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annotate src/proc.c @ 55:88a6c4e192f9

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Fixed most important task switching bugs. Now it seems that I can switch in and out of user space reliably.
author John Tsiombikas <nuclear@member.fsf.org>
date Mon, 15 Aug 2011 04:03:39 +0300
parents 4eaecb14fe31
children 0be4615594df
rev   line source
nuclear@52 1 #include <stdio.h>
nuclear@47 2 #include <string.h>
nuclear@52 3 #include <assert.h>
nuclear@55 4 #include "config.h"
nuclear@42 5 #include "proc.h"
nuclear@42 6 #include "tss.h"
nuclear@45 7 #include "vm.h"
nuclear@47 8 #include "segm.h"
nuclear@47 9 #include "intr.h"
nuclear@47 10 #include "panic.h"
nuclear@51 11 #include "syscall.h"
nuclear@51 12 #include "sched.h"
nuclear@54 13 #include "tss.h"
nuclear@47 14
nuclear@55 15 #define FLAGS_INTR_BIT (1 << 9)
nuclear@47 16
nuclear@54 17 static void start_first_proc(void);
nuclear@54 18
nuclear@55 19 /* defined in proc-asm.S */
nuclear@55 20 uint32_t switch_stack(uint32_t new_stack);
nuclear@54 21
nuclear@47 22 /* defined in test_proc.S */
nuclear@47 23 void test_proc(void);
nuclear@47 24 void test_proc_end(void);
nuclear@42 25
nuclear@42 26 static struct process proc[MAX_PROC];
nuclear@42 27 static int cur_pid;
nuclear@42 28
nuclear@54 29 static struct task_state *tss;
nuclear@54 30
nuclear@54 31
nuclear@42 32 void init_proc(void)
nuclear@42 33 {
nuclear@54 34 int tss_page;
nuclear@51 35
nuclear@54 36 /* allocate a page for the task state segment, to make sure
nuclear@54 37 * it doesn't cross page boundaries
nuclear@54 38 */
nuclear@54 39 if((tss_page = pgalloc(1, MEM_KERNEL)) == -1) {
nuclear@54 40 panic("failed to allocate memory for the task state segment\n");
nuclear@54 41 }
nuclear@55 42 tss = (struct task_state*)PAGE_TO_ADDR(tss_page);
nuclear@54 43
nuclear@54 44 /* the kernel stack segment never changes so we might as well set it now
nuclear@54 45 * the only other thing that we use in the tss is the kernel stack pointer
nuclear@54 46 * which is different for each process, and thus managed by context_switch
nuclear@54 47 */
nuclear@54 48 memset(tss, 0, sizeof *tss);
nuclear@54 49 tss->ss0 = selector(SEGM_KDATA, 0);
nuclear@54 50
nuclear@55 51 set_tss((uint32_t)tss);
nuclear@54 52
nuclear@54 53 /* initialize system call handler (see syscall.c) */
nuclear@51 54 init_syscall();
nuclear@42 55
nuclear@54 56 start_first_proc(); /* XXX never returns */
nuclear@54 57 }
nuclear@54 58
nuclear@54 59
nuclear@54 60 static void start_first_proc(void)
nuclear@54 61 {
nuclear@54 62 struct process *p;
nuclear@54 63 int proc_size_pg, img_start_pg, stack_pg;
nuclear@55 64 uint32_t img_start_addr;
nuclear@54 65 struct intr_frame ifrm;
nuclear@54 66
nuclear@42 67 /* prepare the first process */
nuclear@54 68 p = proc + 1;
nuclear@54 69 p->id = 1;
nuclear@54 70 p->parent = 0; /* no parent for init */
nuclear@42 71
nuclear@55 72 p->ticks_left = TIMESLICE_TICKS;
nuclear@55 73 p->next = p->prev = 0;
nuclear@55 74
nuclear@55 75 /* the first process may keep this existing page table */
nuclear@55 76 p->ctx.pgtbl_paddr = get_pgdir_addr();
nuclear@55 77
nuclear@42 78 /* allocate a chunk of memory for the process image
nuclear@42 79 * and copy the code of test_proc there.
