/*===========================================================================*
* do_exec *
*===========================================================================*/
PUBLIC int do_exec()
{
/* Perform the execve(name, argv, envp) call. The user library builds a
* complete stack image, including pointers, args, environ, etc. The stack
* is copied to a buffer inside PM, and then to the new core image.
*/
/*
* 执行 execve(name, argv, envp) 调用. 用户库函数构造了一个完整的栈映像,
* 包括指针, 命令行参数, 环境变量等等. 栈先复制到 PM 内的一个缓冲区中,
* 再复制给新的堆栈映像.
*/
register struct mproc *rmp;
struct mproc *sh_mp;
int m, r, fd, ft, sn;
static char mbuf[ARG_MAX]; /* buffer for stack and zeroes */
static char name_buf[PATH_MAX]; /* the name of the file to exec */
char *new_sp, *name, *basename;
vir_bytes src, dst, text_bytes, data_bytes, bss_bytes, stk_bytes, vsp;
phys_bytes tot_bytes; /* total space for program, including gap */
long sym_bytes;
vir_clicks sc;
struct stat s_buf[2], *s_p;
vir_bytes pc;
/* Do some validity checks. */
rmp = mp; // rmp = mp = 当前进程的 struct mproc 结构
stk_bytes = (vir_bytes) m_in.stack_bytes;
if (stk_bytes > ARG_MAX) return(ENOMEM); /* stack too big */
if (m_in.exec_len <= 0 || m_in.exec_len > PATH_MAX) return(EINVAL);
/* Get the exec file name and see if the file is executable. */
src = (vir_bytes) m_in.exec_name;
dst = (vir_bytes) name_buf;
// 将可执行文件的路径名从主调进程复制到 PM 的 name_buf[] 中.
r = sys_datacopy(who, (vir_bytes) src,
PM_PROC_NR, (vir_bytes) dst, (phys_bytes) m_in.exec_len);
if (r != OK) return(r); /* file name not in user data segment */
/* Fetch the stack from the user before destroying the old core image. */
// 将主调进程的栈复制到 mbuf[], 在毁掉旧的核心映像之前
src = (vir_bytes) m_in.stack_ptr;
dst = (vir_bytes) mbuf;
r = sys_datacopy(who, (vir_bytes) src,
PM_PROC_NR, (vir_bytes) dst, (phys_bytes)stk_bytes);
/* can't fetch stack (e.g. bad virtual addr) */
if (r != OK) return(EACCES);
r = 0; /* r = 0 (first attempt), or 1 (interpreted script) */
name = name_buf; /* name of file to exec. */
do {
s_p = &s_buf[r];
// 切换到主调进程的当前工作目录
tell_fs(CHDIR, who, FALSE, 0); /* switch to the user's FS environ */
// 检查文件是否可执行, 如果可执行, 返回文件描述符
fd = allowed(name, s_p, X_BIT); /* is file executable? */
if (fd < 0) return(fd); /* file was not executable */
/* Read the file header and extract the segment sizes. */
sc = (stk_bytes + CLICK_SIZE - 1) >> CLICK_SHIFT;
// 读取文件头部数据, 并赋值给相应参数
m = read_header(fd, &ft, &text_bytes, &data_bytes, &bss_bytes,
&tot_bytes, &sym_bytes, sc, &pc);
if (m != ESCRIPT || ++r > 1) break;
} while ((name = patch_stack(fd, mbuf, &stk_bytes, name_buf)) != NULL);
if (m < 0) {
close(fd); /* something wrong with header */
return(stk_bytes > ARG_MAX ? ENOMEM : ENOEXEC);
}
/* Can the process' text be shared with that of one already running? */
sh_mp = find_share(rmp, s_p->st_ino, s_p->st_dev, s_p->st_ctime);
/* Allocate new memory and release old memory. Fix map and tell kernel. */
