From 92f848244796881994c1f147633123c45da219b6 Mon Sep 17 00:00:00 2001
From: Anton Kling <anton@kling.gg>
Date: Sat, 13 Apr 2024 21:07:02 +0200
Subject: Kernel: Don't hard fail if the kernel can't allocate memory.
Currently this is just a improvement of error handling but it should
also try to free up memory where it is possible.
---
kernel/arch/i386/mmu.c | 72 ++++++++++++++++++++++++++++++++++--------------
kernel/elf.c | 9 +++---
kernel/fs/shm.c | 4 ++-
kernel/includes/mmu.h | 4 +--
kernel/process.s | 5 +++-
kernel/sched/scheduler.c | 19 +++++++++++--
6 files changed, 79 insertions(+), 34 deletions(-)
diff --git a/kernel/arch/i386/mmu.c b/kernel/arch/i386/mmu.c
index b9501ff..ce20208 100644
--- a/kernel/arch/i386/mmu.c
+++ b/kernel/arch/i386/mmu.c
@@ -26,7 +26,8 @@ u32 *tmp_small_frames = tmp_array;
extern uintptr_t data_end;
void change_frame(u32 frame, int on);
-u32 get_free_frame(void);
+int get_free_frame(u32 *frame);
+int allocate_frame(Page *page, int rw, int is_kernel);
void *ksbrk(size_t s) {
uintptr_t rc = (uintptr_t)align_page((void *)data_end);
@@ -55,9 +56,11 @@ void *ksbrk(size_t s) {
active_directory->physical_tables[table_index];
return ksbrk(s);
}
- mmu_allocate_shared_kernel_region((void *)rc, (data_end - (uintptr_t)rc));
+ if (!mmu_allocate_shared_kernel_region((void *)rc,
+ (data_end - (uintptr_t)rc))) {
+ return NULL;
+ }
assert(((uintptr_t)rc % PAGE_SIZE) == 0);
-
return (void *)rc;
}
@@ -118,7 +121,7 @@ void mmu_free_pages(void *a, u32 n) {
}
u32 start_frame_search = 1;
-u32 first_free_frame(void) {
+int get_free_frame(u32 *frame) {
u32 i = start_frame_search;
for (; i < INDEX_FROM_BIT(num_array_frames * 32); i++) {
if (tmp_small_frames[i] == 0xFFFFFFFF) {
@@ -128,11 +131,13 @@ u32 first_free_frame(void) {
for (u32 c = 0; c < 32; c++) {
if (!(tmp_small_frames[i] & ((u32)1 << c))) {
start_frame_search = i;
- return i * 32 + c;
+ *frame = i * 32 + c;
+ return 1;
}
}
}
- assert(0);
+ klog("MMU: Ran out of free frames. TODO: free up memory", LOG_WARN);
+ *frame = 0;
return 0;
}
@@ -166,7 +171,11 @@ PageTable *clone_table(u32 src_index, PageDirectory *src_directory,
new_table->pages[i].present = 0;
continue;
}
- u32 frame_address = first_free_frame();
+ u32 frame_address;
+ if (!get_free_frame(&frame_address)) {
+ kmalloc_align_free(new_table, sizeof(PageTable));
+ return NULL;
+ }
write_to_frame(frame_address * 0x1000, 1);
new_table->pages[i].frame = frame_address;
@@ -254,6 +263,10 @@ PageDirectory *clone_directory(PageDirectory *original) {
if (i >= 635 && i <= 641) {
u32 physical;
new_directory->tables[i] = clone_table(i, original, &physical);
+ if (!new_directory->tables[i]) {
+ mmu_free_pagedirectory(new_directory);
+ return NULL;
+ }
new_directory->physical_tables[i] =
physical | (original->physical_tables[i] & 0xFFF);
continue;
@@ -270,6 +283,10 @@ PageDirectory *clone_directory(PageDirectory *original) {
u32 physical;
new_directory->tables[i] = clone_table(i, original, &physical);
+ if (!new_directory->tables[i]) {
+ mmu_free_pagedirectory(new_directory);
+ return NULL;
+ }
new_directory->physical_tables[i] =
physical | (original->physical_tables[i] & 0xFFF);
}
@@ -277,14 +294,18 @@ PageDirectory *clone_directory(PageDirectory *original) {
return new_directory;
}
-void mmu_allocate_shared_kernel_region(void *rc, size_t n) {
+int mmu_allocate_shared_kernel_region(void *rc, size_t n) {
