/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2007 Robert N. M. Watson
 * 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.
 */

/*-
 * Kernel text-dump support: write a series of text files to the dump
 * partition for later recovery, including captured DDB output, kernel
 * configuration, message buffer, and panic message.  This allows for a more
 * compact representation of critical debugging information than traditional
 * binary dumps, as well as allowing dump information to be used without
 * access to kernel symbols, source code, etc.
 *
 * Storage Layout
 * --------------
 *
 * Crash dumps are aligned to the end of the dump or swap partition in order
 * to minimize the chances of swap duing fsck eating into the dump.  However,
 * unlike a memory dump, we don't know the size of the textdump a priori, so
 * can't just write it out sequentially in order from a known starting point
 * calculated with respect to the end of the partition.  In order to address
 * this, we actually write out the textdump in reverse block order, allowing
 * us to directly align it to the end of the partition and then write out the
 * dump header and trailer before and after it once done.  savecore(8) must
 * know to reverse the order of the blocks in order to produce a readable
 * file.
 *
 * Data is written out in the ustar file format so that we can write data
 * incrementally as a stream without reference to previous files.
 *
 * TODO
 * ----
 *
 * - Allow subsystems to register to submit files for inclusion in the text
 *   dump in a generic way.
 */

#include <sys/cdefs.h>
#include "opt_config.h"

#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/kerneldump.h>
#include <sys/msgbuf.h>
#include <sys/sysctl.h>
#include <sys/systm.h>

#include <ddb/ddb.h>
#include <ddb/db_lex.h>

static SYSCTL_NODE(_debug_ddb, OID_AUTO, textdump,
    CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "DDB textdump options");

/*
 * Don't touch the first SIZEOF_METADATA bytes on the dump device.  This is
 * to protect us from metadata and metadata from us.
 */
#define SIZEOF_METADATA         (64*1024)

/*
 * Data is written out as a series of files in the ustar tar format.  ustar
 * is a simple streamed format consiting of a series of files prefixed with
 * headers, and all padded to 512-byte block boundaries, which maps
 * conveniently to our requirements.
 */
struct ustar_header {
        char    uh_filename[100];
        char    uh_mode[8];
        char    uh_tar_owner[8];
        char    uh_tar_group[8];
        char    uh_size[12];
        char    uh_mtime[12];
        char    uh_sum[8];
        char    uh_type;
        char    uh_linkfile[100];
        char    uh_ustar[6];
        char    uh_version[2];
        char    uh_owner[32];
        char    uh_group[32];
        char    uh_major[8];
        char    uh_minor[8];
        char    uh_filenameprefix[155];
        char    uh_zeropad[12];
} __packed;

/*
 * Various size assertions -- pretty much everything must be one block in
 * size.
 */
CTASSERT(sizeof(struct kerneldumpheader) == TEXTDUMP_BLOCKSIZE);
CTASSERT(sizeof(struct ustar_header) == TEXTDUMP_BLOCKSIZE);

/*
 * Is a textdump scheduled?  If so, the shutdown code will invoke our dumpsys
 * routine instead of the machine-dependent kernel dump routine.
 */
#ifdef TEXTDUMP_PREFERRED
int     textdump_pending = 1;
#else
int     textdump_pending = 0;
#endif
SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, pending, CTLFLAG_RW,
    &textdump_pending, 0,
    "Perform textdump instead of regular kernel dump.");

/*
 * Various constants for tar headers and contents.
 */
#define TAR_USER        "root"
#define TAR_GROUP       "wheel"
#define TAR_UID         "0"
#define TAR_GID         "0"
#define TAR_MODE        "0600"
#define TAR_USTAR       "ustar"

#define TAR_CONFIG_FILENAME     "config.txt"    /* Kernel configuration. */
#define TAR_MSGBUF_FILENAME     "msgbuf.txt"    /* Kernel message buffer. */
#define TAR_PANIC_FILENAME      "panic.txt"     /* Panic message. */
#define TAR_VERSION_FILENAME    "version.txt"   /* Kernel version. */

/*
 * Configure which files will be dumped.
 */
#ifdef INCLUDE_CONFIG_FILE
static int textdump_do_config = 1;
SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_config, CTLFLAG_RW,
    &textdump_do_config, 0, "Dump kernel configuration in textdump");
#endif

static int textdump_do_ddb = 1;
SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_ddb, CTLFLAG_RW,
    &textdump_do_ddb, 0, "Dump DDB captured output in textdump");

static int textdump_do_msgbuf = 1;
SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_msgbuf, CTLFLAG_RW,
    &textdump_do_msgbuf, 0, "Dump kernel message buffer in textdump");

static int textdump_do_panic = 1;
SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_panic, CTLFLAG_RW,
    &textdump_do_panic, 0, "Dump kernel panic message in textdump");

static int textdump_do_version = 1;
SYSCTL_INT(_debug_ddb_textdump, OID_AUTO, do_version, CTLFLAG_RW,
    &textdump_do_version, 0, "Dump kernel version string in textdump");