r = new_mem(sh_mp, text_bytes, data_bytes, bss_bytes, stk_bytes, tot_bytes);
if (r != OK) {
close(fd); /* insufficient core or program too big */
return(r);
}
/* Save file identification to allow it to be shared. */
rmp->mp_ino = s_p->st_ino;
rmp->mp_dev = s_p->st_dev;
rmp->mp_ctime = s_p->st_ctime;
/* Patch up stack and copy it from PM to new core image. */
vsp = (vir_bytes) rmp->mp_seg[S].mem_vir << CLICK_SHIFT;
vsp += (vir_bytes) rmp->mp_seg[S].mem_len << CLICK_SHIFT;
vsp -= stk_bytes;
patch_ptr(mbuf, vsp);
src = (vir_bytes) mbuf;
r = sys_datacopy(PM_PROC_NR, (vir_bytes) src,
who, (vir_bytes) vsp, (phys_bytes)stk_bytes);
if (r != OK) panic(__FILE__,"do_exec stack copy err on", who);
/* Read in text and data segments. */
if (sh_mp != NULL) {
lseek(fd, (off_t) text_bytes, SEEK_CUR); /* shared: skip text */
} else {
rw_seg(0, fd, who, T, text_bytes);
}
rw_seg(0, fd, who, D, data_bytes);
close(fd); /* don't need exec file any more */
/* Take care of setuid/setgid bits. */
if ((rmp->mp_flags & TRACED) == 0) { /* suppress if tracing */
if (s_buf[0].st_mode & I_SET_UID_BIT) {
rmp->mp_effuid = s_buf[0].st_uid;
tell_fs(SETUID,who, (int)rmp->mp_realuid, (int)rmp->mp_effuid);
}
if (s_buf[0].st_mode & I_SET_GID_BIT) {
rmp->mp_effgid = s_buf[0].st_gid;
tell_fs(SETGID,who, (int)rmp->mp_realgid, (int)rmp->mp_effgid);
}
}
/* Save offset to initial argc (for ps) */
rmp->mp_procargs = vsp;
/* Fix 'mproc' fields, tell kernel that exec is done, reset caught sigs. */
for (sn = 1; sn <= _NSIG; sn++) {
if (sigismember(&rmp->mp_catch, sn)) {
sigdelset(&rmp->mp_catch, sn);
rmp->mp_sigact[sn].sa_handler = SIG_DFL;
sigemptyset(&rmp->mp_sigact[sn].sa_mask);
}
}
rmp->mp_flags &= ~SEPARATE; /* turn off SEPARATE bit */
rmp->mp_flags |= ft; /* turn it on for separate I & D files */
new_sp = (char *) vsp;
tell_fs(EXEC, who, 0, 0); /* allow FS to handle FD_CLOEXEC files */
/* System will save command line for debugging, ps(1) output, etc. */
basename = strrchr(name, '/');
if (basename == NULL) basename = name; else basename++;
strncpy(rmp->mp_name, basename, PROC_NAME_LEN-1);
rmp->mp_name[PROC_NAME_LEN] = '\0';
sys_exec(who, new_sp, basename, pc);
/* Cause a signal if this process is traced. */
if (rmp->mp_flags & TRACED) check_sig(rmp->mp_pid, SIGTRAP);
return(SUSPEND); /* no reply, new program just runs */
}
/*===========================================================================*
* pm_exec *
*===========================================================================*/
int pm_exec(endpoint_t proc_e, vir_bytes path, size_t path_len,
vir_bytes frame, size_t frame_len, vir_bytes *pc,
vir_bytes *newsp, int user_exec_flags)
{
/* Perform the execve(name, argv, envp) call. The user library builds a
* complete stack image, including pointers, args, environ, etc. The stack
* is copied to a buffer inside VFS, and then to the new core image.
