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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright IBM Corp. 2019
*/
#include <linux/pgtable.h>
#include <asm/mem_detect.h>
#include <asm/cpacf.h>
#include <asm/timex.h>
#include <asm/sclp.h>
#include <asm/kasan.h>
#include "decompressor.h"
#include "boot.h"
#define PRNG_MODE_TDES 1
#define PRNG_MODE_SHA512 2
#define PRNG_MODE_TRNG 3
struct prno_parm {
u32 res;
u32 reseed_counter;
u64 stream_bytes;
u8 V[112];
u8 C[112];
};
struct prng_parm {
u8 parm_block[32];
u32 reseed_counter;
u64 byte_counter;
};
static int check_prng(void)
{
if (!cpacf_query_func(CPACF_KMC, CPACF_KMC_PRNG)) {
sclp_early_printk("KASLR disabled: CPU has no PRNG\n");
return 0;
}
if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_TRNG))
return PRNG_MODE_TRNG;
if (cpacf_query_func(CPACF_PRNO, CPACF_PRNO_SHA512_DRNG_GEN))
return PRNG_MODE_SHA512;
else
return PRNG_MODE_TDES;
}
static int get_random(unsigned long limit, unsigned long *value)
{
struct prng_parm prng = {
/* initial parameter block for tdes mode, copied from libica */
.parm_block = {
0x0F, 0x2B, 0x8E, 0x63, 0x8C, 0x8E, 0xD2, 0x52,
0x64, 0xB7, 0xA0, 0x7B, 0x75, 0x28, 0xB8, 0xF4,
0x75, 0x5F, 0xD2, 0xA6, 0x8D, 0x97, 0x11, 0xFF,
0x49, 0xD8, 0x23, 0xF3, 0x7E, 0x21, 0xEC, 0xA0
},
};
unsigned long seed, random;
struct prno_parm prno;
__u64 entropy[4];
int mode, i;
mode = check_prng();
seed = get_tod_clock_fast();
switch (mode) {
case PRNG_MODE_TRNG:
cpacf_trng(NULL, 0, (u8 *) &random, sizeof(random));
break;
case PRNG_MODE_SHA512:
cpacf_prno(CPACF_PRNO_SHA512_DRNG_SEED, &prno, NULL, 0,
(u8 *) &seed, sizeof(seed));
cpacf_prno(CPACF_PRNO_SHA512_DRNG_GEN, &prno, (u8 *) &random,
sizeof(random), NULL, 0);
break;
case PRNG_MODE_TDES:
/* add entropy */
*(unsigned long *) prng.parm_block ^= seed;
for (i = 0; i < 16; i++) {
cpacf_kmc(CPACF_KMC_PRNG, prng.parm_block,
(u8 *) entropy, (u8 *) entropy,
sizeof(entropy));
memcpy(prng.parm_block, entropy, sizeof(entropy));
}
random = seed;
cpacf_kmc(CPACF_KMC_PRNG, prng.parm_block, (u8 *) &random,
(u8 *) &random, sizeof(random));
break;
default:
return -1;
}
*value = random % limit;
return 0;
}
/*
* To randomize kernel base address we have to consider several facts:
* 1. physical online memory might not be continuous and have holes. mem_detect
* info contains list of online memory ranges we should consider.
* 2. we have several memory regions which are occupied and we should not
* overlap and destroy them. Currently safe_addr tells us the border below
* which all those occupied regions are. We are safe to use anything above
* safe_addr.
* 3. the upper limit might apply as well, even if memory above that limit is
* online. Currently those limitations are:
* 3.1. Limit set by "mem=" kernel command line option
* 3.2. memory reserved at the end for kasan initialization.
* 4. kernel base address must be aligned to THREAD_SIZE (kernel stack size).
* Which is required for CONFIG_CHECK_STACK. Currently THREAD_SIZE is 4 pages
* (16 pages when the kernel is built with kasan enabled)
* Assumptions:
* 1. kernel size (including .bss size) and upper memory limit are page aligned.
* 2. mem_detect memory region start is THREAD_SIZE aligned / end is PAGE_SIZE
* aligned (in practice memory configurations granularity on z/VM and LPAR
* is 1mb).
*
* To guarantee uniform distribution of kernel base address among all suitable
* addresses we generate random value just once. For that we need to build a
* continuous range in which every value would be suitable. We can build this
* range by simply counting all suitable addresses (let's call them positions)
* which would be valid as kernel base address. To count positions we iterate
* over online memory ranges. For each range which is big enough for the
* kernel image we count all suitable addresses we can put the kernel image at
* that is
* (end - start - kernel_size) / THREAD_SIZE + 1
* Two functions count_valid_kernel_positions and position_to_address help
* to count positions in memory range given and then convert position back
* to address.
*/
static unsigned long count_valid_kernel_positions(unsigned long kernel_size,
unsigned long _min,
unsigned long _max)
{
unsigned long start, end, pos = 0;
int i;
for_each_mem_detect_block(i, &start, &end) {
if (_min >= end)
continue;
if (start >= _max)
break;
start = max(_min, start);
end = min(_max, end);
if (end - start < kernel_size)
continue;
pos += (end - start - kernel_size) / THREAD_SIZE + 1;
}
return pos;
}
static unsigned long position_to_address(unsigned long pos, unsigned long kernel_size,
unsigned long _min, unsigned long _max)
{
unsigned long start, end;
int i;
for_each_mem_detect_block(i, &start, &end) {
if (_min >= end)
continue;
if (start >= _max)
break;
start = max(_min, start);
end = min(_max, end);
if (end - start < kernel_size)
continue;
if ((end - start - kernel_size) / THREAD_SIZE + 1 >= pos)
return start + (pos - 1) * THREAD_SIZE;
pos -= (end - start - kernel_size) / THREAD_SIZE + 1;
}
return 0;
}
unsigned long get_random_base(unsigned long safe_addr)
{
unsigned long memory_limit = get_mem_detect_end();
unsigned long base_pos, max_pos, kernel_size;
unsigned long kasan_needs;
int i;
memory_limit = min(memory_limit, ident_map_size);
/*
* Avoid putting kernel in the end of physical memory
* which kasan will use for shadow memory and early pgtable
* mapping allocations.
*/
memory_limit -= kasan_estimate_memory_needs(memory_limit);
if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && initrd_data.start && initrd_data.size) {
if (safe_addr < initrd_data.start + initrd_data.size)
safe_addr = initrd_data.start + initrd_data.size;
}
safe_addr = ALIGN(safe_addr, THREAD_SIZE);
kernel_size = vmlinux.image_size + vmlinux.bss_size;
if (safe_addr + kernel_size > memory_limit)
return 0;
max_pos = count_valid_kernel_positions(kernel_size, safe_addr, memory_limit);
if (!max_pos) {
sclp_early_printk("KASLR disabled: not enough memory\n");
return 0;
}
/* we need a value in the range [1, base_pos] inclusive */
if (get_random(max_pos, &base_pos))
return 0;
return position_to_address(base_pos + 1, kernel_size, safe_addr, memory_limit);
}
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