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minix/servers/vfs/exec.c
Arun Thomas 1bf6d23f34 Make exec() use entry point in a.out header
2010-06-10 14:59:10 +00:00

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/* This file handles the EXEC system call. It performs the work as follows:
* - see if the permissions allow the file to be executed
* - read the header and extract the sizes
* - fetch the initial args and environment from the user space
* - allocate the memory for the new process
* - copy the initial stack from PM to the process
* - read in the text and data segments and copy to the process
* - take care of setuid and setgid bits
* - fix up 'mproc' table
* - tell kernel about EXEC
* - save offset to initial argc (for ps)
*
* The entry points into this file are:
* pm_exec: perform the EXEC system call
*/
#include "fs.h"
#include <sys/stat.h>
#include <minix/callnr.h>
#include <minix/endpoint.h>
#include <minix/com.h>
#include <minix/u64.h>
#include <a.out.h>
#include <signal.h>
#include <string.h>
#include <dirent.h>
#include "fproc.h"
#include "param.h"
#include "vnode.h"
#include "vmnt.h"
#include <minix/vfsif.h>
FORWARD _PROTOTYPE( int exec_newmem, (int proc_e, vir_bytes text_bytes,
vir_bytes data_bytes, vir_bytes bss_bytes, vir_bytes tot_bytes,
vir_bytes frame_len, int sep_id,
dev_t st_dev, ino_t st_ino, time_t st_ctime, char *progname,
int new_uid, int new_gid,
vir_bytes *stack_topp, int *load_textp, int *allow_setuidp) );
FORWARD _PROTOTYPE( int read_header, (struct vnode *vp, int *sep_id,
vir_bytes *text_bytes, vir_bytes *data_bytes,
vir_bytes *bss_bytes, phys_bytes *tot_bytes, vir_bytes *pc,
int *hdrlenp) );
FORWARD _PROTOTYPE( int patch_stack, (struct vnode *vp,
char stack[ARG_MAX], vir_bytes *stk_bytes) );
FORWARD _PROTOTYPE( int insert_arg, (char stack[ARG_MAX],
vir_bytes *stk_bytes, char *arg, int replace) );
FORWARD _PROTOTYPE( void patch_ptr, (char stack[ARG_MAX],
vir_bytes base) );
FORWARD _PROTOTYPE( int read_seg, (struct vnode *vp, off_t off,
int proc_e, int seg, phys_bytes seg_bytes) );
FORWARD _PROTOTYPE( void clo_exec, (struct fproc *rfp) );
#define ESCRIPT (-2000) /* Returned by read_header for a #! script. */
#define PTRSIZE sizeof(char *) /* Size of pointers in argv[] and envp[]. */
/*===========================================================================*
* pm_exec *
*===========================================================================*/
PUBLIC int pm_exec(proc_e, path, path_len, frame, frame_len, pc)
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, sep_id, round, proc_s, hdrlen, load_text, allow_setuid;
vir_bytes text_bytes, data_bytes, bss_bytes;
phys_bytes tot_bytes; /* total space for program, including gap */
vir_bytes stack_top, vsp;
off_t off;
uid_t new_uid;
gid_t new_gid;
struct fproc *rfp;
struct vnode *vp;
time_t v_ctime;
char *cp;
struct stat sb;
char progname[PROC_NAME_LEN];
static char mbuf[ARG_MAX]; /* buffer for stack and zeroes */
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) 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 */
new_uid = rfp->fp_effuid;
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(progname, cp, PROC_NAME_LEN-1);
progname[PROC_NAME_LEN-1] = '\0';
/* Open executable */
if ((vp = eat_path(PATH_NOFLAGS)) == NULL) return(err_code);
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 *) &sb, 0);
if (r != OK) {
