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ladybird/Kernel/Syscalls/execve.cpp
Brian Gianforcaro 54b9a4ec1e Kernel: Handle promise violations in the syscall handler 
Previously we would crash the process immediately when a promise
violation was found during a syscall. This is error prone, as we
don't unwind the stack. This means that in certain cases we can
leak resources, like an OwnPtr / RefPtr tracked on the stack. Or
even leak a lock acquired in a ScopeLockLocker.

To remedy this situation we move the promise violation handling to
the syscall handler, right before we return to user space. This
allows the code to follow the normal unwind path, and grantees
there is no longer any cleanup that needs to occur.

The Process::require_promise() and Process::require_no_promises()
functions were modified to return ErrorOr<void> so we enforce that
the errors are always propagated by the caller.
2021-12-29 18:08:15 +01:00

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/*
* Copyright (c) 2018-2021, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/ScopeGuard.h>
#include <AK/TemporaryChange.h>
#include <AK/WeakPtr.h>
#include <Kernel/Debug.h>
#include <Kernel/FileSystem/Custody.h>
#include <Kernel/FileSystem/OpenFileDescription.h>
#include <Kernel/Memory/AllocationStrategy.h>
#include <Kernel/Memory/MemoryManager.h>
#include <Kernel/Memory/PageDirectory.h>
#include <Kernel/Memory/Region.h>
#include <Kernel/Memory/SharedInodeVMObject.h>
#include <Kernel/Panic.h>
#include <Kernel/PerformanceManager.h>
#include <Kernel/Process.h>
#include <Kernel/Random.h>
#include <Kernel/Time/TimeManagement.h>
#include <LibC/limits.h>
#include <LibELF/AuxiliaryVector.h>
#include <LibELF/Image.h>
#include <LibELF/Validation.h>
namespace Kernel {
extern Memory::Region* g_signal_trampoline_region;
struct LoadResult {
OwnPtr<Memory::AddressSpace> space;
FlatPtr load_base { 0 };
FlatPtr entry_eip { 0 };
size_t size { 0 };
WeakPtr<Memory::Region> tls_region;
size_t tls_size { 0 };
size_t tls_alignment { 0 };
WeakPtr<Memory::Region> stack_region;
};
static Vector<ELF::AuxiliaryValue> generate_auxiliary_vector(FlatPtr load_base, FlatPtr entry_eip, UserID uid, UserID euid, GroupID gid, GroupID egid, StringView executable_path, Optional<Process::ScopedDescriptionAllocation> const& main_program_fd_allocation);
static bool validate_stack_size(NonnullOwnPtrVector<KString> const& arguments, NonnullOwnPtrVector<KString>& environment)
{
size_t total_arguments_size = 0;
size_t total_environment_size = 0;
for (auto const& a : arguments)
total_arguments_size += a.length() + 1;
for (auto const& e : environment)
total_environment_size += e.length() + 1;
total_arguments_size += sizeof(char*) * (arguments.size() + 1);
total_environment_size += sizeof(char*) * (environment.size() + 1);
static constexpr size_t max_arguments_size = Thread::default_userspace_stack_size / 8;
static constexpr size_t max_environment_size = Thread::default_userspace_stack_size / 8;
if (total_arguments_size > max_arguments_size)
return false;
if (total_environment_size > max_environment_size)
return false;
// FIXME: This doesn't account for the size of the auxiliary vector
return true;
}
static ErrorOr<FlatPtr> make_userspace_context_for_main_thread([[maybe_unused]] ThreadRegisters& regs, Memory::Region& region, NonnullOwnPtrVector<KString> const& arguments,
NonnullOwnPtrVector<KString> const& environment, Vector<ELF::AuxiliaryValue> auxiliary_values)
{
FlatPtr new_sp = region.range().end().get();
// Add some bits of randomness to the user stack pointer.
