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363 lines
9.0 KiB
363 lines
9.0 KiB
/*
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* linux/fs/exec.c
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*
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* (C) 1991 Linus Torvalds
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*/
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/*
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* #!-checking implemented by tytso.
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*/
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/*
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* Demand-loading implemented 01.12.91 - no need to read anything but
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* the header into memory. The inode of the executable is put into
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* "current->executable", and page faults do the actual loading. Clean.
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*
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* Once more I can proudly say that linux stood up to being changed: it
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* was less than 2 hours work to get demand-loading completely implemented.
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*/
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#include <errno.h>
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#include <string.h>
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#include <sys/stat.h>
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#include <a.out.h>
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#include <linux/fs.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <asm/segment.h>
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extern int sys_exit(int exit_code);
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extern int sys_close(int fd);
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/*
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* MAX_ARG_PAGES defines the number of pages allocated for arguments
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* and envelope for the new program. 32 should suffice, this gives
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* a maximum env+arg of 128kB !
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*/
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#define MAX_ARG_PAGES 32
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int sys_uselib()
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{
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return -ENOSYS;
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}
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/*
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* create_tables() parses the env- and arg-strings in new user
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* memory and creates the pointer tables from them, and puts their
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* addresses on the "stack", returning the new stack pointer value.
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*/
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static unsigned long * create_tables(char * p,int argc,int envc)
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{
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unsigned long *argv,*envp;
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unsigned long * sp;
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sp = (unsigned long *) (0xfffffffc & (unsigned long) p);
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sp -= envc+1;
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envp = sp;
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sp -= argc+1;
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argv = sp;
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put_fs_long((unsigned long)envp,--sp);
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put_fs_long((unsigned long)argv,--sp);
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put_fs_long((unsigned long)argc,--sp);
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while (argc-->0) {
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put_fs_long((unsigned long) p,argv++);
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while (get_fs_byte(p++)) /* nothing */ ;
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}
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put_fs_long(0,argv);
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while (envc-->0) {
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put_fs_long((unsigned long) p,envp++);
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while (get_fs_byte(p++)) /* nothing */ ;
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}
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put_fs_long(0,envp);
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return sp;
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}
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/*
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* count() counts the number of arguments/envelopes
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*/
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static int count(char ** argv)
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{
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int i=0;
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char ** tmp;
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if (tmp = argv)
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while (get_fs_long((unsigned long *) (tmp++)))
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i++;
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return i;
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}
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/*
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* 'copy_string()' copies argument/envelope strings from user
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* memory to free pages in kernel mem. These are in a format ready
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* to be put directly into the top of new user memory.
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*
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* Modified by TYT, 11/24/91 to add the from_kmem argument, which specifies
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* whether the string and the string array are from user or kernel segments:
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*
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* from_kmem argv * argv **
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* 0 user space user space
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* 1 kernel space user space
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* 2 kernel space kernel space
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*
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* We do this by playing games with the fs segment register. Since it
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* it is expensive to load a segment register, we try to avoid calling
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* set_fs() unless we absolutely have to.
