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Diffstat (limited to '')
-rw-r--r-- | arch/powerpc/mm/nohash/kaslr_booke.c | 396 |
1 files changed, 396 insertions, 0 deletions
diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c b/arch/powerpc/mm/nohash/kaslr_booke.c new file mode 100644 index 000000000..0d04f9d5d --- /dev/null +++ b/arch/powerpc/mm/nohash/kaslr_booke.c @@ -0,0 +1,396 @@ +// SPDX-License-Identifier: GPL-2.0-only +// +// Copyright (C) 2019 Jason Yan <yanaijie@huawei.com> + +#include <linux/kernel.h> +#include <linux/errno.h> +#include <linux/string.h> +#include <linux/types.h> +#include <linux/mm.h> +#include <linux/swap.h> +#include <linux/stddef.h> +#include <linux/init.h> +#include <linux/delay.h> +#include <linux/memblock.h> +#include <linux/libfdt.h> +#include <linux/crash_core.h> +#include <linux/of.h> +#include <linux/of_fdt.h> +#include <asm/cacheflush.h> +#include <asm/kdump.h> +#include <mm/mmu_decl.h> +#include <generated/utsrelease.h> + +struct regions { + unsigned long pa_start; + unsigned long pa_end; + unsigned long kernel_size; + unsigned long dtb_start; + unsigned long dtb_end; + unsigned long initrd_start; + unsigned long initrd_end; + unsigned long crash_start; + unsigned long crash_end; + int reserved_mem; + int reserved_mem_addr_cells; + int reserved_mem_size_cells; +}; + +struct regions __initdata regions; + +static __init void kaslr_get_cmdline(void *fdt) +{ + early_init_dt_scan_chosen(boot_command_line); +} + +static unsigned long __init rotate_xor(unsigned long hash, const void *area, + size_t size) +{ + size_t i; + const unsigned long *ptr = area; + + for (i = 0; i < size / sizeof(hash); i++) { + /* Rotate by odd number of bits and XOR. */ + hash = (hash << ((sizeof(hash) * 8) - 7)) | (hash >> 7); + hash ^= ptr[i]; + } + + return hash; +} + +/* Attempt to create a simple starting entropy. This can make it defferent for + * every build but it is still not enough. Stronger entropy should + * be added to make it change for every boot. + */ +static unsigned long __init get_boot_seed(void *fdt) +{ + unsigned long hash = 0; + + /* build-specific string for starting entropy. */ + hash = rotate_xor(hash, linux_banner, strlen(linux_banner)); + hash = rotate_xor(hash, fdt, fdt_totalsize(fdt)); + + return hash; +} + +static __init u64 get_kaslr_seed(void *fdt) +{ + int node, len; + fdt64_t *prop; + u64 ret; + + node = fdt_path_offset(fdt, "/chosen"); + if (node < 0) + return 0; + + prop = fdt_getprop_w(fdt, node, "kaslr-seed", &len); + if (!prop || len != sizeof(u64)) + return 0; + + ret = fdt64_to_cpu(*prop); + *prop = 0; + return ret; +} + +static __init bool regions_overlap(u32 s1, u32 e1, u32 s2, u32 e2) +{ + return e1 >= s2 && e2 >= s1; +} + +static __init bool overlaps_reserved_region(const void *fdt, u32 start, + u32 end) +{ + int subnode, len, i; + u64 base, size; + + /* check for overlap with /memreserve/ entries */ + for (i = 0; i < fdt_num_mem_rsv(fdt); i++) { + if (fdt_get_mem_rsv(fdt, i, &base, &size) < 0) + continue; + if (regions_overlap(start, end, base, base + size)) + return true; + } + + if (regions.reserved_mem < 0) + return false; + + /* check for overlap with static reservations in /reserved-memory */ + for (subnode = fdt_first_subnode(fdt, regions.reserved_mem); + subnode >= 0; + subnode = fdt_next_subnode(fdt, subnode)) { + const fdt32_t *reg; + u64 rsv_end; + + len = 0; + reg = fdt_getprop(fdt, subnode, "reg", &len); + while (len >= (regions.reserved_mem_addr_cells + + regions.reserved_mem_size_cells)) { + base = fdt32_to_cpu(reg[0]); + if (regions.reserved_mem_addr_cells == 2) + base = (base << 32) | fdt32_to_cpu(reg[1]); + + reg += regions.reserved_mem_addr_cells; + len -= 4 * regions.reserved_mem_addr_cells; + + size = fdt32_to_cpu(reg[0]); + if (regions.reserved_mem_size_cells == 2) + size = (size << 32) | fdt32_to_cpu(reg[1]); + + reg += regions.reserved_mem_size_cells; + len -= 4 * regions.reserved_mem_size_cells; + + if (base >= regions.pa_end) + continue; + + rsv_end = min(base + size, (u64)U32_MAX); + + if (regions_overlap(start, end, base, rsv_end)) + return true; + } + } + return false; +} + +static __init bool overlaps_region(const void *fdt, u32 start, + u32 end) +{ + if (regions_overlap(start, end, __pa(_stext), __pa(_end))) + return true; + + if (regions_overlap(start, end, regions.dtb_start, + regions.dtb_end)) + return true; + + if (regions_overlap(start, end, regions.initrd_start, + regions.initrd_end)) + return true; + + if (regions_overlap(start, end, regions.crash_start, + regions.crash_end)) + return true; + + return overlaps_reserved_region(fdt, start, end); +} + +static void __init get_crash_kernel(void *fdt, unsigned long size) +{ +#ifdef CONFIG_CRASH_CORE + unsigned long long crash_size, crash_base; + int ret; + + ret = parse_crashkernel(boot_command_line, size, &crash_size, + &crash_base); + if (ret != 0 || crash_size == 0) + return; + if (crash_base == 0) + crash_base = KDUMP_KERNELBASE; + + regions.crash_start = (unsigned long)crash_base; + regions.crash_end = (unsigned long)(crash_base + crash_size); + + pr_debug("crash_base=0x%llx crash_size=0x%llx\n", crash_base, crash_size); +#endif +} + +static void __init get_initrd_range(void *fdt) +{ + u64 start, end; + int node, len; + const __be32 *prop; + + node = fdt_path_offset(fdt, "/chosen"); + if (node < 0) + return; + + prop = fdt_getprop(fdt, node, "linux,initrd-start", &len); + if (!prop) + return; + start = of_read_number(prop, len / 4); + + prop = fdt_getprop(fdt, node, "linux,initrd-end", &len); + if (!prop) + return; + end = of_read_number(prop, len / 4); + + regions.initrd_start = (unsigned long)start; + regions.initrd_end = (unsigned long)end; + + pr_debug("initrd_start=0x%llx initrd_end=0x%llx\n", start, end); +} + +static __init unsigned long get_usable_address(const void *fdt, + unsigned long start, + unsigned long offset) +{ + unsigned long pa; + unsigned long pa_end; + + for (pa = offset; (long)pa > (long)start; pa -= SZ_16K) { + pa_end = pa + regions.kernel_size; + if (overlaps_region(fdt, pa, pa_end)) + continue; + + return pa; + } + return 0; +} + +static __init void get_cell_sizes(const void *fdt, int node, int *addr_cells, + int *size_cells) +{ + const int *prop; + int len; + + /* + * Retrieve the #address-cells and #size-cells properties + * from the 'node', or use the default if not provided. + */ + *addr_cells = *size_cells = 1; + + prop = fdt_getprop(fdt, node, "#address-cells", &len); + if (len == 4) + *addr_cells = fdt32_to_cpu(*prop); + prop = fdt_getprop(fdt, node, "#size-cells", &len); + if (len == 4) + *size_cells = fdt32_to_cpu(*prop); +} + +static unsigned long __init kaslr_legal_offset(void *dt_ptr, unsigned long index, + unsigned long offset) +{ + unsigned long koffset = 0; + unsigned long start; + + while ((long)index >= 0) { + offset = memstart_addr + index * SZ_64M + offset; + start = memstart_addr + index * SZ_64M; + koffset = get_usable_address(dt_ptr, start, offset); + if (koffset) + break; + index--; + } + + if (koffset != 0) + koffset -= memstart_addr; + + return koffset; +} + +static inline __init bool kaslr_disabled(void) +{ + return strstr(boot_command_line, "nokaslr") != NULL; +} + +static unsigned long __init kaslr_choose_location(void *dt_ptr, phys_addr_t size, + unsigned long kernel_sz) +{ + unsigned long offset, random; + unsigned long ram, linear_sz; + u64 seed; + unsigned long index; + + kaslr_get_cmdline(dt_ptr); + if (kaslr_disabled()) + return 0; + + random = get_boot_seed(dt_ptr); + + seed = get_tb() << 32; + seed ^= get_tb(); + random = rotate_xor(random, &seed, sizeof(seed)); + + /* + * Retrieve (and wipe) the seed from the FDT + */ + seed = get_kaslr_seed(dt_ptr); + if (seed) + random = rotate_xor(random, &seed, sizeof(seed)); + else + pr_warn("KASLR: No safe seed for randomizing the kernel base.\n"); + + ram = min_t(phys_addr_t, __max_low_memory, size); + ram = map_mem_in_cams(ram, CONFIG_LOWMEM_CAM_NUM, true, true); + linear_sz = min_t(unsigned long, ram, SZ_512M); + + /* If the linear size is smaller than 64M, do not randomize */ + if (linear_sz < SZ_64M) + return 0; + + /* check for a reserved-memory node and record its cell sizes */ + regions.reserved_mem = fdt_path_offset(dt_ptr, "/reserved-memory"); + if (regions.reserved_mem >= 0) + get_cell_sizes(dt_ptr, regions.reserved_mem, + ®ions.reserved_mem_addr_cells, + ®ions.reserved_mem_size_cells); + + regions.pa_start = memstart_addr; + regions.pa_end = memstart_addr + linear_sz; + regions.dtb_start = __pa(dt_ptr); + regions.dtb_end = __pa(dt_ptr) + fdt_totalsize(dt_ptr); + regions.kernel_size = kernel_sz; + + get_initrd_range(dt_ptr); + get_crash_kernel(dt_ptr, ram); + + /* + * Decide which 64M we want to start + * Only use the low 8 bits of the random seed + */ + index = random & 0xFF; + index %= linear_sz / SZ_64M; + + /* Decide offset inside 64M */ + offset = random % (SZ_64M - kernel_sz); + offset = round_down(offset, SZ_16K); + + return kaslr_legal_offset(dt_ptr, index, offset); +} + +/* + * To see if we need to relocate the kernel to a random offset + * void *dt_ptr - address of the device tree + * phys_addr_t size - size of the first memory block + */ +notrace void __init kaslr_early_init(void *dt_ptr, phys_addr_t size) +{ + unsigned long tlb_virt; + phys_addr_t tlb_phys; + unsigned long offset; + unsigned long kernel_sz; + + kernel_sz = (unsigned long)_end - (unsigned long)_stext; + + offset = kaslr_choose_location(dt_ptr, size, kernel_sz); + if (offset == 0) + return; + + kernstart_virt_addr += offset; + kernstart_addr += offset; + + is_second_reloc = 1; + + if (offset >= SZ_64M) { + tlb_virt = round_down(kernstart_virt_addr, SZ_64M); + tlb_phys = round_down(kernstart_addr, SZ_64M); + + /* Create kernel map to relocate in */ + create_kaslr_tlb_entry(1, tlb_virt, tlb_phys); + } + + /* Copy the kernel to it's new location and run */ + memcpy((void *)kernstart_virt_addr, (void *)_stext, kernel_sz); + flush_icache_range(kernstart_virt_addr, kernstart_virt_addr + kernel_sz); + + reloc_kernel_entry(dt_ptr, kernstart_virt_addr); +} + +void __init kaslr_late_init(void) +{ + /* If randomized, clear the original kernel */ + if (kernstart_virt_addr != KERNELBASE) { + unsigned long kernel_sz; + + kernel_sz = (unsigned long)_end - kernstart_virt_addr; + memzero_explicit((void *)KERNELBASE, kernel_sz); + } +} |