new_sp -= round_up_to_power_of_two(get_fast_random<u32>() % 4096, 16);
auto push_on_new_stack = [&new_sp](FlatPtr value) {
new_sp -= sizeof(FlatPtr);
Userspace<FlatPtr*> stack_ptr = new_sp;
auto result = copy_to_user(stack_ptr, &value);
VERIFY(!result.is_error());
};
auto push_aux_value_on_new_stack = [&new_sp](auxv_t value) {
new_sp -= sizeof(auxv_t);
Userspace<auxv_t*> stack_ptr = new_sp;
auto result = copy_to_user(stack_ptr, &value);
VERIFY(!result.is_error());
};
auto push_string_on_new_stack = [&new_sp](StringView string) {
new_sp -= round_up_to_power_of_two(string.length() + 1, sizeof(FlatPtr));
Userspace<FlatPtr*> stack_ptr = new_sp;
auto result = copy_to_user(stack_ptr, string.characters_without_null_termination(), string.length() + 1);
VERIFY(!result.is_error());
};
Vector<FlatPtr> argv_entries;
for (auto const& argument : arguments) {
push_string_on_new_stack(argument.view());
TRY(argv_entries.try_append(new_sp));
}
Vector<FlatPtr> env_entries;
for (auto const& variable : environment) {
push_string_on_new_stack(variable.view());
TRY(env_entries.try_append(new_sp));
}
for (auto& value : auxiliary_values) {
if (!value.optional_string.is_empty()) {
push_string_on_new_stack(value.optional_string);
value.auxv.a_un.a_ptr = (void*)new_sp;
}
}
for (ssize_t i = auxiliary_values.size() - 1; i >= 0; --i) {
auto& value = auxiliary_values[i];
push_aux_value_on_new_stack(value.auxv);
}
push_on_new_stack(0);
for (ssize_t i = env_entries.size() - 1; i >= 0; --i)
push_on_new_stack(env_entries[i]);
FlatPtr envp = new_sp;
push_on_new_stack(0);
for (ssize_t i = argv_entries.size() - 1; i >= 0; --i)
push_on_new_stack(argv_entries[i]);
FlatPtr argv = new_sp;
// NOTE: The stack needs to be 16-byte aligned.
new_sp -= new_sp % 16;
#if ARCH(I386)
// GCC assumes that the return address has been pushed to the stack when it enters the function,
// so we need to reserve an extra pointer's worth of bytes below this to make GCC's stack alignment
// calculations work
new_sp -= sizeof(void*);
push_on_new_stack(envp);
push_on_new_stack(argv);
push_on_new_stack(argv_entries.size());
#else
regs.rdi = argv_entries.size();
regs.rsi = argv;
regs.rdx = envp;
#endif
VERIFY(new_sp % 16 == 0);
// FIXME: The way we're setting up the stack and passing arguments to the entry point isn't ABI-compliant
return new_sp;
}
struct RequiredLoadRange {
FlatPtr start { 0 };
FlatPtr end { 0 };
};
static ErrorOr<RequiredLoadRange> get_required_load_range(OpenFileDescription& program_description)
{
auto& inode = *(program_description.inode());
auto vmobject = TRY(Memory::SharedInodeVMObject::try_create_with_inode(inode));
size_t executable_size = inode.size();
size_t rounded_executable_size = TRY(Memory::page_round_up(executable_size));
auto region = TRY(MM.allocate_kernel_region_with_vmobject(*vmobject, rounded_executable_size, "ELF memory range calculation", Memory::Region::Access::Read));
auto elf_image = ELF::Image(region->vaddr().as_ptr(), executable_size);
if (!elf_image.is_valid()) {
return EINVAL;
}
RequiredLoadRange range {};
elf_image.for_each_program_header([&range](const auto& pheader) {
if (pheader.type() != PT_LOAD)
return;
auto region_start = (FlatPtr)pheader.vaddr().as_ptr();
auto region_end = region_start + pheader.size_in_memory();
if (range.start == 0 || region_start < range.start)
range.start = region_start;
if (range.end == 0 || region_end > range.end)
range.end = region_end;
});
VERIFY(range.end > range.start);
return range;
};
static ErrorOr<FlatPtr> get_load_offset(const ElfW(Ehdr) & main_program_header, OpenFileDescription& main_program_description, OpenFileDescription* interpreter_description)
{
constexpr FlatPtr load_range_start = 0x08000000;
constexpr FlatPtr load_range_size = 65536 * PAGE_SIZE; // 2**16 * PAGE_SIZE = 256MB
constexpr FlatPtr minimum_load_offset_randomization_size = 10 * MiB;
auto random_load_offset_in_range([](auto start, auto size) {
return Memory::page_round_down(start + get_good_random<FlatPtr>() % size);
});
if (main_program_header.e_type == ET_DYN) {
return random_load_offset_in_range(load_range_start, load_range_size);
}
if (main_program_header.e_type != ET_EXEC)
return EINVAL;
auto main_program_load_range = TRY(get_required_load_range(main_program_description));
RequiredLoadRange selected_range {};
if (interpreter_description) {
auto interpreter_load_range = TRY(get_required_load_range(*interpreter_description));
auto interpreter_size_in_memory = interpreter_load_range.end - interpreter_load_range.start;
