FreeBSD/Linux Kernel Cross Reference
sys/bsd/kern/kern_symfile.c

     /*
      * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
      *
      * @APPLE_LICENSE_HEADER_START@
      * 
      * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
      * 
      * This file contains Original Code and/or Modifications of Original Code
      * as defined in and that are subject to the Apple Public Source License
     * Version 2.0 (the 'License'). You may not use this file except in
     * compliance with the License. Please obtain a copy of the License at
     * http://www.opensource.apple.com/apsl/ and read it before using this
     * file.
     * 
     * The Original Code and all software distributed under the License are
     * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
     * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
     * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
     * Please see the License for the specific language governing rights and
     * limitations under the License.
     * 
     * @APPLE_LICENSE_HEADER_END@
     */
    /* Copyright (c) 1998 Apple Computer, Inc.  All rights reserved.
     *
     *      File:   bsd/kern/kern_symfile.c
     *
     *      This file contains creates a dummy symbol file for mach_kernel based on
     *      the symbol table information passed by the SecondaryLoader/PlatformExpert.
     *      This allows us to correctly link other executables (drivers, etc) against the 
     *      the kernel in cases where the kernel image on the root device does not match
     *      the live kernel. This can occur during net-booting where the actual kernel
     *      image is obtained from the network via tftp rather than the root
     *      device.
     *
     *      If a symbol table is available, then the file /mach.sym will be created
     *      containing a Mach Header and a LC_SYMTAB load command followed by the
     *      the symbol table data for mach_kernel.
     *
     * HISTORY
     * 
     *      .
     */
    
    #include <mach/vm_param.h>
    
    #include <sys/param.h>
    #include <sys/systm.h>
    #include <sys/signalvar.h>
    #include <sys/resourcevar.h>
    #include <sys/namei.h>
    #include <sys/vnode.h>
    #include <sys/proc.h>
    #include <sys/timeb.h>
    #include <sys/times.h>
    #include <sys/buf.h>
    #include <sys/acct.h>
    #include <sys/file.h>
    #include <sys/uio.h>
    #include <sys/kernel.h>
    #include <sys/stat.h>
    
    #include <mach-o/loader.h>
    #include <mach-o/nlist.h>
    
    #include <vm/vm_kern.h>
    
    extern unsigned char    rootdevice[];
    extern struct mach_header _mh_execute_header;
    
    static int kernel_symfile_opened = 0;
    static int error_code = 0;
    
    extern int  IODTGetLoaderInfo(char *key, void **infoAddr, int *infoSize);
    extern void IODTFreeLoaderInfo(char *key, void *infoAddr, int infoSize);
    
    /*
     * 
     */
    static int output_kernel_symbols(struct proc *p)
    {
        struct vnode                *vp;
        struct pcred                *pcred = p->p_cred;
        struct ucred                *cred = pcred->pc_ucred;
        struct nameidata            nd;
        struct vattr                vattr;
        struct load_command         *cmd;
        struct mach_header          *orig_mh, *mh;
        struct segment_command      *orig_ds, *orig_ts, *orig_le, *sg;
        struct section              *se, *const_text;
        struct symtab_command       *st, *orig_st;
        struct nlist                *sym;
        vm_size_t                   orig_mhsize, orig_st_size;
        vm_offset_t                 header;
        vm_size_t                   header_size;
        int                         error, error1;
        int                         i, j;
        caddr_t                     addr;
       vm_offset_t                 offset;
       int                         rc_mh, rc_sc;
   
       error = EFAULT;
   
       vp          = NULL;
       header      = NULL;
       orig_mh     = NULL;
       orig_st     = NULL;
       
       // Dispose of unnecessary gumf, the booter doesn't need to load these
       rc_mh = IODTGetLoaderInfo("Kernel-__HEADER",
                                   (void **)&orig_mh, &orig_mhsize);
       if (rc_mh == 0 && orig_mh)
           IODTFreeLoaderInfo("Kernel-__HEADER",
                               (void *)orig_mh, round_page_32(orig_mhsize));
   
       rc_sc = IODTGetLoaderInfo("Kernel-__SYMTAB",
                                   (void **) &orig_st, &orig_st_size);
       if (rc_sc == 0 && orig_st)
           IODTFreeLoaderInfo("Kernel-__SYMTAB",
                               (void *)orig_st, round_page_32(orig_st_size));
   
       if (pcred->p_svuid != pcred->p_ruid || pcred->p_svgid != pcred->p_rgid)
           goto out;
   
