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 <common.h> 30 #include <asm/relocs.h> 31 #include <asm/sections.h> 32 33 /** 34 * read_uint() - Read an unsigned integer from the buffer 35 * @buf: pointer to a pointer to the reloc buffer 36 * 37 * Read one whole unsigned integer from the relocation data pointed to by @buf, 38 * advancing @buf past the bytes encoding the integer. 39 * 40 * Returns: the integer read from @buf 41 */ 42 static unsigned long read_uint(uint8_t **buf) 43 { 44 unsigned long val = 0; 45 unsigned int shift = 0; 46 uint8_t new; 47 48 do { 49 new = *(*buf)++; 50 val |= (new & 0x7f) << shift; 51 shift += 7; 52 } while (new & 0x80); 53 54 return val; 55 } 56 57 /** 58 * apply_reloc() - Apply a single relocation 59 * @type: the type of reloc (R_MIPS_*) 60 * @addr: the address that the reloc should be applied to 61 * @off: the relocation offset, ie. number of bytes we're moving U-Boot by 62 * 63 * Apply a single relocation of type @type at @addr. This function is 64 * intentionally simple, and does the bare minimum needed to fixup the 65 * relocated U-Boot - in particular, it does not check for overflows. 66 */ 67 static void apply_reloc(unsigned int type, void *addr, long off) 68 { 69 uint32_t u32; 70 71 switch (type) { 72 case R_MIPS_26: 73 u32 = *(uint32_t *)addr; 74 u32 = (u32 & GENMASK(31, 26)) | 75 ((u32 + (off >> 2)) & GENMASK(25, 0)); 76 *(uint32_t *)addr = u32; 77 break; 78 79 case R_MIPS_32: 80 *(uint32_t *)addr += off; 81 break; 82 83 case R_MIPS_64: 84 *(uint64_t *)addr += off; 85 break; 86 87 case R_MIPS_HI16: 88 *(uint32_t *)addr += off >> 16; 89 break; 90 91 default: 92 panic("Unhandled reloc type %u\n", type); 93 } 94 } 95 96 /** 97 * relocate_code() - Relocate U-Boot, generally from flash to DDR 98 * @start_addr_sp: new stack pointer 99 * @new_gd: pointer to relocated global data 100 * @relocaddr: the address to relocate to 101 * 102 * Relocate U-Boot from its current location (generally in flash) to a new one 103 * (generally in DDR). This function will copy the U-Boot binary & apply 104 * relocations as necessary, then jump to board_init_r in the new build of 105 * U-Boot. As such, this function does not return. 106 */ 107 void relocate_code(ulong start_addr_sp, gd_t *new_gd, ulong relocaddr) 108 { 109 unsigned long addr, length, bss_len; 110 uint8_t *buf, *bss_start; 111 unsigned int type; 112 long off; 113 114 /* 115 * Ensure that we're relocating by an offset which is a multiple of 116 * 64KiB, ie. doesn't change the least significant 16 bits of any 117 * addresses. This allows us to discard R_MIPS_LO16 relocs, saving 118 * space in the U-Boot binary & complexity in handling them. 119 */ 120 off = relocaddr - (unsigned long)__text_start; 121 if (off & 0xffff) 122 panic("Mis-aligned relocation\n"); 123 124 /* Copy U-Boot to RAM */ 125 length = __image_copy_end - __text_start; 126 memcpy((void *)relocaddr, __text_start, length); 127 128 /* Now apply relocations to the copy in RAM */ 129 buf = __rel_start; 130 addr = relocaddr; 131 while (true) { 132 type = read_uint(&buf); 133 if (type == R_MIPS_NONE) 134 break; 135 136 addr += read_uint(&buf) << 2; 137 apply_reloc(type, (void *)addr, off); 138 } 139 140 /* Ensure the icache is coherent */ 141 flush_cache(relocaddr, length); 142 143 /* Clear the .bss section */ 144 bss_start = (uint8_t *)((unsigned long)__bss_start + off); 145 bss_len = (unsigned long)&__bss_end - (unsigned long)__bss_start; 146 memset(bss_start, 0, bss_len); 147 148 /* Jump to the relocated U-Boot */ 149 asm volatile( 150 "move $29, %0\n" 151 " move $4, %1\n" 152 " move $5, %2\n" 153 " move $31, $0\n" 154 " jr %3" 155 : /* no outputs */ 156 : "r"(start_addr_sp), 157 "r"(new_gd), 158 "r"(relocaddr), 159 "r"((unsigned long)board_init_r + off)); 160 161 /* Since we jumped to the new U-Boot above, we won't get here */ 162 unreachable(); 163 } 164