/*      $NetBSD: kern_core.c,v 1.42 2026/01/03 23:57:09 riastradh Exp $ */

/*
 * Copyright (c) 1982, 1986, 1989, 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * (c) UNIX System Laboratories, Inc.
 * All or some portions of this file are derived from material licensed
 * to the University of California by American Telephone and Telegraph
 * Co. or Unix System Laboratories, Inc. and are reproduced herein with
 * the permission of UNIX System Laboratories, Inc.
 *
 * 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. 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.
 *
 *      @(#)kern_sig.c  8.14 (Berkeley) 5/14/95
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: kern_core.c,v 1.42 2026/01/03 23:57:09 riastradh Exp $");

#ifdef _KERNEL_OPT
#include "opt_execfmt.h"
#include "opt_compat_netbsd32.h"
#endif

#include <sys/param.h>
#include <sys/types.h>

#include <sys/acct.h>
#include <sys/compat_stub.h>
#include <sys/exec.h>
#include <sys/exec_elf.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/kauth.h>
#include <sys/module.h>
#include <sys/namei.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>
#include <sys/sdt.h>
#include <sys/stat.h>
#include <sys/vnode.h>

MODULE(MODULE_CLASS_MISC, coredump, NULL);

struct coredump_iostate {
        struct lwp *io_lwp;
        struct vnode *io_vp;
        kauth_cred_t io_cred;
        off_t io_offset;
};

static int      coredump(struct lwp *, const char *);
static int      coredump_buildname(struct proc *, char *, const char *, size_t);
static int      coredump_write(struct coredump_iostate *, enum uio_seg segflg,
                    const void *, size_t);
static off_t    coredump_offset(struct coredump_iostate *);

static int
coredump_modcmd(modcmd_t cmd, void *arg)
{

        switch (cmd) {
        case MODULE_CMD_INIT:
                MODULE_HOOK_SET(coredump_hook, coredump);
                MODULE_HOOK_SET(coredump_write_hook, coredump_write);
                MODULE_HOOK_SET(coredump_offset_hook, coredump_offset);
                MODULE_HOOK_SET(coredump_netbsd_hook, real_coredump_netbsd);
#if defined(EXEC_ELF64)
                MODULE_HOOK_SET(coredump_elf64_hook, real_coredump_elf64);
#elif defined(EXEC_ELF32)
                MODULE_HOOK_SET(coredump_elf32_hook, real_coredump_elf32);
#endif
                MODULE_HOOK_SET(uvm_coredump_walkmap_hook,
                    uvm_coredump_walkmap);
                MODULE_HOOK_SET(uvm_coredump_count_segs_hook,
                    uvm_coredump_count_segs);
                return 0;
        case MODULE_CMD_FINI:
                MODULE_HOOK_UNSET(uvm_coredump_count_segs_hook);
                MODULE_HOOK_UNSET(uvm_coredump_walkmap_hook);
#if defined(EXEC_ELF64)
                MODULE_HOOK_UNSET(coredump_elf64_hook);
#elif defined(EXEC_ELF32)
                MODULE_HOOK_UNSET(coredump_elf32_hook);
#endif
                MODULE_HOOK_UNSET(coredump_netbsd_hook);
                MODULE_HOOK_UNSET(coredump_offset_hook);
                MODULE_HOOK_UNSET(coredump_write_hook);
                MODULE_HOOK_UNSET(coredump_hook);
                return 0;
        default:
                return SET_ERROR(ENOTTY);
        }
}

/*
 * Dump core, into a file named "progname.core" or "core" (depending on the
 * value of shortcorename), unless the process was setuid/setgid.
 */
static int
coredump(struct lwp *l, const char *pattern)
{
        struct vnode            *vp;
        struct proc             *p;
        struct vmspace          *vm;
        kauth_cred_t            cred = NULL;
        struct pathbuf          *pb;
        struct vattr            vattr;
        struct coredump_iostate io;
        struct plimit           *lim;
        int                     error, error1;
        char                    *name, *lastslash = NULL /* XXXgcc */;

        name = PNBUF_GET();

        p = l->l_proc;
        vm = p->p_vmspace;

        mutex_enter(&proc_lock);                /* p_session */
        mutex_enter(p->p_lock);

        /*
         * Refuse to core if the data + stack + user size is larger than
         * the core dump limit.  XXX THIS IS WRONG, because of mapped
         * data.
         */
        if (USPACE + ctob(vm->vm_dsize + vm->vm_ssize) >=
            p->p_rlimit[RLIMIT_CORE].rlim_cur) {
                error = SET_ERROR(EFBIG);       /* better error code? */
                goto release;
        }

        /*
         * It may well not be curproc, so grab a reference to its current
         * credentials.
         */
        cred = kauth_cred_hold(p->p_cred);

        /*
         * Make sure the process has not set-id, to prevent data leaks,
         * unless it was specifically requested to allow set-id coredumps.
         */
        if (p->p_flag & PK_SUGID) {
                if (!security_setidcore_dump) {
                        error = SET_ERROR(EPERM);
                        goto release;
                }
                pattern = security_setidcore_path;
        }

        /* Lock, as p_limit and pl_corename might change. */
        lim = p->p_limit;
        mutex_enter(&lim->pl_lock);
        if (pattern == NULL) {
                pattern = lim->pl_corename;
        }
        error = coredump_buildname(p, name, pattern, MAXPATHLEN);
        mutex_exit(&lim->pl_lock);

        if (error)
                goto release;