auto interpreter_load_range_end = load_range_start + load_range_size - interpreter_size_in_memory;
// No intersection
if (main_program_load_range.end < load_range_start || main_program_load_range.start > interpreter_load_range_end)
return random_load_offset_in_range(load_range_start, load_range_size);
RequiredLoadRange first_available_part = { load_range_start, main_program_load_range.start };
RequiredLoadRange second_available_part = { main_program_load_range.end, interpreter_load_range_end };
// Select larger part
if (first_available_part.end - first_available_part.start > second_available_part.end - second_available_part.start)
selected_range = first_available_part;
else
selected_range = second_available_part;
} else
selected_range = main_program_load_range;
// If main program is too big and leaves us without enough space for adequate loader randomization
if (selected_range.end - selected_range.start < minimum_load_offset_randomization_size)
return E2BIG;
return random_load_offset_in_range(selected_range.start, selected_range.end - selected_range.start);
}
enum class ShouldAllocateTls {
No,
Yes,
};
enum class ShouldAllowSyscalls {
No,
Yes,
};
static ErrorOr<LoadResult> load_elf_object(NonnullOwnPtr<Memory::AddressSpace> new_space, OpenFileDescription& object_description,
FlatPtr load_offset, ShouldAllocateTls should_allocate_tls, ShouldAllowSyscalls should_allow_syscalls)
{
auto& inode = *(object_description.inode());
auto vmobject = TRY(Memory::SharedInodeVMObject::try_create_with_inode(inode));
if (vmobject->writable_mappings()) {
dbgln("Refusing to execute a write-mapped program");
return ETXTBSY;
}
size_t executable_size = inode.size();
size_t rounded_executable_size = TRY(Memory::page_round_up(executable_size));
auto executable_region = TRY(MM.allocate_kernel_region_with_vmobject(*vmobject, rounded_executable_size, "ELF loading", Memory::Region::Access::Read));
auto elf_image = ELF::Image(executable_region->vaddr().as_ptr(), executable_size);
if (!elf_image.is_valid())
return ENOEXEC;
Memory::Region* master_tls_region { nullptr };
size_t master_tls_size = 0;
size_t master_tls_alignment = 0;
FlatPtr load_base_address = 0;
auto elf_name = TRY(object_description.pseudo_path());
VERIFY(!Processor::in_critical());
Memory::MemoryManager::enter_address_space(*new_space);
auto load_tls_section = [&](auto& program_header) -> ErrorOr<void> {
VERIFY(should_allocate_tls == ShouldAllocateTls::Yes);
VERIFY(program_header.size_in_memory());
if (!elf_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
dbgln("Shenanigans! ELF PT_TLS header sneaks outside of executable.");
return ENOEXEC;
}
auto range = TRY(new_space->try_allocate_range({}, program_header.size_in_memory()));
master_tls_region = TRY(new_space->allocate_region(range, String::formatted("{} (master-tls)", elf_name), PROT_READ | PROT_WRITE, AllocationStrategy::Reserve));
master_tls_size = program_header.size_in_memory();
master_tls_alignment = program_header.alignment();
TRY(copy_to_user(master_tls_region->vaddr().as_ptr(), program_header.raw_data(), program_header.size_in_image()));
return {};
};
auto load_writable_section = [&](auto& program_header) -> ErrorOr<void> {
// Writable section: create a copy in memory.
VERIFY(program_header.alignment() == PAGE_SIZE);
if (!elf_image.is_within_image(program_header.raw_data(), program_header.size_in_image())) {
dbgln("Shenanigans! Writable ELF PT_LOAD header sneaks outside of executable.");
return ENOEXEC;
}
int prot = 0;
if (program_header.is_readable())
prot |= PROT_READ;
if (program_header.is_writable())
prot |= PROT_WRITE;
auto region_name = String::formatted("{} (data-{}{})", elf_name, program_header.is_readable() ? "r" : "", program_header.is_writable() ? "w" : "");
auto range_base = VirtualAddress { Memory::page_round_down(program_header.vaddr().offset(load_offset).get()) };
size_t rounded_range_end = TRY(Memory::page_round_up(program_header.vaddr().offset(load_offset).offset(program_header.size_in_memory()).get()));
auto range_end = VirtualAddress { rounded_range_end };
auto range = TRY(new_space->try_allocate_range(range_base, range_end.get() - range_base.get()));
auto region = TRY(new_space->allocate_region(range, region_name, prot, AllocationStrategy::Reserve));
// It's not always the case with PIE executables (and very well shouldn't be) that the
// virtual address in the program header matches the one we end up giving the process.
