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minix/servers/pm/exec.c
Ben Gras 447b988154 exec now uses phys_zero system call to zero bss segments (instead of 
using phys_copy to copy zeroes there for every kb), which is a big
optimisation in some cases

fixed a bug that was introduced when function keys became notifies
2005-06-01 09:39:45 +00:00

605 lines
22 KiB
C
Raw Blame History

/* 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:
* do_exec: perform the EXEC system call
* rw_seg: read or write a segment from or to a file
* find_share: find a process whose text segment can be shared
*/
#include "pm.h"
#include <sys/stat.h>
#include <minix/callnr.h>
#include <minix/com.h>
#include <a.out.h>
#include <signal.h>
#include <string.h>
#include "mproc.h"
#include "param.h"
FORWARD _PROTOTYPE( int new_mem, (struct mproc *sh_mp, vir_bytes text_bytes,
vir_bytes data_bytes, vir_bytes bss_bytes,
vir_bytes stk_bytes, phys_bytes tot_bytes) );
FORWARD _PROTOTYPE( void patch_ptr, (char stack[ARG_MAX], vir_bytes base) );
FORWARD _PROTOTYPE( int insert_arg, (char stack[ARG_MAX],
vir_bytes *stk_bytes, char *arg, int replace) );
FORWARD _PROTOTYPE( char *patch_stack, (int fd, char stack[ARG_MAX],
vir_bytes *stk_bytes, char *script) );
FORWARD _PROTOTYPE( int read_header, (int fd, int *ft, vir_bytes *text_bytes,
vir_bytes *data_bytes, vir_bytes *bss_bytes,
phys_bytes *tot_bytes, long *sym_bytes, vir_clicks sc,
vir_bytes *pc) );
#define ESCRIPT (-2000) /* Returned by read_header for a #! script. */
#define PTRSIZE sizeof(char *) /* Size of pointers in argv[] and envp[]. */
/*===========================================================================*
* 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.
*/
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;
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;
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. */
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);
if (r != OK) return(EACCES); /* can't fetch stack (e.g. bad virtual addr) */
r = 0; /* r = 0 (first attempt), or 1 (interpreted script) */
name = name_buf; /* name of file to exec. */
do {
s_p = &s_buf[r];
tell_fs(CHDIR, who, FALSE, 0); /* switch to the user's FS environ */
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;
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("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, rmp->mp_flags & TRACED, basename, pc);
return(SUSPEND); /* no reply, new program just runs */
}
/*===========================================================================*
* read_header *
*===========================================================================*/
PRIVATE int read_header(fd, ft, text_bytes, data_bytes, bss_bytes,
tot_bytes, sym_bytes, sc, pc)
int fd; /* file descriptor for reading exec file */
int *ft; /* place to return ft number */
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 */
long *sym_bytes; /* place to return symbol table size */
vir_clicks sc; /* stack size in clicks */
vir_bytes *pc; /* program entry point (initial PC) */
{
/* Read the header and extract the text, data, bss and total sizes from it. */
int m, ct;
vir_clicks tc, dc, s_vir, dvir;
phys_clicks totc;
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.
*/
if ((m= read(fd, &hdr, A_MINHDR)) < 2) return(ENOEXEC);
/* Interpreted script? */
if (((char *) &hdr)[0] == '#' && ((char *) &hdr)[1] == '!') return(ESCRIPT);
if (m != 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);
*ft = ( (hdr.a_flags & A_SEP) ? SEPARATE : 0); /* 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 */
*sym_bytes = hdr.a_syms; /* symbol table size in bytes */
if (*tot_bytes == 0) return(ENOEXEC);
if (*ft != SEPARATE) {
/* 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 */
/* Check to see if segment sizes are feasible. */
tc = ((unsigned long) *text_bytes + CLICK_SIZE - 1) >> CLICK_SHIFT;
dc = (*data_bytes + *bss_bytes + CLICK_SIZE - 1) >> CLICK_SHIFT;
totc = (*tot_bytes + CLICK_SIZE - 1) >> CLICK_SHIFT;
if (dc >= totc) return(ENOEXEC); /* stack must be at least 1 click */
dvir = (*ft == SEPARATE ? 0 : tc);
s_vir = dvir + (totc - sc);
m = size_ok(*ft, tc, dc, sc, dvir, s_vir);
ct = hdr.a_hdrlen & BYTE; /* header length */
if (ct > A_MINHDR) lseek(fd, (off_t) ct, SEEK_SET); /* skip unused hdr */
return(m);
}
/*===========================================================================*
* new_mem *
*===========================================================================*/
PRIVATE int new_mem(sh_mp, text_bytes, data_bytes,bss_bytes,stk_bytes,tot_bytes)
struct mproc *sh_mp; /* text can be shared with this process */
vir_bytes text_bytes; /* text segment size in bytes */
vir_bytes data_bytes; /* size of initialized data in bytes */
vir_bytes bss_bytes; /* size of bss in bytes */
vir_bytes stk_bytes; /* size of initial stack segment in bytes */
phys_bytes tot_bytes; /* total memory to allocate, including gap */
{
/* Allocate new memory and release the old memory. Change the map and report
* the new map to the kernel. Zero the new core image's bss, gap and stack.
