 {
     VERIFY(is_user_process());
     VERIFY(!Processor::in_critical());
@@ -537,7 +507,7 @@ ErrorOr<void> Process::do_exec(NonnullRefPtr<OpenFileDescription> main_program_d
         Memory::MemoryManager::enter_process_address_space(*this);
     });
 
-    auto load_result = TRY(load(new_space, main_program_description, interpreter_description, main_program_header));
+    auto load_result = TRY(load(new_space, main_program_description, interpreter_description, main_program_header, minimum_stack_size));
 
     // NOTE: We don't need the interpreter executable description after this point.
     //       We destroy it here to prevent it from getting destroyed when we return from this function.
@@ -826,15 +796,18 @@ static ErrorOr<Vector<NonnullOwnPtr<KString>>> find_shebang_interpreter_for_exec
     return ENOEXEC;
 }
 
-ErrorOr<RefPtr<OpenFileDescription>> Process::find_elf_interpreter_for_executable(StringView path, ElfW(Ehdr) const& main_executable_header, size_t main_executable_header_size, size_t file_size)
+ErrorOr<RefPtr<OpenFileDescription>> Process::find_elf_interpreter_for_executable(StringView path, ElfW(Ehdr) const& main_executable_header, size_t main_executable_header_size, size_t file_size, Optional<size_t>& minimum_stack_size)
 {
     // Not using ErrorOr here because we'll want to do the same thing in userspace in the RTLD
     StringBuilder interpreter_path_builder;
-    if (!TRY(ELF::validate_program_headers(main_executable_header, file_size, { &main_executable_header, main_executable_header_size }, &interpreter_path_builder))) {
+    Optional<size_t> main_executable_requested_stack_size {};
+    if (!TRY(ELF::validate_program_headers(main_executable_header, file_size, { &main_executable_header, main_executable_header_size }, &interpreter_path_builder, &main_executable_requested_stack_size))) {
         dbgln("exec({}): File has invalid ELF Program headers", path);
         return ENOEXEC;
     }
     auto interpreter_path = interpreter_path_builder.string_view();
+    if (main_executable_requested_stack_size.has_value() && (!minimum_stack_size.has_value() || *minimum_stack_size < *main_executable_requested_stack_size))
+        minimum_stack_size = main_executable_requested_stack_size;
 
     if (!interpreter_path.is_empty()) {
         dbgln_if(EXEC_DEBUG, "exec({}): Using program interpreter {}", path, interpreter_path);
@@ -863,11 +836,14 @@ ErrorOr<RefPtr<OpenFileDescription>> Process::find_elf_interpreter_for_executabl
 
         // Not using ErrorOr here because we'll want to do the same thing in userspace in the RTLD
         StringBuilder interpreter_interpreter_path_builder;
-        if (!TRY(ELF::validate_program_headers(*elf_header, interp_metadata.size, { first_page, nread }, &interpreter_interpreter_path_builder))) {
+        Optional<size_t> interpreter_requested_stack_size {};
+        if (!TRY(ELF::validate_program_headers(*elf_header, interp_metadata.size, { first_page, nread }, &interpreter_interpreter_path_builder, &interpreter_requested_stack_size))) {
             dbgln("exec({}): Interpreter ({}) has invalid ELF Program headers", path, interpreter_path);
             return ENOEXEC;
         }
         auto interpreter_interpreter_path = interpreter_interpreter_path_builder.string_view();
+        if (interpreter_requested_stack_size.has_value() && (!minimum_stack_size.has_value() || *minimum_stack_size < *interpreter_requested_stack_size))
+            minimum_stack_size = interpreter_requested_stack_size;
 
         if (!interpreter_interpreter_path.is_empty()) {
             dbgln("exec({}): Interpreter ({}) has its own interpreter ({})! No thank you!", path, interpreter_path, interpreter_interpreter_path);
@@ -945,8 +921,9 @@ ErrorOr<void> Process::exec(NonnullOwnPtr<KString> path, Vector<NonnullOwnPtr<KS
         return ENOEXEC;
     }
 
-    auto interpreter_description = TRY(find_elf_interpreter_for_executable(path->view(), *main_program_header, nread, metadata.size));
-    return do_exec(move(description), move(arguments), move(environment), move(interpreter_description), new_main_thread, previous_interrupts_state, *main_program_header);
+    Optional<size_t> minimum_stack_size {};
+    auto interpreter_description = TRY(find_elf_interpreter_for_executable(path->view(), *main_program_header, nread, metadata.size, minimum_stack_size));
+    return do_exec(move(description), move(arguments), move(environment), move(interpreter_description), new_main_thread, previous_interrupts_state, *main_program_header, minimum_stack_size);
 }
 
 ErrorOr<FlatPtr> Process::sys$execve(Userspace<Syscall::SC_execve_params const*> user_params)

Kernel/Tasks/Process.h

@@ -494,7 +494,7 @@ public:
 
     ErrorOr<void> exec(NonnullOwnPtr<KString> path, Vector<NonnullOwnPtr<KString>> arguments, Vector<NonnullOwnPtr<KString>> environment, Thread*& new_main_thread, InterruptsState& previous_interrupts_state, int recursion_depth = 0);
 
