1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * Copyright (C) 2014 Imagination Technologies
4 * Author: Paul Burton <paul.burton@mips.com>
5 */
6
7 #include <linux/binfmts.h>
8 #include <linux/elf.h>
9 #include <linux/export.h>
10 #include <linux/sched.h>
11
12 #include <asm/cpu-features.h>
13 #include <asm/cpu-info.h>
14 #include <asm/fpu.h>
15
16 #ifdef CONFIG_MIPS_FP_SUPPORT
17
18 /* Whether to accept legacy-NaN and 2008-NaN user binaries. */
19 bool mips_use_nan_legacy;
20 bool mips_use_nan_2008;
21
22 /* FPU modes */
23 enum {
24 FP_FRE,
25 FP_FR0,
26 FP_FR1,
27 };
28
29 /**
30 * struct mode_req - ABI FPU mode requirements
31 * @single: The program being loaded needs an FPU but it will only issue
32 * single precision instructions meaning that it can execute in
33 * either FR0 or FR1.
34 * @soft: The soft(-float) requirement means that the program being
35 * loaded needs has no FPU dependency at all (i.e. it has no
36 * FPU instructions).
37 * @fr1: The program being loaded depends on FPU being in FR=1 mode.
38 * @frdefault: The program being loaded depends on the default FPU mode.
39 * That is FR0 for O32 and FR1 for N32/N64.
40 * @fre: The program being loaded depends on FPU with FRE=1. This mode is
41 * a bridge which uses FR=1 whilst still being able to maintain
42 * full compatibility with pre-existing code using the O32 FP32
43 * ABI.
44 *
45 * More information about the FP ABIs can be found here:
46 *
47 * https://dmz-portal.mips.com/wiki/MIPS_O32_ABI_-_FR0_and_FR1_Interlinking#10.4.1._Basic_mode_set-up
48 *
49 */
50
51 struct mode_req {
52 bool single;
53 bool soft;
54 bool fr1;
55 bool frdefault;
56 bool fre;
57 };
58
59 static const struct mode_req fpu_reqs[] = {
60 [MIPS_ABI_FP_ANY] = { true, true, true, true, true },
61 [MIPS_ABI_FP_DOUBLE] = { false, false, false, true, true },
62 [MIPS_ABI_FP_SINGLE] = { true, false, false, false, false },
63 [MIPS_ABI_FP_SOFT] = { false, true, false, false, false },
64 [MIPS_ABI_FP_OLD_64] = { false, false, false, false, false },
65 [MIPS_ABI_FP_XX] = { false, false, true, true, true },
66 [MIPS_ABI_FP_64] = { false, false, true, false, false },
67 [MIPS_ABI_FP_64A] = { false, false, true, false, true }
68 };
69
70 /*
71 * Mode requirements when .MIPS.abiflags is not present in the ELF.
72 * Not present means that everything is acceptable except FR1.
73 */
74 static struct mode_req none_req = { true, true, false, true, true };
75
arch_elf_pt_proc(void * _ehdr,void * _phdr,struct file * elf,bool is_interp,struct arch_elf_state * state)76 int arch_elf_pt_proc(void *_ehdr, void *_phdr, struct file *elf,
77 bool is_interp, struct arch_elf_state *state)
78 {
79 union {
80 struct elf32_hdr e32;
81 struct elf64_hdr e64;
82 } *ehdr = _ehdr;
83 struct elf32_phdr *phdr32 = _phdr;
84 struct elf64_phdr *phdr64 = _phdr;
85 struct mips_elf_abiflags_v0 abiflags;
86 bool elf32;
87 u32 flags;
88 int ret;
89 loff_t pos;
90
91 elf32 = ehdr->e32.e_ident[EI_CLASS] == ELFCLASS32;
92 flags = elf32 ? ehdr->e32.e_flags : ehdr->e64.e_flags;
93
94 /* Let's see if this is an O32 ELF */
95 if (elf32) {
96 if (flags & EF_MIPS_FP64) {
97 /*
98 * Set MIPS_ABI_FP_OLD_64 for EF_MIPS_FP64. We will override it
99 * later if needed
100 */
101 if (is_interp)
102 state->interp_fp_abi = MIPS_ABI_FP_OLD_64;
103 else
104 state->fp_abi = MIPS_ABI_FP_OLD_64;
105 }
106 if (phdr32->p_type != PT_MIPS_ABIFLAGS)
107 return 0;
108
109 if (phdr32->p_filesz < sizeof(abiflags))
110 return -EINVAL;
111 pos = phdr32->p_offset;
112 } else {
113 if (phdr64->p_type != PT_MIPS_ABIFLAGS)
