204 lines
6.1 KiB
C
204 lines
6.1 KiB
C
// 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_usable_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_usable_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 usable_total = get_mem_detect_usable_total();
|
|
unsigned long memory_limit = get_mem_detect_end();
|
|
unsigned long base_pos, max_pos, kernel_size;
|
|
int i;
|
|
|
|
/*
|
|
* Avoid putting kernel in the end of physical memory
|
|
* which vmem and kasan code will use for shadow memory and
|
|
* pgtable mapping allocations.
|
|
*/
|
|
memory_limit -= kasan_estimate_memory_needs(usable_total);
|
|
memory_limit -= vmem_estimate_memory_needs(usable_total);
|
|
|
|
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);
|
|
}
|