arch/mips/kernel/elf.c

   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 #include <asm/cpu-info.h>
  15
  16 /* Whether to accept legacy-NaN and 2008-NaN user binaries.  */
  17 bool mips_use_nan_legacy;
  18 bool mips_use_nan_2008;
  19
  20 /* FPU modes */
  21 enum {
  22         FP_FRE,
  23         FP_FR0,
  24         FP_FR1,
  25 };
  26
  27 /**
  28  * struct mode_req - ABI FPU mode requirements
  29  * @single:     The program being loaded needs an FPU but it will only issue
  30  *              single precision instructions meaning that it can execute in
  31  *              either FR0 or FR1.
  32  * @soft:       The soft(-float) requirement means that the program being
  33  *              loaded needs has no FPU dependency at all (i.e. it has no
  34  *              FPU instructions).
  35  * @fr1:        The program being loaded depends on FPU being in FR=1 mode.
  36  * @frdefault:  The program being loaded depends on the default FPU mode.
  37  *              That is FR0 for O32 and FR1 for N32/N64.
  38  * @fre:        The program being loaded depends on FPU with FRE=1. This mode is
  39  *              a bridge which uses FR=1 whilst still being able to maintain
  40  *              full compatibility with pre-existing code using the O32 FP32
  41  *              ABI.
  42  *
  43  * More information about the FP ABIs can be found here:
  44  *
  45  * https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking#10.4.1._Basic_mode_set-up
  46  *
  47  */
  48
  49 struct mode_req {
  50         bool single;
  51         bool soft;
  52         bool fr1;
  53         bool frdefault;
  54         bool fre;
  55 };
  56
  57 static const struct mode_req fpu_reqs[] = {
  58         [MIPS_ABI_FP_ANY]    = { true,  true,  true,  true,  true  },
  59         [MIPS_ABI_FP_DOUBLE] = { false, false, false, true,  true  },
  60         [MIPS_ABI_FP_SINGLE] = { true,  false, false, false, false },
  61         [MIPS_ABI_FP_SOFT]   = { false, true,  false, false, false },
  62         [MIPS_ABI_FP_OLD_64] = { false, false, false, false, false },
  63         [MIPS_ABI_FP_XX]     = { false, false, true,  true,  true  },
  64         [MIPS_ABI_FP_64]     = { false, false, true,  false, false },
  65         [MIPS_ABI_FP_64A]    = { false, false, true,  false, true  }
  66 };
  67
  68 /*
  69  * Mode requirements when .MIPS.abiflags is not present in the ELF.
  70  * Not present means that everything is acceptable except FR1.
  71  */
  72 static struct mode_req none_req = { true, true, false, true, true };
  73
  74 int arch_elf_pt_proc(void *_ehdr, void *_phdr, struct file *elf,
  75                      bool is_interp, struct arch_elf_state *state)
  76 {
  77         union {
  78                 struct elf32_hdr e32;
  79                 struct elf64_hdr e64;
  80         } *ehdr = _ehdr;
  81         struct elf32_phdr *phdr32 = _phdr;
  82         struct elf64_phdr *phdr64 = _phdr;
  83         struct mips_elf_abiflags_v0 abiflags;
  84         bool elf32;
  85         u32 flags;
  86         int ret;
  87
  88         elf32 = ehdr->e32.e_ident[EI_CLASS] == ELFCLASS32;
  89         flags = elf32 ? ehdr->e32.e_flags : ehdr->e64.e_flags;
  90
  91         /* Let's see if this is an O32 ELF */
  92         if (elf32) {
  93                 if (flags & EF_MIPS_FP64) {
  94                         /*
  95                          * Set MIPS_ABI_FP_OLD_64 for EF_MIPS_FP64. We will override it
  96                          * later if needed
  97                          */
  98                         if (is_interp)
  99                                 state->interp_fp_abi = MIPS_ABI_FP_OLD_64;
 100                         else
 101                                 state->fp_abi = MIPS_ABI_FP_OLD_64;
 102                 }
 103                 if (phdr32->p_type != PT_MIPS_ABIFLAGS)
 104                         return 0;
 105
 106                 if (phdr32->p_filesz < sizeof(abiflags))
 107                         return -EINVAL;
 108
 109                 ret = kernel_read(elf, phdr32->p_offset,
 110                                   (char *)&abiflags,
 111                                   sizeof(abiflags));
