diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:49:45 +0000 |
commit | 2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch) | |
tree | 848558de17fb3008cdf4d861b01ac7781903ce39 /arch/s390/boot/kaslr.c | |
parent | Initial commit. (diff) | |
download | linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip |
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/s390/boot/kaslr.c')
-rw-r--r-- | arch/s390/boot/kaslr.c | 203 |
1 files changed, 203 insertions, 0 deletions
diff --git a/arch/s390/boot/kaslr.c b/arch/s390/boot/kaslr.c new file mode 100644 index 000000000..58a8d8c8a --- /dev/null +++ b/arch/s390/boot/kaslr.c @@ -0,0 +1,203 @@ +// 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; + 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); + + 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); +} |