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![Paul Burton](/assets/img/avatar_default.png)
Clean up instances of casts to the type that a value already has, since they are effectively no-ops and only serve to complicate the code. This is the result of the following semantic patch: @identitycast@ type T; T *A; @@ - (T *)(A) + A Signed-off-by: Paul Burton <paul.burton@mips.com> Patchwork: https://patchwork.linux-mips.org/patch/19599/
440 lines
11 KiB
C
440 lines
11 KiB
C
/*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Support for Kernel relocation at boot time
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*
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* Copyright (C) 2015, Imagination Technologies Ltd.
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* Authors: Matt Redfearn (matt.redfearn@mips.com)
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*/
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#include <asm/bootinfo.h>
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#include <asm/cacheflush.h>
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#include <asm/fw/fw.h>
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#include <asm/sections.h>
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#include <asm/setup.h>
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#include <asm/timex.h>
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#include <linux/elf.h>
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#include <linux/kernel.h>
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#include <linux/libfdt.h>
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#include <linux/of_fdt.h>
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#include <linux/sched/task.h>
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#include <linux/start_kernel.h>
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#include <linux/string.h>
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#include <linux/printk.h>
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#define RELOCATED(x) ((void *)((long)x + offset))
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extern u32 _relocation_start[]; /* End kernel image / start relocation table */
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extern u32 _relocation_end[]; /* End relocation table */
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extern long __start___ex_table; /* Start exception table */
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extern long __stop___ex_table; /* End exception table */
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extern void __weak plat_fdt_relocated(void *new_location);
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/*
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* This function may be defined for a platform to perform any post-relocation
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* fixup necessary.
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* Return non-zero to abort relocation
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*/
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int __weak plat_post_relocation(long offset)
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{
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return 0;
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}
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static inline u32 __init get_synci_step(void)
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{
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u32 res;
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__asm__("rdhwr %0, $1" : "=r" (res));
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return res;
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}
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static void __init sync_icache(void *kbase, unsigned long kernel_length)
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{
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void *kend = kbase + kernel_length;
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u32 step = get_synci_step();
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do {
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__asm__ __volatile__(
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"synci 0(%0)"
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: /* no output */
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: "r" (kbase));
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kbase += step;
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} while (kbase < kend);
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/* Completion barrier */
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__sync();
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}
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static int __init apply_r_mips_64_rel(u32 *loc_orig, u32 *loc_new, long offset)
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{
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*(u64 *)loc_new += offset;
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return 0;
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}
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static int __init apply_r_mips_32_rel(u32 *loc_orig, u32 *loc_new, long offset)
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{
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*loc_new += offset;
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return 0;
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}
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static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset)
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{
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unsigned long target_addr = (*loc_orig) & 0x03ffffff;
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if (offset % 4) {
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pr_err("Dangerous R_MIPS_26 REL relocation\n");
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return -ENOEXEC;
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}
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/* Original target address */
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target_addr <<= 2;
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target_addr += (unsigned long)loc_orig & ~0x03ffffff;
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/* Get the new target address */
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target_addr += offset;
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if ((target_addr & 0xf0000000) != ((unsigned long)loc_new & 0xf0000000)) {
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pr_err("R_MIPS_26 REL relocation overflow\n");
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return -ENOEXEC;
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}
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target_addr -= (unsigned long)loc_new & ~0x03ffffff;
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target_addr >>= 2;
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*loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff);
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return 0;
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}
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static int __init apply_r_mips_hi16_rel(u32 *loc_orig, u32 *loc_new, long offset)
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{
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unsigned long insn = *loc_orig;
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unsigned long target = (insn & 0xffff) << 16; /* high 16bits of target */
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target += offset;
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*loc_new = (insn & ~0xffff) | ((target >> 16) & 0xffff);
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return 0;
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}
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static int (*reloc_handlers_rel[]) (u32 *, u32 *, long) __initdata = {
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[R_MIPS_64] = apply_r_mips_64_rel,
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[R_MIPS_32] = apply_r_mips_32_rel,
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[R_MIPS_26] = apply_r_mips_26_rel,
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[R_MIPS_HI16] = apply_r_mips_hi16_rel,
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};
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int __init do_relocations(void *kbase_old, void *kbase_new, long offset)
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{
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u32 *r;
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u32 *loc_orig;
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u32 *loc_new;
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int type;
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int res;
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for (r = _relocation_start; r < _relocation_end; r++) {
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/* Sentinel for last relocation */
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if (*r == 0)
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break;
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type = (*r >> 24) & 0xff;
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loc_orig = kbase_old + ((*r & 0x00ffffff) << 2);
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loc_new = RELOCATED(loc_orig);
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if (reloc_handlers_rel[type] == NULL) {
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/* Unsupported relocation */
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pr_err("Unhandled relocation type %d at 0x%pK\n",
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type, loc_orig);
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return -ENOEXEC;
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}
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res = reloc_handlers_rel[type](loc_orig, loc_new, offset);
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if (res)
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return res;
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}
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return 0;
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}
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/*
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* The exception table is filled in by the relocs tool after vmlinux is linked.