*/
register struct mproc *rmp;
vir_clicks text_clicks, data_clicks, gap_clicks, stack_clicks, tot_clicks;
phys_clicks new_base;
phys_bytes bytes, base, count, bss_offset;
int s;
/* No need to allocate text if it can be shared. */
if (sh_mp != NULL) text_bytes = 0;
/* Allow the old data to be swapped out to make room. (Which is really a
* waste of time, because we are going to throw it away anyway.)
*/
rmp->mp_flags |= WAITING;
/* Acquire the new memory. Each of the 4 parts: text, (data+bss), gap,
* and stack occupies an integral number of clicks, starting at click
* boundary. The data and bss parts are run together with no space.
*/
text_clicks = ((unsigned long) text_bytes + CLICK_SIZE - 1) >> CLICK_SHIFT;
data_clicks = (data_bytes + bss_bytes + CLICK_SIZE - 1) >> CLICK_SHIFT;
stack_clicks = (stk_bytes + CLICK_SIZE - 1) >> CLICK_SHIFT;
tot_clicks = (tot_bytes + CLICK_SIZE - 1) >> CLICK_SHIFT;
gap_clicks = tot_clicks - data_clicks - stack_clicks;
if ( (int) gap_clicks < 0) return(ENOMEM);
/* Try to allocate memory for the new process. */
new_base = alloc_mem(text_clicks + tot_clicks);
if (new_base == NO_MEM) return(ENOMEM);
/* We've got memory for the new core image. Release the old one. */
rmp = mp;
if (find_share(rmp, rmp->mp_ino, rmp->mp_dev, rmp->mp_ctime) == NULL) {
/* No other process shares the text segment, so free it. */
free_mem(rmp->mp_seg[T].mem_phys, rmp->mp_seg[T].mem_len);
}
/* Free the data and stack segments. */
free_mem(rmp->mp_seg[D].mem_phys,
rmp->mp_seg[S].mem_vir + rmp->mp_seg[S].mem_len - rmp->mp_seg[D].mem_vir);
/* We have now passed the point of no return. The old core image has been
* forever lost, memory for a new core image has been allocated. Set up
* and report new map.
*/
if (sh_mp != NULL) {
/* Share the text segment. */
rmp->mp_seg[T] = sh_mp->mp_seg[T];
} else {
rmp->mp_seg[T].mem_phys = new_base;
rmp->mp_seg[T].mem_vir = 0;
rmp->mp_seg[T].mem_len = text_clicks;
}
rmp->mp_seg[D].mem_phys = new_base + text_clicks;
rmp->mp_seg[D].mem_vir = 0;
rmp->mp_seg[D].mem_len = data_clicks;
rmp->mp_seg[S].mem_phys = rmp->mp_seg[D].mem_phys + data_clicks + gap_clicks;
rmp->mp_seg[S].mem_vir = rmp->mp_seg[D].mem_vir + data_clicks + gap_clicks;
rmp->mp_seg[S].mem_len = stack_clicks;
#if (CHIP == M68000)
rmp->mp_seg[T].mem_vir = 0;
rmp->mp_seg[D].mem_vir = rmp->mp_seg[T].mem_len;
rmp->mp_seg[S].mem_vir = rmp->mp_seg[D].mem_vir + rmp->mp_seg[D].mem_len + gap_clicks;
#endif
sys_newmap(who, rmp->mp_seg); /* report new map to the kernel */
/* The old memory may have been swapped out, but the new memory is real. */
rmp->mp_flags &= ~(WAITING|ONSWAP|SWAPIN);
/* Zero the bss, gap, and stack segment. */
bytes = (phys_bytes)(data_clicks + gap_clicks + stack_clicks) << CLICK_SHIFT;
base = (phys_bytes) rmp->mp_seg[D].mem_phys << CLICK_SHIFT;
bss_offset = (data_bytes >> CLICK_SHIFT) << CLICK_SHIFT;
base += bss_offset;
bytes -= bss_offset;
if ((s=sys_physzero(base, bytes)) != OK) {
panic("new_mem can't zero", s);
}
#if DEAD_CODE
while (bytes > 0) {
static char zero[1024]; /* used to zero bss */
count = MIN(bytes, (phys_bytes) sizeof(zero));
if ((s=sys_physcopy(PM_PROC_NR, D, (phys_bytes) zero,
NONE, PHYS_SEG, base, count)) != OK) {
panic("new_mem can't zero", s);
}
base += count;
bytes -= count;
}
#endif
return(OK);
}
/*===========================================================================*
* 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++;
}
}
/*===========================================================================*
* 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_stack *
*===========================================================================*/
PRIVATE char *patch_stack(fd, stack, stk_bytes, script)
int fd; /* file descriptor to open script file */
char stack[ARG_MAX]; /* pointer to stack image within PM */
vir_bytes *stk_bytes; /* size of initial stack */
char *script; /* name of script to interpret */
{
/* 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.
