1/* 2 * Code to process dynamic relocations for PPC32. 3 * 4 * Copyrights (C) IBM Corporation, 2011. 5 * Author: Suzuki Poulose <suzuki@in.ibm.com> 6 * 7 * - Based on ppc64 code - reloc_64.S 8 * 9 * This program is free software; you can redistribute it and/or 10 * modify it under the terms of the GNU General Public License 11 * as published by the Free Software Foundation; either version 12 * 2 of the License, or (at your option) any later version. 13 */ 14 15#include <asm/ppc_asm.h> 16 17/* Dynamic section table entry tags */ 18DT_RELA = 7 /* Tag for Elf32_Rela section */ 19DT_RELASZ = 8 /* Size of the Rela relocs */ 20DT_RELAENT = 9 /* Size of one Rela reloc entry */ 21 22STN_UNDEF = 0 /* Undefined symbol index */ 23STB_LOCAL = 0 /* Local binding for the symbol */ 24 25R_PPC_ADDR16_LO = 4 /* Lower half of (S+A) */ 26R_PPC_ADDR16_HI = 5 /* Upper half of (S+A) */ 27R_PPC_ADDR16_HA = 6 /* High Adjusted (S+A) */ 28R_PPC_RELATIVE = 22 29 30/* 31 * r3 = desired final address 32 */ 33 34_GLOBAL(relocate) 35 36 mflr r0 /* Save our LR */ 37 bl 0f /* Find our current runtime address */ 380: mflr r12 /* Make it accessible */ 39 mtlr r0 40 41 lwz r11, (p_dyn - 0b)(r12) 42 add r11, r11, r12 /* runtime address of .dynamic section */ 43 lwz r9, (p_rela - 0b)(r12) 44 add r9, r9, r12 /* runtime address of .rela.dyn section */ 45 lwz r10, (p_st - 0b)(r12) 46 add r10, r10, r12 /* runtime address of _stext section */ 47 lwz r13, (p_sym - 0b)(r12) 48 add r13, r13, r12 /* runtime address of .dynsym section */ 49 50 /* 51 * Scan the dynamic section for RELA, RELASZ entries 52 */ 53 li r6, 0 54 li r7, 0 55 li r8, 0 561: lwz r5, 0(r11) /* ELF_Dyn.d_tag */ 57 cmpwi r5, 0 /* End of ELF_Dyn[] */ 58 beq eodyn 59 cmpwi r5, DT_RELA 60 bne relasz 61 lwz r7, 4(r11) /* r7 = rela.link */ 62 b skip 63relasz: 64 cmpwi r5, DT_RELASZ 65 bne relaent 66 lwz r8, 4(r11) /* r8 = Total Rela relocs size */ 67 b skip 68relaent: 69 cmpwi r5, DT_RELAENT 70 bne skip 71 lwz r6, 4(r11) /* r6 = Size of one Rela reloc */ 72skip: 73 addi r11, r11, 8 74 b 1b 75eodyn: /* End of Dyn Table scan */ 76 77 /* Check if we have found all the entries */ 78 cmpwi r7, 0 79 beq done 80 cmpwi r8, 0 81 beq done 82 cmpwi r6, 0 83 beq done 84 85 86 /* 87 * Work out the current offset from the link time address of .rela 88 * section. 89 * cur_offset[r7] = rela.run[r9] - rela.link [r7] 90 * _stext.link[r12] = _stext.run[r10] - cur_offset[r7] 91 * final_offset[r3] = _stext.final[r3] - _stext.link[r12] 92 */ 93 subf r7, r7, r9 /* cur_offset */ 94 subf r12, r7, r10 95 subf r3, r12, r3 /* final_offset */ 96 97 subf r8, r6, r8 /* relaz -= relaent */ 98 /* 99 * Scan through the .rela table and process each entry 100 * r9 - points to the current .rela table entry 101 * r13 - points to the symbol table 102 */ 103 104 /* 105 * Check if we have a relocation based on symbol 106 * r5 will hold the value of the symbol. 