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