       // Check to see if the root is 'e' or 'n', is this a test for network?
       if (rootdevice[0] == 'e' && rootdevice[1] == 'n')
           goto out;
   
       NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, "mach.sym", p);
       if((error = vn_open(&nd, O_CREAT | FWRITE, S_IRUSR | S_IRGRP | S_IROTH))) goto out;
   
       vp = nd.ni_vp;
       
       /* Don't dump to non-regular files or files with links. */
       error = EFAULT;
       if (vp->v_type != VREG || VOP_GETATTR(vp, &vattr, cred, p)
       ||  vattr.va_nlink != 1)
           goto out;
   
       VATTR_NULL(&vattr);
       vattr.va_size = 0;
       VOP_LEASE(vp, p, cred, LEASE_WRITE);
       VOP_SETATTR(vp, &vattr, cred, p);
       p->p_acflag |= ACORE;
   
       // If the file type is MH_EXECUTE then this must be a kernel
       // as all Kernel extensions must be of type MH_OBJECT
       orig_ds = orig_ts = orig_le = NULL;
       orig_st = NULL;
       orig_mh = &_mh_execute_header;
       cmd = (struct load_command *) &orig_mh[1];
       for (i = 0; i < orig_mh->ncmds; i++) {
           if (cmd->cmd == LC_SEGMENT) {
               struct segment_command *sg = (struct segment_command *) cmd;
       
               if (!strcmp(SEG_TEXT, sg->segname))
                   orig_ts = sg;
               else if (!strcmp(SEG_DATA, sg->segname))
                   orig_ds = sg;
               else if (!strcmp(SEG_LINKEDIT, sg->segname))
                   orig_le = sg;
           }
           else if (cmd->cmd == LC_SYMTAB)
               orig_st = (struct symtab_command *) cmd;
       
           cmd = (struct load_command *) ((caddr_t) cmd + cmd->cmdsize);
       }
   
       if (!orig_ts || !orig_ds || !orig_le || !orig_st) 
           goto out;
   
       const_text = NULL;
       se = (struct section *) &orig_ts[1];
       for (i = 0; i < orig_ts->nsects; i++, se++) {
           if (!strcmp("__const", se->sectname)) {
               const_text = se;
               break;
           }
       }
       if (!const_text)
           goto out;
   
       header_size =   sizeof(struct mach_header) 
                       + orig_ts->cmdsize
                       + orig_ds->cmdsize
                       + sizeof(struct symtab_command);
   
       (void) kmem_alloc_wired(kernel_map,
                               (vm_offset_t *) &header,
                               (vm_size_t) header_size);
       if (header)
           bzero((void *) header, header_size);
       else
           goto out;
   
       /*
        *  Set up Mach-O header.
        */
       mh = (struct mach_header *) header;
       mh->magic      = orig_mh->magic;
       mh->cputype    = orig_mh->cputype;
       mh->cpusubtype = orig_mh->cpusubtype;
       mh->filetype   = orig_mh->filetype;
       mh->ncmds      = 3;
       mh->sizeofcmds = header_size - sizeof(struct mach_header);
       mh->flags      = orig_mh->flags;
   
       // Initialise the current file offset and addr
       offset = round_page_32(header_size);
       addr = (caddr_t) const_text->addr;  // Load address of __TEXT,__const
   