nuclear@42 80 */
nuclear@51 81 proc_size_pg = (test_proc_end - test_proc) / PGSIZE + 1;
nuclear@45 82 if((img_start_pg = pgalloc(proc_size_pg, MEM_USER)) == -1) {
nuclear@45 83 panic("failed to allocate space for the init process image\n");
nuclear@45 84 }
nuclear@54 85 img_start_addr = PAGE_TO_ADDR(img_start_pg);
nuclear@54 86 memcpy((void*)img_start_addr, test_proc, proc_size_pg * PGSIZE);
nuclear@54 87 printf("copied init process at: %x\n", img_start_addr);
nuclear@47 88
nuclear@47 89 /* allocate the first page of the process stack */
nuclear@47 90 stack_pg = ADDR_TO_PAGE(KMEM_START) - 1;
nuclear@47 91 if(pgalloc_vrange(stack_pg, 1) == -1) {
nuclear@47 92 panic("failed to allocate user stack page\n");
nuclear@47 93 }
nuclear@54 94 p->user_stack_pg = stack_pg;
nuclear@52 95
nuclear@54 96 /* allocate a kernel stack for this process */
nuclear@54 97 if((p->kern_stack_pg = pgalloc(KERN_STACK_SIZE / PGSIZE, MEM_KERNEL)) == -1) {
nuclear@54 98 panic("failed to allocate kernel stack for the init process\n");
nuclear@54 99 }
nuclear@54 100 /* when switching from user space to kernel space, the ss0:esp0 from TSS
nuclear@54 101 * will be used to switch to the per-process kernel stack, so we need to
nuclear@54 102 * set it correctly before switching to user space.
nuclear@54 103 * tss->ss0 is already set in init_proc above.
nuclear@54 104 */
nuclear@54 105 tss->esp0 = PAGE_TO_ADDR(p->kern_stack_pg) + KERN_STACK_SIZE;
nuclear@45 106
nuclear@45 107
nuclear@54 108 /* now we need to fill in the fake interrupt stack frame */
nuclear@54 109 memset(&ifrm, 0, sizeof ifrm);
nuclear@54 110 /* after the priviledge switch, this ss:esp will be used in userspace */
nuclear@54 111 ifrm.esp = PAGE_TO_ADDR(stack_pg) + PGSIZE;
nuclear@54 112 ifrm.ss = selector(SEGM_UDATA, 3);
nuclear@54 113 /* instruction pointer at the beginning of the process image */
nuclear@55 114 ifrm.eip = img_start_addr;
nuclear@54 115 ifrm.cs = selector(SEGM_UCODE, 3);
nuclear@54 116 /* make sure the user will run with interrupts enabled */
nuclear@54 117 ifrm.eflags = FLAGS_INTR_BIT;
nuclear@54 118 /* user data selectors should all be the same */
nuclear@54 119 ifrm.ds = ifrm.es = ifrm.fs = ifrm.gs = ifrm.ss;
nuclear@42 120
nuclear@51 121 /* add it to the scheduler queues */
nuclear@55 122 add_proc(p->id);
nuclear@55 123
nuclear@55 124 cur_pid = p->id; /* make it current */
nuclear@42 125
nuclear@54 126 /* execute a fake return from interrupt with the fake stack frame */
nuclear@54 127 intr_ret(ifrm);
nuclear@42 128 }
nuclear@42 129
nuclear@47 130
nuclear@47 131 void context_switch(int pid)
nuclear@42 132 {
nuclear@54 133 struct process *prev, *new;
nuclear@49 134
nuclear@55 135 assert(get_intr_state() == 0);
nuclear@55 136
nuclear@52 137 if(cur_pid == pid) {
nuclear@54 138 return; /* nothing to be done */
nuclear@52 139 }
nuclear@54 140 prev = proc + cur_pid;
nuclear@54 141 new = proc + pid;
nuclear@52 142
nuclear@54 143 /* push all registers onto the stack before switching stacks */
nuclear@54 144 push_regs();
nuclear@47 145
nuclear@54 146 prev->ctx.stack_ptr = switch_stack(new->ctx.stack_ptr);
nuclear@47 147
nuclear@54 148 /* restore registers from the new stack */
nuclear@54 149 pop_regs();
nuclear@47 150
nuclear@54 151 /* switch to the new process' address space */
nuclear@54 152 set_pgdir_addr(new->ctx.pgtbl_paddr);
nuclear@47 153
nuclear@54 154 /* make sure we'll return to the correct kernel stack next time
nuclear@54 155 * we enter from userspace
nuclear@54 156 */
nuclear@55 157 tss->esp0 = PAGE_TO_ADDR(new->kern_stack_pg) + KERN_STACK_SIZE;
nuclear@47 158 }
nuclear@51 159
nuclear@51 160 int get_current_pid(void)
nuclear@51 161 {
nuclear@51 162 return cur_pid;
nuclear@51 163 }
nuclear@51 164
nuclear@51 165 struct process *get_current_proc(void)
nuclear@51 166 {
nuclear@51 167 return cur_pid ? &proc[cur_pid] : 0;
nuclear@51 168 }
nuclear@51 169
nuclear@51 170 struct process *get_process(int pid)
nuclear@51 171 {
nuclear@51 172 return &proc[pid];
nuclear@51 173 }