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* It must be relocated separately since there will not be any relocation
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* information for it filled in by the linker.
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*/
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static int __init relocate_exception_table(long offset)
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{
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unsigned long *etable_start, *etable_end, *e;
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etable_start = RELOCATED(&__start___ex_table);
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etable_end = RELOCATED(&__stop___ex_table);
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for (e = etable_start; e < etable_end; e++)
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*e += offset;
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return 0;
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}
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#ifdef CONFIG_RANDOMIZE_BASE
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static inline __init unsigned long rotate_xor(unsigned long hash,
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const void *area, size_t size)
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{
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size_t i;
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unsigned long *ptr = (unsigned long *)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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static inline __init unsigned long get_random_boot(void)
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{
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unsigned long entropy = random_get_entropy();
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unsigned long hash = 0;
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/* Attempt to create a simple but unpredictable starting entropy. */
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hash = rotate_xor(hash, linux_banner, strlen(linux_banner));
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/* Add in any runtime entropy we can get */
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hash = rotate_xor(hash, &entropy, sizeof(entropy));
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#if defined(CONFIG_USE_OF)
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/* Get any additional entropy passed in device tree */
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if (initial_boot_params) {
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int node, len;
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u64 *prop;
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node = fdt_path_offset(initial_boot_params, "/chosen");
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if (node >= 0) {
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prop = fdt_getprop_w(initial_boot_params, node,
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"kaslr-seed", &len);
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if (prop && (len == sizeof(u64)))
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hash = rotate_xor(hash, prop, sizeof(*prop));
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}
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}
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#endif /* CONFIG_USE_OF */
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return hash;
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}
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static inline __init bool kaslr_disabled(void)
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{
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char *str;
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#if defined(CONFIG_CMDLINE_BOOL)
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const char *builtin_cmdline = CONFIG_CMDLINE;
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str = strstr(builtin_cmdline, "nokaslr");
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if (str == builtin_cmdline ||
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(str > builtin_cmdline && *(str - 1) == ' '))
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return true;
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#endif
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str = strstr(arcs_cmdline, "nokaslr");
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if (str == arcs_cmdline || (str > arcs_cmdline && *(str - 1) == ' '))
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return true;
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return false;
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}
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static inline void __init *determine_relocation_address(void)
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{
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/* Choose a new address for the kernel */
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unsigned long kernel_length;
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void *dest = &_text;
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unsigned long offset;
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if (kaslr_disabled())
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return dest;
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kernel_length = (long)_end - (long)(&_text);
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offset = get_random_boot() << 16;
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offset &= (CONFIG_RANDOMIZE_BASE_MAX_OFFSET - 1);
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if (offset < kernel_length)
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offset += ALIGN(kernel_length, 0xffff);
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return RELOCATED(dest);
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}
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#else
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static inline void __init *determine_relocation_address(void)
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{
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/*
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* Choose a new address for the kernel
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* For now we'll hard code the destination
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*/
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return (void *)0xffffffff81000000;
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}
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#endif
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static inline int __init relocation_addr_valid(void *loc_new)
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{
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if ((unsigned long)loc_new & 0x0000ffff) {
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/* Inappropriately aligned new location */
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return 0;
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}
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if ((unsigned long)loc_new < (unsigned long)&_end) {
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/* New location overlaps original kernel */
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return 0;
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}
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return 1;
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}
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void *__init relocate_kernel(void)
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{
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void *loc_new;
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unsigned long kernel_length;
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unsigned long bss_length;
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long offset = 0;
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int res = 1;
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/* Default to original kernel entry point */
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void *kernel_entry = start_kernel;
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void *fdt = NULL;
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/* Get the command line */
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fw_init_cmdline();
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#if defined(CONFIG_USE_OF)
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/* Deal with the device tree */
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fdt = plat_get_fdt();
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early_init_dt_scan(fdt);
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if (boot_command_line[0]) {