// In order to copy the data image correctly into memory, we need to copy the data starting at
// the right initial page offset into the pages allocated for the elf_alloc-XX section.
// FIXME: There's an opportunity to munmap, or at least mprotect, the padding space between
// the .text and .data PT_LOAD sections of the executable.
// Accessing it would definitely be a bug.
auto page_offset = program_header.vaddr();
page_offset.mask(~PAGE_MASK);
TRY(copy_to_user((u8*)region->vaddr().as_ptr() + page_offset.get(), program_header.raw_data(), program_header.size_in_image()));
return {};
};
auto load_section = [&](auto& program_header) -> ErrorOr<void> {
if (program_header.size_in_memory() == 0)
return {};
if (program_header.is_writable())
return load_writable_section(program_header);
// Non-writable section: map the executable itself in memory.
VERIFY(program_header.alignment() == PAGE_SIZE);
int prot = 0;
if (program_header.is_readable())
prot |= PROT_READ;
if (program_header.is_writable())
prot |= PROT_WRITE;
if (program_header.is_executable())
prot |= PROT_EXEC;
auto range_base = VirtualAddress { Memory::page_round_down(program_header.vaddr().offset(load_offset).get()) };
size_t rounded_range_end = TRY(Memory::page_round_up(program_header.vaddr().offset(load_offset).offset(program_header.size_in_memory()).get()));
auto range_end = VirtualAddress { rounded_range_end };
auto range = TRY(new_space->try_allocate_range(range_base, range_end.get() - range_base.get()));
auto region = TRY(new_space->allocate_region_with_vmobject(range, *vmobject, program_header.offset(), elf_name->view(), prot, true));
if (should_allow_syscalls == ShouldAllowSyscalls::Yes)
region->set_syscall_region(true);
if (program_header.offset() == 0)
load_base_address = (FlatPtr)region->vaddr().as_ptr();
return {};
};
auto load_elf_program_header = [&](auto& program_header) -> ErrorOr<void> {
if (program_header.type() == PT_TLS)
return load_tls_section(program_header);
if (program_header.type() == PT_LOAD)
return load_section(program_header);
// NOTE: We ignore other program header types.
return {};
};
TRY([&] {
ErrorOr<void> result;
elf_image.for_each_program_header([&](ELF::Image::ProgramHeader const& program_header) {
result = load_elf_program_header(program_header);
return result.is_error() ? IterationDecision::Break : IterationDecision::Continue;
});
return result;
}());
if (!elf_image.entry().offset(load_offset).get()) {
dbgln("do_exec: Failure loading program, entry pointer is invalid! {})", elf_image.entry().offset(load_offset));
return ENOEXEC;
}
auto stack_range = TRY(new_space->try_allocate_range({}, Thread::default_userspace_stack_size));
auto* stack_region = TRY(new_space->allocate_region(stack_range, "Stack (Main thread)", PROT_READ | PROT_WRITE, AllocationStrategy::Reserve));
stack_region->set_stack(true);
return LoadResult {
move(new_space),
load_base_address,
elf_image.entry().offset(load_offset).get(),
executable_size,
AK::try_make_weak_ptr(master_tls_region),
master_tls_size,
master_tls_alignment,
stack_region->make_weak_ptr()
};
}
ErrorOr<LoadResult>
Process::load(NonnullRefPtr<OpenFileDescription> main_program_description,
RefPtr<OpenFileDescription> interpreter_description, const ElfW(Ehdr) & main_program_header)
{
auto new_space = TRY(Memory::AddressSpace::try_create(nullptr));
ScopeGuard space_guard([&]() {
Memory::MemoryManager::enter_process_address_space(*this);
});
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(move(new_space), main_program_description, load_offset, ShouldAllocateTls::Yes, ShouldAllowSyscalls::No));
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;
}
auto interpreter_load_result = TRY(load_elf_object(move(new_space), *interpreter_description, load_offset, ShouldAllocateTls::No, ShouldAllowSyscalls::Yes));
// TLS allocation will be done in userspace by the loader
VERIFY(!interpreter_load_result.tls_region);
VERIFY(!interpreter_load_result.tls_alignment);
VERIFY(!interpreter_load_result.tls_size);
return interpreter_load_result;
}
ErrorOr<void> Process::do_exec(NonnullRefPtr<OpenFileDescription> main_program_description, NonnullOwnPtrVector<KString> arguments, NonnullOwnPtrVector<KString> environment,
RefPtr<OpenFileDescription> interpreter_description, Thread*& new_main_thread, u32& prev_flags, const ElfW(Ehdr) & main_program_header)
{
VERIFY(is_user_process());
VERIFY(!Processor::in_critical());
// Although we *could* handle a pseudo_path here, trying to execute something that doesn't have
// a custody (e.g. BlockDevice or RandomDevice) is pretty suspicious anyway.
