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