1
0
Fork 0
mirror of https://gitlab.com/sortix/sortix.git synced 2023-02-13 20:55:38 -05:00
sortix--sortix/kernel/x86-family/memorymanagement.cpp

844 lines
21 KiB
C++
Raw Normal View History

/*
* Copyright (c) 2011, 2012, 2014, 2015 Jonas 'Sortie' Termansen.
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*
* x86-family/memorymanagement.cpp
* Handles memory for the x86 family of architectures.
*/
#include <assert.h>
2012-09-22 10:44:50 -04:00
#include <errno.h>
#include <string.h>
2013-01-08 18:41:35 -05:00
2013-10-26 20:42:10 -04:00
#include <sortix/mman.h>
#include <sortix/kernel/kernel.h>
#include <sortix/kernel/kthread.h>
#include <sortix/kernel/memorymanagement.h>
#include <sortix/kernel/panic.h>
#include <sortix/kernel/pat.h>
2013-10-26 20:42:10 -04:00
#include <sortix/kernel/syscall.h>
#include "multiboot.h"
#include "memorymanagement.h"
#include "msr.h"
namespace Sortix {
extern size_t end;
} // namespace Sortix
namespace Sortix {
namespace Page {
void InitPushRegion(addr_t position, size_t length);
2015-03-16 12:24:42 -04:00
size_t pagesnotonstack = 0;
size_t stackused = 0;
size_t stackreserved = 0;
size_t stacklength = 4096 / sizeof(addr_t);
size_t totalmem = 0;
size_t page_usage_counts[PAGE_USAGE_NUM_KINDS];
2015-03-16 12:24:42 -04:00
kthread_mutex_t pagelock = KTHREAD_MUTEX_INITIALIZER;
} // namespace Page
} // namespace Sortix
namespace Sortix {
namespace Memory {
addr_t PAT2PMLFlags[PAT_NUM];
static bool CheckUsedRange(addr_t test,
addr_t from_unaligned,
size_t size_unaligned,
size_t* dist_ptr)
{
addr_t from = Page::AlignDown(from_unaligned);
size_unaligned += from_unaligned - from;
size_t size = Page::AlignUp(size_unaligned);
if ( from <= test && test < from + size )
return *dist_ptr = from + size - test, true;
if ( test < from && from - test < *dist_ptr )
*dist_ptr = from - test;
return false;
}
static bool CheckUsedString(addr_t test,
const char* string,
size_t* dist_ptr)
{
size_t size = strlen(string) + 1;
return CheckUsedRange(test, (addr_t) string, size, dist_ptr);
}
static bool CheckUsedRanges(multiboot_info_t* bootinfo,
addr_t test,
size_t* dist_ptr)
{
addr_t kernel_end = (addr_t) &end;
if ( CheckUsedRange(test, 0, kernel_end, dist_ptr) )
return true;
if ( CheckUsedRange(test, (addr_t) bootinfo, sizeof(*bootinfo), dist_ptr) )
return true;
const char* cmdline = (const char*) (uintptr_t) bootinfo->cmdline;
if ( CheckUsedString(test, cmdline, dist_ptr) )
return true;
size_t mods_size = bootinfo->mods_count * sizeof(struct multiboot_mod_list);
if ( CheckUsedRange(test, bootinfo->mods_addr, mods_size, dist_ptr) )
return true;
struct multiboot_mod_list* modules =
(struct multiboot_mod_list*) (uintptr_t) bootinfo->mods_addr;
for ( uint32_t i = 0; i < bootinfo->mods_count; i++ )
{
struct multiboot_mod_list* module = &modules[i];
assert(module->mod_start <= module->mod_end);
size_t mod_size = module->mod_end - module->mod_start;
if ( CheckUsedRange(test, module->mod_start, mod_size, dist_ptr) )
return true;
const char* mod_cmdline = (const char*) (uintptr_t) module->cmdline;
if ( CheckUsedString(test, mod_cmdline, dist_ptr) )
return true;
}
if ( CheckUsedRange(test, bootinfo->mmap_addr, bootinfo->mmap_length,
dist_ptr) )
return true;
return false;
}
void Init(multiboot_info_t* bootinfo)
{
2015-03-16 12:24:42 -04:00
if ( !(bootinfo->flags & MULTIBOOT_INFO_MEM_MAP) )
Panic("The memory map flag was't set in the multiboot structure.");
// If supported, setup the Page Attribute Table feature that allows
// us to control the memory type (caching) of memory more precisely.
if ( IsPATSupported() )
{
InitializePAT();
for ( addr_t i = 0; i < PAT_NUM; i++ )
PAT2PMLFlags[i] = EncodePATAsPMLFlag(i);
}
2015-03-16 12:24:42 -04:00
// Otherwise, reroute all requests to the backwards compatible scheme.
