/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <limits.h>

#include "libproc.h"
#include "Pcontrol.h"
#include "Pisadep.h"
#include "Putil.h"

#define BLKSIZE (8 * 1024)

/*
 * Look for a SYSCALL instruction in the process's address space.
 */
int
Pscantext(struct ps_prochandle *P)
{
        char mapfile[PATH_MAX];
        int mapfd;
        off_t offset;           /* offset in text section */
        off_t endoff;           /* ending offset in text section */
        uintptr_t sysaddr;      /* address of SYSCALL instruction */
        int syspri;             /* priority of SYSCALL instruction */
        int nbytes;             /* number of bytes in buffer */
        int n2bytes;            /* number of bytes in second buffer */
        int nmappings;          /* current number of mappings */
        prmap_t *pdp;           /* pointer to map descriptor */
        prmap_t *prbuf;         /* buffer for map descriptors */
        unsigned nmap;          /* number of map descriptors */
        uint32_t buf[2 * BLKSIZE / sizeof (uint32_t)];  /* text buffer */
        uchar_t *p;

        /* try the most recently-seen syscall address */
        syspri = 0;
        sysaddr = 0;
        if (P->sysaddr != 0 &&
            (syspri = Pissyscall(P, P->sysaddr)))
                sysaddr = P->sysaddr;

        /* try the previous instruction */
        if (sysaddr == 0 || syspri != 1)
                syspri = Pissyscall_prev(P, P->status.pr_lwp.pr_reg[R_PC],
                    &sysaddr);

        if (sysaddr != 0 && syspri == 1) {
                P->sysaddr = sysaddr;
                return (0);
        }

        /* open the /proc/<pid>/map file */
        (void) snprintf(mapfile, sizeof (mapfile), "%s/%d/map",
            procfs_path, (int)P->pid);
        if ((mapfd = open(mapfile, O_RDONLY)) < 0) {
                Pdprintf("failed to open %s: %s\n", mapfile, strerror(errno));
                return (-1);
        }

        /* allocate a plausible initial buffer size */
        nmap = 50;

        /* read all the map structures, allocating more space as needed */
        for (;;) {
                prbuf = malloc(nmap * sizeof (prmap_t));
                if (prbuf == NULL) {
                        Pdprintf("Pscantext: failed to allocate buffer\n");
                        (void) close(mapfd);
                        return (-1);
                }
                nmappings = pread(mapfd, prbuf, nmap * sizeof (prmap_t), 0L);
                if (nmappings < 0) {
                        Pdprintf("Pscantext: failed to read map file: %s\n",
                            strerror(errno));
                        free(prbuf);
                        (void) close(mapfd);
                        return (-1);
                }
                nmappings /= sizeof (prmap_t);
                if (nmappings < nmap)   /* we read them all */
                        break;
                /* allocate a bigger buffer */
                free(prbuf);
                nmap *= 2;
        }
        (void) close(mapfd);

        /*
         * Scan each executable mapping looking for a syscall instruction.
         * In dynamically linked executables, syscall instructions are
         * typically only found in shared libraries.  Because shared libraries
         * are most often mapped at the top of the address space, we minimize
         * our expected search time by starting at the last mapping and working
         * our way down to the first mapping.
         */
        for (pdp = &prbuf[nmappings - 1]; sysaddr == 0 && syspri != 1 &&
            pdp >= prbuf; pdp--) {

                offset = (off_t)pdp->pr_vaddr;  /* beginning of text */
                endoff = offset + pdp->pr_size;

                /* avoid non-EXEC mappings; avoid the stack and heap */
                if ((pdp->pr_mflags&MA_EXEC) == 0 ||
                    (endoff > P->status.pr_stkbase &&
                    offset < P->status.pr_stkbase + P->status.pr_stksize) ||
                    (endoff > P->status.pr_brkbase &&
                    offset < P->status.pr_brkbase + P->status.pr_brksize))
                        continue;

                (void) lseek(P->asfd, (off_t)offset, 0);

                if ((nbytes = read(P->asfd, buf, 2*BLKSIZE)) <= 0)
                        continue;

                if (nbytes < BLKSIZE)
                        n2bytes = 0;
                else {
                        n2bytes = nbytes - BLKSIZE;
                        nbytes  = BLKSIZE;
                }

                p = (uchar_t *)buf;

                /* search text for a SYSCALL instruction */
                while (sysaddr == 0 && syspri != 1 && offset < endoff) {
                        if (nbytes <= 0) {      /* shift buffers */
                                if ((nbytes = n2bytes) <= 0)
                                        break;
                                (void) memcpy(buf,
                                    &buf[BLKSIZE / sizeof (buf[0])],
                                    nbytes);
                                n2bytes = 0;
                                p = (uchar_t *)buf;
                                if (nbytes == BLKSIZE &&
                                    offset + BLKSIZE < endoff)
                                        n2bytes = read(P->asfd,
                                            &buf[BLKSIZE / sizeof (buf[0])],
                                            BLKSIZE);
                        }

                        if (syspri = Pissyscall_text(P, p, nbytes))
                                sysaddr = offset;

                        p += sizeof (instr_t);
                        offset += sizeof (instr_t);
                        nbytes -= sizeof (instr_t);
                }
        }

        free(prbuf);

        if ((P->sysaddr = sysaddr) != 0)
                return (0);
        else
                return (-1);
}