*/
int r, slot;
vir_bytes vsp;
struct fproc *rfp;
int extrabase = 0;
static char mbuf[ARG_MAX]; /* buffer for stack and zeroes */
struct vfs_exec_info execi;
int i;
static char fullpath[PATH_MAX],
elf_interpreter[PATH_MAX],
firstexec[PATH_MAX],
finalexec[PATH_MAX];
struct lookup resolve;
struct fproc *vmfp = &fproc[VM_PROC_NR];
stackhook_t makestack = NULL;
static int n;
n++;
struct filp *newfilp = NULL;
lock_exec();
lock_proc(vmfp, 0);
/* unset execi values are 0. */
memset(&execi, 0, sizeof(execi));
execi.vmfd = -1;
/* passed from exec() libc code */
execi.userflags = user_exec_flags;
execi.args.stack_high = kinfo.user_sp;
execi.args.stack_size = DEFAULT_STACK_LIMIT;
okendpt(proc_e, &slot);
rfp = fp = &fproc[slot];
lookup_init(&resolve, fullpath, PATH_NOFLAGS, &execi.vmp, &execi.vp);
resolve.l_vmnt_lock = VMNT_READ;
resolve.l_vnode_lock = VNODE_READ;
/* Fetch the stack from the user before destroying the old core image. */
if (frame_len > ARG_MAX)
FAILCHECK(ENOMEM); /* stack too big */
r = sys_datacopy(proc_e, (vir_bytes) frame, SELF, (vir_bytes) mbuf,
(size_t) frame_len);
if (r != OK) { /* can't fetch stack (e.g. bad virtual addr) */
printf("VFS: pm_exec: sys_datacopy failed\n");
FAILCHECK(r);
}
/* The default is to keep the original user and group IDs */
execi.args.new_uid = rfp->fp_effuid;
execi.args.new_gid = rfp->fp_effgid;
/* Get the exec file name. */
FAILCHECK(fetch_name(path, path_len, fullpath));
strlcpy(finalexec, fullpath, PATH_MAX);
strlcpy(firstexec, fullpath, PATH_MAX);
/* Get_read_vp will return an opened vn in execi.
* if necessary it releases the existing vp so we can
* switch after we find out what's inside the file.
* It reads the start of the file.
*/
Get_read_vp(execi, fullpath, 1, 1, &resolve, fp);
/* If this is a script (i.e. has a #!/interpreter line),
* retrieve the name of the interpreter and open that
* executable instead.
*/
if(is_script(&execi)) {
/* patch_stack will add interpreter name and
* args to stack and retrieve the new binary
* name into fullpath.
*/
FAILCHECK(fetch_name(path, path_len, fullpath));
FAILCHECK(patch_stack(execi.vp, mbuf, &frame_len, fullpath));
strlcpy(finalexec, fullpath, PATH_MAX);
strlcpy(firstexec, fullpath, PATH_MAX);
Get_read_vp(execi, fullpath, 1, 0, &resolve, fp);
}
/* If this is a dynamically linked executable, retrieve
* the name of that interpreter in elf_interpreter and open that
* executable instead. But open the current executable in an
* fd for the current process.
*/
if(elf_has_interpreter(execi.args.hdr, execi.args.hdr_len,
elf_interpreter, sizeof(elf_interpreter))) {
/* Switch the executable vnode to the interpreter */
execi.is_dyn = 1;
/* The interpreter (loader) needs an fd to the main program,
* which is currently in finalexec
*/
if((r = execi.elf_main_fd = common_open(finalexec, O_RDONLY, 0)) < 0) {
printf("VFS: exec: dynamic: open main exec failed %s (%d)\n",
fullpath, r);
FAILCHECK(r);
}
/* ld.so is linked at 0, but it can relocate itself; we
* want it higher to trap NULL pointer dereferences.