put_vnode(vp);
return(r);
}
v_ctime = sb.st_ctime;
if (round == 0) {
/* Deal with setuid/setgid executables */
if (vp->v_mode & I_SET_UID_BIT) new_uid = vp->v_uid;
if (vp->v_mode & I_SET_GID_BIT) new_gid = vp->v_gid;
}
/* Read the file header and extract the segment sizes. */
r = read_header(vp, &sep_id, &text_bytes, &data_bytes, &bss_bytes,
&tot_bytes, pc, &hdrlen);
if (r != ESCRIPT || 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);
}
if (r != OK) {
put_vnode(vp);
return(ENOEXEC);
}
r = exec_newmem(proc_e, text_bytes, data_bytes, bss_bytes, tot_bytes,
frame_len, sep_id, vp->v_dev, vp->v_inode_nr, v_ctime,
progname, new_uid, new_gid, &stack_top, &load_text,
&allow_setuid);
if (r != OK) {
printf("VFS: pm_exec: exec_newmem failed: %d\n", r);
put_vnode(vp);
return(r);
}
/* Patch up stack and copy it from VFS to new core image. */
vsp = 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 %p\n", r, vsp);
return(r);
}
off = hdrlen;
/* Read in text and data segments. */
if (load_text) r = read_seg(vp, off, proc_e, T, text_bytes);
off += text_bytes;
if (r == OK) r = read_seg(vp, off, proc_e, D, data_bytes);
put_vnode(vp);
if (r != OK) return(r);
clo_exec(rfp);
if (allow_setuid) {
rfp->fp_effuid = new_uid;
rfp->fp_effgid = new_gid;
}
/* This child has now exec()ced. */
rfp->fp_execced = 1;
return(OK);
}
/*===========================================================================*
* exec_newmem *
*===========================================================================*/
PRIVATE int exec_newmem(
int proc_e,
vir_bytes text_bytes,
vir_bytes data_bytes,
vir_bytes bss_bytes,
vir_bytes tot_bytes,
vir_bytes frame_len,
int sep_id,
dev_t st_dev,
ino_t st_ino,
time_t st_ctime,
char *progname,
int new_uid,
int new_gid,
vir_bytes *stack_topp,
int *load_textp,
int *allow_setuidp
)
{
int r;
struct exec_newmem e;
message m;
e.text_bytes = text_bytes;
e.data_bytes = data_bytes;
e.bss_bytes = bss_bytes;
e.tot_bytes = tot_bytes;
e.args_bytes = frame_len;
e.sep_id = sep_id;
e.st_dev = st_dev;
e.st_ino = st_ino;
e.st_ctime = st_ctime;
e.new_uid = new_uid;
e.new_gid = new_gid;
strncpy(e.progname, progname, sizeof(e.progname)-1);
e.progname[sizeof(e.progname)-1] = '\0';
m.m_type = EXEC_NEWMEM;
m.EXC_NM_PROC = proc_e;
m.EXC_NM_PTR = (char *)&e;
if ((r = sendrec(PM_PROC_NR, &m)) != OK) return(r);
*stack_topp = m.m1_i1;
*load_textp = !!(m.m1_i2 & EXC_NM_RF_LOAD_TEXT);
*allow_setuidp = !!(m.m1_i2 & EXC_NM_RF_ALLOW_SETUID);
return(m.m_type);
}
/*===========================================================================*
* read_header *
*===========================================================================*/
PRIVATE int read_header(
struct vnode *vp, /* inode for reading exec file */
int *sep_id, /* true iff sep I&D */
vir_bytes *text_bytes, /* place to return text size */
vir_bytes *data_bytes, /* place to return initialized data size */
vir_bytes *bss_bytes, /* place to return bss size */
phys_bytes *tot_bytes, /* place to return total size */
vir_bytes *pc, /* program entry point (initial PC) */
int *hdrlenp
)
{
/* Read the header and extract the text, data, bss and total sizes from it. */
off_t pos;
int r;
u64_t new_pos;
unsigned int cum_io;
struct exec hdr; /* a.out header is read in here */
/* Read the header and check the magic number. The standard MINIX header
* is defined in <a.out.h>. It consists of 8 chars followed by 6 longs.
