mirror of
https://github.com/Fennix-Project/Kernel.git
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100 lines
2.9 KiB
C++
100 lines
2.9 KiB
C++
/*
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This file is part of Fennix Kernel.
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Fennix Kernel is free software: you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation, either version 3 of
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the License, or (at your option) any later version.
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Fennix Kernel is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with Fennix Kernel. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include <syscalls.hpp>
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#include <cpu.hpp>
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#include "cpu/gdt.hpp"
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// https://supercip971.github.io/02-wingos-syscalls.html
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using namespace CPU::x64;
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// "core/SystemCalls.cpp"
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extern "C" uint64_t SystemCallsHandler(SyscallsFrame *regs);
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extern "C" void SystemCallHandlerStub();
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extern "C" __naked __used __no_stack_protector __aligned(16) void SystemCallHandlerStub()
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{
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asmv("swapgs\n"); /* Swap GS to get the gsTCB */
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asmv("mov %rsp, %gs:0x8\n"); /* We save the current rsp to gsTCB->TempStack */
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asmv("mov %gs:0x0, %rsp\n"); /* Get gsTCB->SystemCallStack and set it as rsp */
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asmv("push $0x1b\n"); /* Push user data segment for SyscallsFrame */
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asmv("push %gs:0x8\n"); /* Push gsTCB->TempStack (old rsp) for SyscallsFrame */
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asmv("push %r11\n"); /* Push the flags for SyscallsFrame */
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asmv("push $0x23\n"); /* Push user code segment for SyscallsFrame */
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asmv("push %rcx\n"); /* Push the return address for SyscallsFrame + sysretq (https://www.felixcloutier.com/x86/sysret) */
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/* Push registers */
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asmv("push %rax\n"
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"push %rbx\n"
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"push %rcx\n"
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"push %rdx\n"
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"push %rsi\n"
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"push %rdi\n"
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"push %rbp\n"
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"push %r8\n"
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"push %r9\n"
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"push %r10\n"
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"push %r11\n"
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"push %r12\n"
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"push %r13\n"
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"push %r14\n"
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"push %r15\n");
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/* Set the first argument to the SyscallsFrame pointer */
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asmv("mov %rsp, %rdi\n");
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asmv("mov $0, %rbp\n");
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asmv("call SystemCallsHandler\n");
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/* Pop registers except rax */
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asmv("pop %r15\n"
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"pop %r14\n"
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"pop %r13\n"
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"pop %r12\n"
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"pop %r11\n"
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"pop %r10\n"
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"pop %r9\n"
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"pop %r8\n"
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"pop %rbp\n"
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"pop %rdi\n"
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"pop %rsi\n"
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"pop %rdx\n"
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"pop %rcx\n"
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"pop %rbx\n");
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/* Restore rsp from gsTCB->TempStack */
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asmv("mov %gs:0x8, %rsp\n");
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#ifdef DEBUG
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/* Easier to debug stacks */
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asmv("movq $0, %gs:0x8\n");
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#endif
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asmv("swapgs\n"); /* Swap GS back to the user GS */
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asmv("sti\n"); /* Enable interrupts */
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asmv("sysretq\n"); /* Return to rcx address in user mode */
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}
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void InitializeSystemCalls()
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{
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wrmsr(MSR_EFER, rdmsr(MSR_EFER) | 1);
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wrmsr(MSR_STAR, ((uint64_t)(GDT_KERNEL_CODE) << 32) | ((uint64_t)(GDT_KERNEL_DATA | 3) << 48));
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wrmsr(MSR_LSTAR, (uint64_t)SystemCallHandlerStub);
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wrmsr(MSR_SYSCALL_MASK, (uint64_t)(1 << 9));
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}
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