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/* Boot command line was passed in device tree */
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strlcpy(arcs_cmdline, boot_command_line, COMMAND_LINE_SIZE);
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}
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#endif /* CONFIG_USE_OF */
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kernel_length = (long)(&_relocation_start) - (long)(&_text);
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bss_length = (long)&__bss_stop - (long)&__bss_start;
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loc_new = determine_relocation_address();
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/* Sanity check relocation address */
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if (relocation_addr_valid(loc_new))
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offset = (unsigned long)loc_new - (unsigned long)(&_text);
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/* Reset the command line now so we don't end up with a duplicate */
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arcs_cmdline[0] = '\0';
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if (offset) {
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void (*fdt_relocated_)(void *) = NULL;
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#if defined(CONFIG_USE_OF)
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unsigned long fdt_phys = virt_to_phys(fdt);
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/*
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* If built-in dtb is used then it will have been relocated
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* during kernel _text relocation. If appended DTB is used
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* then it will not be relocated, but it should remain
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* intact in the original location. If dtb is loaded by
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* the bootloader then it may need to be moved if it crosses
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* the target memory area
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*/
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if (fdt_phys >= virt_to_phys(RELOCATED(&_text)) &&
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fdt_phys <= virt_to_phys(RELOCATED(&_end))) {
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void *fdt_relocated =
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RELOCATED(ALIGN((long)&_end, PAGE_SIZE));
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memcpy(fdt_relocated, fdt, fdt_totalsize(fdt));
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fdt = fdt_relocated;
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fdt_relocated_ = RELOCATED(&plat_fdt_relocated);
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}
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#endif /* CONFIG_USE_OF */
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/* Copy the kernel to it's new location */
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memcpy(loc_new, &_text, kernel_length);
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/* Perform relocations on the new kernel */
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res = do_relocations(&_text, loc_new, offset);
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if (res < 0)
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goto out;
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/* Sync the caches ready for execution of new kernel */
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sync_icache(loc_new, kernel_length);
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res = relocate_exception_table(offset);
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if (res < 0)
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goto out;
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/*
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* The original .bss has already been cleared, and
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* some variables such as command line parameters
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* stored to it so make a copy in the new location.
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*/
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memcpy(RELOCATED(&__bss_start), &__bss_start, bss_length);
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/*
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* If fdt was stored outside of the kernel image and
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* had to be moved then update platform's state data
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* with the new fdt location
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*/
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if (fdt_relocated_)
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fdt_relocated_(fdt);
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/*
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* Last chance for the platform to abort relocation.
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* This may also be used by the platform to perform any
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* initialisation required now that the new kernel is
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* resident in memory and ready to be executed.
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*/
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if (plat_post_relocation(offset))
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goto out;
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/* The current thread is now within the relocated image */
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__current_thread_info = RELOCATED(&init_thread_union);
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/* Return the new kernel's entry point */
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kernel_entry = RELOCATED(start_kernel);
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}
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out:
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return kernel_entry;
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}
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/*
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* Show relocation information on panic.
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*/
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void show_kernel_relocation(const char *level)
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{
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unsigned long offset;
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offset = __pa_symbol(_text) - __pa_symbol(VMLINUX_LOAD_ADDRESS);
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if (IS_ENABLED(CONFIG_RELOCATABLE) && offset > 0) {
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printk(level);
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pr_cont("Kernel relocated by 0x%pK\n", (void *)offset);
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pr_cont(" .text @ 0x%pK\n", _text);
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pr_cont(" .data @ 0x%pK\n", _sdata);
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pr_cont(" .bss @ 0x%pK\n", __bss_start);
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}
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}
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static int kernel_location_notifier_fn(struct notifier_block *self,
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unsigned long v, void *p)
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{
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show_kernel_relocation(KERN_EMERG);
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return NOTIFY_DONE;
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}
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static struct notifier_block kernel_location_notifier = {
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.notifier_call = kernel_location_notifier_fn
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};
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static int __init register_kernel_offset_dumper(void)
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{
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atomic_notifier_chain_register(&panic_notifier_list,
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&kernel_location_notifier);
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return 0;
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}
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__initcall(register_kernel_offset_dumper);
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