*/
execi.args.load_offset = 0x10000;
/* Remember it */
strlcpy(execi.execname, finalexec, PATH_MAX);
/* The executable we need to execute first (loader)
* is in elf_interpreter, and has to be in fullpath to
* be looked up
*/
strlcpy(fullpath, elf_interpreter, PATH_MAX);
strlcpy(firstexec, elf_interpreter, PATH_MAX);
Get_read_vp(execi, fullpath, 0, 0, &resolve, fp);
}
/* We also want an FD for VM to mmap() the process in if possible. */
{
struct vnode *vp = execi.vp;
assert(vp);
if(vp->v_vmnt->m_haspeek && major(vp->v_dev) != MEMORY_MAJOR) {
int newfd = -1;
if(get_fd(vmfp, 0, R_BIT, &newfd, &newfilp) == OK) {
assert(newfd >= 0 && newfd < OPEN_MAX);
assert(!vmfp->fp_filp[newfd]);
newfilp->filp_count = 1;
newfilp->filp_vno = vp;
newfilp->filp_flags = O_RDONLY;
FD_SET(newfd, &vmfp->fp_filp_inuse);
vmfp->fp_filp[newfd] = newfilp;
/* dup_vnode(vp); */
execi.vmfd = newfd;
execi.args.memmap = vfs_memmap;
}
}
}
/* callback functions and data */
execi.args.copymem = read_seg;
execi.args.clearproc = libexec_clearproc_vm_procctl;
execi.args.clearmem = libexec_clear_sys_memset;
execi.args.allocmem_prealloc_cleared = libexec_alloc_mmap_prealloc_cleared;
execi.args.allocmem_prealloc_junk = libexec_alloc_mmap_prealloc_junk;
execi.args.allocmem_ondemand = libexec_alloc_mmap_ondemand;
execi.args.opaque = &execi;
execi.args.proc_e = proc_e;
execi.args.frame_len = frame_len;
execi.args.filesize = execi.vp->v_size;
for (i = 0; exec_loaders[i].load_object != NULL; i++) {
r = (*exec_loaders[i].load_object)(&execi.args);
/* Loaded successfully, so no need to try other loaders */
if (r == OK) { makestack = exec_loaders[i].setup_stack; break; }
}
FAILCHECK(r);
/* Inform PM */
FAILCHECK(libexec_pm_newexec(proc_e, &execi.args));
/* Save off PC */
*pc = execi.args.pc;
/* call a stack-setup function if this executable type wants it */
vsp = execi.args.stack_high - frame_len;
if(makestack) FAILCHECK(makestack(&execi, mbuf, &frame_len, &vsp, &extrabase));
/* Patch up stack and copy it from VFS to new core image. */
libexec_patch_ptr(mbuf, vsp + extrabase);
FAILCHECK(sys_datacopy(SELF, (vir_bytes) mbuf, proc_e, (vir_bytes) vsp,
(phys_bytes)frame_len));
/* Return new stack pointer to caller */
*newsp = vsp;
clo_exec(rfp);
if (execi.args.allow_setuid) {
/* If after loading the image we're still allowed to run with
* setuid or setgid, change credentials now */
rfp->fp_effuid = execi.args.new_uid;
rfp->fp_effgid = execi.args.new_gid;
}
/* Remember the new name of the process */
strlcpy(rfp->fp_name, execi.args.progname, PROC_NAME_LEN);
pm_execfinal:
if(newfilp) unlock_filp(newfilp);
else if (execi.vp != NULL) {
unlock_vnode(execi.vp);
put_vnode(execi.vp);
}
if(execi.vmfd >= 0 && !execi.vmfd_used) {
if(OK != close_fd(vmfp, execi.vmfd)) {
printf("VFS: unexpected close fail of vm fd\n");
}
}
unlock_proc(vmfp);
unlock_exec();
return(r);
}
/*===========================================================================*
* pm_exec *
*===========================================================================*/
PUBLIC int pm_exec(int proc_e, char *path, vir_bytes path_len, char *frame,
vir_bytes frame_len, vir_bytes *pc)
{
/* Perform the execve(name, argv, envp) call. The user library builds a
* complete stack image, including pointers, args, environ, etc. The stack
* is copied to a buffer inside VFS, and then to the new core image.