* Then come 4 more longs that are not used here.
* Byte 0: magic number 0x01
* Byte 1: magic number 0x03
* Byte 2: normal = 0x10 (not checked, 0 is OK), separate I/D = 0x20
* Byte 3: CPU type, Intel 16 bit = 0x04, Intel 32 bit = 0x10,
* Motorola = 0x0B, Sun SPARC = 0x17
* Byte 4: Header length = 0x20
* Bytes 5-7 are not used.
*
* Now come the 6 longs
* Bytes 8-11: size of text segments in bytes
* Bytes 12-15: size of initialized data segment in bytes
* Bytes 16-19: size of bss in bytes
* Bytes 20-23: program entry point
* Bytes 24-27: total memory allocated to program (text, data + stack)
* Bytes 28-31: size of symbol table in bytes
* The longs are represented in a machine dependent order,
* little-endian on the 8088, big-endian on the 68000.
* The header is followed directly by the text and data segments, and the
* symbol table (if any). The sizes are given in the header. Only the
* text and data segments are copied into memory by exec. The header is
* used here only. The symbol table is for the benefit of a debugger and
* is ignored here.
*/
pos= 0; /* Read from the start of the file */
/* Issue request */
r = req_readwrite(vp->v_fs_e, vp->v_inode_nr, cvul64(pos), READING,
VFS_PROC_NR, (char*)&hdr, sizeof(hdr), &new_pos, &cum_io);
if (r != OK) return r;
/* Interpreted script? */
if (((char*)&hdr)[0] == '#' && ((char*)&hdr)[1] == '!' && vp->v_size >= 2)
return(ESCRIPT);
if (vp->v_size < A_MINHDR) return(ENOEXEC);
/* Check magic number, cpu type, and flags. */
if (BADMAG(hdr)) return(ENOEXEC);
#if (CHIP == INTEL && _WORD_SIZE == 2)
if (hdr.a_cpu != A_I8086) return(ENOEXEC);
#endif
#if (CHIP == INTEL && _WORD_SIZE == 4)
if (hdr.a_cpu != A_I80386) return(ENOEXEC);
#endif
if ((hdr.a_flags & ~(A_NSYM | A_EXEC | A_SEP)) != 0) return(ENOEXEC);
*sep_id = !!(hdr.a_flags & A_SEP); /* separate I & D or not */
/* Get text and data sizes. */
*text_bytes = (vir_bytes) hdr.a_text; /* text size in bytes */
*data_bytes = (vir_bytes) hdr.a_data; /* data size in bytes */
*bss_bytes = (vir_bytes) hdr.a_bss; /* bss size in bytes */
*tot_bytes = hdr.a_total; /* total bytes to allocate for prog */
if (*tot_bytes == 0) return(ENOEXEC);
if (!*sep_id) {
/* If I & D space is not separated, it is all considered data. Text=0*/
*data_bytes += *text_bytes;
*text_bytes = 0;
}
*pc = hdr.a_entry; /* initial address to start execution */
*hdrlenp = hdr.a_hdrlen & BYTE; /* header length */
return(OK);
}
/*===========================================================================*
* patch_stack *
*===========================================================================*/
PRIVATE int patch_stack(vp, stack, stk_bytes)
struct vnode *vp; /* pointer for open script file */
char stack[ARG_MAX]; /* pointer to stack image within VFS */
vir_bytes *stk_bytes; /* size of initial stack */
{
/* Patch the argument vector to include the path name of the script to be
* interpreted, and all strings on the #! line. Returns the path name of
* the interpreter.
