1 /* 2 * Copyright (c) 1982, 1986, 1989, 1991 Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 * 7 * @(#)kern_fork.c 7.29 (Berkeley) 05/15/91 8 */ 9 10 #include "param.h" 11 #include "systm.h" 12 #include "map.h" 13 #include "filedesc.h" 14 #include "kernel.h" 15 #include "malloc.h" 16 #include "proc.h" 17 #include "resourcevar.h" 18 #include "vnode.h" 19 #include "seg.h" 20 #include "file.h" 21 #include "acct.h" 22 #include "ktrace.h" 23 24 /* ARGSUSED */ 25 fork(p, uap, retval) 26 struct proc *p; 27 void *uap; 28 int retval[]; 29 { 30 31 return (fork1(p, 0, retval)); 32 } 33 34 /* ARGSUSED */ 35 vfork(p, uap, retval) 36 struct proc *p; 37 void *uap; 38 int retval[]; 39 { 40 41 return (fork1(p, 1, retval)); 42 } 43 44 int nprocs = 1; /* process 0 */ 45 46 fork1(p1, isvfork, retval) 47 register struct proc *p1; 48 int isvfork, retval[]; 49 { 50 register struct proc *p2; 51 register int count, uid; 52 static int nextpid, pidchecked = 0; 53 54 count = 0; 55 if ((uid = p1->p_ucred->cr_uid) != 0) { 56 for (p2 = allproc; p2; p2 = p2->p_nxt) 57 if (p2->p_ucred->cr_uid == uid) 58 count++; 59 for (p2 = zombproc; p2; p2 = p2->p_nxt) 60 if (p2->p_ucred->cr_uid == uid) 61 count++; 62 } 63 /* 64 * Although process entries are dynamically entries, 65 * we still keep a global limit on the maximum number 66 * we will create. Don't allow a nonprivileged user 67 * to exceed its current limit or to bring us within one 68 * of the global limit; don't let root exceed the limit. 69 * nprocs is the current number of processes, 70 * maxproc is the limit. 71 */ 72 if (nprocs >= maxproc || uid == 0 && nprocs >= maxproc + 1) { 73 tablefull("proc"); 74 return (EAGAIN); 75 } 76 if (count > p1->p_rlimit[RLIMIT_NPROC].rlim_cur) 77 return (EAGAIN); 78 79 /* 80 * Find an unused process ID. 81 * We remember a range of unused IDs ready to use 82 * (from nextpid+1 through pidchecked-1). 83 */ 84 nextpid++; 85 retry: 86 /* 87 * If the process ID prototype has wrapped around, 88 * restart somewhat above 0, as the low-numbered procs 89 * tend to include daemons that don't exit. 90 */ 91 if (nextpid >= PID_MAX) { 92 nextpid = 100; 93 pidchecked = 0; 94 } 95 if (nextpid >= pidchecked) { 96 int doingzomb = 0; 97 98 pidchecked = PID_MAX; 99 /* 100 * Scan the active and zombie procs to check whether this pid 101 * is in use. Remember the lowest pid that's greater 102 * than nextpid, so we can avoid checking for a while. 103 */ 104 p2 = allproc; 105 again: 106 for (; p2 != NULL; p2 = p2->p_nxt) { 107 if (p2->p_pid == nextpid || 108 p2->p_pgrp->pg_id == nextpid) { 109 nextpid++; 110 if (nextpid >= pidchecked) 111 goto retry; 112 } 113 if (p2->p_pid > nextpid && pidchecked > p2->p_pid) 114 pidchecked = p2->p_pid; 115 if (p2->p_pgrp->pg_id > nextpid && 116 pidchecked > p2->p_pgrp->pg_id) 117 pidchecked = p2->p_pgrp->pg_id; 118 } 119 if (!doingzomb) { 120 doingzomb = 1; 121 p2 = zombproc; 122 goto again; 123 } 124 } 125 126 127 /* 128 * Allocate new proc. 129 * Link onto allproc (this should probably be delayed). 130 */ 131 MALLOC(p2, struct proc *, sizeof(struct proc), M_PROC, M_WAITOK); 132 nprocs++; 133 p2->p_nxt = allproc; 134 p2->p_nxt->p_prev = &p2->p_nxt; /* allproc is never NULL */ 135 p2->p_prev = &allproc; 136 allproc = p2; 137 p2->p_link = NULL; /* shouldn't be necessary */ 138 p2->p_rlink = NULL; /* shouldn't be necessary */ 139 140 /* 141 * Make a proc table entry for the new process. 142 * Start by zeroing the section of proc that is zero-initialized, 143 * then copy the section that is copied directly from the parent. 