[英]Java volatile memory ordering and its compilation on x86-64
[英]What causes x86-64 Page Fault with only the Write bit set when a hardware interrupt happens while CPL=3
我正在編寫我自己的kernel,使用Rust(Loosely基於Phil-Opp的博客, Z5E05E05E56C500A1C4B6AA.71B6AA )用戶模式應用程序代碼和數據,將裸function映射到虛擬地址0x40000000000,設置堆棧並跳轉到代碼。 我還有一個使用 syscall/sysret 工作的系統調用處理程序,它在遇到系統調用時簡單地打印一條消息。 我注意到,無論何時發生 PIC 定時器中斷,它總是在 CPL=0 時發生,因為系統調用處理程序的代碼比用戶模式應用程序長很多倍,用戶模式應用程序只是在無限循環中進行系統調用。 如果我禁用打印(需要大多數指令),在循環的幾百次迭代之后,當 CPL=3 時發生定時器中斷。 但是,CPU 沒有調用中斷處理程序,而是拋出一個錯誤代碼為 2 的頁面錯誤(僅對應於寫入位設置)。 在我看來,這沒有任何意義,問題可能是什么?
GDT:
static ref GDT: (gdt::GlobalDescriptorTable, Selectors) = {
let mut gdt = gdt::GlobalDescriptorTable::new();
let kernel_code_selector = gdt.add_entry(gdt::Descriptor::kernel_code_segment());
let kernel_data_selector = gdt.add_entry(gdt::Descriptor::kernel_data_segment());
let tss_selector = gdt.add_entry(gdt::Descriptor::tss_segment(&TSS));
let user_data_selector = gdt.add_entry(gdt::Descriptor::user_data_segment());
let user_code_selector = gdt.add_entry(gdt::Descriptor::user_code_segment());
(gdt, Selectors { kernel_code_selector, kernel_data_selector, tss_selector, user_code_selector, user_data_selector })
};
身份證:
const DOUBLE_FAULT_IST_INDEX: u16 = 0;
let mut IDT: idt::InterruptDescriptorTable = idt::InterruptDescriptorTable::new();
IDT.breakpoint.set_handler_fn(interrupts::breakpoint::breakpoint_handler);
IDT.double_fault.set_handler_fn(interrupts::double_fault::double_fault_handler).set_stack_index(DOUBLE_FAULT_IST_INDEX);
IDT.page_fault.set_handler_fn(interrupts::page_fault::page_fault_handler);
IDT.general_protection_fault.set_handler_fn(interrupts::general_protection_fault::general_protection_fault_handler);
IDT.stack_segment_fault.set_handler_fn(interrupts::stack_segment_fault::stack_segment_fault_handler);
IDT.segment_not_present.set_handler_fn(interrupts::segment_not_present::segment_not_present_handler);
IDT.invalid_tss.set_handler_fn(interrupts::invalid_tss::invalid_tss_handler);
IDT.debug.set_handler_fn(interrupts::debug::debug_handler);
IDT[interrupts::HardwareInterrupt::Timer.as_usize()].set_handler_fn(interrupts::timer::timer_handler);
IDT.load();
技術支持:
let mut tss = tss::TaskStateSegment::new();
tss.interrupt_stack_table[DOUBLE_FAULT_IST_INDEX as usize] = {
const STACK_SIZE: usize = 4096 * 5;
static mut STACK: [u8; STACK_SIZE] = [0; STACK_SIZE];
let stack_start = x86_64::VirtAddr::from_ptr(unsafe { &STACK });
let stack_end = stack_start + STACK_SIZE;
stack_end
};
定時器中斷處理程序:
pub extern "x86-interrupt" fn timer_handler(_stack_frame: idt::InterruptStackFrame) {
print!(".");
cpu::pic_end_of_interrupt(0x20);
}
用戶空間應用程序:
#[naked]
#[no_mangle]
#[allow(named_asm_labels)]
pub unsafe fn userspace_app_1() {
asm!("\
push 0
prog1start:
mov rax, 1234h
pop rdi
inc rdi
push rdi
mov rsi, 3
mov rdx, 4
mov r8, 5
syscall
jmp prog1start
", options(noreturn));
}
QEMU 中斷日志:
7: v=20 e=0000 i=0 cpl=3 IP=0033:0000040000000066 pc=0000040000000066 SP=002b:0000060000000ff8 env->regs[R_EAX]=00000000515ca11a
RAX=0000000000001234 RBX=0000000000006062 RCX=0000040000000066 RDX=0000000000000004
RSI=0000000000000003 RDI=00000000001e91c5 RBP=0000008040201000 RSP=0000060000000ff8
R8 =0000000000000005 R9 =0000060000000f78 R10=0000000000203080 R11=0000000000000206
R12=0000000100000000 R13=0000000000005fea R14=0000018000000000 R15=0000000000006692
RIP=0000040000000066 RFL=00000206 [-----P-] CPL=3 II=0 A20=1 SMM=0 HLT=0