auto path = TRY(main_program_description->original_absolute_path());
dbgln_if(EXEC_DEBUG, "do_exec: {}", path);
// FIXME: How much stack space does process startup need?
if (!validate_stack_size(arguments, environment))
return E2BIG;
// FIXME: split_view() currently allocates (Vector) without checking for failure.
auto parts = path->view().split_view('/');
if (parts.is_empty())
return ENOENT;
auto new_process_name = TRY(KString::try_create(parts.last()));
auto new_main_thread_name = TRY(new_process_name->try_clone());
auto load_result = TRY(load(main_program_description, interpreter_description, main_program_header));
// 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.
// That's important because when we're returning from this function, we're in a very delicate
// state where we can't block (e.g by trying to acquire a mutex in description teardown.)
bool has_interpreter = interpreter_description;
interpreter_description = nullptr;
auto signal_trampoline_range = TRY(load_result.space->try_allocate_range({}, PAGE_SIZE));
auto* signal_trampoline_region = TRY(load_result.space->allocate_region_with_vmobject(signal_trampoline_range, g_signal_trampoline_region->vmobject(), 0, "Signal trampoline", PROT_READ | PROT_EXEC, true));
signal_trampoline_region->set_syscall_region(true);
// (For dynamically linked executable) Allocate an FD for passing the main executable to the dynamic loader.
Optional<ScopedDescriptionAllocation> main_program_fd_allocation;
if (has_interpreter)
main_program_fd_allocation = TRY(m_fds.allocate());
// We commit to the new executable at this point. There is no turning back!
// Prevent other processes from attaching to us with ptrace while we're doing this.
MutexLocker ptrace_locker(ptrace_lock());
// Disable profiling temporarily in case it's running on this process.
auto was_profiling = m_profiling;
TemporaryChange profiling_disabler(m_profiling, false);
kill_threads_except_self();
bool executable_is_setid = false;
if (!(main_program_description->custody()->mount_flags() & MS_NOSUID)) {
auto main_program_metadata = main_program_description->metadata();
if (main_program_metadata.is_setuid()) {
executable_is_setid = true;
ProtectedDataMutationScope scope { *this };
m_protected_values.euid = main_program_metadata.uid;
m_protected_values.suid = main_program_metadata.uid;
}
if (main_program_metadata.is_setgid()) {
executable_is_setid = true;
ProtectedDataMutationScope scope { *this };
m_protected_values.egid = main_program_metadata.gid;
m_protected_values.sgid = main_program_metadata.gid;
}
}
set_dumpable(!executable_is_setid);
// We make sure to enter the new address space before destroying the old one.
// This ensures that the process always has a valid page directory.
Memory::MemoryManager::enter_address_space(*load_result.space);
m_space = load_result.space.release_nonnull();
m_executable = main_program_description->custody();
m_arguments = move(arguments);
m_environment = move(environment);
m_veil_state = VeilState::None;
m_unveiled_paths.clear();
m_unveiled_paths.set_metadata({ "/", UnveilAccess::None, false });
for (auto& property : m_coredump_properties)
property = {};
auto* current_thread = Thread::current();
current_thread->reset_signals_for_exec();
clear_futex_queues_on_exec();
fds().change_each([&](auto& file_description_metadata) {
if (file_description_metadata.is_valid() && file_description_metadata.flags() & FD_CLOEXEC)
file_description_metadata = {};
});
if (main_program_fd_allocation.has_value()) {
main_program_description->set_readable(true);
m_fds[main_program_fd_allocation->fd].set(move(main_program_description), FD_CLOEXEC);
}
new_main_thread = nullptr;
if (&current_thread->process() == this) {
new_main_thread = current_thread;
} else {
for_each_thread([&](auto& thread) {
new_main_thread = &thread;
return IterationDecision::Break;
});
}
VERIFY(new_main_thread);
auto auxv = generate_auxiliary_vector(load_result.load_base, load_result.entry_eip, uid(), euid(), gid(), egid(), path->view(), main_program_fd_allocation);
// NOTE: We create the new stack before disabling interrupts since it will zero-fault
// and we don't want to deal with faults after this point.
auto new_userspace_sp = TRY(make_userspace_context_for_main_thread(new_main_thread->regs(), *load_result.stack_region.unsafe_ptr(), m_arguments, m_environment, move(auxv)));
if (wait_for_tracer_at_next_execve()) {
// Make sure we release the ptrace lock here or the tracer will block forever.
ptrace_locker.unlock();
Thread::current()->send_urgent_signal_to_self(SIGSTOP);
} else {
// Unlock regardless before disabling interrupts.
