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发信人: GyeaonWoo (柏林恋人), 信区: Linux
标 题: Linus's Linux--fs/exec.c
发信站: 荔园晨风BBS站 (Mon Aug 25 19:57:39 2003), 站内信件
#include <errno.h>
#include <sys/stat.h>
#include <a.out.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/mm.h>
#include <asm/segment.h>
extern int sys_exit(int exit_code);
extern int sys_close(int fd);
/*
* MAX_ARG_PAGES defines the number of pages allocated for arguments
* and envelope for the new program. 32 should suffice, this gives
* a maximum env+arg of 128kB !
*/
#define MAX_ARG_PAGES 32
#define cp_block(from,to) \
__asm__("pushl $0x10\n\t" \
"pushl $0x17\n\t" \
"pop %%es\n\t" \
"cld\n\t" \
"rep\n\t" \
"movsl\n\t" \
"pop %%es" \
::"c" (BLOCK_SIZE/4),"S" (from),"D" (to) \
:"cx","di","si")
/*
* read_head() reads blocks 1-6 (not 0). Block 0 has already been
* read for header information.
*/
int read_head(struct m_inode * inode,int blocks)
{
struct buffer_head * bh;
int count;
if (blocks>6)
blocks=6;
for(count = 0 ; count<blocks ; count++) {
if (!inode->i_zone[count+1])
continue;
if (!(bh=bread(inode->i_dev,inode->i_zone[count+1])))
return -1;
cp_block(bh->b_data,count*BLOCK_SIZE);
brelse(bh);
}
return 0;
}
int read_ind(int dev,int ind,long size,unsigned long offset)
{
struct buffer_head * ih, * bh;
unsigned short * table,block;
if (size<=0)
panic("size<=0 in read_ind");
if (size>512*BLOCK_SIZE)
size=512*BLOCK_SIZE;
if (!ind)
return 0;
if (!(ih=bread(dev,ind)))
return -1;
table = (unsigned short *) ih->b_data;
while (size>0) {
if (block=*(table++))
if (!(bh=bread(dev,block))) {
brelse(ih);
return -1;
} else {
cp_block(bh->b_data,offset);
brelse(bh);
}
size -= BLOCK_SIZE;
offset += BLOCK_SIZE;
}
brelse(ih);
return 0;
}
/*
* read_area() reads an area into %fs:mem.
*/
int read_area(struct m_inode * inode,long size)
{
struct buffer_head * dind;
unsigned short * table;
int i,count;
if ((i=read_head(inode,(size+BLOCK_SIZE-1)/BLOCK_SIZE)) ||
(size -= BLOCK_SIZE*6)<=0)
return i;
if ((i=read_ind(inode->i_dev,inode->i_zone[7],size,BLOCK_SIZE*6)) ||
(size -= BLOCK_SIZE*512)<=0)
return i;
if (!(i=inode->i_zone[8]))
return 0;
if (!(dind = bread(inode->i_dev,i)))
return -1;
table = (unsigned short *) dind->b_data;
for(count=0 ; count<512 ; count++)
if ((i=read_ind(inode->i_dev,*(table++),size,
BLOCK_SIZE*(518+count))) || (size -= BLOCK_SIZE*512)<=0)
return i;
panic("Impossibly long executable");
}
/*
* create_tables() parses the env- and arg-strings in new user
* memory and creates the pointer tables from them, and puts their
* addresses on the "stack", returning the new stack pointer value.
*/
static unsigned long * create_tables(char * p,int argc,int envc)
{
unsigned long *argv,*envp;
unsigned long * sp;
sp = (unsigned long *) (0xfffffffc & (unsigned long) p);
sp -= envc+1;
envp = sp;
sp -= argc+1;
argv = sp;
put_fs_long((unsigned long)envp,--sp);
put_fs_long((unsigned long)argv,--sp);
put_fs_long((unsigned long)argc,--sp);
while (argc-->0) {
put_fs_long((unsigned long) p,argv++);
while (get_fs_byte(p++)) /* nothing */ ;
}
put_fs_long(0,argv);
while (envc-->0) {
put_fs_long((unsigned long) p,envp++);
while (get_fs_byte(p++)) /* nothing */ ;
}
put_fs_long(0,envp);
return sp;
}
/*
* count() counts the number of arguments/envelopes
*/
static int count(char ** argv)
{
int i=0;
char ** tmp;
if (tmp = argv)
while (get_fs_long((unsigned long *) (tmp++)))
i++;
return i;
}
/*
* 'copy_string()' copies argument/envelope strings from user
* memory to free pages in kernel mem. These are in a format ready
* to be put directly into the top of new user memory.