114 return 0;
115 if (phdr64->p_filesz < sizeof(abiflags))
116 return -EINVAL;
117 pos = phdr64->p_offset;
118 }
119
120 ret = kernel_read(elf, &abiflags, sizeof(abiflags), &pos);
121 if (ret < 0)
122 return ret;
123 if (ret != sizeof(abiflags))
124 return -EIO;
125
126 /* Record the required FP ABIs for use by mips_check_elf */
127 if (is_interp)
128 state->interp_fp_abi = abiflags.fp_abi;
129 else
130 state->fp_abi = abiflags.fp_abi;
131
132 return 0;
133 }
134
arch_check_elf(void * _ehdr,bool has_interpreter,void * _interp_ehdr,struct arch_elf_state * state)135 int arch_check_elf(void *_ehdr, bool has_interpreter, void *_interp_ehdr,
136 struct arch_elf_state *state)
137 {
138 union {
139 struct elf32_hdr e32;
140 struct elf64_hdr e64;
141 } *ehdr = _ehdr;
142 union {
143 struct elf32_hdr e32;
144 struct elf64_hdr e64;
145 } *iehdr = _interp_ehdr;
146 struct mode_req prog_req, interp_req;
147 int fp_abi, interp_fp_abi, abi0, abi1, max_abi;
148 bool elf32;
149 u32 flags;
150
151 elf32 = ehdr->e32.e_ident[EI_CLASS] == ELFCLASS32;
152 flags = elf32 ? ehdr->e32.e_flags : ehdr->e64.e_flags;
153
154 /*
155 * Determine the NaN personality, reject the binary if not allowed.
156 * Also ensure that any interpreter matches the executable.
157 */
158 if (flags & EF_MIPS_NAN2008) {
159 if (mips_use_nan_2008)
160 state->nan_2008 = 1;
161 else
162 return -ENOEXEC;
163 } else {
164 if (mips_use_nan_legacy)
165 state->nan_2008 = 0;
166 else
167 return -ENOEXEC;
168 }
169 if (has_interpreter) {
170 bool ielf32;
171 u32 iflags;
172
173 ielf32 = iehdr->e32.e_ident[EI_CLASS] == ELFCLASS32;
174 iflags = ielf32 ? iehdr->e32.e_flags : iehdr->e64.e_flags;
175
176 if ((flags ^ iflags) & EF_MIPS_NAN2008)
177 return -ELIBBAD;
178 }
179
180 if (!IS_ENABLED(CONFIG_MIPS_O32_FP64_SUPPORT))
181 return 0;
182
183 fp_abi = state->fp_abi;
184
185 if (has_interpreter) {
186 interp_fp_abi = state->interp_fp_abi;
187
188 abi0 = min(fp_abi, interp_fp_abi);
189 abi1 = max(fp_abi, interp_fp_abi);
190 } else {
191 abi0 = abi1 = fp_abi;
192 }
193
194 if (elf32 && !(flags & EF_MIPS_ABI2)) {
195 /* Default to a mode capable of running code expecting FR=0 */
196 state->overall_fp_mode = cpu_has_mips_r6 ? FP_FRE : FP_FR0;
197
198 /* Allow all ABIs we know about */
199 max_abi = MIPS_ABI_FP_64A;
200 } else {
201 /* MIPS64 code always uses FR=1, thus the default is easy */
202 state->overall_fp_mode = FP_FR1;
203
204 /* Disallow access to the various FPXX & FP64 ABIs */
205 max_abi = MIPS_ABI_FP_SOFT;
206 }
207
208 if ((abi0 > max_abi && abi0 != MIPS_ABI_FP_UNKNOWN) ||
209 (abi1 > max_abi && abi1 != MIPS_ABI_FP_UNKNOWN))
210 return -ELIBBAD;
211
212 /* It's time to determine the FPU mode requirements */
213 prog_req = (abi0 == MIPS_ABI_FP_UNKNOWN) ? none_req : fpu_reqs[abi0];
214 interp_req = (abi1 == MIPS_ABI_FP_UNKNOWN) ? none_req : fpu_reqs[abi1];
215
216 /*
217 * Check whether the program's and interp's ABIs have a matching FPU
218 * mode requirement.
219 */
220 prog_req.single = interp_req.single && prog_req.single;
221 prog_req.soft = interp_req.soft && prog_req.soft;
222 prog_req.fr1 = interp_req.fr1 && prog_req.fr1;
223 prog_req.frdefault = interp_req.frdefault && prog_req.frdefault;
224 prog_req.fre = interp_req.fre && prog_req.fre;
225
226 /*
227 * Determine the desired FPU mode
228 *
229 * Decision making:
230 *
231 * - We want FR_FRE if FRE=1 and both FR=1 and FR=0 are false. This
232 * means that we have a combination of program and interpreter
233 * that inherently require the hybrid FP mode.
