diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/Makefile | 2 | ||||
| -rw-r--r-- | kernel/asm.s | 60 | ||||
| -rw-r--r-- | kernel/boot.s | 4 | ||||
| -rw-r--r-- | kernel/kmain.c | 5 | ||||
| -rw-r--r-- | kernel/memory.c | 129 | ||||
| -rw-r--r-- | kernel/page.s | 55 | ||||
| -rw-r--r-- | kernel/sched.c | 131 | ||||
| -rw-r--r-- | kernel/usrspace.s | 45 |
8 files changed, 327 insertions, 104 deletions
diff --git a/kernel/Makefile b/kernel/Makefile index c6cf24e..29b5566 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -4,7 +4,7 @@ SRCS = $(wildcard *.c) ASMS = $(wildcard *.s) OBJS = $(SRCS:.c=.o) $(ASMS:.s=.o) -CFLAGS = -m32 -I../include -ffreestanding -nostdinc -nostdlib -fno-stack-protector -fno-pie -gstabs+ +CFLAGS = -m32 -I../include -ffreestanding -nostdinc -nostdlib -fno-stack-protector -fno-pie -gstabs+ -g LDFLAGS = -m elf_i386 -r ASMFLAGS = -f elf32 diff --git a/kernel/asm.s b/kernel/asm.s new file mode 100644 index 0000000..4abe607 --- /dev/null +++ b/kernel/asm.s @@ -0,0 +1,60 @@ +global switch_to +extern ctask +extern tss + +switch_to: + push ebp + mov ebp, esp + mov eax, [ebp+8] + mov [ctask], eax + mov esi, [ebp+12] + mov ecx, 13 +.loop: + lodsd + push eax + dec ecx + jz .end + jmp .loop +.end: + mov ax, 0x23 + mov ds, ax + mov es, ax + mov fs, ax + mov gs, ax + popa + iret + +; uint32_t ss; +; uint32_t esp; +; uint32_t eflags; +; uint32_t cs; +; uint32_t eip; +; uint32_t eax; +; uint32_t ecx; +; uint32_t edx; +; uint32_t ebx; +; uint32_t esp_garbage; +; uint32_t ebp; +; uint32_t esi; +; uint32_t edi; + +; switch_to: + ; push ebp + ; mov ebp, esp + ; cli + ; mov ax, 0x23 + ; mov ds, ax + ; mov es, ax + ; mov fs, ax + ; mov gs, ax + ; mov eax, esp + ; ; save ESP in the TSS + ; mov [tss+4], eax + ; push dword 0x23 + ; push dword 0x00180000 + ; pushf + ; push dword 0x1B + ; push dword 0x00100000 + ; iret + ; pop ebp + ; ret diff --git a/kernel/boot.s b/kernel/boot.s index 80f8be9..9d948cf 100644 --- a/kernel/boot.s +++ b/kernel/boot.s @@ -22,6 +22,8 @@ section .text kboot: cli ; put the stack pointer near the end of conventional memory + ; WARNING: don't change this without changing the corresponding + ; entry in the TSS mov esp, 0x80000 ; setup descriptor tables call flush_gdt @@ -37,7 +39,7 @@ kboot: tss: dd 0 - dd 0 ; kernel stack pointer + dd 0x80000 ; kernel stack pointer dd 0x10 ; kernel stack segment times 60 db 0 dd 0x13 ; ES segment diff --git a/kernel/kmain.c b/kernel/kmain.c index ece7012..558df42 100644 --- a/kernel/kmain.c +++ b/kernel/kmain.c @@ -1,12 +1,13 @@ #include <kernel/con.h> +#include <kernel/memory.h> #include <kernel/sys.h> #include <stdint.h> #include <sys/types.h> -uint32_t ticks = 0; - extern void userspace_init(void); +uint32_t ticks = 0; + void kmain(void) { con_init(); diff --git a/kernel/memory.c b/kernel/memory.c new file mode 100644 index 0000000..465b44f --- /dev/null +++ b/kernel/memory.c @@ -0,0 +1,129 @@ +#include <kernel/memory.h> +#include <stdint.h> +#include <sys/types.h> + +static char __attribute__((aligned (4096))) mapped_page[4096]; + +static pdir_t kpdir; + +ptab_t ktab; + +static ptab_t flow; +static ptab_t fupp; + +void *alloc_physical_page(void) { + int i; + void *ret; + + for(i = 0; i < PGENT; i++) { + if(flow[i] & 1) { + ret = (void*) (flow[i] & ~1); + flow[i] = 0; + return ret; + } + + if(fupp[i] & 1) { + ret = (void*) (fupp[i] & ~1); + fupp[i] = 0; + return ret; + } + } + + return NULL; +} + +int free_physical_page(void *page) { + int i; + page = (void*) ((uint32_t) page & ~0xFFF); + + for(int i = 0; i < PGENT; i++) { + if(!