size_t num_pages = n / PAGE_SIZE;
for (size_t i = 0; i <= num_pages; i++) {
Page *p = get_page((void *)(rc + i * 0x1000), NULL, PAGE_ALLOCATE, 0);
if (!p->present || !p->frame) {
- allocate_frame(p, 0, 1);
+ if (!allocate_frame(p, 0, 1)) {
+ mmu_free_address_range(rc, n, NULL);
+ return 0;
+ }
}
}
+ return 1;
}
void mmu_remove_virtual_physical_address_mapping(void *ptr, size_t length) {
@@ -327,7 +348,7 @@ int mmu_allocate_region(void *ptr, size_t n, mmu_flags flags,
int rw = (flags & MMU_FLAG_RW);
int kernel = (flags & MMU_FLAG_KERNEL);
if (!allocate_frame(p, rw, kernel)) {
- klog("MMU: Frame allocation failed", LOG_WARN);
+ mmu_free_address_range(ptr, n, pd);
return 0;
}
}
@@ -370,22 +391,23 @@ void *mmu_map_frames(void *const ptr, size_t s) {
return r;
}
-void *allocate_frame(Page *page, int rw, int is_kernel) {
+int allocate_frame(Page *page, int rw, int is_kernel) {
if (page->present) {
- dump_backtrace(5);
klog("Page is already set", 1);
- for (;;)
- ;
+ assert(0);
+ return 0;
+ }
+ u32 frame_address;
+ if (!get_free_frame(&frame_address)) {
return 0;
}
- u32 frame_address = first_free_frame();
write_to_frame(frame_address * 0x1000, 1);
page->present = 1;
page->rw = rw;
page->user = !is_kernel;
page->frame = frame_address;
- return (void *)(frame_address * 0x1000);
+ return 1;
}
void mmu_free_pagedirectory(PageDirectory *pd) {
@@ -518,9 +540,11 @@ void *virtual_to_physical(void *address, PageDirectory *directory) {
}
extern u32 inital_esp;
-void move_stack(u32 new_stack_address, u32 size) {
- mmu_allocate_region((void *)(new_stack_address - size), size, MMU_FLAG_KERNEL,
- NULL);
+int move_stack(u32 new_stack_address, u32 size) {
+ if (!mmu_allocate_region((void *)(new_stack_address - size), size,
+ MMU_FLAG_KERNEL, NULL)) {
+ return 0;
+ }
u32 old_stack_pointer, old_base_pointer;
@@ -548,6 +572,7 @@ void move_stack(u32 new_stack_address, u32 size) {
// Actually change the stack
set_sp(new_stack_pointer + 8);
set_sbp(new_base_pointer);
+ return 1;
}
// C strings have a unknown length so it does not makes sense to check
@@ -675,10 +700,15 @@ void paging_init(u64 memsize, multiboot_info_t *mb) {
create_table(770 + i);
}
kernel_directory = clone_directory(kernel_directory);
+ assert(kernel_directory);
switch_page_directory(kernel_directory);
- switch_page_directory(clone_directory(kernel_directory));
- move_stack(0xA0000000, 0x80000);
+ {
+ PageDirectory *tmp = clone_directory(kernel_directory);
+ assert(tmp);
+ switch_page_directory(tmp);
+ }
+ assert(move_stack(0xA0000000, 0x80000));
available_memory_kb = memsize;
diff --git a/kernel/elf.c b/kernel/elf.c
index 3d03335..01f1e53 100644
--- a/kernel/elf.c
+++ b/kernel/elf.c
@@ -6,7 +6,6 @@
#include <typedefs.h>
void *load_elf_file(const char *f, u32 *ds) {
- // ELFHeader *header = kmalloc(sizeof(ELFHeader));
ELFHeader header;
int fd = vfs_open(f, O_RDONLY, 0);
if (fd < 0) {
@@ -46,10 +45,10 @@ void *load_elf_file(const char *f, u32 *ds) {
pages_to_allocate -= p_vaddr - (p_vaddr % 0x1000);
pages_to_allocate /= 0x1000;
- mmu_allocate_region((void *)p_vaddr, pages_to_allocate * 0x1000,
- MMU_FLAG_RW, NULL);
-
- flush_tlb();
+ if(!mmu_allocate_region((void *)p_vaddr, pages_to_allocate * 0x1000,
+ MMU_FLAG_RW, NULL)) {
+ return NULL;
+ }
uintptr_t e = program_header.p_vaddr + program_header.p_memsz;
if (e > end_of_code) {
