/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2008 John Birrell (jb@freebsd.org)
 * All rights reserved.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 */

#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/user.h>
#include <sys/wait.h>

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

#include <libelf.h>
#include <libprocstat.h>

#include "_libproc.h"

extern char * const *environ;

static int      getelfclass(int);
static int      proc_init(pid_t, int, int, struct proc_handle **);

static int
getelfclass(int fd)
{
        GElf_Ehdr ehdr;
        Elf *e;
        int class;

        class = ELFCLASSNONE;

        if ((e = elf_begin(fd, ELF_C_READ, NULL)) == NULL)
                goto out;
        if (gelf_getehdr(e, &ehdr) == NULL)
                goto out;
        class = ehdr.e_ident[EI_CLASS];
out:
        (void)elf_end(e);
        return (class);
}

static int
proc_init(pid_t pid, int flags, int status, struct proc_handle **pphdl)
{
        struct kinfo_proc *kp;
        struct proc_handle *phdl;
        int error, class, count, fd;

        error = ENOMEM;
        if ((phdl = malloc(sizeof(*phdl))) == NULL)
                goto out;

        memset(phdl, 0, sizeof(*phdl));
        phdl->public.pid = pid;
        phdl->flags = flags;
        phdl->status = status;
        phdl->procstat = procstat_open_sysctl();
        if (phdl->procstat == NULL)
                goto out;

        /* Obtain a path to the executable. */
        if ((kp = procstat_getprocs(phdl->procstat, KERN_PROC_PID, pid,
            &count)) == NULL)
                goto out;
        error = procstat_getpathname(phdl->procstat, kp, phdl->execpath,
            sizeof(phdl->execpath));
        procstat_freeprocs(phdl->procstat, kp);
        if (error != 0)
                goto out;

        /* Use it to determine the data model for the process. */
        if ((fd = open(phdl->execpath, O_RDONLY)) < 0) {
                error = errno;
                goto out;
        }
        class = getelfclass(fd);
        switch (class) {
        case ELFCLASS64:
                phdl->model = PR_MODEL_LP64;
                break;
        case ELFCLASS32:
                phdl->model = PR_MODEL_ILP32;
                break;
        case ELFCLASSNONE:
        default:
                error = EINVAL;
                break;
        }
        (void)close(fd);

out:
        *pphdl = phdl;
        return (error);
}

int
proc_attach(pid_t pid, int flags, struct proc_handle **pphdl)
{
        struct proc_handle *phdl;
        int error, status;

        if (pid == 0 || (pid == getpid() && (flags & PATTACH_RDONLY) == 0))
                return (EINVAL);
        if (elf_version(EV_CURRENT) == EV_NONE)
                return (ENOENT);

        /*
         * Allocate memory for the process handle, a structure containing
         * all things related to the process.
         */
        error = proc_init(pid, flags, PS_RUN, &phdl);
        if (error != 0)
                goto out;

        if ((flags & PATTACH_RDONLY) == 0) {
                if (ptrace(PT_ATTACH, proc_getpid(phdl), 0, 0) != 0) {
                        error = errno;
                        DPRINTF("ERROR: cannot ptrace child process %d", pid);
                        goto out;
                }

                /* Wait for the child process to stop. */
                if (waitpid(pid, &status, WUNTRACED) == -1) {
                        error = errno;
                        DPRINTF("ERROR: child process %d didn't stop as expected", pid);
                        goto out;
                }

                /* Check for an unexpected status. */
                if (!WIFSTOPPED(status))
                        DPRINTFX("ERROR: child process %d status 0x%x", pid, status);
                else
                        phdl->status = PS_STOP;

                if ((flags & PATTACH_NOSTOP) != 0)
                        proc_continue(phdl);
        }

out:
        if (error != 0 && phdl != NULL) {
                proc_free(phdl);
                phdl = NULL;
        }
        *pphdl = phdl;
        return (error);
}

int
proc_create(const char *file, char * const *argv, char * const *envp,
    proc_child_func *pcf, void *child_arg, struct proc_handle **pphdl)
{
        struct proc_handle *phdl;
        int error, status;
        pid_t pid;

        if (elf_version(EV_CURRENT) == EV_NONE)
                return (ENOENT);

        error = 0;
        phdl = NULL;

        if ((pid = fork()) == -1)
                error = errno;
        else if (pid == 0) {
                /* The child expects to be traced. */
                if (ptrace(PT_TRACE_ME, 0, 0, 0) != 0)
                        _exit(1);

                if (pcf != NULL)
                        (*pcf)(child_arg);

                if (envp != NULL)
                        environ = envp;

                execvp(file, argv);

                _exit(2);
                /* NOTREACHED */
        } else {
                /* Wait for the child process to stop. */
                if (waitpid(pid, &status, WUNTRACED) == -1) {
                        error = errno;
                        DPRINTF("ERROR: child process %d didn't stop as expected", pid);
                        goto bad;
                }

                /* Check for an unexpected status. */
                if (!WIFSTOPPED(status)) {
                        error = ENOENT;
                        DPRINTFX("ERROR: child process %d status 0x%x", pid, status);
                        goto bad;
                }

                /* The parent owns the process handle. */
                error = proc_init(pid, 0, PS_IDLE, &phdl);
                if (error == 0)
                        phdl->status = PS_STOP;

bad:
                if (error != 0 && phdl != NULL) {
                        proc_free(phdl);
                        phdl = NULL;
                }
        }
        *pphdl = phdl;
        return (error);
}

void
proc_free(struct proc_handle *phdl)
{
        struct file_info *file;
        size_t i;

        for (i = 0; i < phdl->nmappings; i++) {
                file = phdl->mappings[i].file;
                if (file != NULL && --file->refs == 0) {
                        if (file->elf != NULL) {
                                (void)elf_end(file->elf);
                                (void)close(file->fd);
                                if (file->symtab.nsyms > 0)
                                        free(file->symtab.index);
                                if (file->dynsymtab.nsyms > 0)
                                        free(file->dynsymtab.index);
                        }
                        free(file);
                }
        }
        if (phdl->maparrsz > 0)
                free(phdl->mappings);
        if (phdl->procstat != NULL)
                procstat_close(phdl->procstat);
        if (phdl->rdap != NULL)
                rd_delete(phdl->rdap);
        free(phdl);
}