// Ensure we always unlock after checking ptrace status to avoid TOCTOU ptrace issues
ptrace_locker.unlock();
}
// We enter a critical section here because we don't want to get interrupted between do_exec()
// and Processor::assume_context() or the next context switch.
// If we used an InterruptDisabler that sti()'d on exit, we might timer tick'd too soon in exec().
Processor::enter_critical();
prev_flags = cpu_flags();
cli();
// NOTE: Be careful to not trigger any page faults below!
m_name = move(new_process_name);
new_main_thread->set_name(move(new_main_thread_name));
{
ProtectedDataMutationScope scope { *this };
m_protected_values.promises = m_protected_values.execpromises.load();
m_protected_values.has_promises = m_protected_values.has_execpromises.load();
m_protected_values.execpromises = 0;
m_protected_values.has_execpromises = false;
m_protected_values.signal_trampoline = signal_trampoline_region->vaddr();
// FIXME: PID/TID ISSUE
m_protected_values.pid = new_main_thread->tid().value();
}
auto tsr_result = new_main_thread->make_thread_specific_region({});
if (tsr_result.is_error()) {
// FIXME: We cannot fail this late. Refactor this so the allocation happens before we commit to the new executable.
VERIFY_NOT_REACHED();
}
new_main_thread->reset_fpu_state();
auto& regs = new_main_thread->m_regs;
#if ARCH(I386)
regs.cs = GDT_SELECTOR_CODE3 | 3;
regs.ds = GDT_SELECTOR_DATA3 | 3;
regs.es = GDT_SELECTOR_DATA3 | 3;
regs.ss = GDT_SELECTOR_DATA3 | 3;
regs.fs = GDT_SELECTOR_DATA3 | 3;
regs.gs = GDT_SELECTOR_TLS | 3;
regs.eip = load_result.entry_eip;
regs.esp = new_userspace_sp;
#else
regs.rip = load_result.entry_eip;
regs.rsp = new_userspace_sp;
#endif
regs.cr3 = address_space().page_directory().cr3();
{
TemporaryChange profiling_disabler(m_profiling, was_profiling);
PerformanceManager::add_process_exec_event(*this);
}
{
SpinlockLocker lock(g_scheduler_lock);
new_main_thread->set_state(Thread::State::Runnable);
}
u32 lock_count_to_restore;
[[maybe_unused]] auto rc = big_lock().force_unlock_if_locked(lock_count_to_restore);
VERIFY_INTERRUPTS_DISABLED();
VERIFY(Processor::in_critical());
return {};
}
static Vector<ELF::AuxiliaryValue> generate_auxiliary_vector(FlatPtr load_base, FlatPtr entry_eip, UserID uid, UserID euid, GroupID gid, GroupID egid, StringView executable_path, Optional<Process::ScopedDescriptionAllocation> const& main_program_fd_allocation)
{
Vector<ELF::AuxiliaryValue> auxv;
// PHDR/EXECFD
// PH*
auxv.append({ ELF::AuxiliaryValue::PageSize, PAGE_SIZE });
auxv.append({ ELF::AuxiliaryValue::BaseAddress, (void*)load_base });
auxv.append({ ELF::AuxiliaryValue::Entry, (void*)entry_eip });
// NOTELF
auxv.append({ ELF::AuxiliaryValue::Uid, (long)uid.value() });
auxv.append({ ELF::AuxiliaryValue::EUid, (long)euid.value() });
auxv.append({ ELF::AuxiliaryValue::Gid, (long)gid.value() });
auxv.append({ ELF::AuxiliaryValue::EGid, (long)egid.value() });
auxv.append({ ELF::AuxiliaryValue::Platform, Processor::platform_string() });
// FIXME: This is platform specific
auxv.append({ ELF::AuxiliaryValue::HwCap, (long)CPUID(1).edx() });
auxv.append({ ELF::AuxiliaryValue::ClockTick, (long)TimeManagement::the().ticks_per_second() });
// FIXME: Also take into account things like extended filesystem permissions? That's what linux does...