diff --git a/kernel/fs/shm.c b/kernel/fs/shm.c
index 2a2995b..0735efc 100644
--- a/kernel/fs/shm.c
+++ b/kernel/fs/shm.c
@@ -60,7 +60,9 @@ int shm_ftruncate(vfs_fd_t *fd, size_t length) {
}
p->real_pointer = mmu_find_unallocated_virtual_range(NULL, length);
- mmu_allocate_region(p->real_pointer, length, MMU_FLAG_RW, NULL);
+ if (!mmu_allocate_region(p->real_pointer, length, MMU_FLAG_RW, NULL)) {
+ return -ENOMEM;
+ }
p->size = length;
p->virtual_object = p->real_pointer;
diff --git a/kernel/includes/mmu.h b/kernel/includes/mmu.h
index 211a950..83ea6e0 100644
--- a/kernel/includes/mmu.h
+++ b/kernel/includes/mmu.h
@@ -41,7 +41,7 @@ typedef struct PageDirectory {
int mmu_allocate_region(void *ptr, size_t n, mmu_flags flags,
PageDirectory *pd);
void mmu_free_pagedirectory(PageDirectory *pd);
-void mmu_allocate_shared_kernel_region(void *rc, size_t n);
+int mmu_allocate_shared_kernel_region(void *rc, size_t n);
void *mmu_find_unallocated_virtual_range(void *addr, size_t length);
void mmu_remove_virtual_physical_address_mapping(void *ptr, size_t length);
void mmu_free_address_range(void *ptr, size_t length, PageDirectory *pd);
@@ -59,9 +59,7 @@ void *mmu_is_valid_user_c_string(const char *ptr, size_t *size);
void flush_tlb(void);
void paging_init(u64 memsize, multiboot_info_t *mb);
PageDirectory *get_active_pagedirectory(void);
-void move_stack(u32 new_stack_address, u32 size);
void switch_page_directory(PageDirectory *directory);
-void *allocate_frame(Page *page, int rw, int is_kernel);
PageDirectory *clone_directory(PageDirectory *original);
void *virtual_to_physical(void *address, PageDirectory *directory);
void *ksbrk(size_t s);
diff --git a/kernel/process.s b/kernel/process.s
index ed87959..fd0462f 100644
--- a/kernel/process.s
+++ b/kernel/process.s
@@ -67,7 +67,10 @@ internal_fork:
push eax
call create_process
add esp, 0xC
-
+ cmp eax, 0
+ jnz internal_fork_ret
+ mov eax, 1
+internal_fork_ret:
pop ebp
ret
after_internal_fork:
diff --git a/kernel/sched/scheduler.c b/kernel/sched/scheduler.c
index 45969b0..6f36a76 100644
--- a/kernel/sched/scheduler.c
+++ b/kernel/sched/scheduler.c
@@ -111,8 +111,15 @@ process_t *create_process(process_t *p, u32 esp, u32 eip) {
sizeof(current_task->program_name));
}
- r->cr3 = (p) ? clone_directory(get_active_pagedirectory())
- : get_active_pagedirectory();
+ if (p) {
+ r->cr3 = clone_directory(p->cr3);
+ if (!r->cr3) {
+ kfree(r);
+ return NULL;
+ }
+ } else {
+ r->cr3 = get_active_pagedirectory();
+ }
r->parent = p;
r->tcb = kcalloc(1, sizeof(struct TCB));
@@ -168,6 +175,7 @@ process_t *create_process(process_t *p, u32 esp, u32 eip) {
void tasking_init(void) {
current_task = ready_queue = create_process(NULL, 0, 0);
+ assert(current_task);
current_task_TCB = current_task->tcb;
current_task->tcb->CR3 = current_task->cr3->physical_address;
}
@@ -321,9 +329,14 @@ process_t *internal_fork(process_t *parent);
int fork(void) {
process_t *new_task;
new_task = internal_fork(current_task);
- if (NULL == new_task) {
+ if (0 == new_task) {
return 0;
}
+ if ((process_t *)1 == new_task) {
+ return -ENOMEM; // FIXME: This is probably the reason it failed now but is
+ // not the only reason it could fail(at least in the
+ // future).
+ }
process_t *tmp_task = (process_t *)ready_queue;
for (; tmp_task->next;) {
--
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