/*- * Copyright (c) 1989, 1992, 1993 * The Regents of the University of California. All rights reserved. * * This code is derived from software developed by the Computer Systems * Engineering group at Lawrence Berkeley Laboratory under DARPA contract * BG 91-66 and contributed to Berkeley. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * $FreeBSD$ */ #if defined(LIBC_SCCS) && !defined(lint) static char sccsid[] = "@(#)kvm_proc.c 8.3 (Berkeley) 9/23/93"; #endif /* LIBC_SCCS and not lint */ /* * Proc traversal interface for kvm. ps and w are (probably) the exclusive * users of this code, so we've factored it out into a separate module. * Thus, we keep this grunge out of the other kvm applications (i.e., * most other applications are interested only in open/close/read/nlist). */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "kvm_private.h" #if used static char * kvm_readswap(kd, p, va, cnt) kvm_t *kd; const struct proc *p; u_long va; u_long *cnt; { #ifdef __FreeBSD__ /* XXX Stubbed out, our vm system is differnet */ _kvm_err(kd, kd->program, "kvm_readswap not implemented"); return(0); #endif /* __FreeBSD__ */ } #endif #define KREAD(kd, addr, obj) \ (kvm_read(kd, addr, (char *)(obj), sizeof(*obj)) != sizeof(*obj)) /* * Read proc's from memory file into buffer bp, which has space to hold * at most maxcnt procs. */ static int kvm_proclist(kd, what, arg, p, bp, maxcnt) kvm_t *kd; int what, arg; struct proc *p; struct kinfo_proc *bp; int maxcnt; { register int cnt = 0; struct kinfo_proc kinfo_proc, *kp; struct pgrp pgrp; struct session sess; struct tty tty; struct vmspace vmspace; struct procsig procsig; struct pcred pcred; struct pstats pstats; struct ucred ucred; struct proc proc; struct proc pproc; kp = &kinfo_proc; kp->ki_structsize = sizeof(kinfo_proc); for (; cnt < maxcnt && p != NULL; p = LIST_NEXT(&proc, p_list)) { if (KREAD(kd, (u_long)p, &proc)) { _kvm_err(kd, kd->program, "can't read proc at %x", p); return (-1); } if (KREAD(kd, (u_long)proc.p_cred, &pcred) == 0) { kp->ki_ruid = pcred.p_ruid; kp->ki_svuid = pcred.p_svuid; kp->ki_rgid = pcred.p_rgid; kp->ki_svgid = pcred.p_svgid; (void)(KREAD(kd, (u_long)pcred.pc_ucred, &ucred)); kp->ki_ngroups = ucred.cr_ngroups; bcopy(ucred.cr_groups, kp->ki_groups, NGROUPS * sizeof(gid_t)); kp->ki_uid = ucred.cr_uid; } switch(what) { case KERN_PROC_PID: if (proc.p_pid != (pid_t)arg) continue; break; case KERN_PROC_UID: if (kp->ki_uid != (uid_t)arg) continue; break; case KERN_PROC_RUID: if (kp->ki_ruid != (uid_t)arg) continue; break; } /* * We're going to add another proc to the set. If this * will overflow the buffer, assume the reason is because * nprocs (or the proc list) is corrupt and declare an error. */ if (cnt >= maxcnt) { _kvm_err(kd, kd->program, "nprocs corrupt"); return (-1); } /* * gather kinfo_proc */ kp->ki_paddr = p; kp->ki_addr = proc.p_addr; kp->ki_args = proc.p_args; kp->ki_tracep = proc.p_tracep; kp->ki_textvp = proc.p_textvp; kp->ki_fd = proc.p_fd; kp->ki_vmspace = proc.p_vmspace; if (proc.p_procsig != NULL) { if (KREAD(kd, (u_long)proc.p_procsig, &procsig)) { _kvm_err(kd, kd->program, "can't read procsig at %x", proc.p_procsig); return (-1); } kp->ki_sigignore = procsig.ps_sigignore; kp->ki_sigcatch = procsig.ps_sigcatch; } if ((proc.p_sflag & PS_INMEM) && proc.p_stats != NULL) { if (KREAD(kd, (u_long)proc.p_stats, &pstats)) { _kvm_err(kd, kd->program, "can't read stats at %x", proc.p_stats); return (-1); } kp->ki_start = pstats.p_start; kp->ki_rusage = pstats.p_ru; kp->ki_childtime.tv_sec = pstats.p_cru.ru_utime.tv_sec + pstats.p_cru.ru_stime.tv_sec; kp->ki_childtime.tv_usec = pstats.p_cru.ru_utime.tv_usec + pstats.p_cru.ru_stime.tv_usec; } if (KREAD(kd, (u_long)proc.p_pgrp, &pgrp)) { _kvm_err(kd, kd->program, "can't read pgrp at %x", proc.p_pgrp); return (-1); } if (proc.p_oppid) kp->ki_ppid = proc.p_oppid; else if (proc.p_pptr) { if (KREAD(kd, (u_long)proc.p_pptr, &pproc)) { _kvm_err(kd, kd->program, "can't read pproc at %x", proc.p_pptr); return (-1); } kp->ki_ppid = pproc.p_pid; } else kp->ki_ppid = 0; kp->ki_pgid = pgrp.pg_id; kp->ki_jobc = pgrp.pg_jobc; if (KREAD(kd, (u_long)pgrp.pg_session, &sess)) { _kvm_err(kd, kd->program, "can't read session at %x", pgrp.pg_session); return (-1); } kp->ki_sid = sess.s_sid; (void)memcpy(kp->ki_login, sess.s_login, sizeof(kp->ki_login)); kp->ki_kiflag = sess.s_ttyvp ? KI_CTTY : 0; if (sess.s_leader == p) kp->ki_kiflag |= KI_SLEADER; if ((proc.p_flag & P_CONTROLT) && sess.s_ttyp != NULL) { if (KREAD(kd, (u_long)sess.s_ttyp, &tty)) { _kvm_err(kd, kd->program, "can't read tty at %x", sess.s_ttyp); return (-1); } kp->ki_tdev = tty.t_dev; if (tty.t_pgrp != NULL) { if (KREAD(kd, (u_long)tty.t_pgrp, &pgrp)) { _kvm_err(kd, kd->program, "can't read tpgrp at &x", tty.t_pgrp); return (-1); } kp->ki_tpgid = pgrp.pg_id; } else kp->ki_tpgid = -1; if (tty.t_session != NULL) { if (KREAD(kd, (u_long)tty.t_session, &sess)) { _kvm_err(kd, kd->program, "can't read session at %x", tty.t_session); return (-1); } kp->ki_tsid = sess.s_sid; } } else kp->ki_tdev = NODEV; if (proc.p_wmesg) (void)kvm_read(kd, (u_long)proc.p_wmesg, kp->ki_wmesg, WMESGLEN); #ifdef sparc (void)kvm_read(kd, (u_long)&proc.p_vmspace->vm_rssize, (char *)&kp->ki_rssize, sizeof(kp->ki_rssize)); (void)kvm_read(kd, (u_long)&proc.p_vmspace->vm_tsize, (char *)&kp->ki_tsize, 3 * sizeof(kp->ki_rssize)); /* XXX */ #else (void)kvm_read(kd, (u_long)proc.p_vmspace, (char *)&vmspace, sizeof(vmspace)); kp->ki_size = vmspace.vm_map.size; kp->ki_rssize = vmspace.vm_swrss; /* XXX */ kp->ki_swrss = vmspace.vm_swrss; kp->ki_tsize = vmspace.vm_tsize; kp->ki_dsize = vmspace.vm_dsize; kp->ki_ssize = vmspace.vm_ssize; #endif switch (what) { case KERN_PROC_PGRP: if (kp->ki_pgid != (pid_t)arg) continue; break; case KERN_PROC_TTY: if ((proc.p_flag & P_CONTROLT) == 0 || kp->ki_tdev != (dev_t)arg) continue; break; } if (proc.p_comm[0] != 0) { strncpy(kp->ki_comm, proc.p_comm, MAXCOMLEN); kp->ki_comm[MAXCOMLEN] = 0; } if (proc.p_blocked != 0) { kp->ki_kiflag |= KI_MTXBLOCK; if (proc.p_mtxname) (void)kvm_read(kd, (u_long)proc.p_mtxname, kp->ki_mtxname, MTXNAMELEN); kp->ki_mtxname[MTXNAMELEN] = 