// TODO: Not all early 32-bit x86 CPUs supports these values.
else
{
PAT2PMLFlags[PAT_UC] = PML_WRTHROUGH | PML_NOCACHE;
PAT2PMLFlags[PAT_WC] = PML_WRTHROUGH | PML_NOCACHE; // Approx.
PAT2PMLFlags[2] = 0; // No such flag.
PAT2PMLFlags[3] = 0; // No such flag.
PAT2PMLFlags[PAT_WT] = PML_WRTHROUGH;
PAT2PMLFlags[PAT_WP] = PML_WRTHROUGH; // Approx.
PAT2PMLFlags[PAT_WB] = 0;
PAT2PMLFlags[PAT_UCM] = PML_NOCACHE;
}
typedef const multiboot_memory_map_t* mmap_t;
// Loop over every detected memory region.
for ( mmap_t mmap = (mmap_t) (addr_t) bootinfo->mmap_addr;
(addr_t) mmap < bootinfo->mmap_addr + bootinfo->mmap_length;
mmap = (mmap_t) ((addr_t) mmap + mmap->size + sizeof(mmap->size)) )
{
// Check that we can use this kind of RAM.
if ( mmap->type != 1 )
continue;
// Truncate the memory area if needed.
uint64_t mmap_addr = mmap->addr;
uint64_t mmap_len = mmap->len;
#if defined(__i386__)
if ( 0xFFFFFFFFULL < mmap_addr )
continue;
if ( 0xFFFFFFFFULL < mmap_addr + mmap_len )
mmap_len = 0x100000000ULL - mmap_addr;
#endif
// Properly page align the entry if needed.
// TODO: Is the bootloader required to page align this? This could be
// raw BIOS data that might not be page aligned? But that would
// be a silly computer.
addr_t base_unaligned = (addr_t) mmap_addr;
addr_t base = Page::AlignUp(base_unaligned);
if ( mmap_len < base - base_unaligned )
continue;
size_t length_unaligned = mmap_len - (base - base_unaligned);
size_t length = Page::AlignDown(length_unaligned);
if ( !length )
continue;
// Count the amount of usable RAM.
Page::totalmem += length;
// Give all the physical memory to the physical memory allocator
// but make sure not to give it things we already use.
addr_t processed = base;
while ( processed < base + length )
{
size_t distance = base + length - processed;
if ( !CheckUsedRanges(bootinfo, processed, &distance) )
Page::InitPushRegion(processed, distance);
processed += distance;
}
}
// Prepare the non-forkable kernel PMLs such that forking the kernel address
// space will always keep the kernel mapped.
for ( size_t i = ENTRIES / 2; i < ENTRIES; i++ )
{
PML* const pml = PMLS[TOPPMLLEVEL];
if ( pml->entry[i] & PML_PRESENT )
continue;
addr_t page = Page::Get(PAGE_USAGE_PAGING_OVERHEAD);
if ( !page )
Panic("Out of memory allocating boot PMLs.");
pml->entry[i] = page | PML_WRITABLE | PML_PRESENT;
// Invalidate the new PML and reset it to zeroes.
addr_t pmladdr = (addr_t) (PMLS[TOPPMLLEVEL-1] + i);
InvalidatePage(pmladdr);
memset((void*) pmladdr, 0, sizeof(PML));
}
}
void Statistics(size_t* amountused, size_t* totalmem)
{
size_t memfree = (Page::stackused - Page::stackreserved) << 12UL;
size_t memused = Page::totalmem - memfree;
if ( amountused )
*amountused = memused;
if ( totalmem )
*totalmem = Page::totalmem;
}
} // namespace Memory
} // namespace Sortix
namespace Sortix {
namespace Page {
void PageUsageRegisterUse(addr_t where, enum page_usage usage)
{
if ( PAGE_USAGE_NUM_KINDS <= usage )
return;
(void) where;
page_usage_counts[usage]++;
}
void PageUsageRegisterFree(addr_t where, enum page_usage usage)
{
if ( PAGE_USAGE_NUM_KINDS <= usage )
return;
(void) where;
assert(page_usage_counts[usage] != 0);
page_usage_counts[usage]--;
}
void ExtendStack()
{
// This call will always succeed, if it didn't, then the stack
// wouldn't be full, and thus this function won't be called.