*/
enum { INSERT=FALSE, REPLACE=TRUE };
int n, r;
off_t pos;
char *sp, *interp = NULL;
u64_t new_pos;
unsigned int cum_io;
char buf[_MAX_BLOCK_SIZE];
/* Make user_fullpath the new argv[0]. */
if (!insert_arg(stack, stk_bytes, user_fullpath, REPLACE)) return(ENOMEM);
pos = 0; /* Read from the start of the file */
/* Issue request */
r = req_readwrite(vp->v_fs_e, vp->v_inode_nr, cvul64(pos), READING,
VFS_PROC_NR, buf, _MAX_BLOCK_SIZE, &new_pos, &cum_io);
if (r != OK) return(r);
n = vp->v_size;
if (n > _MAX_BLOCK_SIZE)
n = _MAX_BLOCK_SIZE;
if (n < 2) return ENOEXEC;
sp = &(buf[2]); /* just behind the #! */
n -= 2;
if (n > PATH_MAX) n = PATH_MAX;
/* Use the user_fullpath variable for temporary storage */
memcpy(user_fullpath, sp, n);
if ((sp = memchr(user_fullpath, '\n', n)) == NULL) /* must be a proper line */
return(ENOEXEC);
/* Move sp backwards through script[], prepending each string to stack. */
for (;;) {
/* skip spaces behind argument. */
while (sp > user_fullpath && (*--sp == ' ' || *sp == '\t')) {}
if (sp == user_fullpath) break;
sp[1] = 0;
/* Move to the start of the argument. */
while (sp > user_fullpath && sp[-1] != ' ' && sp[-1] != '\t') --sp;
interp = sp;
if (!insert_arg(stack, stk_bytes, sp, INSERT)) return(ENOMEM);
}
/* Round *stk_bytes up to the size of a pointer for alignment contraints. */
*stk_bytes= ((*stk_bytes + PTRSIZE - 1) / PTRSIZE) * PTRSIZE;
if (interp != user_fullpath)
memmove(user_fullpath, interp, strlen(interp)+1);
return(OK);
}
/*===========================================================================*
* insert_arg *
*===========================================================================*/
PRIVATE int insert_arg(stack, stk_bytes, arg, replace)
char stack[ARG_MAX]; /* pointer to stack image within PM */
vir_bytes *stk_bytes; /* size of initial stack */
char *arg; /* argument to prepend/replace as new argv[0] */
int replace;
{
/* Patch the stack so that arg will become argv[0]. Be careful, the stack may
* be filled with garbage, although it normally looks like this:
* nargs argv[0] ... argv[nargs-1] NULL envp[0] ... NULL
* followed by the strings "pointed" to by the argv[i] and the envp[i]. The
* pointers are really offsets from the start of stack.
* Return true iff the operation succeeded.
*/
int offset, a0, a1, old_bytes = *stk_bytes;
/* Prepending arg adds at least one string and a zero byte. */
offset = strlen(arg) + 1;
a0 = (int) ((char **) stack)[1]; /* argv[0] */
if (a0 < 4 * PTRSIZE || a0 >= old_bytes) return(FALSE);
a1 = a0; /* a1 will point to the strings to be moved */
if (replace) {
/* Move a1 to the end of argv[0][] (argv[1] if nargs > 1). */
do {
if (a1 == old_bytes) return(FALSE);
--offset;
} while (stack[a1++] != 0);
} else {
offset += PTRSIZE; /* new argv[0] needs new pointer in argv[] */
a0 += PTRSIZE; /* location of new argv[0][]. */
}
/* stack will grow by offset bytes (or shrink by -offset bytes) */
if ((*stk_bytes += offset) > ARG_MAX) return(FALSE);
/* Reposition the strings by offset bytes */
memmove(stack + a1 + offset, stack + a1, old_bytes - a1);
strcpy(stack + a0, arg); /* Put arg in the new space. */
if (!replace) {
/* Make space for a new argv[0]. */
memmove(stack + 2 * PTRSIZE, stack + 1 * PTRSIZE, a0 - 2 * PTRSIZE);
((char **) stack)[0]++; /* nargs++; */
}
/* Now patch up argv[] and envp[] by offset. */
patch_ptr(stack, (vir_bytes) offset);
((char **) stack)[1] = (char *) a0; /* set argv[0] correctly */
return(TRUE);
}
/*===========================================================================*
* patch_ptr *
*===========================================================================*/
PRIVATE void patch_ptr(stack, base)
char stack[ARG_MAX]; /* pointer to stack image within PM */
vir_bytes base; /* virtual address of stack base inside user */
{
/* When doing an exec(name, argv, envp) call, the user builds up a stack
* image with arg and env pointers relative to the start of the stack. Now
* these pointers must be relocated, since the stack is not positioned at
* address 0 in the user's address space.
