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Implement COW pages! :^)

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sys$fork() now clones all writable regions with per-page COW bits.
The pages are then mapped read-only and we handle a PF by COWing the pages.

This is quite delightful. Obviously there's lots of work to do still,
and it needs better data structures, but the general concept works.
This commit is contained in:
Andreas Kling 2018-11-05 13:48:07 +01:00
parent e85c22fe58
commit 2d045d2a64
11 changed files with 271 additions and 97 deletions
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58
Kernel/i386.cpp
View file

@ -56,24 +56,12 @@ asm(
" iret\n"
);
extern volatile dword exception_state_dump;
extern volatile word exception_code;
asm(
".globl exception_state_dump\n"
"exception_state_dump:\n"
".long 0\n"
".globl exception_code\n"
"exception_code:\n"
".short 0\n"
);
#define EH_ENTRY(ec) \
extern "C" void exception_ ## ec ## _handler(); \
extern "C" void exception_ ## ec ## _handler(RegisterDumpWithExceptionCode&); \
extern "C" void exception_ ## ec ## _entry(); \
asm( \
".globl exception_" # ec "_entry\n" \
"exception_" # ec "_entry: \n" \
" pop exception_code\n" \
" pusha\n" \
" pushw %ds\n" \
" pushw %es\n" \
@ -88,7 +76,7 @@ asm( \
" popw %es\n" \
" popw %fs\n" \
" popw %gs\n" \
" mov %esp, exception_state_dump\n" \
" mov %esp, %eax\n" \
" call exception_" # ec "_handler\n" \
" popw %gs\n" \
" popw %gs\n" \
@ -96,11 +84,12 @@ asm( \
" popw %es\n" \
" popw %ds\n" \
" popa\n" \
" add $0x4, %esp\n" \
" iret\n" \
);
#define EH_ENTRY_NO_CODE(ec) \
extern "C" void exception_ ## ec ## _handler(); \
extern "C" void exception_ ## ec ## _handler(RegisterDump&); \
extern "C" void exception_ ## ec ## _entry(); \
asm( \
".globl exception_" # ec "_entry\n" \
@ -119,7 +108,7 @@ asm( \
" popw %es\n" \
" popw %fs\n" \
" popw %gs\n" \
" mov %esp, exception_state_dump\n" \
" mov %esp, %eax\n" \
" call exception_" # ec "_handler\n" \
" popw %gs\n" \
" popw %gs\n" \
@ -132,9 +121,8 @@ asm( \
// 6: Invalid Opcode
EH_ENTRY_NO_CODE(6);
void exception_6_handler()
void exception_6_handler(RegisterDump& regs)
{
auto& regs = *reinterpret_cast<RegisterDump*>(exception_state_dump);
kprintf("%s invalid opcode: %u(%s)\n", current->isRing0() ? "Kernel" : "Process", current->pid(), current->name().characters());
word ss;
@ -147,7 +135,6 @@ void exception_6_handler()
esp = regs.esp_if_crossRing;
}
kprintf("exception code: %w\n", exception_code);
kprintf("pc=%w:%x ds=%w es=%w fs=%w gs=%w\n", regs.cs, regs.eip, regs.ds, regs.es, regs.fs, regs.gs);
kprintf("eax=%x ebx=%x ecx=%x edx=%x\n", regs.eax, regs.ebx, regs.ecx, regs.edx);
kprintf("ebp=%x esp=%x esi=%x edi=%x\n", regs.ebp, esp, regs.esi, regs.edi);
@ -163,10 +150,9 @@ void exception_6_handler()
// 13: General Protection Fault
EH_ENTRY(13);
void exception_13_handler()
void exception_13_handler(RegisterDumpWithExceptionCode& regs)
{