0; } kp->ki_rtprio = proc.p_rtprio; kp->ki_runtime = proc.p_runtime; kp->ki_pid = proc.p_pid; kp->ki_siglist = proc.p_siglist; kp->ki_sigmask = proc.p_sigmask; kp->ki_xstat = proc.p_xstat; kp->ki_acflag = proc.p_acflag; kp->ki_pctcpu = proc.p_pctcpu; kp->ki_estcpu = proc.p_estcpu; kp->ki_slptime = proc.p_slptime; kp->ki_swtime = proc.p_swtime; kp->ki_flag = proc.p_flag; kp->ki_sflag = proc.p_sflag; kp->ki_wchan = proc.p_wchan; kp->ki_traceflag = proc.p_traceflag; kp->ki_priority = proc.p_priority; kp->ki_usrpri = proc.p_usrpri; kp->ki_nativepri = proc.p_nativepri; kp->ki_stat = proc.p_stat; kp->ki_nice = proc.p_nice; kp->ki_lock = proc.p_lock; kp->ki_rqindex = proc.p_rqindex; kp->ki_oncpu = proc.p_oncpu; kp->ki_lastcpu = proc.p_lastcpu; bcopy(&kinfo_proc, bp, sizeof(kinfo_proc)); ++bp; ++cnt; } return (cnt); } /* * Build proc info array by reading in proc list from a crash dump. * Return number of procs read. maxcnt is the max we will read. */ static int kvm_deadprocs(kd, what, arg, a_allproc, a_zombproc, maxcnt) kvm_t *kd; int what, arg; u_long a_allproc; u_long a_zombproc; int maxcnt; { register struct kinfo_proc *bp = kd->procbase; register int acnt, zcnt; struct proc *p; if (KREAD(kd, a_allproc, &p)) { _kvm_err(kd, kd->program, "cannot read allproc"); return (-1); } acnt = kvm_proclist(kd, what, arg, p, bp, maxcnt); if (acnt < 0) return (acnt); if (KREAD(kd, a_zombproc, &p)) { _kvm_err(kd, kd->program, "cannot read zombproc"); return (-1); } zcnt = kvm_proclist(kd, what, arg, p, bp + acnt, maxcnt - acnt); if (zcnt < 0) zcnt = 0; return (acnt + zcnt); } struct kinfo_proc * kvm_getprocs(kd, op, arg, cnt) kvm_t *kd; int op, arg; int *cnt; { int mib[4], st, nprocs; size_t size; if (kd->procbase != 0) { free((void *)kd->procbase); /* * Clear this pointer in case this call fails. Otherwise, * kvm_close() will free it again. */ kd->procbase = 0; } if (ISALIVE(kd)) { size = 0; mib[0] = CTL_KERN; mib[1] = KERN_PROC; mib[2] = op; mib[3] = arg; st = sysctl(mib, op == KERN_PROC_ALL ? 3 : 4, NULL, &size, NULL, 0); if (st == -1) { _kvm_syserr(kd, kd->program, "kvm_getprocs"); return (0); } do { size += size / 10; kd->procbase = (struct kinfo_proc *) _kvm_realloc(kd, kd->procbase, size); if (kd->procbase == 0) return (0); st = sysctl(mib, op == KERN_PROC_ALL ? 3 : 4, kd->procbase, &size, NULL, 0); } while (st == -1 && errno == ENOMEM); if (st == -1) { _kvm_syserr(kd, kd->program, "kvm_getprocs"); return (0); } if (kd->procbase->ki_structsize != sizeof(struct kinfo_proc)) { _kvm_err(kd, kd->program, "kinfo_proc size mismatch (expected %d, got %d)", sizeof(struct kinfo_proc), kd->procbase->ki_structsize); return (0); } nprocs = size / kd->procbase->ki_structsize; } else { struct nlist nl[4], *p; nl[0].n_name = "_nprocs"; nl[1].n_name = "_allproc"; nl[2].n_name = "_zombproc"; nl[3].n_name = 0; if (kvm_nlist(kd, nl) != 0) { for (p = nl; p->n_type != 0; ++p) ; _kvm_err(kd, kd->program, "%s: no such symbol", p->n_name); return (0); } if (KREAD(kd, nl[0].n_value, &nprocs)) { _kvm_err(kd, kd->program, "can't read nprocs"); return (0); } size = nprocs * sizeof(struct kinfo_proc); kd->procbase = (struct kinfo_proc *)_kvm_malloc(kd, size); if (kd->procbase == 0) return (0); nprocs = kvm_deadprocs(kd, op, arg, nl[1].n_value, nl[2].n_value, nprocs); #ifdef notdef size = nprocs * sizeof(struct kinfo_proc); (void)realloc(kd->procbase, size); #endif } *cnt = nprocs; return (kd->procbase); } void _kvm_freeprocs(kd) kvm_t *kd; { if (kd->procbase) { free(kd->procbase); kd->procbase = 0; } } void * _kvm_realloc(kd, p, n) kvm_t *kd; void *p; size_t n; { void *np = (void *)realloc(p, n); if (np == 0) { free(p); _kvm_err(kd, kd->program, "out of memory"); } return (np); } #ifndef MAX #define MAX(a, b) ((a) > (b) ? (a) : (b)) #endif /* * Read in an argument vector from the user address space of process kp. * addr if the user-space base address of narg null-terminated contiguous * strings. This is used to read in both the command arguments and * environment strings. Read at most maxcnt characters of strings. */ static char ** kvm_argv(kd, kp, addr, narg, maxcnt) kvm_t *kd; struct kinfo_proc *kp; register u_long addr; register int narg; register int maxcnt; { register char *np, *cp, *ep, *ap; register u_long oaddr = -1; register int len, cc; register char **argv; /* * Check that there aren't an unreasonable number of agruments, * and that the address is in user space. */ if (narg > 512 || addr < VM_MIN_ADDRESS || addr >= VM_MAXUSER_ADDRESS) return (0); /* * kd->argv : work space for fetching the strings from the target * process's space, and is converted for returning to caller */ if (kd->argv == 0) { /* * Try to avoid reallocs. */ kd->argc = MAX(narg + 1, 32); kd->argv = (char **)_kvm_malloc(kd, kd->argc * sizeof(*kd->argv)); if (kd->argv == 0) return (0); } else if (narg + 1 > kd->argc) { kd->argc = MAX(2 * kd->argc, narg + 1); kd->argv = (char **)_kvm_realloc(kd, kd->argv, kd->argc * sizeof(*kd->argv)); if (kd->argv == 0) return (0); } /* * kd->argspc : returned to user, this is where the kd->argv * arrays are left pointing to the collected strings. */ if (kd->argspc == 0) { kd->argspc = (char *)_kvm_malloc(kd, PAGE_SIZE); if (kd->argspc == 0) return (0); kd->arglen = PAGE_SIZE; } /* * kd->argbuf : used to pull in pages from the target process. * the strings are copied out of here. */ if (kd->argbuf == 0) { kd->argbuf = (char *)_kvm_malloc(kd, PAGE_SIZE); if (kd->argbuf == 0) return (0); } /* Pull in the target process'es argv vector */ cc = sizeof(char *) * narg; if (kvm_uread(kd, kp, addr, (char *)kd->argv, cc) != cc) return (0); /* * ap : saved start address of string we're working on in kd->argspc * np : pointer to next place to write in kd->argspc * len: length of data in kd->argspc * argv: pointer to the argv vector that we are hunting around the * target process space for, and converting to addresses in * our address space (kd->argspc). */ ap = np = kd->argspc; argv = kd->argv; len = 0; /* * Loop over pages, filling in the argument vector. * Note that the argv strings could be pointing *anywhere* in * the user address space and are no longer contiguous. * Note