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Fix race condition in page fault handler. 

We enabled interrupts before getting the value of cr2 in the handler.
If the handler was preempted, cr2 could have been overriden by a page
fault in a separate thread or process.
This commit is contained in:
Drew Galbraith 2023-06-07 22:24:50 -07:00
parent 3e1e37bf03
commit bd32e85164
2 changed files with 16 additions and 12 deletions
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13
zion/interrupt/interrupt.cpp
View File

@ -43,6 +43,7 @@ InterruptDescriptor CreateDescriptor(void isr(void)) {
} }
struct InterruptFrame { struct InterruptFrame {
uint64_t cr2;
uint64_t rax; uint64_t rax;
uint64_t rbx; uint64_t rbx;
uint64_t rcx; uint64_t rcx;
@ -90,14 +91,14 @@ extern "C" void interrupt_protection_fault(InterruptFrame* frame) {
extern "C" void isr_page_fault(); extern "C" void isr_page_fault();
extern "C" void interrupt_page_fault(InterruptFrame* frame) { extern "C" void interrupt_page_fault(InterruptFrame* frame) {
uint64_t cr2; uint64_t err = frame->error_code;
asm volatile("mov %%cr2, %0" : "=r"(cr2)); if ((err & 0x1) == 0) {
// Page not present error may be resolveable.
if (gScheduler->CurrentProcess().vmas()->HandlePageFault(cr2)) { if (gScheduler->CurrentProcess().vmas()->HandlePageFault(frame->cr2)) {
return; return;
} }
}
dbgln("Unhandled Page Fault:"); dbgln("Unhandled Page Fault:");
uint64_t err = frame->error_code;
if (err & 0x1) { if (err & 0x1) {
dbgln("Page Protection"); dbgln("Page Protection");
} else { } else {
@ -119,7 +120,7 @@ extern "C" void interrupt_page_fault(InterruptFrame* frame) {
} }
dbgln("rip: %m", frame->rip); dbgln("rip: %m", frame->rip);
dbgln("addr: %m", cr2); dbgln("addr: %m", frame->cr2);
panic("PF"); panic("PF");
} }

13
zion/interrupt/interrupt_enter.s
View File

@ -14,9 +14,12 @@
push %rcx # (Return Address) push %rcx # (Return Address)
push %rbx push %rbx
push %rax push %rax
mov %cr2, %rax
push %rax
.endm .endm
.macro interrupt_exit .macro interrupt_exit
add $8, %rsp
pop %rax pop %rax
pop %rbx pop %rbx
pop %rcx pop %rcx
@ -26,11 +29,11 @@
pop %r8 pop %r8
pop %r9 pop %r9
pop %r10 pop %r10
pop %r10 pop %r11
pop %r10 pop %r12
pop %r10 pop %r13
pop %r10 pop %r14
pop %r10 pop %r15
pop %rbp pop %rbp
add $8, %rsp # Remove error code. add $8, %rsp # Remove error code.