1 /* 2 * Copyright (C) 2014 Imagination Technologies 3 * Author: Paul Burton <paul.burton@imgtec.com> 4 * 5 * This program is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License as published by the 7 * Free Software Foundation; either version 2 of the License, or (at your 8 * option) any later version. 9 */ 10 11 #include <linux/elf.h> 12 #include <linux/sched.h> 13 14 /* FPU modes */ 15 enum { 16 FP_FRE, 17 FP_FR0, 18 FP_FR1, 19 }; 20 21 /** 22 * struct mode_req - ABI FPU mode requirements 23 * @single: The program being loaded needs an FPU but it will only issue 24 * single precision instructions meaning that it can execute in 25 * either FR0 or FR1. 26 * @soft: The soft(-float) requirement means that the program being 27 * loaded needs has no FPU dependency at all (i.e. it has no 28 * FPU instructions). 29 * @fr1: The program being loaded depends on FPU being in FR=1 mode. 30 * @frdefault: The program being loaded depends on the default FPU mode. 31 * That is FR0 for O32 and FR1 for N32/N64. 32 * @fre: The program being loaded depends on FPU with FRE=1. This mode is 33 * a bridge which uses FR=1 whilst still being able to maintain 34 * full compatibility with pre-existing code using the O32 FP32 35 * ABI. 36 * 37 * More information about the FP ABIs can be found here: 38 * 39 * https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking#10.4.1._Basic_mode_set-up 40 * 41 */ 42 43 struct mode_req { 44 bool single; 45 bool soft; 46 bool fr1; 47 bool frdefault; 48 bool fre; 49 }; 50 51 static const struct mode_req fpu_reqs[] = { 52 [MIPS_ABI_FP_ANY] = { true, true, true, true, true }, 53 [MIPS_ABI_FP_DOUBLE] = { false, false, false, true, true }, 54 [MIPS_ABI_FP_SINGLE] = { true, false, false, false, false }, 55 [MIPS_ABI_FP_SOFT] = { false, true, false, false, false }, 56 [MIPS_ABI_FP_OLD_64] = { false, false, false, false, false }, 57 [MIPS_ABI_FP_XX] = { false, false, true, true, true }, 58 [MIPS_ABI_FP_64] = { false, false, true, false, false }, 59 [MIPS_ABI_FP_64A] = { false, false, true, false, true } 60 }; 61 62 /* 63 * Mode requirements when .MIPS.abiflags is not present in the ELF. 64 * Not present means that everything is acceptable except FR1. 65 */ 66 static struct mode_req none_req = { true, true, false, true, true }; 67 68 int arch_elf_pt_proc(void *_ehdr, void *_phdr, struct file *elf, 69 bool is_interp, struct arch_elf_state *state) 70 { 71 struct elf32_hdr *ehdr32 = _ehdr; 72 struct elf32_phdr *phdr32 = _phdr; 73 struct elf64_phdr *phdr64 = _phdr; 74 struct mips_elf_abiflags_v0 abiflags; 75 int ret; 76 77 /* Lets see if this is an O32 ELF */ 78 if (ehdr32->e_ident[EI_CLASS] == ELFCLASS32) { 79 /* FR = 1 for N32 */ 80 if (ehdr32->e_flags & EF_MIPS_ABI2) 81 state->overall_fp_mode = FP_FR1; 82 else 83 /* Set a good default FPU mode for O32 */ 84 state->overall_fp_mode = cpu_has_mips_r6 ? 85 FP_FRE : FP_FR0; 86 87 if (ehdr32->e_flags & EF_MIPS_FP64) { 88 /* 89 * Set MIPS_ABI_FP_OLD_64 for EF_MIPS_FP64. We will override it 90 * later if needed 91 */ 92 if (is_interp) 93 state->interp_fp_abi = MIPS_ABI_FP_OLD_64; 94 else 95 state->fp_abi = MIPS_ABI_FP_OLD_64; 96 } 97 if (phdr32->p_type != PT_MIPS_ABIFLAGS) 98 return 0; 99 100 if (phdr32->p_filesz < sizeof(abiflags)) 101 return -EINVAL; 102 103 ret = kernel_read(elf, phdr32->p_offset, 104 (char *)&abiflags, 105 sizeof(abiflags)); 106 } else { 107 /* FR=1 is really the only option for 64-bit */ 108 state->overall_fp_mode = FP_FR1; 109 110 if (phdr64->p_type != PT_MIPS_ABIFLAGS) 111 return 0; 112 if (phdr64->p_filesz < sizeof(abiflags)) 113 return -EINVAL; 114 115 ret = kernel_read(elf, phdr64->p_offset, 116 (char *)&abiflags, 117 sizeof(abiflags)); 118 } 119 120 if (ret < 0) 121 return ret; 122 if (ret != sizeof(abiflags)) 123 return -EIO; 124 125 /* Record the required FP ABIs for use by mips_check_elf */ 126 if (is_interp) 127 state->interp_fp_abi = abiflags.fp_abi; 128 else 129 state->fp_abi = abiflags.fp_abi; 130 131 return 0; 132 } 133 134 static inline unsigned get_fp_abi(int in_abi) 135 { 136 /* If the ABI requirement is provided, simply return that */ 137 if (in_abi != MIPS_ABI_FP_UNKNOWN) 138 return in_abi; 139 140 /* Unknown ABI */ 141 return