addr_t page = GetUnlocked(PAGE_USAGE_PHYSICAL);
// This call will also succeed, since there are plenty of physical
// pages available and it might need some.
addr_t virt = (addr_t) (STACK + stacklength);
if ( !Memory::Map(page, virt, PROT_KREAD | PROT_KWRITE) )
Panic("Unable to extend page stack, which should have worked");
// TODO: This may not be needed during the boot process!
//Memory::InvalidatePage((addr_t) (STACK + stacklength));
stacklength += 4096UL / sizeof(addr_t);
}
void InitPushRegion(addr_t position, size_t length)
{
// Align our entries on page boundaries.
addr_t newposition = Page::AlignUp(position);
length = Page::AlignDown((position + length) - newposition);
position = newposition;
while ( length )
{
if ( unlikely(stackused == stacklength) )
{
if ( stackused == MAXSTACKLENGTH )
{
pagesnotonstack += length / 4096UL;
return;
}
ExtendStack();
}
addr_t* stackentry = &(STACK[stackused++]);
*stackentry = position;
length -= 4096UL;
position += 4096UL;
}
}
bool ReserveUnlocked(size_t* counter, size_t least, size_t ideal)
{
assert(least < ideal);
size_t available = stackused - stackreserved;
if ( least < available )
return errno = ENOMEM, false;
if ( available < ideal )
ideal = available;
stackreserved += ideal;
*counter += ideal;
return true;
}
bool Reserve(size_t* counter, size_t least, size_t ideal)
{
ScopedLock lock(&pagelock);
return ReserveUnlocked(counter, least, ideal);
}
bool ReserveUnlocked(size_t* counter, size_t amount)
{
return ReserveUnlocked(counter, amount, amount);
}
bool Reserve(size_t* counter, size_t amount)
{
ScopedLock lock(&pagelock);
return ReserveUnlocked(counter, amount);
}
addr_t GetReservedUnlocked(size_t* counter, enum page_usage usage)
{
if ( !*counter )
return 0;
assert(stackused); // After all, we did _reserve_ the memory.
addr_t result = STACK[--stackused];
assert(result == AlignDown(result));
stackreserved--;
(*counter)--;
PageUsageRegisterUse(result, usage);
return result;
}
addr_t GetReserved(size_t* counter, enum page_usage usage)
{
ScopedLock lock(&pagelock);
return GetReservedUnlocked(counter, usage);
}
addr_t GetUnlocked(enum page_usage usage)
{
assert(stackreserved <= stackused);
if ( unlikely(stackreserved == stackused) )
return errno = ENOMEM, 0;
addr_t result = STACK[--stackused];
assert(result == AlignDown(result));
PageUsageRegisterUse(result, usage);
return result;
}
addr_t Get(enum page_usage usage)
{
ScopedLock lock(&pagelock);
return GetUnlocked(usage);
}
2015-01-17 16:17:51 -05:00
// TODO: This competes with the normal allocation for precious 32-bit pages, we
// should use different pools for this, and preferably preallocate some
// 32-bit pages exclusively for driver usage. Also, get proper hardware
// without these issues.