*/
int r, r1, round, proc_s;
vir_bytes vsp;
struct fproc *rfp;
struct vnode *vp;
char *cp;
static char mbuf[ARG_MAX]; /* buffer for stack and zeroes */
struct exec_info execi;
int i;
okendpt(proc_e, &proc_s);
rfp = fp = &fproc[proc_s];
who_e = proc_e;
who_p = proc_s;
super_user = (fp->fp_effuid == SU_UID ? TRUE : FALSE); /* su? */
/* Get the exec file name. */
if ((r = fetch_name(path, path_len, 0)) != OK) return(r);
/* Fetch the stack from the user before destroying the old core image. */
if (frame_len > ARG_MAX) {
printf("VFS: pm_exec: stack too big\n");
return(ENOMEM); /* stack too big */
}
r = sys_datacopy(proc_e, (vir_bytes) frame, SELF, (vir_bytes) mbuf,
(phys_bytes) frame_len);
if (r != OK) { /* can't fetch stack (e.g. bad virtual addr) */
printf("pm_exec: sys_datacopy failed\n");
return(r);
}
/* The default is to keep the original user and group IDs */
execi.new_uid = rfp->fp_effuid;
execi.new_gid = rfp->fp_effgid;
for (round= 0; round < 2; round++) {
/* round = 0 (first attempt), or 1 (interpreted script) */
/* Save the name of the program */
(cp= strrchr(user_fullpath, '/')) ? cp++ : (cp= user_fullpath);
strncpy(execi.progname, cp, PROC_NAME_LEN-1);
execi.progname[PROC_NAME_LEN-1] = '\0';
execi.setugid = 0;
/* Open executable */
if ((vp = eat_path(PATH_NOFLAGS, fp)) == NULL) return(err_code);
execi.vp = vp;
if ((vp->v_mode & I_TYPE) != I_REGULAR)
r = ENOEXEC;
else if ((r1 = forbidden(vp, X_BIT)) != OK)
r = r1;
else
r = req_stat(vp->v_fs_e, vp->v_inode_nr, VFS_PROC_NR,
(char *) &(execi.sb), 0, 0);
if (r != OK) {
put_vnode(vp);
return(r);
}
if (round == 0) {
/* Deal with setuid/setgid executables */
if (vp->v_mode & I_SET_UID_BIT) {
execi.new_uid = vp->v_uid;
execi.setugid = 1;
}
if (vp->v_mode & I_SET_GID_BIT) {
execi.new_gid = vp->v_gid;
execi.setugid = 1;
}
}
r = map_header(&execi.hdr, execi.vp);
if (r != OK) {
put_vnode(vp);
return(r);
}
if (!is_script(execi.hdr, execi.vp->v_size) || round != 0)
break;
/* Get fresh copy of the file name. */
if ((r = fetch_name(path, path_len, 0)) != OK)
printf("VFS pm_exec: 2nd fetch_name failed\n");
else if ((r = patch_stack(vp, mbuf, &frame_len)) != OK)
printf("VFS pm_exec: patch_stack failed\n");
put_vnode(vp);
if (r != OK) return(r);
}
execi.proc_e = proc_e;
execi.frame_len = frame_len;
for(i = 0; exec_loaders[i].load_object != NULL; i++) {
r = (*exec_loaders[i].load_object)(&execi);
/* Loaded successfully, so no need to try other loaders */
if (r == OK) break;
}
put_vnode(vp);
/* No exec loader could load the object */
if (r != OK) {
return(ENOEXEC);
}
/* Save off PC */
*pc = execi.pc;
/* Patch up stack and copy it from VFS to new core image. */
vsp = execi.stack_top;
vsp -= frame_len;
patch_ptr(mbuf, vsp);
if ((r = sys_datacopy(SELF, (vir_bytes) mbuf, proc_e, (vir_bytes) vsp,
(phys_bytes)frame_len)) != OK) {
printf("VFS: datacopy failed (%d) trying to copy to %lu\n", r, vsp);
return(r);
}
if (r != OK) return(r);
clo_exec(rfp);
if (execi.setugid) {
/* If after loading the image we're still allowed to run with
* setuid or setgid, change the credentials now */
rfp->fp_effuid = execi.new_uid;
rfp->fp_effgid = execi.new_gid;
}
/* This child has now exec()ced. */
rfp->fp_execced = 1;
return(OK);
}