 112         } else {
 113                 if (phdr64->p_type != PT_MIPS_ABIFLAGS)
 114                         return 0;
 115                 if (phdr64->p_filesz < sizeof(abiflags))
 116                         return -EINVAL;
 117
 118                 ret = kernel_read(elf, phdr64->p_offset,
 119                                   (char *)&abiflags,
 120                                   sizeof(abiflags));
 121         }
 122
 123         if (ret < 0)
 124                 return ret;
 125         if (ret != sizeof(abiflags))
 126                 return -EIO;
 127
 128         /* Record the required FP ABIs for use by mips_check_elf */
 129         if (is_interp)
 130                 state->interp_fp_abi = abiflags.fp_abi;
 131         else
 132                 state->fp_abi = abiflags.fp_abi;
 133
 134         return 0;
 135 }
 136
 137 int arch_check_elf(void *_ehdr, bool has_interpreter, void *_interp_ehdr,
 138                    struct arch_elf_state *state)
 139 {
 140         union {
 141                 struct elf32_hdr e32;
 142                 struct elf64_hdr e64;
 143         } *ehdr = _ehdr;
 144         union {
 145                 struct elf32_hdr e32;
 146                 struct elf64_hdr e64;
 147         } *iehdr = _interp_ehdr;
 148         struct mode_req prog_req, interp_req;
 149         int fp_abi, interp_fp_abi, abi0, abi1, max_abi;
 150         bool elf32;
 151         u32 flags;
 152
 153         elf32 = ehdr->e32.e_ident[EI_CLASS] == ELFCLASS32;
 154         flags = elf32 ? ehdr->e32.e_flags : ehdr->e64.e_flags;
 155
 156         /*
 157          * Determine the NaN personality, reject the binary if not allowed.
 158          * Also ensure that any interpreter matches the executable.
 159          */
 160         if (flags & EF_MIPS_NAN2008) {
 161                 if (mips_use_nan_2008)
 162                         state->nan_2008 = 1;
 163                 else
 164                         return -ENOEXEC;
 165         } else {
 166                 if (mips_use_nan_legacy)
 167                         state->nan_2008 = 0;
 168                 else
 169                         return -ENOEXEC;
 170         }
 171         if (has_interpreter) {
 172                 bool ielf32;
 173                 u32 iflags;
 174
 175                 ielf32 = iehdr->e32.e_ident[EI_CLASS] == ELFCLASS32;
 176                 iflags = ielf32 ? iehdr->e32.e_flags : iehdr->e64.e_flags;
 177
 178                 if ((flags ^ iflags) & EF_MIPS_NAN2008)
 179                         return -ELIBBAD;
 180         }
 181
 182         if (!config_enabled(CONFIG_MIPS_O32_FP64_SUPPORT))
 183                 return 0;
 184
 185         fp_abi = state->fp_abi;
 186
 187         if (has_interpreter) {
 188                 interp_fp_abi = state->interp_fp_abi;
 189
 190                 abi0 = min(fp_abi, interp_fp_abi);
 191                 abi1 = max(fp_abi, interp_fp_abi);
 192         } else {
 193                 abi0 = abi1 = fp_abi;
 194         }
 195
 196         if (elf32 && !(flags & EF_MIPS_ABI2)) {
 197                 /* Default to a mode capable of running code expecting FR=0 */
 198                 state->overall_fp_mode = cpu_has_mips_r6 ? FP_FRE : FP_FR0;
 199
 200                 /* Allow all ABIs we know about */
 201                 max_abi = MIPS_ABI_FP_64A;
 202         } else {
 203                 /* MIPS64 code always uses FR=1, thus the default is easy */
 204                 state->overall_fp_mode = FP_FR1;
 205
 206                 /* Disallow access to the various FPXX & FP64 ABIs */
 207                 max_abi = MIPS_ABI_FP_SOFT;
 208         }
 209
 210         if ((abi0 > max_abi && abi0 != MIPS_ABI_FP_UNKNOWN) ||
 211             (abi1 > max_abi && abi1 != MIPS_ABI_FP_UNKNOWN))
 212                 return -ELIBBAD;
 213
 214         /* It's time to determine the FPU mode requirements */
 215         prog_req = (abi0 == MIPS_ABI_FP_UNKNOWN) ? none_req : fpu_reqs[abi0];
 216         interp_req = (abi1 == MIPS_ABI_FP_UNKNOWN) ? none_req : fpu_reqs[abi1];
 217
 218         /*
 219          * Check whether the program's and interp's ABIs have a matching FPU
 220          * mode requirement.
