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Kernel: Support thread-local storage

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This patch adds support for TLS according to the x86 System V ABI.
Each thread gets a thread-specific memory region, and the GS segment
register always points _to a pointer_ to the thread-specific memory.

In other words, to access thread-local variables, userspace programs
start by dereferencing the pointer at [gs:0].

The Process keeps a master copy of the TLS segment that new threads
should use, and when a new thread is created, they get a copy of it.
It's basically whatever the PT_TLS program header in the ELF says.
This commit is contained in:
Andreas Kling 2019-09-07 15:50:44 +02:00
parent bcfdf9ffa7
commit ec6bceaa08
7 changed files with 92 additions and 5 deletions
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26
Kernel/Process.cpp
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@ -310,6 +310,9 @@ Process* Process::fork(RegisterDump& regs)
auto cloned_region = region.clone();
child->m_regions.append(move(cloned_region));
MM.map_region(*child, child->m_regions.last());
if (&region == m_master_tls_region)
child->m_master_tls_region = child->m_regions.last();
}
for (auto gid : m_gids)
@ -403,6 +406,10 @@ int Process::do_exec(String path, Vector<String> arguments, Vector<String> envir
RefPtr<Region> region = allocate_region_with_vmo(VirtualAddress(), metadata.size, vmo, 0, description->absolute_path(), PROT_READ);
ASSERT(region);
RefPtr<Region> master_tls_region;
size_t master_tls_size = 0;
size_t master_tls_alignment = 0;
OwnPtr<ELFLoader> loader;
{
// Okay, here comes the sleight of hand, pay close attention..
@ -433,6 +440,13 @@ int Process::do_exec(String path, Vector<String> arguments, Vector<String> envir
(void)allocate_region(vaddr, size, String(name), prot);
return vaddr.as_ptr();
};
loader->tls_section_hook = [&](size_t size, size_t alignment) {
ASSERT(size);
master_tls_region = allocate_region({}, size, String(), PROT_READ | PROT_WRITE);
master_tls_size = size;
master_tls_alignment = alignment;
return master_tls_region->vaddr().as_ptr();
};
bool success = loader->load();
if (!success || !loader->entry().get()) {
m_page_directory = move(old_page_directory);
@ -451,6 +465,9 @@ int Process::do_exec(String path, Vector<String> arguments, Vector<String> envir
m_elf_loader = move(loader);
m_executable = description->custody();
// Copy of the master TLS region that we will clone for new threads
m_master_tls_region = master_tls_region.ptr();
if (metadata.is_setuid())
m_euid = metadata.uid;
if (metadata.is_setgid())
@ -483,6 +500,11 @@ int Process::do_exec(String path, Vector<String> arguments, Vector<String> envir
// ss0 sp!!!!!!!!!
u32 old_esp0 = main_thread().m_tss.esp0;
m_master_tls_size = master_tls_size;
m_master_tls_alignment = master_tls_alignment;
main_thread().make_thread_specific_region({});
memset(&main_thread().m_tss, 0, sizeof(main_thread().m_tss));
main_thread().m_tss.eflags = 0x0202;
main_thread().m_tss.eip = entry_eip;
@ -490,7 +512,7 @@ int Process::do_exec(String path, Vector<String> arguments, Vector<String> envir
main_thread().m_tss.ds = 0x23;
main_thread().m_tss.es = 0x23;
main_thread().m_tss.fs = 0x23;
main_thread().m_tss.gs = 0x23;
main_thread().m_tss.gs = thread_specific_selector() | 3;
main_thread().m_tss.ss = 0x23;
main_thread().m_tss.cr3 = page_directory().cr3();
main_thread().make_userspace_stack_for_main_thread(move(arguments), move(environment));
@ -2661,7 +2683,7 @@ int Process::sys$create_thread(int (*entry)(void*), void* argument)
tss.eflags = 0x0202;
tss.cr3 = page_directory().cr3();
thread->make_userspace_stack_for_secondary_thread(argument);
thread->make_thread_specific_region({});
thread->set_state(Thread::State::Runnable);
return thread->tid();
}