addr_t Get32BitUnlocked(enum page_usage usage)
{
assert(stackreserved <= stackused);
if ( unlikely(stackreserved == stackused) )
return errno = ENOMEM, 0;
for ( size_t ii = stackused; 0 < ii; ii-- )
{
size_t i = ii - 1;
addr_t result = STACK[i];
assert(result == AlignDown(result));
if ( 4 < sizeof(void*) && UINT32_MAX < result )
continue;
if ( i + 1 != stackused )
{
STACK[i] = STACK[stackused - 1];
STACK[stackused - 1] = result;
}
stackused--;
PageUsageRegisterUse(result, usage);
return result;
}
return errno = ENOMEM, 0;
}
addr_t Get32Bit(enum page_usage usage)
{
ScopedLock lock(&pagelock);
return Get32BitUnlocked(usage);
}
void PutUnlocked(addr_t page, enum page_usage usage)
{
assert(page == AlignDown(page));
if ( unlikely(stackused == stacklength) )
{
if ( stackused == MAXSTACKLENGTH )
{
pagesnotonstack++;
return;
}
ExtendStack();
}
STACK[stackused++] = page;
PageUsageRegisterFree(page, usage);
}
void Put(addr_t page, enum page_usage usage)
{
ScopedLock lock(&pagelock);
PutUnlocked(page, usage);
}
void Lock()
{
kthread_mutex_lock(&pagelock);
}
void Unlock()
{
kthread_mutex_unlock(&pagelock);
}
} // namespace Page
} // namespace Sortix
namespace Sortix {
namespace Memory {
addr_t ProtectionToPMLFlags(int prot)
{
addr_t result = PML_NX;
if ( prot & PROT_EXEC )
{
result |= PML_USERSPACE;
result &= ~PML_NX;
}
if ( prot & PROT_READ )
result |= PML_USERSPACE;
if ( prot & PROT_WRITE )
result |= PML_USERSPACE | PML_WRITABLE;
if ( prot & PROT_KEXEC )
result &= ~PML_NX;
if ( prot & PROT_KREAD )
result |= 0;
if ( prot & PROT_KWRITE )
result |= PML_WRITABLE;
if ( prot & PROT_FORK )
result |= PML_FORK;
return result;
}
int PMLFlagsToProtection(addr_t flags)
{
int prot = PROT_KREAD;
if ( (flags & PML_USERSPACE) && !(flags & PML_NX) )
prot |= PROT_EXEC;
if ( (flags & PML_USERSPACE) )
prot |= PROT_READ;
if ( (flags & PML_USERSPACE) && (flags & PML_WRITABLE) )
prot |= PROT_WRITE;
if ( !(flags & PML_NX) )
prot |= PROT_KEXEC;
if ( flags & PML_WRITABLE )
prot |= PROT_KWRITE;
2014-11-04 21:53:32 -05:00
if ( flags & PML_FORK )
prot |= PROT_FORK;
return prot;
}
int ProvidedProtection(int prot)
{
2014-11-04 21:53:32 -05:00
return PMLFlagsToProtection(ProtectionToPMLFlags(prot));
}
bool LookUp(addr_t mapto, addr_t* physical, int* protection)
{
// Translate the virtual address into PML indexes.
const size_t MASK = (1<<TRANSBITS)-1;
size_t pmlchildid[TOPPMLLEVEL + 1];
for ( size_t i = 1; i <= TOPPMLLEVEL; i++ )
pmlchildid[i] = mapto >> (12 + (i-1) * TRANSBITS) & MASK;
int prot = PROT_USER | PROT_KERNEL | PROT_FORK;
// For each PML level, make sure it exists.
size_t offset = 0;
for ( size_t i = TOPPMLLEVEL; i > 1; i-- )
{
size_t childid = pmlchildid[i];
PML* pml = PMLS[i] + offset;
addr_t entry = pml->entry[childid];
if ( !(entry & PML_PRESENT) )
return false;
2014-11-04 21:53:32 -05:00
addr_t entryflags = entry & ~PML_ADDRESS;
int entryprot = PMLFlagsToProtection(entryflags);
prot &= entryprot;
// Find the index of the next PML in the fractal mapped memory.
offset = offset * ENTRIES + childid;
}
addr_t entry = (PMLS[1] + offset)->entry[pmlchildid[1]];
if ( !(entry & PML_PRESENT) )
return false;
2014-11-04 21:53:32 -05:00
addr_t entryflags = entry & ~PML_ADDRESS;
int entryprot = PMLFlagsToProtection(entryflags);
prot &= entryprot;
addr_t phys = entry & PML_ADDRESS;
if ( physical )
*physical = phys;
if ( protection )
*protection = prot;
return true;
}
void InvalidatePage(addr_t /*addr*/)
{
// TODO: Actually just call the instruction.
