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Kernel/Process: Move protected values to the end of the object

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The compiler can re-order the structure (class) members if that's
necessary, so if we make Process to inherit from ProcFSExposedComponent,
even if the declaration is to inherit first from ProcessBase, then from
ProcFSExposedComponent and last from Weakable<Process>, the members of
class ProcFSExposedComponent (including the Ref-counted parts) are the
first members of the Process class.

This problem made it impossible to safely use the current toggling
method with the write-protection bit on the ProcessBase members, so
instead of inheriting from it, we make its members the last ones in the
Process class so we can safely locate and modify the corresponding page
write protection bit of these values.

We make sure that the Process class doesn't expand beyond 8192 bytes and
the protected values are always aligned on a page boundary.
This commit is contained in:
Liav A 2021-08-07 22:30:06 +03:00 • committed by Andreas Kling
parent e405f436b6
commit 01b79910b3
12 changed files with 130 additions and 128 deletions
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40
Kernel/Process.cpp
View file

@ -216,14 +216,14 @@ RefPtr<Process> Process::create_kernel_process(RefPtr<Thread>& first_thread, Str
void Process::protect_data()
{
m_protected_data_refs.unref([&]() {
MM.set_page_writable_direct(VirtualAddress { this }, false);
MM.set_page_writable_direct(VirtualAddress { &this->m_protected_values }, false);
});
}
void Process::unprotect_data()
{
m_protected_data_refs.ref([&]() {
MM.set_page_writable_direct(VirtualAddress { this }, true);
MM.set_page_writable_direct(VirtualAddress { &this->m_protected_values }, true);
});
}
@ -249,14 +249,14 @@ Process::Process(const String& name, uid_t uid, gid_t gid, ProcessID ppid, bool
// Ensure that we protect the process data when exiting the constructor.
ProtectedDataMutationScope scope { *this };
m_pid = allocate_pid();
m_ppid = ppid;
m_uid = uid;
m_gid = gid;
m_euid = uid;
m_egid = gid;
m_suid = uid;
m_sgid = gid;
m_protected_values.pid = allocate_pid();
m_protected_values.ppid = ppid;
m_protected_values.uid = uid;
m_protected_values.gid = gid;
m_protected_values.euid = uid;
m_protected_values.egid = gid;
m_protected_values.suid = uid;
m_protected_values.sgid = gid;
dbgln_if(PROCESS_DEBUG, "Created new process {}({})", m_name, this->pid().value());
}
@ -386,7 +386,7 @@ void Process::crash(int signal, FlatPtr ip, bool out_of_memory)
}
{
ProtectedDataMutationScope scope { *this };
m_termination_signal = signal;
m_protected_values.termination_signal = signal;
}
set_dump_core(!out_of_memory);
address_space().dump_regions();
@ -482,11 +482,11 @@ siginfo_t Process::wait_info()
siginfo.si_pid = pid().value();
siginfo.si_uid = uid();
if (m_termination_signal) {
siginfo.si_status = m_termination_signal;
if (m_protected_values.termination_signal) {
siginfo.si_status = m_protected_values.termination_signal;
siginfo.si_code = CLD_KILLED;
} else {
siginfo.si_status = m_termination_status;
siginfo.si_status = m_protected_values.termination_status;
siginfo.si_code = CLD_EXITED;
}
return siginfo;
@ -690,8 +690,8 @@ void Process::terminate_due_to_signal(u8 signal)
dbgln("Terminating {} due to signal {}", *this, signal);
{
ProtectedDataMutationScope scope { *this };
m_termination_status = 0;
m_termination_signal = signal;
m_protected_values.termination_status = 0;
m_protected_values.termination_signal = signal;
}
die();
}
@ -832,7 +832,7 @@ void Process::delete_perf_events_buffer()
bool Process::remove_thread(Thread& thread)
{
ProtectedDataMutationScope scope { *this };
auto thread_cnt_before = m_thread_count.fetch_sub(1, AK::MemoryOrder::memory_order_acq_rel);
auto thread_cnt_before = m_protected_values.thread_count.fetch_sub(1, AK::MemoryOrder::memory_order_acq_rel);
VERIFY(thread_cnt_before != 0);
thread_list().with([&](auto& thread_list) {
thread_list.remove(thread);
@ -843,7 +843,7 @@ bool Process::remove_thread(Thread& thread)
bool Process::add_thread(Thread& thread)
{
ProtectedDataMutationScope scope { *this };
bool is_first = m_thread_count.fetch_add(1, AK::MemoryOrder::memory_order_relaxed) == 0;
bool is_first = m_protected_values.thread_count.fetch_add(1, AK::MemoryOrder::memory_order_relaxed) == 0;
thread_list().with([&](auto& thread_list) {
thread_list.append(thread);
});
@ -852,10 +852,10 @@ bool Process::add_thread(Thread& thread)
void Process::set_dumpable(bool dumpable)
{
if (dumpable == m_dumpable)
if (dumpable == m_protected_values.dumpable)
return;
ProtectedDataMutationScope scope { *this };
m_dumpable = dumpable;
m_protected_values.dumpable = dumpable;
}
KResult Process::set_coredump_property(NonnullOwnPtr<KString> key, NonnullOwnPtr<KString> value)