        /*
         * On a simple filename, see if the filesystem allow us to write
         * core dumps there.
         */
        lastslash = strrchr(name, '/');
        if (!lastslash) {
                vp = p->p_cwdi->cwdi_cdir;
                if (vp->v_mount == NULL ||
                    (vp->v_mount->mnt_flag & MNT_NOCOREDUMP) != 0)
                        error = SET_ERROR(EPERM);
        }

release:
        mutex_exit(p->p_lock);
        mutex_exit(&proc_lock);
        if (error)
                goto done;

        /*
         * On a complex filename, see if the filesystem allow us to write
         * core dumps there.
         *
         * XXX: We should have an API that avoids double lookups
         */
        if (lastslash) {
                char c[2];

                if (lastslash - name >= MAXPATHLEN - 2) {
                        error = SET_ERROR(EPERM);
                        goto done;
                }

                c[0] = lastslash[1];
                c[1] = lastslash[2];
                lastslash[1] = '.';
                lastslash[2] = '\0';
                error = namei_simple_kernel(name, NSM_FOLLOW_NOEMULROOT, &vp);
                if (error)
                        goto done;
                if (vp->v_mount == NULL ||
                    (vp->v_mount->mnt_flag & MNT_NOCOREDUMP) != 0)
                        error = SET_ERROR(EPERM);
                vrele(vp);
                if (error)
                        goto done;
                lastslash[1] = c[0];
                lastslash[2] = c[1];
        }

        pb = pathbuf_create(name);
        if (pb == NULL) {
                error = SET_ERROR(ENOMEM);
                goto done;
        }
        error = vn_open(NULL, pb, 0, O_CREAT | O_NOFOLLOW | FWRITE,
            S_IRUSR | S_IWUSR, &vp, NULL, NULL);
        if (error != 0) {
                pathbuf_destroy(pb);
                goto done;
        }
        pathbuf_destroy(pb);

        /*
         * Don't dump to:
         *      - non-regular files
         *      - files with links
         *      - files we don't own
         */
        if (vp->v_type != VREG ||
            VOP_GETATTR(vp, &vattr, cred) || vattr.va_nlink != 1 ||
            vattr.va_uid != kauth_cred_geteuid(cred)) {
                error = SET_ERROR(EACCES);
                goto out;
        }
        vattr_null(&vattr);
        vattr.va_size = 0;

        if ((p->p_flag & PK_SUGID) && security_setidcore_dump) {
                vattr.va_uid = security_setidcore_owner;
                vattr.va_gid = security_setidcore_group;
                vattr.va_mode = security_setidcore_mode;
        }

        VOP_SETATTR(vp, &vattr, cred);
        p->p_acflag |= ACORE;

        io.io_lwp = l;
        io.io_vp = vp;
        io.io_cred = cred;
        io.io_offset = 0;

        /* Now dump the actual core file. */
        error = (*p->p_execsw->es_coredump)(l, &io);
 out:
        VOP_UNLOCK(vp);
        error1 = vn_close(vp, FWRITE, cred);
        if (error == 0)
                error = error1;
done:
        if (cred != NULL)
                kauth_cred_free(cred);
        if (name != NULL)
                PNBUF_PUT(name);
        return error;
}

static int
coredump_buildname(struct proc *p, char *dst, const char *src, size_t len)
{
        const char      *s;
        char            *d, *end;
        int             i;

        KASSERT(mutex_owned(&proc_lock));

        for (s = src, d = dst, end = d + len; *s != '\0'; s++) {
                if (*s == '%') {
                        switch (*(s + 1)) {
                        case 'n':
                                i = snprintf(d, end - d, "%s", p->p_comm);
                                break;
                        case 'p':
                                i = snprintf(d, end - d, "%d", p->p_pid);
                                break;
                        case 'u':
                                i = snprintf(d, end - d, "%.*s",
                                    (int)sizeof p->p_pgrp->pg_session->s_login,
                                    p->p_pgrp->pg_session->s_login);
                                break;
                        case 't':
                                i = snprintf(d, end - d, "%lld",
                                    (long long)p->p_stats->p_start.tv_sec);
                                break;
                        default:
                                goto copy;
                        }
                        d += i;
                        s++;
                } else {
 copy:                  *d = *s;
                        d++;
                }
                if (d >= end)
                        return SET_ERROR(ENAMETOOLONG);
        }
        *d = '\0';
        return 0;
}

static int
coredump_write(struct coredump_iostate *io, enum uio_seg segflg,
    const void *data, size_t len)
{
        int error;

        error = vn_rdwr(UIO_WRITE, io->io_vp, __UNCONST(data), len,
            io->io_offset, segflg,
            IO_NODELOCKED|IO_UNIT, io->io_cred, NULL,
            segflg == UIO_USERSPACE ? io->io_lwp : NULL);
        if (error) {
                printf("pid %d (%s): %s write of %zu@%p at %lld failed: %d\n",
                    io->io_lwp->l_proc->p_pid, io->io_lwp->l_proc->p_comm,
                    segflg == UIO_USERSPACE ? "user" : "system",
                    len, data, (long long) io->io_offset, error);
                return (error);
        }

        io->io_offset += len;
        return (0);
}

static off_t
coredump_offset(struct coredump_iostate *io)
{
        return io->io_offset;
}