Flush();
}
addr_t GetAddressSpace()
{
addr_t result;
asm ( "mov %%cr3, %0" : "=r"(result) );
return result;
}
addr_t SwitchAddressSpace(addr_t addrspace)
{
assert(Page::IsAligned(addrspace));
addr_t previous = GetAddressSpace();
asm volatile ( "mov %0, %%cr3" : : "r"(addrspace) );
return previous;
}
void Flush()
{
addr_t previous;
asm ( "mov %%cr3, %0" : "=r"(previous) );
asm volatile ( "mov %0, %%cr3" : : "r"(previous) );
}
bool MapRange(addr_t where, size_t bytes, int protection, enum page_usage usage)
{
for ( addr_t page = where; page < where + bytes; page += 4096UL )
{
addr_t physicalpage = Page::Get(usage);
if ( physicalpage == 0 )
{
while ( where < page )
{
page -= 4096UL;
physicalpage = Unmap(page);
Page::Put(physicalpage, usage);
}
return false;
}
Map(physicalpage, page, protection);
}
return true;
}
bool UnmapRange(addr_t where, size_t bytes, enum page_usage usage)
{
for ( addr_t page = where; page < where + bytes; page += 4096UL )
{
addr_t physicalpage = Unmap(page);
Page::Put(physicalpage, usage);
}
return true;
}
static bool MapInternal(addr_t physical, addr_t mapto, int prot, addr_t extraflags = 0)
{
addr_t flags = ProtectionToPMLFlags(prot) | PML_PRESENT;
// Translate the virtual address into PML indexes.
const size_t MASK = (1<<TRANSBITS)-1;
size_t pmlchildid[TOPPMLLEVEL + 1];
for ( size_t i = 1; i <= TOPPMLLEVEL; i++ )
pmlchildid[i] = mapto >> (12 + (i-1) * TRANSBITS) & MASK;
// For each PML level, make sure it exists.
size_t offset = 0;
for ( size_t i = TOPPMLLEVEL; i > 1; i-- )
{
size_t childid = pmlchildid[i];
PML* pml = PMLS[i] + offset;
addr_t& entry = pml->entry[childid];
// Find the index of the next PML in the fractal mapped memory.
size_t childoffset = offset * ENTRIES + childid;
if ( !(entry & PML_PRESENT) )
{
// TODO: Possible memory leak when page allocation fails.
addr_t page = Page::Get(PAGE_USAGE_PAGING_OVERHEAD);
if ( !page )
return false;
addr_t pmlflags = PML_PRESENT | PML_WRITABLE | PML_USERSPACE
| PML_FORK;
entry = page | pmlflags;
// Invalidate the new PML and reset it to zeroes.
addr_t pmladdr = (addr_t) (PMLS[i-1] + childoffset);
InvalidatePage(pmladdr);
memset((void*) pmladdr, 0, sizeof(PML));
}
offset = childoffset;
}
// Actually map the physical page to the virtual page.
const addr_t entry = physical | flags | extraflags;
(PMLS[1] + offset)->entry[pmlchildid[1]] = entry;
return true;
}
bool Map(addr_t physical, addr_t mapto, int prot)
{
return MapInternal(physical, mapto, prot);
}
void PageProtect(addr_t mapto, int protection)
{
addr_t phys;
if ( !LookUp(mapto, &phys, NULL) )
return;
Map(phys, mapto, protection);
}
void PageProtectAdd(addr_t mapto, int protection)
{
addr_t phys;
int prot;
if ( !LookUp(mapto, &phys, &prot) )
return;
prot |= protection;
Map(phys, mapto, prot);
}
void PageProtectSub(addr_t mapto, int protection)
{
addr_t phys;
int prot;
if ( !LookUp(mapto, &phys, &prot) )
return;
prot &= ~protection;
Map(phys, mapto, prot);
}
addr_t Unmap(addr_t mapto)
{
// Translate the virtual address into PML indexes.
const size_t MASK = (1<<TRANSBITS)-1;
size_t pmlchildid[TOPPMLLEVEL + 1];
for ( size_t i = 1; i <= TOPPMLLEVEL; i++ )
{
pmlchildid[i] = mapto >> (12 + (i-1) * TRANSBITS) & MASK;
}
// For each PML level, make sure it exists.
size_t offset = 0;
for ( size_t i = TOPPMLLEVEL; i > 1; i-- )
{
size_t childid = pmlchildid[i];
PML* pml = PMLS[i] + offset;
addr_t& entry = pml->entry[childid];
if ( !(entry & PML_PRESENT) )
PanicF("Attempted to unmap virtual page 0x%jX, but the virtual"
" page was wasn't mapped. This is a bug in the code "
"code calling this function", (uintmax_t) mapto);
// Find the index of the next PML in the fractal mapped memory.