(flow[i] & 1)) { + flow[i] = (uint32_t) page | 1; + return 0; + } + + if(!(fupp[i] & 1)) { + fupp[i] = (uint32_t) page | 1; + return 0; + } + } + + return -1; +} + +void *alloc_physical_pages(unsigned int n) { + void *p = NULL; + void *last = NULL; + void **page; + + while(n--) { + p = alloc_physical_page(); + if(p == NULL) { + page = &last; + while(*page) { + free_physical_page(*page); + page = *page; + } + return NULL; + } + + map_page(p); + *((void**) mapped_page) = last; + last = p; + } + + return p; +} + +void *map_page(void *page) { + uint32_t p = (uint32_t) mapped_page; + + /* enforce 4KB page alignment */ + page = (void*) ((uint32_t) page & ~0xFFF); + + ktab[(p >> 12) & 0x3FF] = (uint32_t) page | 0x003; + /* + * invalidate any cached entries for + * the mapped page window. + */ + __asm__ ("invlpg %0" :: "m" (mapped_page)); + + return mapped_page; +} + +void paging_init(void) { + int i; + + /* empty the page directory */ + for(i = 0; i < PGENT; i++) + kpdir[i] = 0; + + /* populate the free page tables */ + for(i = 0; i < PGENT; i++) { + /* populate the lower table */ + flow[i] = (i << 12); + /* only pages >1MB can be allocated */ + if(i >= 0x100) + flow[i] |= 0x001; + /* populate the upper table */ + fupp[i] = ((i << 12) + 0x400000) | 0x001; + } + + /* populate the kernel's page table */ + for(i = 0; i < PGENT; i++) { + ktab[i] = 0; + if(i < 256) + ktab[i] = (i << 12) | 0x003; + } + + /* populate the kernel's page directory */ + kpdir[0] = ((pde_t) ktab) | 0x007; + + __asm__ ( + "mov %%eax, %%cr3\n" + "mov %%cr0, %%eax\n" + "or $0x80000000, %%eax\n" + "mov %%eax, %%cr0\n" + :: "a" (&kpdir) + :); +} diff --git a/kernel/page.s b/kernel/page.s deleted file mode 100644 index 4e40822..0000000 --- a/kernel/page.s +++ /dev/null @@ -1,55 +0,0 @@ -global paging_init - -align 4096 -page_dir: - times 4096 db 0 - -align 4096 -page_tables: - ; two page tables - times 4096 db 0 - times 4096 db 0 -.end: - -; here, we initialize paging. since the IDT -; has yet to be populated, we must take extra -; care as we can't afford to trigger a page -; fault. -paging_init: - push ebp - mov ebp, esp - push ebx - ; populate the page directory - mov eax, page_tables - or eax, 0x007 - mov [page_dir], eax - mov eax, (page_tables+4096) - or eax, 0x007 - mov [page_dir+4], eax - ; populate the page tables - mov ebx, page_tables - mov ecx, ((page_tables.end-page_tables)/4) - mov edx, 0 -.loop: - mov eax, edx - or eax, 0x003 - cmp edx, 0x100000 - jb .skip - or eax, 0x004 -.skip: - mov [ebx], eax - dec ecx - jz .end - add ebx, 4 - add edx, 4096 - jmp .loop -.end: - ; load the page directory and enable paging - mov eax, page_dir - mov cr3, eax - mov eax, cr0 - or eax, 0x80000000 - mov cr0, eax - pop ebx - pop ebp - ret diff --git a/kernel/sched.c b/kernel/sched.c new file mode 100644 index 0000000..f0b79fc --- /dev/null +++ b/kernel/sched.c @@ -0,0 +1,131 @@ +#include <asm/system.h> +#include <kernel/con.h> +#include <kernel/memory.h> +#include <kernel/sched.h> +#include <string.h> +#include <sys/types.h> + +#define USRSTART ((void*) 0x40000000) + +#define pages(n) \ + ((n / 4096) + 1) + +#define tables(n) \ + ((n / 1024) + 1) + +#define getpage(name, p) ({\ + void **_next; \ + _next = map_page(p); \ + name = p; \ + p = *_next; \ + }) + +extern char _usrbin_start; +extern char _usrbin_size; + +struct