107 */ 108applyrela: 109 lwz r4, 4(r9) /* r4 = rela.r_info */ 110 srwi r5, r4, 8 /* ELF32_R_SYM(r_info) */ 111 cmpwi r5, STN_UNDEF /* sym == STN_UNDEF ? */ 112 beq get_type /* value = 0 */ 113 /* Find the value of the symbol at index(r5) */ 114 slwi r5, r5, 4 /* r5 = r5 * sizeof(Elf32_Sym) */ 115 add r12, r13, r5 /* r12 = &__dyn_sym[Index] */ 116 117 /* 118 * GNU ld has a bug, where dynamic relocs based on 119 * STB_LOCAL symbols, the value should be assumed 120 * to be zero. - Alan Modra 121 */ 122 /* XXX: Do we need to check if we are using GNU ld ? */ 123 lbz r5, 12(r12) /* r5 = dyn_sym[Index].st_info */ 124 extrwi r5, r5, 4, 24 /* r5 = ELF32_ST_BIND(r5) */ 125 cmpwi r5, STB_LOCAL /* st_value = 0, ld bug */ 126 beq get_type /* We have r5 = 0 */ 127 lwz r5, 4(r12) /* r5 = __dyn_sym[Index].st_value */ 128 129get_type: 130 /* Load the relocation type to r4 */ 131 extrwi r4, r4, 8, 24 /* r4 = ELF32_R_TYPE(r_info) = ((char*)r4)[3] */ 132 133 /* R_PPC_RELATIVE */ 134 cmpwi r4, R_PPC_RELATIVE 135 bne hi16 136 lwz r4, 0(r9) /* r_offset */ 137 lwz r0, 8(r9) /* r_addend */ 138 add r0, r0, r3 /* final addend */ 139 stwx r0, r4, r7 /* memory[r4+r7]) = (u32)r0 */ 140 b nxtrela /* continue */ 141 142 /* R_PPC_ADDR16_HI */ 143hi16: 144 cmpwi r4, R_PPC_ADDR16_HI 145 bne ha16 146 lwz r4, 0(r9) /* r_offset */ 147 lwz r0, 8(r9) /* r_addend */ 148 add r0, r0, r3 149 add r0, r0, r5 /* r0 = (S+A+Offset) */ 150 extrwi r0, r0, 16, 0 /* r0 = (r0 >> 16) */ 151 b store_half 152 153 /* R_PPC_ADDR16_HA */ 154ha16: 155 cmpwi r4, R_PPC_ADDR16_HA 156 bne lo16 157 lwz r4, 0(r9) /* r_offset */ 158 lwz r0, 8(r9) /* r_addend */ 159 add r0, r0, r3 160 add r0, r0, r5 /* r0 = (S+A+Offset) */ 161 extrwi r5, r0, 1, 16 /* Extract bit 16 */ 162 extrwi r0, r0, 16, 0 /* r0 = (r0 >> 16) */ 163 add r0, r0, r5 /* Add it to r0 */ 164 b store_half 165 166 /* R_PPC_ADDR16_LO */ 167lo16: 168 cmpwi r4, R_PPC_ADDR16_LO 169 bne nxtrela 170 lwz r4, 0(r9) /* r_offset */ 171 lwz r0, 8(r9) /* r_addend */ 172 add r0, r0, r3 173 add r0, r0, r5 /* r0 = (S+A+Offset) */ 174 extrwi r0, r0, 16, 16 /* r0 &= 0xffff */ 175 /* Fall through to */ 176 177 /* Store half word */ 178store_half: 179 sthx r0, r4, r7 /* memory[r4+r7] = (u16)r0 */ 180 181nxtrela: 182 /* 183 * We have to flush the modified instructions to the 184 * main storage from the d-cache. And also, invalidate the 185 * cached instructions in i-cache which has been modified. 186 * 187 * We delay the sync / isync operation till the end, since 188 * we won't be executing the modified instructions until 189 * we return from here. 190 */ 191 dcbst r4,r7 192 sync /* Ensure the data is flushed before icbi */ 193 icbi r4,r7 194 cmpwi r8, 0 /* relasz = 0 ? */ 195 ble done 196 add r9, r9, r6 /* move to next entry in the .rela table */ 197 subf r8, r6, r8 /* relasz -= relaent */ 198 b applyrela 199 200done: 201 sync /* Wait for the flush to finish */ 202 isync /* Discard prefetched instructions */ 203 blr 204 205p_dyn: .long __dynamic_start - 0b 206p_rela: .long __rela_dyn_start - 0b 207p_sym: .long __dynamic_symtab - 0b 208p_st: .long _stext - 0b 209