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*/
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static unsigned long copy_strings(int argc,char ** argv,unsigned long *page,
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unsigned long p, int from_kmem)
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{
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char *tmp, *pag;
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int len, offset = 0;
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unsigned long old_fs, new_fs;
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if (!p)
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return 0; /* bullet-proofing */
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new_fs = get_ds();
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old_fs = get_fs();
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if (from_kmem==2)
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set_fs(new_fs);
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while (argc-- > 0) {
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if (from_kmem == 1)
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set_fs(new_fs);
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if (!(tmp = (char *)get_fs_long(((unsigned long *)argv)+argc)))
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panic("argc is wrong");
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if (from_kmem == 1)
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set_fs(old_fs);
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len=0; /* remember zero-padding */
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do {
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len++;
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} while (get_fs_byte(tmp++));
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if (p-len < 0) { /* this shouldn't happen - 128kB */
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set_fs(old_fs);
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return 0;
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}
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while (len) {
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--p; --tmp; --len;
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if (--offset < 0) {
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offset = p % PAGE_SIZE;
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if (from_kmem==2)
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set_fs(old_fs);
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if (!(pag = (char *) page[p/PAGE_SIZE]) &&
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!(pag = (char *) (page[p/PAGE_SIZE] =
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(unsigned long *) get_free_page())))
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return 0;
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if (from_kmem==2)
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set_fs(new_fs);
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}
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*(pag + offset) = get_fs_byte(tmp);
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}
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}
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if (from_kmem==2)
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set_fs(old_fs);
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return p;
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}
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static unsigned long change_ldt(unsigned long text_size,unsigned long * page)
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{
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unsigned long code_limit,data_limit,code_base,data_base;
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int i;
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code_limit = text_size+PAGE_SIZE -1;
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code_limit &= 0xFFFFF000;
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data_limit = 0x4000000;
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code_base = get_base(current->ldt[1]);
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data_base = code_base;
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set_base(current->ldt[1],code_base);
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set_limit(current->ldt[1],code_limit);
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set_base(current->ldt[2],data_base);
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set_limit(current->ldt[2],data_limit);
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/* make sure fs points to the NEW data segment */
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__asm__("pushl $0x17\n\tpop %%fs"::);
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data_base += data_limit;
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for (i=MAX_ARG_PAGES-1 ; i>=0 ; i--) {
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data_base -= PAGE_SIZE;
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if (page[i])
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put_page(page[i],data_base);
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}
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return data_limit;
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}
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/*
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* 'do_execve2()' immdiate loading
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*/
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/*
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* 'do_execve()' executes a new program.
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*/
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int do_execve(unsigned long * eip,long tmp,char * filename,
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char ** argv, char ** envp)
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{
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struct m_inode * inode;
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struct buffer_head * bh;
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struct exec ex;
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unsigned long page[MAX_ARG_PAGES];
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int i,argc,envc;
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int e_uid, e_gid;
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int retval;
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int sh_bang = 0;
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unsigned long p=PAGE_SIZE*MAX_ARG_PAGES-4;
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if ((0xffff & eip[1]) != 0x000f)
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panic("execve called from supervisor mode");
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for (i=0 ; i<MAX_ARG_PAGES ; i++) /* clear page-table */
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page[i]=0;
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if (!(inode=namei(filename))) /* get executables inode */
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return -ENOENT;
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argc = count(argv);
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envc = count(envp);
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restart_interp:
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if (!S_ISREG(inode->i_mode)) { /* must be regular file */
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retval = -EACCES;
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goto exec_error2;
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}
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i = inode->i_mode;
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e_uid = (i & S_ISUID) ? inode->i_uid : current->euid;
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e_gid = (i & S_ISGID) ? inode->i_gid : current->egid;
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if (current->euid == inode->i_uid)
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i >>= 6;
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else if (current->egid == inode->i_gid)
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i >>= 3;
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if (!(i & 1) &&
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!((inode->i_mode & 0111) && suser())) {
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retval = -ENOEXEC;
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goto exec_error2;
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}
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if (!(bh = bread(inode->i_dev,inode->i_zone[0]))) {
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retval = -EACCES;
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goto exec_error2;
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}
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ex = *((struct exec *) bh->b_data); /* read exec-header */
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if ((bh->b_data[0] == '#') && (bh->b_data[1] == '!') && (!sh_bang)) {
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/*
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* This section does the #! interpretation.
