arch/s390/boot/kaslr.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright IBM Corp. 2019
   4  */
   5 #include <asm/mem_detect.h>
   6 #include <asm/cpacf.h>
   7 #include <asm/timex.h>
   8 #include <asm/sclp.h>
   9 #include "compressed/decompressor.h"
  10
  11 #define PRNG_MODE_TDES   1
  12 #define PRNG_MODE_SHA512 2
  13 #define PRNG_MODE_TRNG   3
  14
  15 struct prno_parm {
  16         u32 res;
  17         u32 reseed_counter;
  18         u64 stream_bytes;
  19         u8  V[112];
  20         u8  C[112];
  21 };
  22
  23 struct prng_parm {
  24         u8  parm_block[32];
  25         u32 reseed_counter;
  26         u64 byte_counter;
  27 };
  28
  29 static int check_prng(void)
  30 {
  31         if (!cpacf_query_func(CPACF_KMC, CPACF_KMC_PRNG)) {
  32                 sclp_early_printk("KASLR disabled: CPU has no PRNG\n");
  33                 return 0;
  34         }
  35         if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG))
  36                 return PRNG_MODE_TRNG;
  37         if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_SHA512_DRNG_GEN))
  38                 return PRNG_MODE_SHA512;
  39         else
  40                 return PRNG_MODE_TDES;
  41 }
  42
  43 static unsigned long get_random(unsigned long limit)
  44 {
  45         struct prng_parm prng = {
  46                 /* initial parameter block for tdes mode, copied from libica */
  47                 .parm_block = {
  48                         0x0F, 0x2B, 0x8E, 0x63, 0x8C, 0x8E, 0xD2, 0x52,
  49                         0x64, 0xB7, 0xA0, 0x7B, 0x75, 0x28, 0xB8, 0xF4,
  50                         0x75, 0x5F, 0xD2, 0xA6, 0x8D, 0x97, 0x11, 0xFF,
  51                         0x49, 0xD8, 0x23, 0xF3, 0x7E, 0x21, 0xEC, 0xA0
  52                 },
  53         };
  54         unsigned long seed, random;
  55         struct prno_parm prno;
  56         __u64 entropy[4];
  57         int mode, i;
  58
  59         mode = check_prng();
  60         seed = get_tod_clock_fast();
  61         switch (mode) {
  62         case PRNG_MODE_TRNG:
  63                 cpacf_trng(NULL, 0, (u8 *) &random, sizeof(random));
  64                 break;
  65         case PRNG_MODE_SHA512:
  66                 cpacf_prno(CPACF_PRNO_SHA512_DRNG_SEED, &prno, NULL, 0,
  67                            (u8 *) &seed, sizeof(seed));
  68                 cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN, &prno, (u8 *) &random,
  69                            sizeof(random), NULL, 0);
  70                 break;
  71         case PRNG_MODE_TDES:
  72                 /* add entropy */
  73                 *(unsigned long *) prng.parm_block ^= seed;
  74                 for (i = 0; i < 16; i++) {
  75                         cpacf_kmc(CPACF_KMC_PRNG, prng.parm_block,
  76                                   (char *) entropy, (char *) entropy,
  77                                   sizeof(entropy));
  78                         memcpy(prng.parm_block, entropy, sizeof(entropy));
  79                 }
  80                 random = seed;
  81                 cpacf_kmc(CPACF_KMC_PRNG, prng.parm_block, (u8 *) &random,
  82                           (u8 *) &random, sizeof(random));
  83                 break;
  84         default:
  85                 random = 0;
  86         }
  87         return random % limit;
  88 }
  89
  90 unsigned long get_random_base(unsigned long safe_addr)
  91 {
  92         unsigned long base, start, end, kernel_size;
  93         unsigned long block_sum, offset;
  94         int i;
  95
  96         if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && INITRD_START && INITRD_SIZE) {
  97                 if (safe_addr < INITRD_START + INITRD_SIZE)
  98                         safe_addr = INITRD_START + INITRD_SIZE;
  99         }
 100         safe_addr = ALIGN(safe_addr, THREAD_SIZE);
 101
 102         kernel_size = vmlinux.image_size + vmlinux.bss_size;
 103         block_sum = 0;
 104         for_each_mem_detect_block(i, &start, &end) {
 105                 if (memory_end_set) {
 106                         if (start >= memory_end)
 107                                 break;
 108                         if (end > memory_end)
 109                                 end = memory_end;
 110                 }
 111                 if (end - start < kernel_size)
 112                         continue;
 113                 block_sum += end - start - kernel_size;
 114         }
 115         if (!block_sum) {
 116                 sclp_early_printk("KASLR disabled: not enough memory\n");
 117                 return 0;
 118         }
 119
 120         base = get_random(block_sum);
 121         if (base == 0)
 122                 return 0;
 123         if (base < safe_addr)
 124                 base = safe_addr;
 125         block_sum = offset = 0;
 126         for_each_mem_detect_block(i, &start, &end) {
 127                 if (memory_end_set) {
 128                         if (start >= memory_end)
 129                                 break;
 130                         if (end > memory_end)
 131                                 end = memory_end;
 132                 }
 133                 if (end - start < kernel_size)
 134                         continue;
 135                 block_sum += end - start - kernel_size;
 136                 if (base <= block_sum) {
 137                         base = start + base - offset;
 138                         base = ALIGN_DOWN(base, THREAD_SIZE);
 139                         break;
 140                 }
 141                 offset = block_sum;
 142         }
 143         return base;
 144 }