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-rw-r--r--kernel/include/paging.h2
-rw-r--r--kernel/include/region.h8
-rw-r--r--kernel/l0/kmain.c2
-rw-r--r--kernel/l0/region.c81
4 files changed, 80 insertions, 13 deletions
diff --git a/kernel/include/paging.h b/kernel/include/paging.h
index 5766e65..7082e2e 100644
--- a/kernel/include/paging.h
+++ b/kernel/include/paging.h
@@ -13,6 +13,8 @@ pagedir_t *get_kernel_pagedir();
void switch_pagedir(pagedir_t *pd);
+// The three functions below DO NOT DEPEND on argument pd for
+// addresses above K_HIGHHALF_ADDR, so just pass 0 to map/unmap in kernel space.
uint32_t pd_get_frame(pagedir_t *pd, size_t vaddr); // get physical frame for virtual address
int pd_map_page(pagedir_t *pd,
size_t vaddr, uint32_t frame_id,
diff --git a/kernel/include/region.h b/kernel/include/region.h
index 701e2d9..3c64081 100644
--- a/kernel/include/region.h
+++ b/kernel/include/region.h
@@ -8,8 +8,7 @@
// Region types
#define REGION_T_KERNEL_BASE 0x00000001 // base kernel code & data
#define REGION_T_DESCRIPTORS 0x00000002 // contains more region descriptors
-#define REGION_T_PAGEDIR 0x00000010 // used to map a page directory
-#define REGION_T_PAGETABLE 0x00000020 // used to map a page table
+#define REGION_T_PAGETABLE 0x00000010 // used to map a page table/page directory
#define REGION_T_CORE_HEAP 0x00000100 // used for the core kernel heap
#define REGION_T_PROC_HEAP 0x00000200 // used for a kernel process' heap
#define REGION_T_CACHE 0x00001000 // used for cache
@@ -30,4 +29,9 @@ size_t region_alloc(size_t size, uint32_t type, page_fault_handler_t pf); // ret
region_info_t *find_region(size_t addr);
void region_free(size_t addr);
+#define N_PAGES_IN_PT_REGION 4
+// special call for use by paging code
+// allocates a region of N_PAGES_IN_PT_REGION pages
+size_t region_alloc_for_pt();
+
void dbg_print_region_stats();
diff --git a/kernel/l0/kmain.c b/kernel/l0/kmain.c
index cd84cf7..f07e243 100644
--- a/kernel/l0/kmain.c
+++ b/kernel/l0/kmain.c
@@ -26,7 +26,7 @@ void kmain(struct multiboot_info_t *mbd, int32_t mb_magic) {
idt_init(); dbg_printf("IDT set up.\n");
idt_set_ex_handler(EX_BREAKPOINT, breakpoint_handler);
- asm volatile("int $0x3"); // test breakpoint
+ // asm volatile("int $0x3"); // test breakpoint
size_t total_ram = ((mbd->mem_upper + mbd->mem_lower) * 1024);
dbg_printf("Total ram: %d Kb\n", total_ram / 1024);
diff --git a/kernel/l0/region.c b/kernel/l0/region.c
index 421a018..63e464d 100644
--- a/kernel/l0/region.c
+++ b/kernel/l0/region.c
@@ -1,5 +1,6 @@
#include <region.h>
#include <dbglog.h>
+#include <frame.h>
typedef union region_descriptor {
struct {
@@ -16,10 +17,13 @@ typedef union region_descriptor {
} used;
} descriptor_t;
+#define N_RESERVE_DESCRIPTORS 3 // always keep at least 3 unused descriptors
+
#define N_BASE_DESCRIPTORS 12 // pre-allocate memory for 12 descriptors
static descriptor_t base_descriptors[N_BASE_DESCRIPTORS];
static descriptor_t *first_unused_descriptor;
+uint32_t n_unused_descriptors;
static descriptor_t *first_free_region_by_addr, *first_free_region_by_size;
static descriptor_t *first_used_region;
@@ -28,13 +32,17 @@ static descriptor_t *first_used_region;
// ========================================================= //
static void add_unused_descriptor(descriptor_t *d) {
+ n_unused_descriptors++;
d->unused_descriptor.next = first_unused_descriptor;
first_unused_descriptor = d;
}
static descriptor_t *get_unused_descriptor() {
descriptor_t *r = first_unused_descriptor;
- if (r != 0) first_unused_descriptor = r->unused_descriptor.next;
+ if (r != 0) {
+ first_unused_descriptor = r->unused_descriptor.next;
+ n_unused_descriptors--;
+ }
return r;
}
@@ -207,24 +215,33 @@ void region_allocator_init(void* kernel_data_end) {
f0->free.first_bigger = 0;
first_free_region_by_size = first_free_region_by_addr = f0;
+ n_unused_descriptors = 0;
first_unused_descriptor = 0;
for (int i = 2; i < N_BASE_DESCRIPTORS; i++) {
add_unused_descriptor(&base_descriptors[i]);
}
}
-size_t region_alloc(size_t size, uint32_t type, page_fault_handler_t pf) {
+static size_t region_alloc_inner(size_t size, uint32_t type, page_fault_handler_t pf, bool use_reserve) {
size = PAGE_ALIGN_UP(size);
for (descriptor_t *i = first_free_region_by_size; i != 0; i = i->free.first_bigger) {
if (i->free.size >= size) {
- remove_free_region(i);
+ // region i is the one we want to allocate in
+ descriptor_t *x = 0;
if (i->free.size > size) {
- descriptor_t *x = get_unused_descriptor();
- if (x == 0) {
+ if (n_unused_descriptors <= N_RESERVE_DESCRIPTORS && !use_reserve) {
return 0;
- // TODO: allocate more descriptors
}
+
+ // this assert is a bit tricky to prove,
+ // but basically it means that the allocation function
+ // is called less than N_RESERVE_DESCRIPTORS times with
+ // the use_reserve flag before more descriptors
+ // are allocated.
