151 lines
3.8 KiB
C
151 lines
3.8 KiB
C
#include <assert.h>
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#include <errno.h>
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#include <elf.h>
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#include <string.h>
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#include <x86.h>
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#include <kern/fs.h>
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#include <kern/exec.h>
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#include <kern/kmalloc.h>
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#include <kern/pmap.h>
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#include <kern/protect.h>
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#include <kern/sche.h>
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#include <kern/syscall.h>
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#include <kern/trap.h>
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static inline void
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init_segment_regs(PROCESS_0 *p_proc)
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{
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p_proc->user_regs.cs = (SELECTOR_FLAT_C & SA_RPL_MASK & SA_TI_MASK)
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| SA_TIL | RPL_USER;
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p_proc->user_regs.ds = (SELECTOR_FLAT_RW & SA_RPL_MASK & SA_TI_MASK)
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| SA_TIL | RPL_USER;
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p_proc->user_regs.es = (SELECTOR_FLAT_RW & SA_RPL_MASK & SA_TI_MASK)
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| SA_TIL | RPL_USER;
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p_proc->user_regs.fs = (SELECTOR_FLAT_RW & SA_RPL_MASK & SA_TI_MASK)
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| SA_TIL | RPL_USER;
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p_proc->user_regs.ss = (SELECTOR_FLAT_RW & SA_RPL_MASK & SA_TI_MASK)
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| SA_TIL | RPL_USER;
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p_proc->user_regs.gs = (SELECTOR_VIDEO & SA_RPL_MASK & SA_TI_MASK)
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| RPL_USER;
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}
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static inline void
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init_pagetbl(PROCESS_0 *p_proc)
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{
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phyaddr_t new_cr3 = phy_malloc_4k();
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memset((void *)K_PHY2LIN(new_cr3), 0, PGSIZE);
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struct page_node *new_page_list = kmalloc(sizeof(struct page_node));
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new_page_list->nxt = NULL;
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new_page_list->paddr = new_cr3;
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new_page_list->laddr = -1;
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map_kern(new_cr3, &new_page_list);
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// 这里需要特别注意的是，替换用户页表这种危险行为
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// 无论如何都是要关中断的，不允许中间有任何调度
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// 否则很有可能换到一半，啪，一个中断进来调度了
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// 调度回来时要加载cr3，然后惊喜地发现page fault了
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struct page_node *old_page_list;
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DISABLE_INT();
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old_page_list = p_proc->page_list;
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p_proc->cr3 = new_cr3;
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p_proc->page_list = new_page_list;
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lcr3(p_proc->cr3);
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ENABLE_INT();
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// 最后记得回收进程页面资源
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recycle_pages(old_page_list);
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}
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ssize_t
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kern_exec(PROCESS_0 *p_proc, const char *pathname)
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{
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ssize_t ret = 0;
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// 路径名的地址必须在内核中的地址
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// 因为exec会回收用户程序的页表
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// 这会导致程序中的地址发生缺页触发page fault
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assert((uintptr_t)pathname >= K_PHY2LIN(0));
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// 进来先给自己上个锁
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while (xchg(&p_proc->lock, 1) == 1)
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schedule();
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if ((ret = read_file(pathname, (void *)K_PHY2LIN(48 * MB))) < 0)
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goto free;
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// 这里有一个特判，如果不是elf文件会返回ENOEXEC
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if (*(uintptr_t *)K_PHY2LIN(48 * MB) != ELF_MAGIC) {
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ret = -ENOEXEC;
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goto free;
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}
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assert(p_proc->statu == READY);
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// 初始化用户寄存器
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memset(&p_proc->user_regs, 0, sizeof(p_proc->user_regs));
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init_segment_regs(p_proc);
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p_proc->user_regs.eflags = 0x1202; /* IF=1, IOPL=1 */
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// 初始化页表
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init_pagetbl(p_proc);
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// 将elf加载到文件指定的地址
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map_elf(p_proc, (void *)K_PHY2LIN(48 * MB));
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// 初始化用户栈空间
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map_stack(p_proc);
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free:
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// 最后记得释放锁
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xchg(&p_proc->lock, 0);
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return ret;
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}
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/*
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* 将src路径名转换为段目录项名到dst
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* 如果不能转换会返回-ENOENT
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*/
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static inline ssize_t
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translate_pathname(char *dst, const char *src)
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{
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assert(strlen(dst) == 11);
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char *st = (char *)src;
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char *ed = st + strlen(st);
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char *dot = ed;
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for (char *c = st ; *c ; c++) {
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if (*c == '.')
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dot = c;
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}
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if (dot - st > 8)
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return -ENOENT;
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memcpy(dst, st, dot - st);
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if (ed - dot - 1 > 3)
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return -ENOENT;
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memcpy(dst + 8, dot + 1, ed == dot ? 0 : ed - dot - 1);
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for (char *c = dst ; *c ; c++) {
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if ('a' <= *c && *c <= 'z')
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*c += 'A' - 'a';
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}
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return 0;
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}
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ssize_t
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do_exec(const char *pathname)
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{
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ssize_t ret = 0;
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char *name_cpy;
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// 原来路径名转短目录项名的工作可以交给do_exec来做
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name_cpy = kmalloc(12);
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memset(name_cpy, ' ', 11);
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name_cpy[11] = '\0';
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// 当然如果转文件名失败了会返回-ENOENT
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if ((ret = translate_pathname(name_cpy, pathname)) < 0)
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goto free;
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ret = kern_exec(&p_proc_ready->pcb, name_cpy);
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free:
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if (name_cpy)
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kfree(name_cpy);
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return ret;
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}
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