234 * - If FR1 and FRDEFAULT is true, that means we hit the any-abi or
235 * fpxx case. This is because, in any-ABI (or no-ABI) we have no FPU
236 * instructions so we don't care about the mode. We will simply use
237 * the one preferred by the hardware. In fpxx case, that ABI can
238 * handle both FR=1 and FR=0, so, again, we simply choose the one
239 * preferred by the hardware. Next, if we only use single-precision
240 * FPU instructions, and the default ABI FPU mode is not good
241 * (ie single + any ABI combination), we set again the FPU mode to the
242 * one is preferred by the hardware. Next, if we know that the code
243 * will only use single-precision instructions, shown by single being
244 * true but frdefault being false, then we again set the FPU mode to
245 * the one that is preferred by the hardware.
246 * - We want FP_FR1 if that's the only matching mode and the default one
247 * is not good.
248 * - Return with -ELIBADD if we can't find a matching FPU mode.
249 */
250 if (prog_req.fre && !prog_req.frdefault && !prog_req.fr1)
251 state->overall_fp_mode = FP_FRE;
252 else if ((prog_req.fr1 && prog_req.frdefault) ||
253 (prog_req.single && !prog_req.frdefault))
254 /* Make sure 64-bit MIPS III/IV/64R1 will not pick FR1 */
255 state->overall_fp_mode = ((raw_current_cpu_data.fpu_id & MIPS_FPIR_F64) &&
256 cpu_has_mips_r2_r6) ?
257 FP_FR1 : FP_FR0;
258 else if (prog_req.fr1)
259 state->overall_fp_mode = FP_FR1;
260 else if (!prog_req.fre && !prog_req.frdefault &&
261 !prog_req.fr1 && !prog_req.single && !prog_req.soft)
262 return -ELIBBAD;
263
264 return 0;
265 }
266
set_thread_fp_mode(int hybrid,int regs32)267 static inline void set_thread_fp_mode(int hybrid, int regs32)
268 {
269 if (hybrid)
270 set_thread_flag(TIF_HYBRID_FPREGS);
271 else
272 clear_thread_flag(TIF_HYBRID_FPREGS);
273 if (regs32)
274 set_thread_flag(TIF_32BIT_FPREGS);
275 else
276 clear_thread_flag(TIF_32BIT_FPREGS);
277 }
278
mips_set_personality_fp(struct arch_elf_state * state)279 void mips_set_personality_fp(struct arch_elf_state *state)
280 {
281 /*
282 * This function is only ever called for O32 ELFs so we should
283 * not be worried about N32/N64 binaries.
284 */
285
286 if (!IS_ENABLED(CONFIG_MIPS_O32_FP64_SUPPORT))
287 return;
288
289 switch (state->overall_fp_mode) {
290 case FP_FRE:
291 set_thread_fp_mode(1, 0);
292 break;
293 case FP_FR0:
294 set_thread_fp_mode(0, 1);
295 break;
296 case FP_FR1:
297 set_thread_fp_mode(0, 0);
298 break;
299 default:
300 BUG();
301 }
302 }
303
304 /*
305 * Select the IEEE 754 NaN encoding and ABS.fmt/NEG.fmt execution mode
306 * in FCSR according to the ELF NaN personality.
307 */
mips_set_personality_nan(struct arch_elf_state * state)308 void mips_set_personality_nan(struct arch_elf_state *state)
309 {
310 struct cpuinfo_mips *c = &boot_cpu_data;
311 struct task_struct *t = current;
312
313 /* Do this early so t->thread.fpu.fcr31 won't be clobbered in case
314 * we are preempted before the lose_fpu(0) in start_thread.
315 */
316 lose_fpu(0);
317
318 t->thread.fpu.fcr31 = c->fpu_csr31;
319 switch (state->nan_2008) {
320 case 0:
321 break;
322 case 1:
323 if (!(c->fpu_msk31 & FPU_CSR_NAN2008))
324 t->thread.fpu.fcr31 |= FPU_CSR_NAN2008;
325 if (!(c->fpu_msk31 & FPU_CSR_ABS2008))
326 t->thread.fpu.fcr31 |= FPU_CSR_ABS2008;
327 break;
328 default:
329 BUG();
330 }
331 }
332
333 #endif /* CONFIG_MIPS_FP_SUPPORT */
334
mips_elf_read_implies_exec(void * elf_ex,int exstack)335 int mips_elf_read_implies_exec(void *elf_ex, int exstack)
336 {
337 /*
338 * Set READ_IMPLIES_EXEC only on non-NX systems that
339 * do not request a specific state via PT_GNU_STACK.
340 */
341 return (!cpu_has_rixi && exstack == EXSTACK_DEFAULT);
342 }
343 EXPORT_SYMBOL(mips_elf_read_implies_exec);
344