+ x = get_unused_descriptor();
+ ASSERT(x != 0);
+
x->free.size = i->free.size - size;
if (size >= 0x4000) {
x->free.addr = i->free.addr + size;
@@ -232,18 +249,63 @@ size_t region_alloc(size_t size, uint32_t type, page_fault_handler_t pf) {
x->free.addr = i->free.addr;
i->free.addr += x->free.size;
}
- add_free_region(x);
}
+ // do the allocation
+ remove_free_region(i);
+ if (x != 0) add_free_region(x);
+
size_t addr = i->free.addr;
i->used.i.addr = addr;
i->used.i.size = size;
i->used.i.type = type;
i->used.i.pf = pf;
add_used_region(i);
+
return addr;
}
}
- return 0; //Not found
+ return 0; //No big enough block found
+}
+
+bool region_alloc_for_pt_use_reserve = false;
+size_t region_alloc_for_pt() {
+ if (region_alloc_for_pt_use_reserve) {
+ return region_alloc_inner(
+ N_PAGES_IN_PT_REGION * PAGE_SIZE,
+ REGION_T_PAGETABLE,
+ 0, true);
+ } else {
+ return region_alloc(
+ N_PAGES_IN_PT_REGION * PAGE_SIZE,
+ REGION_T_PAGETABLE, 0);
+ }
+}
+
+size_t region_alloc(size_t size, uint32_t type, page_fault_handler_t pf) {
+ if (n_unused_descriptors <= N_RESERVE_DESCRIPTORS) {
+ uint32_t frame = frame_alloc(1);
+ if (frame == 0) return 0;
+
+ size_t descriptor_region = region_alloc_inner(PAGE_SIZE, REGION_T_DESCRIPTORS, 0, true);
+ ASSERT(descriptor_region != 0);
+
+ region_alloc_for_pt_use_reserve = true;
+ int error = pd_map_page(0, descriptor_region, frame, 1);
+ region_alloc_for_pt_use_reserve = false;
+ if (error) {
+ // this can happen if we weren't able to allocate a frame for
+ // a new pagetable
+ frame_free(frame, 1);
+ return 0;
+ }
+
+ for (descriptor_t *d = (descriptor_t*)descriptor_region;
+ (size_t)(d+1) <= (descriptor_region + PAGE_SIZE);
+ d++) {
+ add_unused_descriptor(d);
+ }
+ }
+ return region_alloc_inner(size, type, pf, false);
}
region_info_t *find_region(size_t addr) {
@@ -280,8 +342,7 @@ void dbg_print_region_stats() {
dbg_printf("| 0x%p - 0x%p", d->used.i.addr, d->used.i.addr + d->used.i.size);
if (d->used.i.type & REGION_T_KERNEL_BASE) dbg_printf(" Kernel code & base data");
if (d->used.i.type & REGION_T_DESCRIPTORS) dbg_printf(" Region descriptors");
- if (d->used.i.type & REGION_T_PAGEDIR) dbg_printf(" Mapped page directory");
- if (d->used.i.type & REGION_T_PAGETABLE) dbg_printf(" Mapped page table");
+ if (d->used.i.type & REGION_T_PAGETABLE) dbg_printf(" Mapped PD/PT");
if (d->used.i.type & REGION_T_CORE_HEAP) dbg_printf(" Core heap");
if (d->used.i.type & REGION_T_PROC_HEAP) dbg_printf(" Kernel process heap");
if (d->used.i.type & REGION_T_CACHE) dbg_printf(" Cache");
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-21 13:33:01 +0000