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Kernel: Implement more x86_64 context switching functionality

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This commit is contained in:
Gunnar Beutner 2021-06-27 19:49:19 +02:00 • committed by Andreas Kling
parent 076692b1ef
commit 32840dfa17
8 changed files with 151 additions and 132 deletions
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37
Kernel/Arch/x86/x86_64/CPU.cpp
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@ -1,37 +0,0 @@
/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/Assertions.h>
#include <AK/Types.h>
#include <Kernel/Arch/x86/CPU.h>
#include <Kernel/Arch/x86/Processor.h>
#include <Kernel/Arch/x86/TrapFrame.h>
#include <Kernel/KSyms.h>
#include <Kernel/Process.h>
#include <Kernel/Thread.h>
namespace Kernel {
// The compiler can't see the calls to these functions inside assembly.
// Declare them, to avoid dead code warnings.
extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread) __attribute__((used));
extern "C" u32 do_init_context(Thread* thread, u32 flags) __attribute__((used));
extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread)
{
(void)from_thread;
(void)to_thread;
TODO();
}
extern "C" u32 do_init_context(Thread* thread, u32 flags)
{
(void)thread;
(void)flags;
TODO();
}
}

71
Kernel/Arch/x86/x86_64/Processor.cpp
View file

@ -91,9 +91,8 @@ u32 Processor::init_context(Thread& thread, bool leave_crit)
auto& regs = thread.regs();
bool return_to_user = (regs.cs & 3) != 0;
stack_top -= 2 * sizeof(u64);
*reinterpret_cast<u64*>(kernel_stack_top - 2 * sizeof(u64)) = regs.rsp;
*reinterpret_cast<u64*>(kernel_stack_top - 3 * sizeof(u64)) = FlatPtr(&exit_kernel_thread);
stack_top -= 1 * sizeof(u64);
*reinterpret_cast<u64*>(kernel_stack_top - 2 * sizeof(u64)) = FlatPtr(&exit_kernel_thread);
stack_top -= sizeof(RegisterState);
@ -167,7 +166,71 @@ void Processor::switch_context(Thread*& from_thread, Thread*& to_thread)
dbgln_if(CONTEXT_SWITCH_DEBUG, "switch_context --> switching out of: {} {}", VirtualAddress(from_thread), *from_thread);
from_thread->save_critical(m_in_critical);
PANIC("Context switching not implemented.");
// clang-format off
// Switch to new thread context, passing from_thread and to_thread
// through to the new context using registers rdx and rax
asm volatile(
// NOTE: changing how much we push to the stack affects thread_context_first_enter()!
"pushfq \n"
"pushq %%rbx \n"
"pushq %%rcx \n"
"pushq %%rbp \n"
"pushq %%rsi \n"
"pushq %%rdi \n"
"pushq %%r8 \n"
"pushq %%r9 \n"
"pushq %%r10 \n"
"pushq %%r11 \n"
"pushq %%r12 \n"
"pushq %%r13 \n"
"pushq %%r14 \n"
"pushq %%r15 \n"
"movq %%rsp, %[from_rsp] \n"
"movabs $1f, %%rbx \n"
"movq %%rbx, %[from_rip] \n"
"movq %[to_rsp0], %%rbx \n"
"movl %%ebx, %[tss_rsp0l] \n"
"shrq $32, %%rbx \n"
"movl %%ebx, %[tss_rsp0h] \n"
"movq %[to_rsp], %%rsp \n"
"pushq %[to_thread] \n"
"pushq %[from_thread] \n"
"pushq %[to_rip] \n"
"cld \n"
"movq 16(%%rsp), %%rsi \n"
"movq 8(%%rsp), %%rdi \n"
"jmp enter_thread_context \n"
"1: \n"
"popq %%rdx \n"
"popq %%rax \n"
"popq %%r15 \n"
"popq %%r14 \n"
"popq %%r13 \n"
"popq %%r12 \n"
"popq %%r11 \n"
"popq %%r10 \n"
"popq %%r9 \n"
"popq %%r8 \n"
"popq %%rdi \n"
"popq %%rsi \n"
"popq %%rbp \n"
"popq %%rcx \n"
"popq %%rbx \n"
"popfq \n"
: [from_rsp] "=m" (from_thread->regs().rsp),
[from_rip] "=m" (from_thread->regs().rip),
[tss_rsp0l] "=m" (m_tss.rsp0l),
[tss_rsp0h] "=m" (m_tss.rsp0h),
"=d" (from_thread), // needed so that from_thread retains the correct value
"=a" (to_thread) // needed so that to_thread retains the correct value
: [to_rsp] "g" (to_thread->regs().rsp),
[to_rsp0] "g" (to_thread->regs().rsp0),
[to_rip] "c" (to_thread->regs().rip),
[from_thread] "d" (from_thread),
[to_thread] "a" (to_thread)
: "memory", "rbx"
);
// clang-format on
dbgln_if(CONTEXT_SWITCH_DEBUG, "switch_context <-- from {} {} to {} {}", VirtualAddress(from_thread), *from_thread, VirtualAddress(to_thread), *to_thread);