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* Sorta complicated, but hopefully it will work. -TYT
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*/
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char buf[1023], *cp, *interp, *i_name, *i_arg;
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unsigned long old_fs;
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strncpy(buf, bh->b_data+2, 1022);
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brelse(bh);
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iput(inode);
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buf[1022] = '\0';
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if (cp = strchr(buf, '\n')) {
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*cp = '\0';
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for (cp = buf; (*cp == ' ') || (*cp == '\t'); cp++);
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}
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if (!cp || *cp == '\0') {
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retval = -ENOEXEC; /* No interpreter name found */
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goto exec_error1;
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}
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interp = i_name = cp;
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i_arg = 0;
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for ( ; *cp && (*cp != ' ') && (*cp != '\t'); cp++) {
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if (*cp == '/')
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i_name = cp+1;
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}
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if (*cp) {
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*cp++ = '\0';
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i_arg = cp;
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}
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/*
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* OK, we've parsed out the interpreter name and
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* (optional) argument.
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*/
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if (sh_bang++ == 0) {
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p = copy_strings(envc, envp, page, p, 0);
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p = copy_strings(--argc, argv+1, page, p, 0);
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}
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/*
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* Splice in (1) the interpreter's name for argv[0]
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* (2) (optional) argument to interpreter
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* (3) filename of shell script
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*
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* This is done in reverse order, because of how the
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* user environment and arguments are stored.
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*/
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p = copy_strings(1, &filename, page, p, 1);
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argc++;
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if (i_arg) {
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p = copy_strings(1, &i_arg, page, p, 2);
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argc++;
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}
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p = copy_strings(1, &i_name, page, p, 2);
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argc++;
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if (!p) {
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retval = -ENOMEM;
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goto exec_error1;
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}
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/*
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* OK, now restart the process with the interpreter's inode.
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*/
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old_fs = get_fs();
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set_fs(get_ds());
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if (!(inode=namei(interp))) { /* get executables inode */
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set_fs(old_fs);
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retval = -ENOENT;
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goto exec_error1;
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}
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set_fs(old_fs);
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goto restart_interp;
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}
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brelse(bh);
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if (N_MAGIC(ex) != ZMAGIC || ex.a_trsize || ex.a_drsize ||
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ex.a_text+ex.a_data+ex.a_bss>0x3000000 ||
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inode->i_size < ex.a_text+ex.a_data+ex.a_syms+N_TXTOFF(ex)) {
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retval = -ENOEXEC;
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goto exec_error2;
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}
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if (N_TXTOFF(ex) != BLOCK_SIZE) {
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printk("%s: N_TXTOFF != BLOCK_SIZE. See a.out.h.", filename);
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retval = -ENOEXEC;
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goto exec_error2;
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}
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if (!sh_bang) {
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p = copy_strings(envc,envp,page,p,0);
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p = copy_strings(argc,argv,page,p,0);
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if (!p) {
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retval = -ENOMEM;
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goto exec_error2;
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}
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}
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/* OK, This is the point of no return */
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if (current->executable)
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iput(current->executable);
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current->executable = inode;
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for (i=0 ; i<32 ; i++)
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current->sigaction[i].sa_handler = NULL;
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for (i=0 ; i<NR_OPEN ; i++)
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if ((current->close_on_exec>>i)&1)
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sys_close(i);
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current->close_on_exec = 0;
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free_page_tables(get_base(current->ldt[1]),get_limit(0x0f));
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free_page_tables(get_base(current->ldt[2]),get_limit(0x17));
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if (last_task_used_math == current)
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last_task_used_math = NULL;
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current->used_math = 0;
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p += change_ldt(ex.a_text,page)-MAX_ARG_PAGES*PAGE_SIZE;
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p = (unsigned long) create_tables((char *)p,argc,envc);
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current->brk = ex.a_bss +
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(current->end_data = ex.a_data +
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(current->end_code = ex.a_text));
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current->start_stack = p & 0xfffff000;
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current->euid = e_uid;
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current->egid = e_gid;
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i = ex.a_text+ex.a_data;
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while (i&0xfff)
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put_fs_byte(0,(char *) (i++));
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eip[0] = ex.a_entry; /* eip, magic happens :-) */
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eip[3] = p; /* stack pointer */
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return 0;
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exec_error2:
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iput(inode);
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exec_error1:
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for (i=0 ; i<MAX_ARG_PAGES ; i++)
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free_page(page[i]);
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return(retval);
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}
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