FreeBSD/Linux Kernel Cross Reference
sys/ddb/db_textdump.c

     /*-
      * 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>
    __FBSDID("$FreeBSD: releng/11.2/sys/ddb/db_textdump.c 298807 2016-04-29 20:53:39Z pfg $");
    
    #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, 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         ""
   #define TAR_GID         ""
   #define TAR_MODE        "0600"
   #define TAR_USTAR       "ustar"
   
   #define TAR_CONFIG_FILENAME     "config.txt"    /* Kernel configuration. */
   #define TAR_MSGBUF_FILENAME     "msgbuf.txt"    /* Kernel messsage 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, 0, 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)
   {
           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;
   
           /*
            * 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);
           mkdumpheader(&kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION, 0, TEXTDUMP_BLOCKSIZE);
           (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 && panicstr != NULL)
                   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);
           mkdumpheader(&kdh, TEXTDUMPMAGIC, KERNELDUMP_TEXT_VERSION, dumplen,
               TEXTDUMP_BLOCKSIZE);
           (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, 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;
   }
   
   /*-
    * 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();
           }
   }

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