/*
 * State related to incremental writing of blocks to disk.
 */
static off_t textdump_offset;           /* Offset of next sequential write. */
static int textdump_error;              /* Carried write error, if any. */

/*
 * Statically allocate space to prepare block-sized headers and data.
 */
char textdump_block_buffer[TEXTDUMP_BLOCKSIZE];
static struct kerneldumpheader kdh;

/*
 * Calculate and fill in the checksum for a ustar header.
 */
static void
ustar_checksum(struct ustar_header *uhp)
{
        u_int sum;
        int i;

        for (i = 0; i < sizeof(uhp->uh_sum); i++)
                uhp->uh_sum[i] = ' ';
        sum = 0;
        for (i = 0; i < sizeof(*uhp); i++)
                sum += ((u_char *)uhp)[i];
        snprintf(uhp->uh_sum, sizeof(uhp->uh_sum), "%6o", sum);
}

/*
 * Each file in the tarball has a block-sized header with its name and other,
 * largely hard-coded, properties.
 */
void
textdump_mkustar(char *block_buffer, const char *filename, u_int size)
{
        struct ustar_header *uhp;

#ifdef TEXTDUMP_VERBOSE
        if (textdump_error == 0)
                printf("textdump: creating '%s'.\n", filename);
#endif
        uhp = (struct ustar_header *)block_buffer;
        bzero(uhp, sizeof(*uhp));
        strlcpy(uhp->uh_filename, filename, sizeof(uhp->uh_filename));
        strlcpy(uhp->uh_mode, TAR_MODE, sizeof(uhp->uh_mode));
        snprintf(uhp->uh_size, sizeof(uhp->uh_size), "%o", size);
        strlcpy(uhp->uh_tar_owner, TAR_UID, sizeof(uhp->uh_tar_owner));
        strlcpy(uhp->uh_tar_group, TAR_GID, sizeof(uhp->uh_tar_group));
        strlcpy(uhp->uh_owner, TAR_USER, sizeof(uhp->uh_owner));
        strlcpy(uhp->uh_group, TAR_GROUP, sizeof(uhp->uh_group));
        snprintf(uhp->uh_mtime, sizeof(uhp->uh_mtime), "%lo",
            (unsigned long)time_second);
        uhp->uh_type = 0;
        strlcpy(uhp->uh_ustar, TAR_USTAR, sizeof(uhp->uh_ustar));
        ustar_checksum(uhp);
}

/*
 * textdump_writeblock() writes TEXTDUMP_BLOCKSIZE-sized blocks of data to
 * the space between di->mediaoffset and di->mediaoffset + di->mediasize.  It
 * accepts an offset relative to di->mediaoffset.  If we're carrying any
 * error from previous I/O, return that error and don't continue to try to
 * write.  Most writers ignore the error and forge ahead on the basis that
 * there's not much you can do.
 */
static int
textdump_writeblock(struct dumperinfo *di, off_t offset, char *buffer)
{

        if (textdump_error)
                return (textdump_error);
        if (offset + TEXTDUMP_BLOCKSIZE > di->mediasize)
                return (EIO);
        if (offset < SIZEOF_METADATA)
                return (ENOSPC);
        textdump_error = dump_write(di, buffer, offset + di->mediaoffset,
            TEXTDUMP_BLOCKSIZE);
        if (textdump_error)
                printf("textdump_writeblock: offset %jd, error %d\n", (intmax_t)offset,
                    textdump_error);
        return (textdump_error);
}

/*
 * Interfaces to save and restore the dump offset, so that printers can go
 * back to rewrite a header if required, while avoiding their knowing about
 * the global layout of the blocks.
 *
 * If we ever want to support writing textdumps to tape or other
 * stream-oriented target, we'll need to remove this.
 */
void
textdump_saveoff(off_t *offsetp)
{