144 */ 145 bzero(&p2->p_startzero, 146 (unsigned) ((caddr_t)&p2->p_endzero - (caddr_t)&p2->p_startzero)); 147 bcopy(&p1->p_startcopy, &p2->p_startcopy, 148 (unsigned) ((caddr_t)&p2->p_endcopy - (caddr_t)&p2->p_startcopy)); 149 p2->p_spare[0] = 0; /* XXX - should be in zero range */ 150 p2->p_spare[1] = 0; /* XXX - should be in zero range */ 151 p2->p_spare[2] = 0; /* XXX - should be in zero range */ 152 p2->p_spare[3] = 0; /* XXX - should be in zero range */ 153 154 /* 155 * Duplicate sub-structures as needed. 156 * Increase reference counts on shared objects. 157 * The p_stats and p_sigacts substructs are set in vm_fork. 158 */ 159 MALLOC(p2->p_cred, struct pcred *, sizeof(struct pcred), 160 M_SUBPROC, M_WAITOK); 161 bcopy(p1->p_cred, p2->p_cred, sizeof(*p2->p_cred)); 162 p2->p_cred->p_refcnt = 1; 163 crhold(p1->p_ucred); 164 165 p2->p_fd = fdcopy(p1); 166 /* 167 * If p_limit is still copy-on-write, bump refcnt, 168 * otherwise get a copy that won't be modified. 169 * (If PL_SHAREMOD is clear, the structure is shared 170 * copy-on-write.) 171 */ 172 if (p1->p_limit->p_lflags & PL_SHAREMOD) 173 p2->p_limit = limcopy(p1->p_limit); 174 else { 175 p2->p_limit = p1->p_limit; 176 p2->p_limit->p_refcnt++; 177 } 178 179 p2->p_flag = SLOAD | (p1->p_flag & SHPUX); 180 if (p1->p_session->s_ttyvp != NULL && p1->p_flag & SCTTY) 181 p2->p_flag |= SCTTY; 182 if (isvfork) 183 p2->p_flag |= SPPWAIT; 184 p2->p_stat = SIDL; 185 p2->p_pid = nextpid; 186 { 187 struct proc **hash = &pidhash[PIDHASH(p2->p_pid)]; 188 189 p2->p_hash = *hash; 190 *hash = p2; 191 } 192 p2->p_pgrpnxt = p1->p_pgrpnxt; 193 p1->p_pgrpnxt = p2; 194 p2->p_pptr = p1; 195 p2->p_osptr = p1->p_cptr; 196 if (p1->p_cptr) 197 p1->p_cptr->p_ysptr = p2; 198 p1->p_cptr = p2; 199 #ifdef KTRACE 200 /* 201 * Copy traceflag and tracefile if enabled. 202 * If not inherited, these were zeroed above. 203 */ 204 if (p1->p_traceflag&KTRFAC_INHERIT) { 205 p2->p_traceflag = p1->p_traceflag; 206 if ((p2->p_tracep = p1->p_tracep) != NULL) 207 VREF(p2->p_tracep); 208 } 209 #endif 210 211 #if defined(tahoe) 212 p2->p_vmspace->p_ckey = p1->p_vmspace->p_ckey; /* XXX move this */ 213 #endif 214 215 /* 216 * This begins the section where we must prevent the parent 217 * from being swapped. 218 */ 219 p1->p_flag |= SKEEP; 220 /* 221 * Set return values for child before vm_fork, 222 * so they can be copied to child stack. 223 * We return parent pid, and mark as child in retval[1]. 224 * NOTE: the kernel stack may be at a different location in the child 225 * process, and thus addresses of automatic variables (including retval) 226 * may be invalid after vm_fork returns in the child process. 227 */ 228 retval[0] = p1->p_pid; 229 retval[1] = 1; 230 if (vm_fork(p1, p2, isvfork)) { 231 /* 232 * Child process. Set start time and get to work. 233 */ 234 (void) splclock(); 235 p2->p_stats->p_start = time; 236 (void) spl0(); 237 p2->p_acflag = AFORK; 238 return (0); 239 } 240 241 /* 242 * Make child runnable and add to run queue. 243 */ 244 (void) splhigh(); 245 p2->p_stat = SRUN; 246 setrq(p2); 247 (void) spl0(); 248 249 /* 250 * Now can be swapped. 251 */ 252 p1->p_flag &= ~SKEEP; 253 254 /* 255 * Preserve synchronization semantics of vfork. 256 * If waiting for child to exec or exit, set SPPWAIT 257 * on child, and sleep on our proc (in case of exit). 258 */ 259 if (isvfork) 260 while (p2->p_flag & SPPWAIT) 261 tsleep((caddr_t)p1, PWAIT, "ppwait", 0); 262 263 /* 264 * Return child pid to parent process, 265 * marking us as parent via retval[1]. 266 */ 267 retval[0] = p2->p_pid; 268 retval[1] = 0; 269 return (0); 270 } 271