       /*
        * Construct a TEXT segment load command
        * the only part of the TEXT segment we keep is the __TEXT,__const
        * which contains the kernel vtables. 
        */
       sg = (struct segment_command *) &mh[1];
       bcopy(orig_ts, sg, orig_ts->cmdsize);
       sg->vmaddr   = (unsigned long) addr;
       sg->vmsize   = const_text->size;
       sg->fileoff  = 0;
       sg->filesize = const_text->size + round_page_32(header_size);
       sg->maxprot  = 0;
       sg->initprot = 0;
       sg->flags    = 0;
       se = (struct section *)(sg+1);
       for ( j = 0; j < sg->nsects; j++, se++ ) {
           se->addr  = (unsigned long) addr;
           se->size  = 0;
           se->offset = offset;
           se->nreloc = 0;
           if (!strcmp("__const", se->sectname)) {
               se->size = const_text->size;
               addr    += const_text->size;
               offset  += const_text->size;
               const_text = se;
           }
       }
       offset = round_page_32((vm_address_t) offset);
   
       // Now copy of the __DATA segment load command, the image need
       // not be stored to disk nobody needs it, yet!
       sg = (struct segment_command *)((int)sg + sg->cmdsize);
       bcopy(orig_ds, sg, orig_ds->cmdsize);
   
       sg->vmaddr   = (unsigned long) addr;
       sg->vmsize   = 0x1000;      // One page for some reason?
       sg->fileoff  = offset;
       sg->filesize = 0;
       sg->maxprot  = 0;
       sg->initprot = 0;
       sg->flags    = 0;
       se = (struct section *)(sg+1);
       for ( j = 0; j < sg->nsects; j++, se++ ) {
           se->addr  = (unsigned long) addr;
           se->size  = 0;
           se->offset = offset;
           se->nreloc = 0;
       }
       offset = round_page_32(offset);
   
   
       /*
        *  Set up LC_SYMTAB command
        */
       st          = (struct symtab_command *)((int)sg + sg->cmdsize);
       st->cmd     = LC_SYMTAB;
       st->cmdsize = sizeof(struct symtab_command);
       st->symoff  = offset;
       st->nsyms   = orig_st->nsyms;
       st->strsize = orig_st->strsize;
       st->stroff =  offset + st->nsyms * sizeof(struct nlist);    
   
       /*
        * Convert the symbol table in place from section references
        * to absolute references.
        */
       sym = (struct nlist *) orig_le->vmaddr;
       for (i = 0; i < st->nsyms; i++, sym++ ) {
           if ( (sym->n_type & N_TYPE) == N_SECT) {
               sym->n_sect = NO_SECT;
               sym->n_type = (sym->n_type & ~N_TYPE) | N_ABS;
           }
       }
   
       /*
        *  Write out the load commands at the beginning of the file.
        */
       error = vn_rdwr(UIO_WRITE, vp, (caddr_t) mh, header_size, (off_t) 0,
                       UIO_SYSSPACE, IO_NODELOCKED|IO_UNIT, cred, (int *) 0, p);
       if (error)
           goto out;
   
       /*
        *  Write out the __TEXT,__const data segment.
        */
       error = vn_rdwr(UIO_WRITE, vp, (caddr_t) const_text->addr,
                       const_text->size, const_text->offset,
                       UIO_SYSSPACE, IO_NODELOCKED|IO_UNIT, cred, (int *) 0, p);
       if (error)
           goto out;
   
       /*
        *  Write out kernel symbols
        */
       offset = st->nsyms * sizeof(struct nlist) + st->strsize;    // symtab size
       error = vn_rdwr(UIO_WRITE, vp,
                      (caddr_t) orig_le->vmaddr, offset, st->symoff,
                       UIO_SYSSPACE, IO_NODELOCKED|IO_UNIT, cred, (int *) 0, p);
       if (error)
           goto out;
   
   out:
       if (header)
           kmem_free(kernel_map, header, header_size);
   
       if (vp) {
           VOP_UNLOCK(vp, 0, p);
           error1 = vn_close(vp, FWRITE, cred, p);
           if (!error) error = error1;
       }
   
       return(error);
   }
   /*
    * 
    */
   int get_kernel_symfile(struct proc *p, char **symfile)
   {
       if (!kernel_symfile_opened) {
           kernel_symfile_opened = 1;
           error_code = output_kernel_symbols(p);
       }
       if (!error_code)
           *symfile = "\\mach.sym";
   
       return error_code;
   }

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