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Kernel: Allocate new main thread stack before committing to exec

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If the allocation fails (e.g ENOMEM) we want to simply return an error
from sys$execve() and continue executing the current executable.

This patch also moves make_userspace_stack_for_main_thread() out of the
Thread class since it had nothing in particular to do with Thread.
This commit is contained in:
Andreas Kling 2020-12-25 16:20:26 +01:00
parent d55fb7b5e2
commit 89d3b09638
4 changed files with 77 additions and 77 deletions
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77
Kernel/Syscalls/execve.cpp
View file

@ -62,6 +62,73 @@ static bool validate_stack_size(const Vector<String>& arguments, const Vector<St
return (total_blob_size + total_meta_size) < Thread::default_userspace_stack_size;
}
static KResultOr<FlatPtr> make_userspace_stack_for_main_thread(Region& region, Vector<String> arguments, Vector<String> environment, Vector<ELF::AuxiliaryValue> auxiliary_values)
{
FlatPtr new_esp = region.vaddr().offset(Thread::default_userspace_stack_size).get();
auto push_on_new_stack = [&new_esp](u32 value) {
new_esp -= 4;
Userspace<u32*> stack_ptr = new_esp;
return copy_to_user(stack_ptr, &value);
};
auto push_aux_value_on_new_stack = [&new_esp](auxv_t value) {
new_esp -= sizeof(auxv_t);
Userspace<auxv_t*> stack_ptr = new_esp;
return copy_to_user(stack_ptr, &value);
};
auto push_string_on_new_stack = [&new_esp](const String& string) {
new_esp -= round_up_to_power_of_two(string.length() + 1, 4);
Userspace<u32*> stack_ptr = new_esp;
return copy_to_user(stack_ptr, string.characters(), string.length() + 1);
};
Vector<FlatPtr> argv_entries;
for (auto& argument : arguments) {
push_string_on_new_stack(argument);
argv_entries.append(new_esp);
}
Vector<FlatPtr> env_entries;
for (auto& variable : environment) {
push_string_on_new_stack(variable);
env_entries.append(new_esp);
}
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_esp;
}
}
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_esp;
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_esp;
// NOTE: The stack needs to be 16-byte aligned.
new_esp -= new_esp % 16;
push_on_new_stack((FlatPtr)envp);
push_on_new_stack((FlatPtr)argv);
push_on_new_stack((FlatPtr)argv_entries.size());
push_on_new_stack(0);
return new_esp;
}
KResultOr<Process::LoadResult> Process::load_elf_object(FileDescription& object_description, FlatPtr load_offset, ShouldAllocateTls should_allocate_tls)
{
auto& inode = *(object_description.inode());
@ -192,6 +259,11 @@ KResultOr<Process::LoadResult> Process::load_elf_object(FileDescription& object_
return KResult(-ENOEXEC);
}
auto* stack_region = allocate_region(VirtualAddress(), Thread::default_userspace_stack_size, "Stack (Main thread)", PROT_READ | PROT_WRITE, false);
if (!stack_region)
return KResult(-ENOMEM);
stack_region->set_stack(true);
return LoadResult {
load_base_address,
elf_image.entry().offset(load_offset).get(),
@ -200,7 +272,8 @@ KResultOr<Process::LoadResult> Process::load_elf_object(FileDescription& object_
elf_image.program_header_count(),
master_tls_region ? master_tls_region->make_weak_ptr() : nullptr,
master_tls_size,
master_tls_alignment
master_tls_alignment,
stack_region->make_weak_ptr()
};
}
@ -368,7 +441,7 @@ int Process::do_exec(NonnullRefPtr<FileDescription> main_program_description, Ve
// 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 make_stack_result = new_main_thread->make_userspace_stack_for_main_thread(move(arguments), move(environment), move(auxv));
auto make_stack_result = make_userspace_stack_for_main_thread(*load_result.stack_region.unsafe_ptr(), move(arguments), move(environment), move(auxv));
if (make_stack_result.is_error())
return make_stack_result.error();
u32 new_userspace_esp = make_stack_result.value();