FreeBSD/Linux Kernel Cross Reference
sys/dev/random/nehemiah.c

     /*-
      * Copyright (c) 2013-2015 Mark R V Murray
      * Copyright (c) 2013 David E. O'Brien <obrien@NUXI.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
     *    in this position and unchanged.
     * 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 ``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 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/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/param.h>
    #include <sys/kernel.h>
    #include <sys/conf.h>
    #include <sys/lock.h>
    #include <sys/malloc.h>
    #include <sys/module.h>
    #include <sys/random.h>
    #include <sys/systm.h>
    
    #include <machine/segments.h>
    #include <machine/pcb.h>
    #include <machine/md_var.h>
    #include <machine/specialreg.h>
    
    #include <dev/random/randomdev.h>
    
    static void random_nehemiah_init(void);
    static void random_nehemiah_deinit(void);
    static u_int random_nehemiah_read(void *, u_int);
    
    static struct random_source random_nehemiah = {
            .rs_ident = "VIA Nehemiah Padlock RNG",
            .rs_source = RANDOM_PURE_NEHEMIAH,
            .rs_read = random_nehemiah_read
    };
    
    static struct fpu_kern_ctx *fpu_ctx_save;
    
    /* This H/W source never stores more than 8 bytes in one go */
    /* ARGSUSED */
    static __inline size_t
    VIA_RNG_store(void *buf)
    {
            uint32_t retval = 0;
            uint32_t rate = 0;
    
            __asm __volatile(
                    "movl   $0,%%edx\n\t"
                    ".byte 0x0f, 0xa7, 0xc0"
                            : "=a" (retval), "+d" (rate), "+D" (buf)
                            :
                            : "memory"
            );
            if (rate == 0)
                    return (retval&0x1f);
            return (0);
    }
    
    static void
    random_nehemiah_init(void)
    {
    
            fpu_ctx_save = fpu_kern_alloc_ctx(FPU_KERN_NORMAL);
    }
    
    static void
    random_nehemiah_deinit(void)
    {
    
            fpu_kern_free_ctx(fpu_ctx_save);
    }
    
    /* It is specifically allowed that buf is a multiple of sizeof(long) */
    static u_int
    random_nehemiah_read(void *buf, u_int c)
    {
            uint8_t *b;
            size_t count, ret;
           uint64_t tmp;
   
           fpu_kern_enter(curthread, fpu_ctx_save, FPU_KERN_NORMAL);
           b = buf;
           for (count = c; count > 0; count -= ret) {
                   ret = MIN(VIA_RNG_store(&tmp), count);
                   memcpy(b, &tmp, ret);
                   b += ret;
           }
           fpu_kern_leave(curthread, fpu_ctx_save);
   
           return (c);
   }
   
   static int
   nehemiah_modevent(module_t mod, int type, void *unused)
   {
           int error = 0;
   
           switch (type) {
           case MOD_LOAD:
                   if (via_feature_rng & VIA_HAS_RNG) {
                           random_source_register(&random_nehemiah);
                           printf("random: fast provider: \"%s\"\n", random_nehemiah.rs_ident);
                           random_nehemiah_init();
                   }
                   break;
   
           case MOD_UNLOAD:
                   if (via_feature_rng & VIA_HAS_RNG) {
                           random_nehemiah_deinit();
                           random_source_deregister(&random_nehemiah);
                   }
                   break;
   
           case MOD_SHUTDOWN:
                   break;
   
           default:
                   error = EOPNOTSUPP;
                   break;
   
           }
   
           return (error);
   }
   
   static moduledata_t nehemiah_mod = {
           "nehemiah",
           nehemiah_modevent,
           0
   };
   
   DECLARE_MODULE(nehemiah, nehemiah_mod, SI_SUB_RANDOM, SI_ORDER_FOURTH);
   MODULE_VERSION(nehemiah, 1);
   MODULE_DEPEND(nehemiah, random_harvestq, 1, 1, 1);

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