*/
char **ap, flag;
vir_bytes v;
flag = 0; /* counts number of 0-pointers seen */
ap = (char **) stack; /* points initially to 'nargs' */
ap++; /* now points to argv[0] */
while (flag < 2) {
if (ap >= (char **) &stack[ARG_MAX]) return; /* too bad */
if (*ap != NULL) {
v = (vir_bytes) *ap; /* v is relative pointer */
v += base; /* relocate it */
*ap = (char *) v; /* put it back */
} else {
flag++;
}
ap++;
}
}
/*===========================================================================*
* read_seg *
*===========================================================================*/
PRIVATE int read_seg(vp, off, proc_e, seg, seg_bytes)
struct vnode *vp; /* inode descriptor to read from */
off_t off; /* offset in file */
int proc_e; /* process number (endpoint) */
int seg; /* T, D, or S */
phys_bytes seg_bytes; /* how much is to be transferred? */
{
/*
* The byte count on read is usually smaller than the segment count, because
* a segment is padded out to a click multiple, and the data segment is only
* partially initialized.
*/
int r;
unsigned n, o;
u64_t new_pos;
unsigned int cum_io;
char buf[1024];
/* Make sure that the file is big enough */
if (vp->v_size < off+seg_bytes) return(EIO);
if (seg != D) {
/* We have to use a copy loop until safecopies support segments */
o = 0;
while (o < seg_bytes) {
n = seg_bytes - o;
if (n > sizeof(buf))
n = sizeof(buf);
if ((r = req_readwrite(vp->v_fs_e,vp->v_inode_nr,cvul64(off+o), READING, VFS_PROC_NR, buf,
n, &new_pos, &cum_io)) != OK) {
printf("VFS: read_seg: req_readwrite failed (text)\n");
return(r);
}
if (cum_io != n) {
printf(
"VFSread_seg segment has not been read properly by exec() \n");
return(EIO);
}
if ((r = sys_vircopy(VFS_PROC_NR, D, (vir_bytes)buf, proc_e,
seg, o, n)) != OK) {
printf("VFS: read_seg: copy failed (text)\n");
return(r);
}
o += n;
}
return(OK);
}
if ((r = req_readwrite(vp->v_fs_e, vp->v_inode_nr, cvul64(off), READING,
proc_e, 0, seg_bytes, &new_pos, &cum_io)) != OK) {
printf("VFS: read_seg: req_readwrite failed (data)\n");
return(r);
}
if (r == OK && cum_io != seg_bytes)
printf("VFSread_seg segment has not been read properly by exec()\n");
return(r);
}
/*===========================================================================*
* clo_exec *
*===========================================================================*/
PRIVATE void clo_exec(rfp)
struct fproc *rfp;
{
/* Files can be marked with the FD_CLOEXEC bit (in fp->fp_cloexec).
*/
int i;
/* Check the file desriptors one by one for presence of FD_CLOEXEC. */
for (i = 0; i < OPEN_MAX; i++)
if ( FD_ISSET(i, &rfp->fp_cloexec_set))
(void) close_fd(rfp, i);
}
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