auto& regs = *reinterpret_cast<RegisterDump*>(exception_state_dump);
kprintf("%s crash: %u(%s)\n", current->isRing0() ? "Kernel" : "Process", current->pid(), current->name().characters());
kprintf("%s GPF: %u(%s)\n", current->isRing0() ? "Kernel" : "User", current->pid(), current->name().characters());
word ss;
dword esp;
@ -178,7 +164,7 @@ void exception_13_handler()
esp = regs.esp_if_crossRing;
}
kprintf("exception code: %w\n", exception_code);
kprintf("exception code: %w\n", regs.exception_code);
kprintf("pc=%w:%x ds=%w es=%w fs=%w gs=%w\n", regs.cs, regs.eip, regs.ds, regs.es, regs.fs, regs.gs);
kprintf("eax=%x ebx=%x ecx=%x edx=%x\n", regs.eax, regs.ebx, regs.ecx, regs.edx);
kprintf("ebp=%x esp=%x esi=%x edi=%x\n", regs.ebp, esp, regs.esi, regs.edi);
@ -193,19 +179,18 @@ void exception_13_handler()
// 14: Page Fault
EH_ENTRY(14);
void exception_14_handler()
void exception_14_handler(RegisterDumpWithExceptionCode& regs)
{
ASSERT(current);
dword faultAddress;
asm ("movl %%cr2, %%eax":"=a"(faultAddress));
auto& regs = *reinterpret_cast<RegisterDump*>(exception_state_dump);
kprintf("Ring%u page fault in %s(%u), %s laddr=%p\n",
dbgprintf("Ring%u page fault in %s(%u), %s laddr=%p\n",
regs.cs & 3,
current->name().characters(),
current->pid(),
exception_code & 2 ? "write" : "read",
regs.exception_code & 2 ? "write" : "read",
faultAddress);
word ss;
@ -218,13 +203,15 @@ void exception_14_handler()
esp = regs.esp_if_crossRing;
}
kprintf("exception code: %w\n", exception_code);
kprintf("pc=%w:%x ds=%w es=%w fs=%w gs=%w\n", regs.cs, regs.eip, regs.ds, regs.es, regs.fs, regs.gs);
kprintf("eax=%x ebx=%x ecx=%x edx=%x\n", regs.eax, regs.ebx, regs.ecx, regs.edx);
kprintf("ebp=%x esp=%x esi=%x edi=%x\n", regs.ebp, esp, regs.esi, regs.edi);
#ifdef PAGE_FAULT_DEBUG
dbgprintf("exception code: %w\n", regs.exception_code);
dbgprintf("pc=%w:%x ds=%w es=%w fs=%w gs=%w\n", regs.cs, regs.eip, regs.ds, regs.es, regs.fs, regs.gs);
dbgprintf("stk=%w:%x\n", ss, esp);
dbgprintf("eax=%x ebx=%x ecx=%x edx=%x\n", regs.eax, regs.ebx, regs.ecx, regs.edx);
dbgprintf("ebp=%x esp=%x esi=%x edi=%x\n", regs.ebp, esp, regs.esi, regs.edi);
byte* codeptr = (byte*)regs.eip;
kprintf("code: %b %b %b %b %b %b %b %b\n",
dbgprintf("code: %b %b %b %b %b %b %b %b\n",
codeptr[0],
codeptr[1],
codeptr[2],
@ -234,17 +221,20 @@ void exception_14_handler()
codeptr[6],
codeptr[7]
);
#endif
if (current->isRing0())
HANG;
auto response = MM.handle_page_fault(PageFault(exception_code, LinearAddress(faultAddress)));
auto response = MM.handle_page_fault(PageFault(regs.exception_code, LinearAddress(faultAddress)));
if (response == PageFaultResponse::ShouldCrash) {
kprintf("Crashing after unresolved page fault\n");
Process::processDidCrash(current);
} else if (response == PageFaultResponse::Continue) {
kprintf("Continuing after resolved page fault\n");
#ifdef PAGE_FAULT_DEBUG
dbgprintf("Continuing after resolved page fault\n");
#endif
} else {
ASSERT_NOT_REACHED();
}