*/
static unsigned long copy_strings(int argc,char ** argv,unsigned long
*page,
unsigned long p)
{
int len,i;
char *tmp;
while (argc-- > 0) {
if (!(tmp = (char *)get_fs_long(((unsigned long *) argv)+argc)))
panic("argc is wrong");
len=0; /* remember zero-padding */
do {
len++;
} while (get_fs_byte(tmp++));
if (p-len < 0) /* this shouldn't happen - 128kB */
return 0;
i = ((unsigned) (p-len)) >> 12;
while (i<MAX_ARG_PAGES && !page[i]) {
if (!(page[i]=get_free_page()))
return 0;
i++;
}
do {
--p;
if (!page[p/PAGE_SIZE])
panic("nonexistent page in exec.c");
((char *) page[p/PAGE_SIZE])[p%PAGE_SIZE] =
get_fs_byte(--tmp);
} while (--len);
}
return p;
}
static unsigned long change_ldt(unsigned long text_size,unsigned long
* page)
{
unsigned long code_limit,data_limit,code_base,data_base;
int i;
code_limit = text_size+PAGE_SIZE -1;
code_limit &= 0xFFFFF000;
data_limit = 0x4000000;
code_base = get_base(current->ldt[1]);
data_base = code_base;
set_base(current->ldt[1],code_base);
set_limit(current->ldt[1],code_limit);
set_base(current->ldt[2],data_base);
set_limit(current->ldt[2],data_limit);
/* make sure fs points to the NEW data segment */
__asm__("pushl $0x17\n\tpop %%fs"::);
data_base += data_limit;
for (i=MAX_ARG_PAGES-1 ; i>=0 ; i--) {
data_base -= PAGE_SIZE;
if (page[i])
put_page(page[i],data_base);
}
return data_limit;
}
/*
* 'do_execve()' executes a new program.
*/
int do_execve(unsigned long * eip,long tmp,char * filename,
char ** argv, char ** envp)
{
struct m_inode * inode;
struct buffer_head * bh;
struct exec ex;
unsigned long page[MAX_ARG_PAGES];
int i,argc,envc;
unsigned long p;
if ((0xffff & eip[1]) != 0x000f)
panic("execve called from supervisor mode");
for (i=0 ; i<MAX_ARG_PAGES ; i++) /* clear page-table */
page[i]=0;
if (!(inode=namei(filename))) /* get executables inode */
return -ENOENT;
if (!S_ISREG(inode->i_mode)) { /* must be regular file */
iput(inode);
return -EACCES;
}
i = inode->i_mode;
if (current->uid && current->euid) {
if (current->euid == inode->i_uid)
i >>= 6;
else if (current->egid == inode->i_gid)
i >>= 3;
} else if (i & 0111)
i=1;
if (!(i & 1)) {
iput(inode);
return -ENOEXEC;
}
if (!(bh = bread(inode->i_dev,inode->i_zone[0]))) {
iput(inode);
return -EACCES;
}
ex = *((struct exec *) bh->b_data); /* read exec-header */
brelse(bh);
if (N_MAGIC(ex) != ZMAGIC || ex.a_trsize || ex.a_drsize ||
ex.a_text+ex.a_data+ex.a_bss>0x3000000 ||
inode->i_size < ex.a_text+ex.a_data+ex.a_syms+N_TXTOFF(ex)) {
iput(inode);
return -ENOEXEC;
}
if (N_TXTOFF(ex) != BLOCK_SIZE)
panic("N_TXTOFF != BLOCK_SIZE. See a.out.h.");
argc = count(argv);
envc = count(envp);
p = copy_strings(envc,envp,page,PAGE_SIZE*MAX_ARG_PAGES-4);
p = copy_strings(argc,argv,page,p);
if (!p) {
for (i=0 ; i<MAX_ARG_PAGES ; i++)
free_page(page[i]);
iput(inode);
return -1;
}
/* OK, This is the point of no return */
for (i=0 ; i<32 ; i++)
current->sig_fn[i] = NULL;
for (i=0 ; i<NR_OPEN ; i++)
if ((current->close_on_exec>>i)&1)
sys_close(i);
current->close_on_exec = 0;
free_page_tables(get_base(current->ldt[1]),get_limit(0x0f));
free_page_tables(get_base(current->ldt[2]),get_limit(0x17));
if (last_task_used_math == current)
last_task_used_math = NULL;
current->used_math = 0;
p += change_ldt(ex.a_text,page)-MAX_ARG_PAGES*PAGE_SIZE;
p = (unsigned long) create_tables((char *)p,argc,envc);
current->brk = ex.a_bss +
(current->end_data = ex.a_data +
(current->end_code = ex.a_text));
current->start_stack = p & 0xfffff000;
i = read_area(inode,ex.a_text+ex.a_data);
iput(inode);
if (i<0)
sys_exit(-1);
i = ex.a_text+ex.a_data;
while (i&0xfff)
put_fs_byte(0,(char *) (i++));
eip[0] = ex.a_entry; /* eip, magic happens :-) */
eip[3] = p; /* stack pointer */
return 0;
}
--
暧昧中透出薄雾的晨花 无意间岁月发出的嫩芽
浅笑里波光闪动的艳影 惬意后醉了眉眼的旧话
旧梦中锋利的剑与白马 传说里等情人白了头发
追忆前寒窗明月的红腊 多年后流水洗尽的铅华桃李春风一杯酒 江湖夜雨十年灯紫薇雨中?
※ 来源:·荔园晨风BBS站 bbs.szu.edu.cn·[FROM: 192.168.35.5]
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