 221          */
 222         prog_req.single = interp_req.single && prog_req.single;
 223         prog_req.soft = interp_req.soft && prog_req.soft;
 224         prog_req.fr1 = interp_req.fr1 && prog_req.fr1;
 225         prog_req.frdefault = interp_req.frdefault && prog_req.frdefault;
 226         prog_req.fre = interp_req.fre && prog_req.fre;
 227
 228         /*
 229          * Determine the desired FPU mode
 230          *
 231          * Decision making:
 232          *
 233          * - We want FR_FRE if FRE=1 and both FR=1 and FR=0 are false. This
 234          *   means that we have a combination of program and interpreter
 235          *   that inherently require the hybrid FP mode.
 236          * - If FR1 and FRDEFAULT is true, that means we hit the any-abi or
 237          *   fpxx case. This is because, in any-ABI (or no-ABI) we have no FPU
 238          *   instructions so we don't care about the mode. We will simply use
 239          *   the one preferred by the hardware. In fpxx case, that ABI can
 240          *   handle both FR=1 and FR=0, so, again, we simply choose the one
 241          *   preferred by the hardware. Next, if we only use single-precision
 242          *   FPU instructions, and the default ABI FPU mode is not good
 243          *   (ie single + any ABI combination), we set again the FPU mode to the
 244          *   one is preferred by the hardware. Next, if we know that the code
 245          *   will only use single-precision instructions, shown by single being
 246          *   true but frdefault being false, then we again set the FPU mode to
 247          *   the one that is preferred by the hardware.
 248          * - We want FP_FR1 if that's the only matching mode and the default one
 249          *   is not good.
 250          * - Return with -ELIBADD if we can't find a matching FPU mode.
 251          */
 252         if (prog_req.fre && !prog_req.frdefault && !prog_req.fr1)
 253                 state->overall_fp_mode = FP_FRE;
 254         else if ((prog_req.fr1 && prog_req.frdefault) ||
 255                  (prog_req.single && !prog_req.frdefault))
 256                 /* Make sure 64-bit MIPS III/IV/64R1 will not pick FR1 */
 257                 state->overall_fp_mode = ((current_cpu_data.fpu_id & MIPS_FPIR_F64) &&
 258                                           cpu_has_mips_r2_r6) ?
 259                                           FP_FR1 : FP_FR0;
 260         else if (prog_req.fr1)
 261                 state->overall_fp_mode = FP_FR1;
 262         else  if (!prog_req.fre && !prog_req.frdefault &&
 263                   !prog_req.fr1 && !prog_req.single && !prog_req.soft)
 264                 return -ELIBBAD;
 265
 266         return 0;
 267 }
 268
 269 static inline void set_thread_fp_mode(int hybrid, int regs32)
 270 {
 271         if (hybrid)
 272                 set_thread_flag(TIF_HYBRID_FPREGS);
 273         else
 274                 clear_thread_flag(TIF_HYBRID_FPREGS);
 275         if (regs32)
 276                 set_thread_flag(TIF_32BIT_FPREGS);
 277         else
 278                 clear_thread_flag(TIF_32BIT_FPREGS);
 279 }
 280
 281 void mips_set_personality_fp(struct arch_elf_state *state)
 282 {
 283         /*
 284          * This function is only ever called for O32 ELFs so we should
 285          * not be worried about N32/N64 binaries.
 286          */
 287
 288         if (!config_enabled(CONFIG_MIPS_O32_FP64_SUPPORT))
 289                 return;
 290
 291         switch (state->overall_fp_mode) {
 292         case FP_FRE:
 293                 set_thread_fp_mode(1, 0);
 294                 break;
 295         case FP_FR0:
 296                 set_thread_fp_mode(0, 1);
 297                 break;
 298         case FP_FR1:
 299                 set_thread_fp_mode(0, 0);
 300                 break;
 301         default:
 302                 BUG();
 303         }
 304 }
 305
 306 /*
 307  * Select the IEEE 754 NaN encoding and ABS.fmt/NEG.fmt execution mode
 308  * in FCSR according to the ELF NaN personality.
 309  */
 310 void mips_set_personality_nan(struct arch_elf_state *state)
 311 {
 312         struct cpuinfo_mips *c = &boot_cpu_data;
 313         struct task_struct *t = current;
 314
 315         t->thread.fpu.fcr31 = c->fpu_csr31;
 316         switch (state->nan_2008) {
 317         case 0:
 318                 break;
 319         case 1:
 320                 if (!(c->fpu_msk31 & FPU_CSR_NAN2008))
 321                         t->thread.fpu.fcr31 |= FPU_CSR_NAN2008;
 322                 if (!(c->fpu_msk31 & FPU_CSR_ABS2008))
 323                         t->thread.fpu.fcr31 |= FPU_CSR_ABS2008;
 324                 break;
 325         default:
 326                 BUG();
 327         }
 328 }