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vmm: copy on write and changes to how page faults are handled

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Matheus
2023-08-02 01:18:35 -03:00
parent 55fc1b7026
commit 7e1443d032
4 changed files with 57 additions and 10 deletions
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kernel-src/mm/pmm.c
+1 -1
View File
@@ -184,7 +184,7 @@ void pmm_init() {
pages = MAKE_HHDM((page_t *)biggest->base);
pagecount = ROUND_UP(top, PAGE_SIZE) / PAGE_SIZE;
memset(pages, 0, pagecount / sizeof(page_t));
memset(pages, 0, pagecount * sizeof(page_t));
printf("pmm: %d pages used for page list\n", ROUND_UP(pagecount * sizeof(page_t), PAGE_SIZE) / PAGE_SIZE);
// place pages in free lists
kernel-src/mm/vmm.c
+43 -9
View File
@@ -285,6 +285,8 @@ static void unmap(vmmspace_t *space, void *address, size_t size) {
}
static void *zeropage;
bool vmm_pagefault(void *addr, bool user, int actions) {
if (user == false && addr > USERSPACE_END)
return false;
@@ -320,20 +322,45 @@ bool vmm_pagefault(void *addr, bool user, int actions) {
if (invalidactions & actions)
goto cleanup;
// TODO CoW
thread_t *thread = _cpu()->thread;
proc_t *proc = thread ? thread->proc : NULL;
cred_t *cred = proc ? &proc->cred : NULL;
if (range->flags & VMM_FLAGS_FILE) {
uintmax_t mapoffset = (uintptr_t)addr - (uintptr_t)range->start;
__assert(VOP_MMAP(range->vnode, addr, range->offset + mapoffset, mmuflagstovnodeflags(range->mmuflags) | (range->flags & VMM_FLAGS_SHARED ? V_FFLAGS_SHARED : 0), cred) == 0);
status = true;
if (arch_mmu_ispresent(_cpu()->vmmctx->pagetable, addr) == false) {
// page not present in the page tables
if (range->flags & VMM_FLAGS_FILE) {
uintmax_t mapoffset = (uintptr_t)addr - (uintptr_t)range->start;
__assert(VOP_MMAP(range->vnode, addr, range->offset + mapoffset, mmuflagstovnodeflags(range->mmuflags) | (range->flags & VMM_FLAGS_SHARED ? V_FFLAGS_SHARED : 0), cred) == 0);
status = true;
} else {
// anonymous memory. map the zero'd page
status = arch_mmu_map(_cpu()->vmmctx->pagetable, zeropage, addr, range->mmuflags & ~ARCH_MMU_FLAGS_WRITE);
if (!status)
printf("vmm: out of memory to map zero page into address space\n");
else
pmm_hold(zeropage);
}
} else if (arch_mmu_iswritable(_cpu()->vmmctx->pagetable, addr) == false){
// page present but not writeable in the page tables
if ((range->flags & VMM_FLAGS_FILE) && (range->flags & VMM_FLAGS_SHARED)) {
// TODO shared file mappings (set as dirty and set as writable on PTE)
} else {
void *oldphys = arch_mmu_getphysical(_cpu()->vmmctx->pagetable, addr);
// do copy on write
void *newphys = pmm_allocpage(PMM_SECTION_DEFAULT);
if (newphys == NULL) {
printf("vmm: out of memory to do copy on write on address space\n");
status = false;
} else {
// this assert should always succeed, here just to make sure
memcpy(MAKE_HHDM(newphys), MAKE_HHDM(oldphys), PAGE_SIZE);
__assert(arch_mmu_map(_cpu()->vmmctx->pagetable, newphys, addr, range->mmuflags));
pmm_release(oldphys);
status = true;
}
}
} else {
void *paddr = pmm_allocpage(PMM_SECTION_DEFAULT);
__assert(paddr); // XXX handle these better than an assert once there are signals and such
__assert(arch_mmu_map(_cpu()->vmmctx->pagetable, paddr, addr, range->mmuflags));
memset(MAKE_HHDM(paddr), 0, PAGE_SIZE);
// another thread already did the work, so just return success
status = true;
}
@@ -576,6 +603,7 @@ extern void *_rodata_end;
extern volatile struct limine_memmap_request pmm_liminemap;
void vmm_init() {
// set up initial state
__assert(sizeof(vmmcache_t) <= PAGE_SIZE);
MUTEX_INIT(&kernelspace.lock);
MUTEX_INIT(&kernelspace.pflock);
@@ -589,12 +617,14 @@ void vmm_init() {
vmm_switchcontext(&vmm_kernelctx);
// map HHDM
for (uint64_t i = 0; i < pmm_liminemap.response->entry_count; ++i) {
struct limine_memmap_entry *e = pmm_liminemap.response->entries[i];
mmuflags_t mmuflags = ARCH_MMU_FLAGS_READ | ARCH_MMU_FLAGS_WRITE | ARCH_MMU_FLAGS_NOEXEC;
__assert(vmm_map(MAKE_HHDM(e->base), e->length, VMM_FLAGS_EXACT, mmuflags, NULL));
}
// map kernel
__assert(vmm_map(&_text_start, (uintptr_t)&_text_end - (uintptr_t)&_text_start, VMM_FLAGS_EXACT, ARCH_MMU_FLAGS_READ, NULL));
__assert(vmm_map(&_rodata_start, (uintptr_t)&_rodata_end - (uintptr_t)&_rodata_start, VMM_FLAGS_EXACT, ARCH_MMU_FLAGS_READ | ARCH_MMU_FLAGS_NOEXEC, NULL));
__assert(vmm_map(&_data_start, (uintptr_t)&_data_end - (uintptr_t)&_data_start, VMM_FLAGS_EXACT, ARCH_MMU_FLAGS_READ | ARCH_MMU_FLAGS_WRITE | ARCH_MMU_FLAGS_NOEXEC, NULL));
@@ -602,5 +632,9 @@ void vmm_init() {
// null page
vmm_map(MAKE_HHDM(NULL), PAGE_SIZE, VMM_FLAGS_EXACT, ARCH_MMU_FLAGS_NOEXEC, NULL);
// zero page
zeropage = pmm_allocpage(PMM_SECTION_DEFAULT);
memset(MAKE_HHDM(zeropage), 0, PAGE_SIZE);
printspace(&kernelspace);
}