auxv.append({ ELF::AuxiliaryValue::Secure, ((uid != euid) || (gid != egid)) ? 1 : 0 });
char random_bytes[16] {};
get_fast_random_bytes({ (u8*)random_bytes, sizeof(random_bytes) });
auxv.append({ ELF::AuxiliaryValue::Random, String(random_bytes, sizeof(random_bytes)) });
auxv.append({ ELF::AuxiliaryValue::ExecFilename, executable_path });
if (main_program_fd_allocation.has_value())
auxv.append({ ELF::AuxiliaryValue::ExecFileDescriptor, main_program_fd_allocation->fd });
auxv.append({ ELF::AuxiliaryValue::Null, 0L });
return auxv;
}
static ErrorOr<NonnullOwnPtrVector<KString>> find_shebang_interpreter_for_executable(char const first_page[], size_t nread)
{
int word_start = 2;
size_t word_length = 0;
if (nread > 2 && first_page[0] == '#' && first_page[1] == '!') {
NonnullOwnPtrVector<KString> interpreter_words;
for (size_t i = 2; i < nread; ++i) {
if (first_page[i] == '\n') {
break;
}
if (first_page[i] != ' ') {
++word_length;
}
if (first_page[i] == ' ') {
if (word_length > 0) {
auto word = TRY(KString::try_create(StringView { &first_page[word_start], word_length }));
interpreter_words.append(move(word));
}
word_length = 0;
word_start = i + 1;
}
}
if (word_length > 0) {
auto word = TRY(KString::try_create(StringView { &first_page[word_start], word_length }));
interpreter_words.append(move(word));
}
if (!interpreter_words.is_empty())
return interpreter_words;
}
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)
{
// Not using ErrorOr here because we'll want to do the same thing in userspace in the RTLD
String interpreter_path;
if (!ELF::validate_program_headers(main_executable_header, file_size, (u8 const*)&main_executable_header, main_executable_header_size, &interpreter_path)) {
dbgln("exec({}): File has invalid ELF Program headers", path);
return ENOEXEC;
}
if (!interpreter_path.is_empty()) {
dbgln_if(EXEC_DEBUG, "exec({}): Using program interpreter {}", path, interpreter_path);
auto interpreter_description = TRY(VirtualFileSystem::the().open(interpreter_path, O_EXEC, 0, current_directory()));
auto interp_metadata = interpreter_description->metadata();
VERIFY(interpreter_description->inode());
// Validate the program interpreter as a valid elf binary.
// If your program interpreter is a #! file or something, it's time to stop playing games :)
if (interp_metadata.size < (int)sizeof(ElfW(Ehdr)))
return ENOEXEC;
char first_page[PAGE_SIZE] = {};
auto first_page_buffer = UserOrKernelBuffer::for_kernel_buffer((u8*)&first_page);
auto nread = TRY(interpreter_description->read(first_page_buffer, sizeof(first_page)));
if (nread < sizeof(ElfW(Ehdr)))
return ENOEXEC;
auto* elf_header = (ElfW(Ehdr)*)first_page;
if (!ELF::validate_elf_header(*elf_header, interp_metadata.size)) {
dbgln("exec({}): Interpreter ({}) has invalid ELF header", path, interpreter_path);
return ENOEXEC;
}
// Not using ErrorOr here because we'll want to do the same thing in userspace in the RTLD
String interpreter_interpreter_path;
if (!ELF::validate_program_headers(*elf_header, interp_metadata.size, (u8*)first_page, nread, &interpreter_interpreter_path)) {
dbgln("exec({}): Interpreter ({}) has invalid ELF Program headers", path, interpreter_path);
return ENOEXEC;
}
if (!interpreter_interpreter_path.is_empty()) {
dbgln("exec({}): Interpreter ({}) has its own interpreter ({})! No thank you!", path, interpreter_path, interpreter_interpreter_path);
return ELOOP;
}
return interpreter_description;
}
if (main_executable_header.e_type == ET_REL) {
// We can't exec an ET_REL, that's just an object file from the compiler
return ENOEXEC;
}
if (main_executable_header.e_type == ET_DYN) {
// If it's ET_DYN with no PT_INTERP, then it's a dynamic executable responsible
// for its own relocation (i.e. it's /usr/lib/Loader.so)
if (path != "/usr/lib/Loader.so")
dbgln("exec({}): WARNING - Dynamic ELF executable without a PT_INTERP header, and isn't /usr/lib/Loader.so", path);
return nullptr;
}
// No interpreter, but, path refers to a valid elf image
return nullptr;
}
ErrorOr<void> Process::exec(NonnullOwnPtr<KString> path, NonnullOwnPtrVector<KString> arguments, NonnullOwnPtrVector<KString> environment, int recursion_depth)
{
if (recursion_depth > 2) {
dbgln("exec({}): SHENANIGANS! recursed too far trying to find #! interpreter", path);