task_struct *ctask; + +static struct task_struct task; + +static inline void empty_table(void *t) { + int i; + + for(i = 0; i < PGENT; i++) + ((uint32_t*) t)[i] = 0; +} + +void userspace_init(void) { + int i, j; + int c; + size_t totpages, npages, ntables; + void *p, *page, *tab, *map; + void *pdir, *stackt, *stackp; + + size_t usrsize = (size_t) &_usrbin_size; + + npages = pages(usrsize); + ntables = tables(pages(usrsize)); + totpages = npages + ntables + 3; + + /* here we allocate pages to setup the process' + * address space. in addition to the pages that + * will hold the binary image, the following + * pages are allocated: + * - page directory (1 page) + * - page tables + * - stack page (1 page) + * - stack table (1 page) + */ + p = alloc_physical_pages(totpages); + printf("Allocating %x pages for userspace process\n", totpages); + if(p == NULL) { + printf("Failed to allocate memory for userspace!\n"); + return; + } + + getpage(pdir, p); + getpage(stackt, p); + getpage(stackp, p); + printf(" Page directory: 0x%08x\n", (uint32_t) pdir); + printf(" Stack table: 0x%08x\n", (uint32_t) stackt); + printf(" Stack page: 0x%08x\n", (uint32_t) stackp); + printf(" Page tables:\n"); + + /* populate the page directory */ + c = npages; + map = map_page(pdir); + empty_table(map); + for(i = 0; i < ntables; i++) { + /* add the table entry to the directory */ + getpage(tab, p); + printf(" 0x%08x\n", (uint32_t) tab); + map = map_page(pdir); + ((uint32_t*) map)[i + (PGENT / 4)] = (uint32_t) tab | 0x007; + + /* populate the page table */ + map = map_page(tab); + for(j = 0; j < PGENT; j++) { + ((uint32_t*) map)[j] = 0; + if(c <= 0) + continue; + + getpage(page, p); + map = map_page(tab); + ((uint32_t*) map)[j] = (uint32_t) page | 0x007; + c--; + } + } + + /* populate the stack table */ + map = map_page(stackt); + empty_table(map); + ((uint32_t*) map)[PGENT - 1] = (uint32_t) stackp | 0x007; + + /* add the stack page table to the directory */ + map = map_page(pdir); + ((uint32_t*) map)[PGENT - 1] = (uint32_t) stackt | 0x007; + /* add the kernel's page table to the directory */ + ((uint32_t*) map)[0] = (uint32_t) ktab | 0x003; + + __asm__ volatile ("mov %%eax, %%cr3" :: "a" (pdir)); + + memcpy(USRSTART, &_usrbin_start, usrsize); + + /* + * here we initialize the task struct. + * currently, we only setup state information + * necessary to begin execution. + */ + memset(&task, 0, sizeof(task)); + task.state.cs = 0x1B; + task.state.ss = 0x23; + task.state.eip = (uint32_t) USRSTART; + task.state.esp = 0xFFFFFFFF; + __asm__ ( + "pushf\n" \ + "pop %%eax" \ + : "=a" (task.state.eflags) \ + ::); + + switch_to(&task, &task.state); +} diff --git a/kernel/usrspace.s b/kernel/usrspace.s deleted file mode 100644 index 1d20f71..0000000 --- a/kernel/usrspace.s +++ /dev/null @@ -1,45 +0,0 @@ -global userspace_init -extern _binary_usrbin_bin_size -extern _binary_usrbin_bin_start -extern tss - -userspace_init: - push ebp - mov ebp, esp - push esi - push edi - mov ecx, _binary_usrbin_bin_size - mov esi, _binary_usrbin_bin_start - mov edi, 0x100000 -.loop: - movsb - dec ecx - jz .end - jmp .loop -.end: - pop edi - pop esi - call usrcall - pop ebp - ret - -usrcall: - push ebp - mov ebp, esp - cli - mov ax, 0x23 - mov ds, ax - mov es, ax - mov fs, ax - mov gs, ax - mov eax, esp - ; save ESP in the TSS - mov [tss+4], eax - push dword 0x23 - push dword 0x00180000 - pushf - push dword 0x1B - push dword 0x00100000 - iret - pop ebp - ret |