*/
char *sp, *interp = NULL;
int n;
enum { INSERT=FALSE, REPLACE=TRUE };
/* Make script[] the new argv[0]. */
if (!insert_arg(stack, stk_bytes, script, REPLACE)) return(NULL);
if (lseek(fd, 2L, 0) == -1 /* just behind the #! */
|| (n= read(fd, script, PATH_MAX)) < 0 /* read line one */
|| (sp= memchr(script, '\n', n)) == NULL) /* must be a proper line */
return(NULL);
/* Move sp backwards through script[], prepending each string to stack. */
for (;;) {
/* skip spaces behind argument. */
while (sp > script && (*--sp == ' ' || *sp == '\t')) {}
if (sp == script) break;
sp[1] = 0;
/* Move to the start of the argument. */
while (sp > script && sp[-1] != ' ' && sp[-1] != '\t') --sp;
interp = sp;
if (!insert_arg(stack, stk_bytes, sp, INSERT)) return(NULL);
}
/* Round *stk_bytes up to the size of a pointer for alignment contraints. */
*stk_bytes= ((*stk_bytes + PTRSIZE - 1) / PTRSIZE) * PTRSIZE;
close(fd);
return(interp);
}
/*===========================================================================*
* rw_seg *
*===========================================================================*/
PUBLIC void rw_seg(rw, fd, proc, seg, seg_bytes0)
int rw; /* 0 = read, 1 = write */
int fd; /* file descriptor to read from / write to */
int proc; /* process number */
int seg; /* T, D, or S */
phys_bytes seg_bytes0; /* how much is to be transferred? */
{
/* Transfer text or data from/to a file and copy to/from a process segment.
* This procedure is a little bit tricky. The logical way to transfer a
* segment would be block by block and copying each block to/from the user
* space one at a time. This is too slow, so we do something dirty here,
* namely send the user space and virtual address to the file system in the
* upper 10 bits of the file descriptor, and pass it the user virtual address
* instead of a PM address. The file system extracts these parameters when
* gets a read or write call from the process manager, which is the only
* process that is permitted to use this trick. The file system then copies
* the whole segment directly to/from user space, bypassing PM completely.
*
* 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 new_fd, bytes, r;
char *ubuf_ptr;
struct mem_map *sp = &mproc[proc].mp_seg[seg];
phys_bytes seg_bytes = seg_bytes0;
new_fd = (proc << 7) | (seg << 5) | fd;
ubuf_ptr = (char *) ((vir_bytes) sp->mem_vir << CLICK_SHIFT);
while (seg_bytes != 0) {
#define PM_CHUNK_SIZE 8192
bytes = MIN((INT_MAX / PM_CHUNK_SIZE) * PM_CHUNK_SIZE, seg_bytes);
if (rw == 0) {
r = read(new_fd, ubuf_ptr, bytes);
} else {
r = write(new_fd, ubuf_ptr, bytes);
}
if (r != bytes) break;
ubuf_ptr += bytes;
seg_bytes -= bytes;
}
}
/*===========================================================================*
* find_share *
*===========================================================================*/
PUBLIC struct mproc *find_share(mp_ign, ino, dev, ctime)
struct mproc *mp_ign; /* process that should not be looked at */
ino_t ino; /* parameters that uniquely identify a file */
dev_t dev;
time_t ctime;
{
/* Look for a process that is the file <ino, dev, ctime> in execution. Don't
* accidentally "find" mp_ign, because it is the process on whose behalf this
* call is made.
*/
struct mproc *sh_mp;
for (sh_mp = &mproc[0]; sh_mp < &mproc[NR_PROCS]; sh_mp++) {
if (!(sh_mp->mp_flags & SEPARATE)) continue;
if (sh_mp == mp_ign) continue;
if (sh_mp->mp_ino != ino) continue;
if (sh_mp->mp_dev != dev) continue;
if (sh_mp->mp_ctime != ctime) continue;
return sh_mp;
}
return(NULL);
}
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