return ELOOP;
}
// Open the file to check what kind of binary format it is
// Currently supported formats:
// - #! interpreted file
// - ELF32
// * ET_EXEC binary that just gets loaded
// * ET_DYN binary that requires a program interpreter
//
auto description = TRY(VirtualFileSystem::the().open(path->view(), O_EXEC, 0, current_directory()));
auto metadata = description->metadata();
if (!metadata.is_regular_file())
return EACCES;
// Always gonna need at least 3 bytes. these are for #!X
if (metadata.size < 3)
return ENOEXEC;
VERIFY(description->inode());
// Read the first page of the program into memory so we can validate the binfmt of it
char first_page[PAGE_SIZE];
auto first_page_buffer = UserOrKernelBuffer::for_kernel_buffer((u8*)&first_page);
auto nread = TRY(description->read(first_page_buffer, sizeof(first_page)));
// 1) #! interpreted file
auto shebang_result = find_shebang_interpreter_for_executable(first_page, nread);
if (!shebang_result.is_error()) {
auto shebang_words = shebang_result.release_value();
auto shebang_path = TRY(shebang_words.first().try_clone());
arguments.ptr_at(0) = move(path);
TRY(arguments.try_prepend(move(shebang_words)));
return exec(move(shebang_path), move(arguments), move(environment), ++recursion_depth);
}
// #2) ELF32 for i386
if (nread < sizeof(ElfW(Ehdr)))
return ENOEXEC;
auto const* main_program_header = (ElfW(Ehdr)*)first_page;
if (!ELF::validate_elf_header(*main_program_header, metadata.size)) {
dbgln("exec({}): File has invalid ELF header", path);
return ENOEXEC;
}
// The bulk of exec() is done by do_exec(), which ensures that all locals
// are cleaned up by the time we yield-teleport below.
Thread* new_main_thread = nullptr;
u32 prev_flags = 0;
auto interpreter_description = TRY(find_elf_interpreter_for_executable(path->view(), *main_program_header, nread, metadata.size));
TRY(do_exec(move(description), move(arguments), move(environment), move(interpreter_description), new_main_thread, prev_flags, *main_program_header));
VERIFY_INTERRUPTS_DISABLED();
VERIFY(Processor::in_critical());
auto* current_thread = Thread::current();
if (current_thread == new_main_thread) {
// We need to enter the scheduler lock before changing the state
// and it will be released after the context switch into that
// thread. We should also still be in our critical section
VERIFY(!g_scheduler_lock.is_locked_by_current_processor());
VERIFY(Processor::in_critical() == 1);
g_scheduler_lock.lock();
current_thread->set_state(Thread::State::Running);
Processor::assume_context(*current_thread, prev_flags);
VERIFY_NOT_REACHED();
}
// NOTE: This code path is taken in the non-syscall case, i.e when the kernel spawns
// a userspace process directly (such as /bin/SystemServer on startup)
if (prev_flags & 0x200)
sti();
Processor::leave_critical();
return {};
}
ErrorOr<FlatPtr> Process::sys$execve(Userspace<const Syscall::SC_execve_params*> user_params)
{
VERIFY_PROCESS_BIG_LOCK_ACQUIRED(this);
TRY(require_promise(Pledge::exec));
// NOTE: Be extremely careful with allocating any kernel memory in exec().
// On success, the kernel stack will be lost.
auto params = TRY(copy_typed_from_user(user_params));
if (params.arguments.length > ARG_MAX || params.environment.length > ARG_MAX)
return E2BIG;
auto path = TRY(get_syscall_path_argument(params.path));
auto copy_user_strings = [](const auto& list, auto& output) -> ErrorOr<void> {
if (!list.length)
return {};
Checked<size_t> size = sizeof(*list.strings);
size *= list.length;
if (size.has_overflow())
return EOVERFLOW;
Vector<Syscall::StringArgument, 32> strings;
TRY(strings.try_resize(list.length));
TRY(copy_from_user(strings.data(), list.strings, size.value()));
for (size_t i = 0; i < list.length; ++i) {
auto string = TRY(try_copy_kstring_from_user(strings[i]));
TRY(output.try_append(move(string)));
}
return {};
};
NonnullOwnPtrVector<KString> arguments;
TRY(copy_user_strings(params.arguments, arguments));
NonnullOwnPtrVector<KString> environment;
TRY(copy_user_strings(params.environment, environment));
TRY(exec(move(path), move(arguments), move(environment)));
// We should never continue after a successful exec!
VERIFY_NOT_REACHED();
}
}
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