that *argv is modified when we are going to fetch a string * that crosses a page boundary. We copy the next part of the string * into to "np" and eventually convert the pointer. */ while (argv < kd->argv + narg && *argv != 0) { /* get the address that the current argv string is on */ addr = (u_long)*argv & ~(PAGE_SIZE - 1); /* is it the same page as the last one? */ if (addr != oaddr) { if (kvm_uread(kd, kp, addr, kd->argbuf, PAGE_SIZE) != PAGE_SIZE) return (0); oaddr = addr; } /* offset within the page... kd->argbuf */ addr = (u_long)*argv & (PAGE_SIZE - 1); /* cp = start of string, cc = count of chars in this chunk */ cp = kd->argbuf + addr; cc = PAGE_SIZE - addr; /* dont get more than asked for by user process */ if (maxcnt > 0 && cc > maxcnt - len) cc = maxcnt - len; /* pointer to end of string if we found it in this page */ ep = memchr(cp, '\0', cc); if (ep != 0) cc = ep - cp + 1; /* * at this point, cc is the count of the chars that we are * going to retrieve this time. we may or may not have found * the end of it. (ep points to the null if the end is known) */ /* will we exceed the malloc/realloced buffer? */ if (len + cc > kd->arglen) { register int off; register char **pp; register char *op = kd->argspc; kd->arglen *= 2; kd->argspc = (char *)_kvm_realloc(kd, kd->argspc, kd->arglen); if (kd->argspc == 0) return (0); /* * Adjust argv pointers in case realloc moved * the string space. */ off = kd->argspc - op; for (pp = kd->argv; pp < argv; pp++) *pp += off; ap += off; np += off; } /* np = where to put the next part of the string in kd->argspc*/ /* np is kinda redundant.. could use "kd->argspc + len" */ memcpy(np, cp, cc); np += cc; /* inc counters */ len += cc; /* * if end of string found, set the *argv pointer to the * saved beginning of string, and advance. argv points to * somewhere in kd->argv.. This is initially relative * to the target process, but when we close it off, we set * it to point in our address space. */ if (ep != 0) { *argv++ = ap; ap = np; } else { /* update the address relative to the target process */ *argv += cc; } if (maxcnt > 0 && len >= maxcnt) { /* * We're stopping prematurely. Terminate the * current string. */ if (ep == 0) { *np = '\0'; *argv++ = ap; } break; } } /* Make sure argv is terminated. */ *argv = 0; return (kd->argv); } static void ps_str_a(p, addr, n) struct ps_strings *p; u_long *addr; int *n; { *addr = (u_long)p->ps_argvstr; *n = p->ps_nargvstr; } static void ps_str_e(p, addr, n) struct ps_strings *p; u_long *addr; int *n; { *addr = (u_long)p->ps_envstr; *n = p->ps_nenvstr; } /* * Determine if the proc indicated by p is still active. * This test is not 100% foolproof in theory, but chances of * being wrong are very low. */ static int proc_verify(curkp) struct kinfo_proc *curkp; { struct kinfo_proc newkp; int mib[4]; size_t len; mib[0] = CTL_KERN; mib[1] = KERN_PROC; mib[2] = KERN_PROC_PID; mib[3] = curkp->ki_pid; len = sizeof(newkp); if (sysctl(mib, 4, &newkp, &len, NULL, 0) == -1) return (0); return (curkp->ki_pid == newkp.ki_pid && (newkp.ki_stat != SZOMB || curkp->ki_stat == SZOMB)); } static char ** kvm_doargv(kd, kp, nchr, info) kvm_t *kd; struct kinfo_proc *kp; int nchr; void (*info)(struct ps_strings *, u_long *, int *); { char **ap; u_long addr; int cnt; static struct ps_strings arginfo; static u_long ps_strings; size_t len; if (ps_strings == NULL) { len = sizeof(ps_strings); if (sysctlbyname("kern.ps_strings", &ps_strings, &len, NULL, 0) == -1) ps_strings = PS_STRINGS; } /* * Pointers are stored at the top of the user stack. */ if (kp->ki_stat == SZOMB || kvm_uread(kd, kp, ps_strings, (char *)&arginfo, sizeof(arginfo)) != sizeof(arginfo)) return (0); (*info)(&arginfo, &addr, &cnt); if (cnt == 0) return (0); ap = kvm_argv(kd, kp, addr, cnt, nchr); /* * For live kernels, make sure this process didn't go away. */ if (ap != 0 && ISALIVE(kd) && !proc_verify(kp)) ap = 0; return (ap); } /* * Get the command args. This code is now machine independent. */ char ** kvm_getargv(kd, kp, nchr) kvm_t *kd; const struct kinfo_proc *kp; int nchr; { int oid[4]; int i; size_t bufsz; static int buflen; static char *buf, *p; static char **bufp; static int argc; if (!ISALIVE(kd)) { _kvm_err(kd, kd->program, "cannot read user space from dead kernel"); return (0); } if (!buflen) { bufsz = sizeof(buflen); i = sysctlbyname("kern.ps_arg_cache_limit", &buflen, &bufsz, NULL, 0); if (i == -1) { buflen = 0; } else { buf = malloc(buflen); if (buf == NULL) buflen = 0; argc = 32; bufp = malloc(sizeof(char *) * argc); } } if (buf != NULL) { oid[0] = CTL_KERN; oid[1] = KERN_PROC; oid[2] = KERN_PROC_ARGS; oid[3] = kp->ki_pid; bufsz = buflen; i = sysctl(oid, 4, buf, &bufsz, 0, 0); if (i == 0 && bufsz > 0) { i = 0; p = buf; do { bufp[i++] = p; p += strlen(p) + 1; if (i >= argc) { argc += argc; bufp = realloc(bufp, sizeof(char *) * argc); } } while (p < buf + bufsz); bufp[i++] = 0; return (bufp); } } if (kp->ki_flag & P_SYSTEM) return (NULL); return (kvm_doargv(kd, kp, nchr, ps_str_a)); } char ** kvm_getenvv(kd, kp, nchr) kvm_t *kd; const struct kinfo_proc *kp; int nchr; { return (kvm_doargv(kd, kp, nchr, ps_str_e)); } /* * Read from user space. The user context is given by p. */ ssize_t kvm_uread(kd, kp, uva, buf, len) kvm_t *kd; struct kinfo_proc *kp; register u_long uva; register char *buf; register size_t len; { register char *cp; char procfile[MAXPATHLEN]; ssize_t amount; int fd; if (!ISALIVE(kd)) { _kvm_err(kd, kd->program, "cannot read user space from dead kernel"); return (0); } sprintf(procfile, "/proc/%d/mem", kp->ki_pid); fd = open(procfile, O_RDONLY, 0); if (fd < 0) { _kvm_err(kd, kd->program, "cannot open %s", procfile); close(fd); return (0); } cp = buf; while (len > 0) { errno = 0; if (lseek(fd, (off_t)uva, 0) == -1 && errno != 0) { _kvm_err(kd, kd->program, "invalid address (%x) in %s", uva, procfile); break; } amount = read(fd, cp, len); if (amount < 0) { _kvm_syserr(kd, kd->program, "error reading %s", procfile); break; } if (amount == 0) { _kvm_err(kd, kd->program, "EOF reading %s", procfile); break; } cp += amount; uva += amount; len -= amount; } close(fd); return ((ssize_t)(cp - buf)); }