1// SPDX-License-Identifier: GPL-2.0+ 2/* 3 * MIPS Relocation 4 * 5 * Copyright (c) 2017 Imagination Technologies Ltd. 6 * 7 * Relocation data, found in the .rel section, is generated by the mips-relocs 8 * tool & contains a record of all locations in the U-Boot binary that need to 9 * be fixed up during relocation. 10 * 11 * The data is a sequence of unsigned integers, which are of somewhat arbitrary 12 * size. This is achieved by encoding integers as a sequence of bytes, each of 13 * which contains 7 bits of data with the most significant bit indicating 14 * whether any further bytes need to be read. The least significant bits of the 15 * integer are found in the first byte - ie. it somewhat resembles little 16 * endian. 17 * 18 * Each pair of two integers represents a relocation that must be applied. The 19 * first integer represents the type of relocation as a standard ELF relocation 20 * type (ie. R_MIPS_*). The second integer represents the offset at which to 21 * apply the relocation, relative to the previous relocation or for the first 22 * relocation the start of the relocated .text section. 23 * 24 * The end of the relocation data is indicated when type R_MIPS_NONE (0) is 25 * read, at which point no further integers should be read. That is, the 26 * terminating R_MIPS_NONE reloc includes no offset. 27 */ 28 29#include <cpu_func.h> 30#include <init.h> 31#include <asm/relocs.h> 32#include <asm/sections.h> 33#include <linux/bitops.h> 34 35/** 36 * read_uint() - Read an unsigned integer from the buffer 37 * @buf: pointer to a pointer to the reloc buffer 38 * 39 * Read one whole unsigned integer from the relocation data pointed to by @buf, 40 * advancing @buf past the bytes encoding the integer. 41 * 42 * Returns: the integer read from @buf 43 */ 44static unsigned long read_uint(uint8_t **buf) 45{ 46 unsigned long val = 0; 47 unsigned int shift = 0; 48 uint8_t new; 49 50 do { 51 new = *(*buf)++; 52 val |= (new & 0x7f) << shift; 53 shift += 7; 54 } while (new & 0x80); 55 56 return val; 57} 58 59/** 60 * apply_reloc() - Apply a single relocation 61 * @type: the type of reloc (R_MIPS_*) 62 * @addr: the address that the reloc should be applied to 63 * @off: the relocation offset, ie. number of bytes we're moving U-Boot by 64 * 65 * Apply a single relocation of type @type at @addr. This function is 66 * intentionally simple, and does the bare minimum needed to fixup the 67 * relocated U-Boot - in particular, it does not check for overflows. 68 */ 69static void apply_reloc(unsigned int type, void *addr, long off, uint8_t *buf) 70{ 71 uint32_t u32; 72 73 switch (type) { 74 case R_MIPS_26: 75 u32 = *(uint32_t *)addr; 76 u32 = (u32 & GENMASK(31, 26)) | 77 ((u32 + (off >> 2)) & GENMASK(25, 0)); 78 *(uint32_t *)addr = u32; 79 break; 80 81 case R_MIPS_32: 82 *(uint32_t *)addr += off; 83 break; 84 85 case R_MIPS_64: 86 *(uint64_t *)addr += off; 87 break; 88 89 case R_MIPS_HI16: 90 *(uint32_t *)addr += off >> 16; 91 break; 92 93 default: 94 panic("Unhandled reloc type %u (@ %p), bss used before relocation?\n", 95 type, buf); 96 } 97} 98 99/** 100 * relocate_code() - Relocate U-Boot, generally from flash to DDR 101 * @start_addr_sp: new stack pointer 102 * @new_gd: pointer to relocated global data 103 * @relocaddr: the address to relocate to 104 * 105 * Relocate U-Boot from its current location (generally in flash) to a new one 106 * (generally in DDR). This function will copy the U-Boot binary & apply 107 * relocations as necessary, then jump to board_init_r in the new build of 108 * U-Boot. As such, this function does not return. 109 */ 110void relocate_code(ulong start_addr_sp, gd_t *new_gd, ulong relocaddr) 111{ 112 unsigned long addr, length, bss_len; 113 uint8_t *buf, *bss_start; 114 unsigned int type; 115 long off; 116 117 /* 118 * Ensure that we're relocating by an offset which is a multiple of 119 * 64KiB, ie. doesn't change the least significant 16 bits of any 120 * addresses. This allows us to discard R_MIPS_LO16 relocs, saving 121 * space in the U-Boot binary & complexity in handling them. 122 */ 123 off = relocaddr - (unsigned long)__text_start; 124 if (off & 0xffff) 125 panic("Mis-aligned relocation\n"); 126 127 /* Copy U-Boot to RAM */ 128 length = __image_copy_end - __text_start; 129 memcpy((void *)relocaddr, __text_start, length); 130 131 /* Now apply relocations to the copy in RAM */ 132 buf = __rel_start; 133 addr = relocaddr; 134 while (true) { 135 type = read_uint(&buf); 136 if (type == R_MIPS_NONE) 137 break; 138 139 addr += read_uint(&buf) << 2; 140 apply_reloc(type, (void *)addr, off, buf); 141 } 142 143 /* Ensure the icache is coherent */ 144 flush_cache(relocaddr, length); 145 146 /* Clear the .bss section */ 147 bss_start = (uint8_t *)((unsigned long)__bss_start + off); 148 bss_len = (unsigned long)__bss_end - (unsigned long)__bss_start; 149 memset(bss_start, 0, bss_len); 150 151 /* Jump to the relocated U-Boot */ 152 asm volatile( 153 "move $29, %0\n" 154 " move $4, %1\n" 155 " move $5, %2\n" 156 " move $31, $0\n" 157 " jr %3" 158 : /* no outputs */ 159 : "r"(start_addr_sp), 160 "r"(new_gd), 161 "r"(relocaddr), 162 "r"((unsigned long)board_init_r + off)); 163 164 /* Since we jumped to the new U-Boot above, we won't get here */ 165 unreachable(); 166} 167