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Kernel/aarch64: Implement thread_context_first_enter

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This requires two new functions, context_first_init and
restore_context_and_eret. With this code in place, we are now running
the first idle thread! :^)
This commit is contained in:
Timon Kruiper 2022-12-27 17:14:35 +01:00 • committed by Andrew Kaster
parent 262309d9bf
commit 0b95d8cd24
2 changed files with 34 additions and 4 deletions
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31
Kernel/Arch/aarch64/Processor.cpp
View file

@ -24,6 +24,7 @@ namespace Kernel {
extern "C" void thread_context_first_enter(void);
extern "C" void exit_kernel_thread(void);
extern "C" void context_first_init(Thread* from_thread, Thread* to_thread) __attribute__((used));
Processor* g_current_processor;
@ -279,8 +280,11 @@ void Processor::check_invoke_scheduler()
NAKED void thread_context_first_enter(void)
{
asm(
// FIXME: Implement this
"wfi \n");
"ldr x0, [sp, #0] \n"
"ldr x1, [sp, #8] \n"
"add sp, sp, 24 \n"
"bl context_first_init \n"
"b restore_context_and_eret \n");
}
void exit_kernel_thread(void)
@ -288,4 +292,27 @@ void exit_kernel_thread(void)
Thread::current()->exit();
}
extern "C" void context_first_init([[maybe_unused]] Thread* from_thread, [[maybe_unused]] Thread* to_thread)
{
VERIFY(!are_interrupts_enabled());
dbgln_if(CONTEXT_SWITCH_DEBUG, "switch_context <-- from {} {} to {} {} (context_first_init)", VirtualAddress(from_thread), *from_thread, VirtualAddress(to_thread), *to_thread);
VERIFY(to_thread == Thread::current());
Scheduler::enter_current(*from_thread);
auto in_critical = to_thread->saved_critical();
VERIFY(in_critical > 0);
Processor::restore_critical(in_critical);
// Since we got here and don't have Scheduler::context_switch in the
// call stack (because this is the first time we switched into this
// context), we need to notify the scheduler so that it can release
// the scheduler lock. We don't want to enable interrupts at this point
// as we're still in the middle of a context switch. Doing so could
// trigger a context switch within a context switch, leading to a crash.
Scheduler::leave_on_first_switch(InterruptsState::Disabled);
}
}

7
Kernel/Arch/aarch64/vector_table.S
View file

@ -85,8 +85,6 @@
msr elr_el1, x0
ldr x0, [sp, #TPIDR_EL0_SLOT]
msr tpidr_el0, x0
ldr x0, [sp, #SP_EL0_SLOT]
msr sp_el0, x0
ldp x0, x1, [sp, #(0 * 0)]
ldp x2, x3, [sp, #(2 * 8)]
@ -186,3 +184,8 @@ system_error_current_elsp_el0:
bl exception_common
restore_previous_context
eret
.global restore_context_and_eret
restore_context_and_eret:
restore_previous_context
eret