        *offsetp = textdump_offset;
}

void
textdump_restoreoff(off_t offset)
{

        textdump_offset = offset;
}

/*
 * Interface to write the "next block" relative to the current offset; since
 * we write backwards from the end of the partition, we subtract, but there's
 * no reason for the caller to know this.
 */
int
textdump_writenextblock(struct dumperinfo *di, char *buffer)
{
        int error;

        error = textdump_writeblock(di, textdump_offset, buffer);
        textdump_offset -= TEXTDUMP_BLOCKSIZE;
        return (error);
}

#ifdef INCLUDE_CONFIG_FILE
extern char kernconfstring[];

/*
 * Dump kernel configuration.
 */
static void
textdump_dump_config(struct dumperinfo *di)
{
        u_int count, fullblocks, len;

        len = strlen(kernconfstring);
        textdump_mkustar(textdump_block_buffer, TAR_CONFIG_FILENAME, len);
        (void)textdump_writenextblock(di, textdump_block_buffer);

        /*
         * Write out all full blocks directly from the string, and handle any
         * left-over bits by copying it to out to the local buffer and
         * zero-padding it.
         */
        fullblocks = len / TEXTDUMP_BLOCKSIZE;
        for (count = 0; count < fullblocks; count++)
                (void)textdump_writenextblock(di, kernconfstring + count *
                    TEXTDUMP_BLOCKSIZE);
        if (len % TEXTDUMP_BLOCKSIZE != 0) {
                bzero(textdump_block_buffer, TEXTDUMP_BLOCKSIZE);
                bcopy(kernconfstring + count * TEXTDUMP_BLOCKSIZE,
                    textdump_block_buffer, len % TEXTDUMP_BLOCKSIZE);
                (void)textdump_writenextblock(di, textdump_block_buffer);
        }
}
#endif /* INCLUDE_CONFIG_FILE */

/*
 * Dump kernel message buffer.
 */
static void
textdump_dump_msgbuf(struct dumperinfo *di)
{
        off_t end_offset, tarhdr_offset;
        u_int i, len, offset, seq, total_len;
        char buf[16];

        /*
         * Write out a dummy tar header to advance the offset; we'll rewrite
         * it later once we know the true size.
         */
        textdump_saveoff(&tarhdr_offset);
        textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME, 0);
        (void)textdump_writenextblock(di, textdump_block_buffer);

        /*
         * Copy out the data in small chunks, but don't copy nuls that may be
         * present if the message buffer has not yet completely filled at
         * least once.
         */
        total_len = 0;
        offset = 0;
        msgbuf_peekbytes(msgbufp, NULL, 0, &seq);
        while ((len = msgbuf_peekbytes(msgbufp, buf, sizeof(buf), &seq)) > 0) {
                for (i = 0; i < len; i++) {
                        if (buf[i] == '\0')
                                continue;
                        textdump_block_buffer[offset] = buf[i];
                        offset++;
                        if (offset != sizeof(textdump_block_buffer))
                                continue;
                        (void)textdump_writenextblock(di,
                            textdump_block_buffer);
                        total_len += offset;
                        offset = 0;
                }
        }
        total_len += offset;    /* Without the zero-padding. */
        if (offset != 0) {
                bzero(textdump_block_buffer + offset,
                    sizeof(textdump_block_buffer) - offset);
                (void)textdump_writenextblock(di, textdump_block_buffer);
        }

        /*
         * Rewrite tar header to reflect how much was actually written.
         */
        textdump_saveoff(&end_offset);
        textdump_restoreoff(tarhdr_offset);
        textdump_mkustar(textdump_block_buffer, TAR_MSGBUF_FILENAME,
            total_len);
        (void)textdump_writenextblock(di, textdump_block_buffer);
        textdump_restoreoff(end_offset);
}

static void
textdump_dump_panic(struct dumperinfo *di)
{
        u_int len;

        /*
         * Write out tar header -- we store up to one block of panic message.
         */
        len = min(strlen(panicstr), TEXTDUMP_BLOCKSIZE);
        textdump_mkustar(textdump_block_buffer, TAR_PANIC_FILENAME, len);
        (void)textdump_writenextblock(di, textdump_block_buffer);

        /*
         * Zero-pad the panic string and write out block.
         */
        bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
        bcopy(panicstr, textdump_block_buffer, len);
        (void)textdump_writenextblock(di, textdump_block_buffer);
}

static void
textdump_dump_version(struct dumperinfo *di)
{
        u_int len;

        /*
         * Write out tar header -- at most one block of version information.
         */
        len = min(strlen(version), TEXTDUMP_BLOCKSIZE);
        textdump_mkustar(textdump_block_buffer, TAR_VERSION_FILENAME, len);
        (void)textdump_writenextblock(di, textdump_block_buffer);