-    ErrorOr<LoadResult> load(Memory::AddressSpace& new_space, NonnullRefPtr<OpenFileDescription> main_program_description, RefPtr<OpenFileDescription> interpreter_description, const ElfW(Ehdr) & main_program_header);
+    ErrorOr<LoadResult> load(Memory::AddressSpace& new_space, NonnullRefPtr<OpenFileDescription> main_program_description, RefPtr<OpenFileDescription> interpreter_description, const ElfW(Ehdr) & main_program_header, Optional<size_t> minimum_stack_size = {});
 
     void terminate_due_to_signal(u8 signal);
     ErrorOr<void> send_signal(u8 signal, Process* sender);
@@ -624,12 +624,12 @@ private:
     bool create_perf_events_buffer_if_needed();
     void delete_perf_events_buffer();
 
-    ErrorOr<void> do_exec(NonnullRefPtr<OpenFileDescription> main_program_description, Vector<NonnullOwnPtr<KString>> arguments, Vector<NonnullOwnPtr<KString>> environment, RefPtr<OpenFileDescription> interpreter_description, Thread*& new_main_thread, InterruptsState& previous_interrupts_state, const ElfW(Ehdr) & main_program_header);
+    ErrorOr<void> do_exec(NonnullRefPtr<OpenFileDescription> main_program_description, Vector<NonnullOwnPtr<KString>> arguments, Vector<NonnullOwnPtr<KString>> environment, RefPtr<OpenFileDescription> interpreter_description, Thread*& new_main_thread, InterruptsState& previous_interrupts_state, const ElfW(Ehdr) & main_program_header, Optional<size_t> minimum_stack_size = {});
     ErrorOr<FlatPtr> do_write(OpenFileDescription&, UserOrKernelBuffer const&, size_t, Optional<off_t> = {});
 
     ErrorOr<FlatPtr> do_statvfs(FileSystem const& path, Custody const*, statvfs* buf);
 
-    ErrorOr<RefPtr<OpenFileDescription>> find_elf_interpreter_for_executable(StringView path, ElfW(Ehdr) const& main_executable_header, size_t main_executable_header_size, size_t file_size);
+    ErrorOr<RefPtr<OpenFileDescription>> find_elf_interpreter_for_executable(StringView path, ElfW(Ehdr) const& main_executable_header, size_t main_executable_header_size, size_t file_size, Optional<size_t>& minimum_stack_size);
 
     ErrorOr<void> do_kill(Process&, int signal);
     ErrorOr<void> do_killpg(ProcessGroupID pgrp, int signal);

Userland/Libraries/LibELF/Image.cpp

@@ -128,7 +128,7 @@ bool Image::parse()
         return false;
     }
 
-    auto result_or_error = validate_program_headers(header(), m_size, { m_buffer, m_size }, nullptr, m_verbose_logging);
+    auto result_or_error = validate_program_headers(header(), m_size, { m_buffer, m_size }, nullptr, nullptr, m_verbose_logging);
     if (result_or_error.is_error()) {
         if (m_verbose_logging)
             dbgln("ELF::Image::parse(): Failed validating ELF Program Headers");

Userland/Libraries/LibELF/Validation.cpp

@@ -187,7 +187,7 @@ bool validate_elf_header(ElfW(Ehdr) const& elf_header, size_t file_size, bool ve
     return true;
 }
 
-ErrorOr<bool> validate_program_headers(ElfW(Ehdr) const& elf_header, size_t file_size, ReadonlyBytes buffer, StringBuilder* interpreter_path_builder, bool verbose)
+ErrorOr<bool> validate_program_headers(ElfW(Ehdr) const& elf_header, size_t file_size, ReadonlyBytes buffer, StringBuilder* interpreter_path_builder, Optional<size_t>* requested_stack_size, bool verbose)
 {
     Checked<size_t> total_size_of_program_headers = elf_header.e_phnum;
     total_size_of_program_headers *= elf_header.e_phentsize;
@@ -306,6 +306,9 @@ ErrorOr<bool> validate_program_headers(ElfW(Ehdr) const& elf_header, size_t file
                         dbgln("PT_GNU_STACK size is not page-aligned.");
                     return false;
                 }
+
+                if (requested_stack_size)
+                    *requested_stack_size = program_header.p_memsz;
             }
 
             break;

Userland/Libraries/LibELF/Validation.h

@@ -12,6 +12,6 @@
 namespace ELF {
 
 bool validate_elf_header(ElfW(Ehdr) const& elf_header, size_t file_size, bool verbose = true);
-ErrorOr<bool> validate_program_headers(ElfW(Ehdr) const& elf_header, size_t file_size, ReadonlyBytes buffer, StringBuilder* interpreter_path_builder = nullptr, bool verbose = true);
+ErrorOr<bool> validate_program_headers(ElfW(Ehdr) const& elf_header, size_t file_size, ReadonlyBytes buffer, StringBuilder* interpreter_path_builder = nullptr, Optional<size_t>* requested_stack_size = nullptr, bool verbose = true);
 
 } // end namespace ELF