MIPS_ABI_FP_UNKNOWN; 142 } 143 144 int arch_check_elf(void *_ehdr, bool has_interpreter, 145 struct arch_elf_state *state) 146 { 147 struct elf32_hdr *ehdr = _ehdr; 148 struct mode_req prog_req, interp_req; 149 int fp_abi, interp_fp_abi, abi0, abi1, max_abi; 150 151 if (!config_enabled(CONFIG_MIPS_O32_FP64_SUPPORT)) 152 return 0; 153 154 fp_abi = get_fp_abi(state->fp_abi); 155 156 if (has_interpreter) { 157 interp_fp_abi = get_fp_abi(state->interp_fp_abi); 158 159 abi0 = min(fp_abi, interp_fp_abi); 160 abi1 = max(fp_abi, interp_fp_abi); 161 } else { 162 abi0 = abi1 = fp_abi; 163 } 164 165 /* ABI limits. O32 = FP_64A, N32/N64 = FP_SOFT */ 166 max_abi = ((ehdr->e_ident[EI_CLASS] == ELFCLASS32) && 167 (!(ehdr->e_flags & EF_MIPS_ABI2))) ? 168 MIPS_ABI_FP_64A : MIPS_ABI_FP_SOFT; 169 170 if ((abi0 > max_abi && abi0 != MIPS_ABI_FP_UNKNOWN) || 171 (abi1 > max_abi && abi1 != MIPS_ABI_FP_UNKNOWN)) 172 return -ELIBBAD; 173 174 /* It's time to determine the FPU mode requirements */ 175 prog_req = (abi0 == MIPS_ABI_FP_UNKNOWN) ? none_req : fpu_reqs[abi0]; 176 interp_req = (abi1 == MIPS_ABI_FP_UNKNOWN) ? none_req : fpu_reqs[abi1]; 177 178 /* 179 * Check whether the program's and interp's ABIs have a matching FPU 180 * mode requirement. 181 */ 182 prog_req.single = interp_req.single && prog_req.single; 183 prog_req.soft = interp_req.soft && prog_req.soft; 184 prog_req.fr1 = interp_req.fr1 && prog_req.fr1; 185 prog_req.frdefault = interp_req.frdefault && prog_req.frdefault; 186 prog_req.fre = interp_req.fre && prog_req.fre; 187 188 /* 189 * Determine the desired FPU mode 190 * 191 * Decision making: 192 * 193 * - We want FR_FRE if FRE=1 and both FR=1 and FR=0 are false. This 194 * means that we have a combination of program and interpreter 195 * that inherently require the hybrid FP mode. 196 * - If FR1 and FRDEFAULT is true, that means we hit the any-abi or 197 * fpxx case. This is because, in any-ABI (or no-ABI) we have no FPU 198 * instructions so we don't care about the mode. We will simply use 199 * the one preferred by the hardware. In fpxx case, that ABI can 200 * handle both FR=1 and FR=0, so, again, we simply choose the one 201 * preferred by the hardware. Next, if we only use single-precision 202 * FPU instructions, and the default ABI FPU mode is not good 203 * (ie single + any ABI combination), we set again the FPU mode to the 204 * one is preferred by the hardware. Next, if we know that the code 205 * will only use single-precision instructions, shown by single being 206 * true but frdefault being false, then we again set the FPU mode to 207 * the one that is preferred by the hardware. 208 * - We want FP_FR1 if that's the only matching mode and the default one 209 * is not good. 210 * - Return with -ELIBADD if we can't find a matching FPU mode. 211 */ 212 if (prog_req.fre && !prog_req.frdefault && !prog_req.fr1) 213 state->overall_fp_mode = FP_FRE; 214 else if ((prog_req.fr1 && prog_req.frdefault) || 215 (prog_req.single && !prog_req.frdefault)) 216 /* Make sure 64-bit MIPS III/IV/64R1 will not pick FR1 */ 217 state->overall_fp_mode = ((current_cpu_data.fpu_id & MIPS_FPIR_F64) && 218 cpu_has_mips_r2_r6) ? 219 FP_FR1 : FP_FR0; 220 else if (prog_req.fr1) 221 state->overall_fp_mode = FP_FR1; 222 else if (!prog_req.fre && !prog_req.frdefault && 223 !prog_req.fr1 && !prog_req.single && !prog_req.soft) 224 return -ELIBBAD; 225 226 return 0; 227 } 228 229 static inline void set_thread_fp_mode(int hybrid, int regs32) 230 { 231 if (hybrid) 232 set_thread_flag(TIF_HYBRID_FPREGS); 233 else 234 clear_thread_flag(TIF_HYBRID_FPREGS); 235 if (regs32) 236 set_thread_flag(TIF_32BIT_FPREGS); 237 else 238 clear_thread_flag(TIF_32BIT_FPREGS); 239 } 240 241 void mips_set_personality_fp(struct arch_elf_state *state) 242 { 243 /* 244 * This function is only ever called for O32 ELFs so we should 245 * not be worried about N32/N64 binaries. 246 */ 247 248 if (!config_enabled(CONFIG_MIPS_O32_FP64_SUPPORT)) 249 return; 250 251 switch (state->overall_fp_mode) { 252 case FP_FRE: 253 set_thread_fp_mode(1, 0); 254 break; 255 case FP_FR0: 256 set_thread_fp_mode(0, 1); 257 break; 258 case FP_FR1: 259 set_thread_fp_mode(0, 0); 260 break; 261 default: 262 BUG(); 263 } 264 } 265