diff options
Diffstat (limited to 'arch/s390/boot/kaslr.c')
| -rw-r--r-- | arch/s390/boot/kaslr.c | 115 |
1 files changed, 9 insertions, 106 deletions
diff --git a/arch/s390/boot/kaslr.c b/arch/s390/boot/kaslr.c index 3e3d846400b4..71f75f03f800 100644 --- a/arch/s390/boot/kaslr.c +++ b/arch/s390/boot/kaslr.c @@ -3,7 +3,7 @@ * Copyright IBM Corp. 2019 */ #include <linux/pgtable.h> -#include <asm/mem_detect.h> +#include <asm/physmem_info.h> #include <asm/cpacf.h> #include <asm/timex.h> #include <asm/sclp.h> @@ -91,113 +91,16 @@ static int get_random(unsigned long limit, unsigned long *value) 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 get_random_base(void) { - 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; + unsigned long vmlinux_size = vmlinux.image_size + vmlinux.bss_size; + unsigned long minimal_pos = vmlinux.default_lma + vmlinux_size; + unsigned long random; - /* - * 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) + /* [vmlinux.default_lma + vmlinux.image_size + vmlinux.bss_size : physmem_info.usable] */ + if (get_random(physmem_info.usable - minimal_pos, &random)) 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); + return physmem_alloc_range(RR_VMLINUX, vmlinux_size, THREAD_SIZE, + vmlinux.default_lma, minimal_pos + random, false); } |