        /*
         * Zero pad the version string and write out block.
         */
        bzero(textdump_block_buffer, sizeof(textdump_block_buffer));
        bcopy(version, textdump_block_buffer, len);
        (void)textdump_writenextblock(di, textdump_block_buffer);
}

/*
 * Commit text dump to disk.
 */
void
textdump_dumpsys(struct dumperinfo *di)
{
        struct kerneldumpcrypto *kdc;
        off_t dumplen, trailer_offset;

        if (di->blocksize != TEXTDUMP_BLOCKSIZE) {
                printf("Dump partition block size (%ju) not textdump "
                    "block size (%ju)", (uintmax_t)di->blocksize,
                    (uintmax_t)TEXTDUMP_BLOCKSIZE);
                return;
        }

        /*
         * We don't know a priori how large the dump will be, but we do know
         * that we need to reserve space for metadata and that we need two
         * dump headers.  Also leave room for one ustar header and one block
         * of data.
         */
        if (di->mediasize < SIZEOF_METADATA + 2 * sizeof(kdh)) {
                printf("Insufficient space on dump partition for minimal textdump.\n");
                return;
        }
        textdump_error = 0;

        /*
         * Disable EKCD because we don't provide encrypted textdumps.
         */
        kdc = di->kdcrypto;
        di->kdcrypto = NULL;

        /*
         * Position the start of the dump so that we'll write the kernel dump
         * trailer immediately before the end of the partition, and then work
         * our way back.  We will rewrite this header later to reflect the
         * true size if things go well.
         */
        textdump_offset = di->mediasize - sizeof(kdh);
        textdump_saveoff(&trailer_offset);
        dump_init_header(di, &kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION, 0);
        (void)textdump_writenextblock(di, (char *)&kdh);

        /*
         * Write a series of files in ustar format.
         */
        if (textdump_do_ddb)
                db_capture_dump(di);
#ifdef INCLUDE_CONFIG_FILE
        if (textdump_do_config)
                textdump_dump_config(di);
#endif
        if (textdump_do_msgbuf)
                textdump_dump_msgbuf(di);
        if (textdump_do_panic && KERNEL_PANICKED())
                textdump_dump_panic(di);
        if (textdump_do_version)
                textdump_dump_version(di);

        /*
         * Now that we know the true size, we can write out the header, then
         * seek back to the end and rewrite the trailer with the correct
         * size.
         */
        dumplen = trailer_offset - (textdump_offset + TEXTDUMP_BLOCKSIZE);
        dump_init_header(di, &kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION,
            dumplen);
        (void)textdump_writenextblock(di, (char *)&kdh);
        textdump_restoreoff(trailer_offset);
        (void)textdump_writenextblock(di, (char *)&kdh);

        /*
         * Terminate the dump, report any errors, and clear the pending flag.
         */
        if (textdump_error == 0)
                (void)dump_write(di, NULL, 0, 0);
        if (textdump_error == ENOSPC)
                printf("Textdump: Insufficient space on dump partition\n");
        else if (textdump_error != 0)
                printf("Textdump: Error %d writing dump\n", textdump_error);
        else
                printf("Textdump complete.\n");
        textdump_pending = 0;

        /*
         * Restore EKCD status.
         */
        di->kdcrypto = kdc;
}

/*-
 * DDB(4) command to manage textdumps:
 *
 * textdump set        - request a textdump
 * textdump status     - print DDB output textdump status
 * textdump unset      - clear textdump request
 */
static void
db_textdump_usage(void)
{

        db_printf("textdump [unset|set|status|dump]\n");
}

void
db_textdump_cmd(db_expr_t addr, bool have_addr, db_expr_t count, char *modif)
{
        int t;

        t = db_read_token();
        if (t != tIDENT) {
                db_textdump_usage();
                return;
        }
        if (db_read_token() != tEOL) {
                db_textdump_usage();
                return;
        }
        if (strcmp(db_tok_string, "set") == 0) {
                textdump_pending = 1;
                db_printf("textdump set\n");
        } else if (strcmp(db_tok_string, "status") == 0) {
                if (textdump_pending)
                        db_printf("textdump is set\n");
                else
                        db_printf("textdump is not set\n");
        } else if (strcmp(db_tok_string, "unset") == 0) {
                textdump_pending = 0;
                db_printf("textdump unset\n");
        } else if (strcmp(db_tok_string, "dump") == 0) {
                textdump_pending = 1;
                doadump(true);
        } else {
                db_textdump_usage();
        }
}