ES =0000 0000000000000000 ffffffff 00cf1300
CS =0033 0000000000000000 ffffffff 00a0fb00 DPL=3 CS64 [-RA]
SS =002b 0000000000000000 ffffffff 00c0f300 DPL=3 DS [-WA]
DS =002b 0000000000000000 ffffffff 00cff300 DPL=3 DS [-WA]
FS =0000 0000000000000000 0000ffff 00009300 DPL=0 DS [-WA]
GS =0000 0000000000000000 0000ffff 00009300 DPL=0 DS [-WA]
LDT=0000 0000000000000000 0000ffff 00008200 DPL=0 LDT
TR =0018 0000000000276014 00000067 00008900 DPL=0 TSS64-avl
GDT= 0000000000276090 00000037
IDT= 000000000026dd80 00000fff
CR0=80010011 CR2=0000000000000000 CR3=00000000002b4018 CR4=00000020
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
CCS=0000000000000004 CCD=0000060000000fa8 CCO=EFLAGS
EFER=0000000000000d01
check_exception old: 0xffffffff new 0xe
8: v=0e e=0002 i=0 cpl=3 IP=0033:0000040000000066 pc=0000040000000066 SP=002b:0000060000000ff8 CR2=fffffffffffffff8
RAX=0000000000001234 RBX=0000000000006062 RCX=0000040000000066 RDX=0000000000000004
RSI=0000000000000003 RDI=00000000001e91c5 RBP=0000008040201000 RSP=0000060000000ff8
R8 =0000000000000005 R9 =0000060000000f78 R10=0000000000203080 R11=0000000000000206
R12=0000000100000000 R13=0000000000005fea R14=0000018000000000 R15=0000000000006692
RIP=0000040000000066 RFL=00000206 [-----P-] CPL=3 II=0 A20=1 SMM=0 HLT=0
ES =0000 0000000000000000 ffffffff 00cf1300
CS =0033 0000000000000000 ffffffff 00a0fb00 DPL=3 CS64 [-RA]
SS =002b 0000000000000000 ffffffff 00c0f300 DPL=3 DS [-WA]
DS =002b 0000000000000000 ffffffff 00cff300 DPL=3 DS [-WA]
FS =0000 0000000000000000 0000ffff 00009300 DPL=0 DS [-WA]
GS =0000 0000000000000000 0000ffff 00009300 DPL=0 DS [-WA]
LDT=0000 0000000000000000 0000ffff 00008200 DPL=0 LDT
TR =0018 0000000000276014 00000067 00008900 DPL=0 TSS64-avl
GDT= 0000000000276090 00000037
IDT= 000000000026dd80 00000fff
CR0=80010011 CR2=fffffffffffffff8 CR3=00000000002b4018 CR4=00000020
DR0=0000000000000000 DR1=0000000000000000 DR2=0000000000000000 DR3=0000000000000000
DR6=00000000ffff0ff0 DR7=0000000000000400
CCS=0000000000000004 CCD=0000060000000fa8 CCO=EFLAGS
EFER=0000000000000d01
我已經解決了這個問題,正如@sj95126 所建議的那樣,問題出在我的 TSS 上,它只為雙重故障處理程序設置了 IST 條目(回顧過去是有道理的,因為以前在用戶模式下發生的任何中斷或異常都會導致一個雙重錯誤。因為據我所知,CPU 不知道要激活哪個堆棧),我已經通過將 IST 位設置為每個中斷處理程序的 TSS 偏移來修復它。 現在我的代碼完美無缺。
身份證:
IDT.breakpoint.set_handler_fn(interrupts::breakpoint::breakpoint_handler).set_stack_index(INTERRUPT_IST_INDEX);
IDT.double_fault.set_handler_fn(interrupts::double_fault::double_fault_handler).set_stack_index(INTERRUPT_IST_INDEX);
IDT.page_fault.set_handler_fn(interrupts::page_fault::page_fault_handler).set_stack_index(INTERRUPT_IST_INDEX);
IDT.general_protection_fault.set_handler_fn(interrupts::general_protection_fault::general_protection_fault_handler).set_stack_index(INTERRUPT_IST_INDEX);
IDT.stack_segment_fault.set_handler_fn(interrupts::stack_segment_fault::stack_segment_fault_handler).set_stack_index(INTERRUPT_IST_INDEX);
IDT.segment_not_present.set_handler_fn(interrupts::segment_not_present::segment_not_present_handler).set_stack_index(INTERRUPT_IST_INDEX);
IDT.debug.set_handler_fn(interrupts::debug::debug_handler).set_stack_index(INTERRUPT_IST_INDEX);
IDT[interrupts::HardwareInterrupt::Timer.as_usize()].set_handler_fn(interrupts::timer::timer_handler).set_stack_index(INTERRUPT_IST_INDEX);
IDT.load();
我自己不得不艱難地學習這一點。 緊隨其后的是第二版和第三版的大雜燴,而不是第一版,但基本思想是相同的。
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