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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. */
17bool mips_use_nan_legacy;
18bool mips_use_nan_2008;
19
20/* FPU modes */
21enum {
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
49struct mode_req {
50 bool single;
51 bool soft;
52 bool fr1;
53 bool frdefault;
54 bool fre;
55};
56
57static 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 */
72static struct mode_req none_req = { true, true, false, true, true };
73
74int 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 /* Lets 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
137int 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
269static 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
281void 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 */
310void 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}