offset = offset * ENTRIES + childid;
}
addr_t& entry = (PMLS[1] + offset)->entry[pmlchildid[1]];
addr_t result = entry & PML_ADDRESS;
entry = 0;
// TODO: If all the entries in PML[N] are not-present, then who
// unmaps its entry from PML[N-1]?
return result;
}
bool MapPAT(addr_t physical, addr_t mapto, int prot, addr_t mtype)
{
addr_t extraflags = PAT2PMLFlags[mtype];
return MapInternal(physical, mapto, prot, extraflags);
}
void ForkCleanup(size_t i, size_t level)
{
PML* destpml = FORKPML + level;
if ( !i )
return;
for ( size_t n = 0; n < i-1; n++ )
{
addr_t entry = destpml->entry[i];
if ( !(entry & PML_FORK ) )
continue;
addr_t phys = entry & PML_ADDRESS;
if ( 1 < level )
{
addr_t destaddr = (addr_t) (FORKPML + level-1);
Map(phys, destaddr, PROT_KREAD | PROT_KWRITE);
InvalidatePage(destaddr);
ForkCleanup(ENTRIES+1UL, level-1);
}
enum page_usage usage = 1 < level ? PAGE_USAGE_PAGING_OVERHEAD
: PAGE_USAGE_USER_SPACE;
Page::Put(phys, usage);
}
}
// TODO: Copying every frame is endlessly useless in many uses. It'd be
// nice to upgrade this to a copy-on-write algorithm.
bool Fork(size_t level, size_t pmloffset)
{
PML* destpml = FORKPML + level;
for ( size_t i = 0; i < ENTRIES; i++ )
{
addr_t entry = (PMLS[level] + pmloffset)->entry[i];
// Link the entry if it isn't supposed to be forked.
if ( !(entry & PML_PRESENT) || !(entry & PML_FORK ) )
{
destpml->entry[i] = entry;
continue;
}
enum page_usage usage = 1 < level ? PAGE_USAGE_PAGING_OVERHEAD
: PAGE_USAGE_USER_SPACE;
addr_t phys = Page::Get(usage);
if ( unlikely(!phys) )
{
ForkCleanup(i, level);
return false;
}
addr_t flags = entry & PML_FLAGS;
destpml->entry[i] = phys | flags;
// Map the destination page.
addr_t destaddr = (addr_t) (FORKPML + level-1);
Map(phys, destaddr, PROT_KREAD | PROT_KWRITE);
InvalidatePage(destaddr);
size_t offset = pmloffset * ENTRIES + i;
if ( 1 < level )
{
if ( !Fork(level-1, offset) )
{
Page::Put(phys, usage);
ForkCleanup(i, level);
return false;
}
continue;
}
// Determine the source page's address.
const void* src = (const void*) (offset * 4096UL);
// Determine the destination page's address.
void* dest = (void*) (FORKPML + level - 1);
memcpy(dest, src, 4096UL);
}
return true;
}
bool Fork(addr_t dir, size_t level, size_t pmloffset)
{
PML* destpml = FORKPML + level;
// This call always succeeds.
Map(dir, (addr_t) destpml, PROT_KREAD | PROT_KWRITE);
InvalidatePage((addr_t) destpml);
return Fork(level, pmloffset);
}
// Create an exact copy of the current address space.
addr_t Fork()
{
addr_t dir = Page::Get(PAGE_USAGE_PAGING_OVERHEAD);
if ( dir == 0 )
return 0;
if ( !Fork(dir, TOPPMLLEVEL, 0) )
{
Page::Put(dir, PAGE_USAGE_PAGING_OVERHEAD);
return 0;
}
// Now, the new top pml needs to have its fractal memory fixed.
const addr_t flags = PML_PRESENT | PML_WRITABLE;
addr_t mapto;
addr_t childaddr;
(FORKPML + TOPPMLLEVEL)->entry[ENTRIES-1] = dir | flags;
childaddr = (FORKPML + TOPPMLLEVEL)->entry[ENTRIES-2] & PML_ADDRESS;
for ( size_t i = TOPPMLLEVEL-1; i > 0; i-- )
{
mapto = (addr_t) (FORKPML + i);
Map(childaddr, mapto, PROT_KREAD | PROT_KWRITE);
InvalidatePage(mapto);
(FORKPML + i)->entry[ENTRIES-1] = dir | flags;
childaddr = (FORKPML + i)->entry[ENTRIES-2] & PML_ADDRESS;
}
return dir;
}
} // namespace Memory
} // namespace Sortix