libproc/common/Pscantext.c

/*
 * 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.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#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) {
        dprintf("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) {
            dprintf("Pscantext: failed to allocate buffer\n");
            (void) close(mapfd);
            return (-1);
        }
        nmappings = pread(mapfd, prbuf, nmap * sizeof (prmap_t), 0L);
        if (nmappings < 0) {
            dprintf("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);
}