1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 *
4 *  Copyright (C) 2001 Rusty Russell.
5 *  Copyright (C) 2003, 2004 Ralf Baechle (ralf@linux-mips.org)
6 *  Copyright (C) 2005 Thiemo Seufer
7 */
8
9#undef DEBUG
10
11#include <linux/extable.h>
12#include <linux/moduleloader.h>
13#include <linux/elf.h>
14#include <linux/mm.h>
15#include <linux/numa.h>
16#include <linux/slab.h>
17#include <linux/fs.h>
18#include <linux/string.h>
19#include <linux/kernel.h>
20#include <linux/spinlock.h>
21#include <linux/jump_label.h>
22#include <asm/jump_label.h>
23
24struct mips_hi16 {
25	struct mips_hi16 *next;
26	Elf_Addr *addr;
27	Elf_Addr value;
28};
29
30static LIST_HEAD(dbe_list);
31static DEFINE_SPINLOCK(dbe_lock);
32
33static void apply_r_mips_32(u32 *location, u32 base, Elf_Addr v)
34{
35	*location = base + v;
36}
37
38static int apply_r_mips_26(struct module *me, u32 *location, u32 base,
39			   Elf_Addr v)
40{
41	if (v % 4) {
42		pr_err("module %s: dangerous R_MIPS_26 relocation\n",
43		       me->name);
44		return -ENOEXEC;
45	}
46
47	if ((v & 0xf0000000) != (((unsigned long)location + 4) & 0xf0000000)) {
48		pr_err("module %s: relocation overflow\n",
49		       me->name);
50		return -ENOEXEC;
51	}
52
53	*location = (*location & ~0x03ffffff) |
54		    ((base + (v >> 2)) & 0x03ffffff);
55
56	return 0;
57}
58
59static int apply_r_mips_hi16(struct module *me, u32 *location, Elf_Addr v,
60			     bool rela)
61{
62	struct mips_hi16 *n;
63
64	if (rela) {
65		*location = (*location & 0xffff0000) |
66			    ((((long long) v + 0x8000LL) >> 16) & 0xffff);
67		return 0;
68	}
69
70	/*
71	 * We cannot relocate this one now because we don't know the value of
72	 * the carry we need to add.  Save the information, and let LO16 do the
73	 * actual relocation.
74	 */
75	n = kmalloc(sizeof *n, GFP_KERNEL);
76	if (!n)
77		return -ENOMEM;
78
79	n->addr = (Elf_Addr *)location;
80	n->value = v;
81	n->next = me->arch.r_mips_hi16_list;
82	me->arch.r_mips_hi16_list = n;
83
84	return 0;
85}
86
87static void free_relocation_chain(struct mips_hi16 *l)
88{
89	struct mips_hi16 *next;
90
91	while (l) {
92		next = l->next;
93		kfree(l);
94		l = next;
95	}
96}
97
98static int apply_r_mips_lo16(struct module *me, u32 *location,
99			     u32 base, Elf_Addr v, bool rela)
100{
101	unsigned long insnlo = base;
102	struct mips_hi16 *l;
103	Elf_Addr val, vallo;
104
105	if (rela) {
106		*location = (*location & 0xffff0000) | (v & 0xffff);
107		return 0;
108	}
109
110	/* Sign extend the addend we extract from the lo insn.	*/
111	vallo = ((insnlo & 0xffff) ^ 0x8000) - 0x8000;
112
113	if (me->arch.r_mips_hi16_list != NULL) {
114		l = me->arch.r_mips_hi16_list;
115		while (l != NULL) {
116			struct mips_hi16 *next;
117			unsigned long insn;
118
119			/*
120			 * The value for the HI16 had best be the same.
121			 */
122			if (v != l->value)
123				goto out_danger;
124
125			/*
126			 * Do the HI16 relocation.  Note that we actually don't
127			 * need to know anything about the LO16 itself, except
128			 * where to find the low 16 bits of the addend needed
129			 * by the LO16.
130			 */
131			insn = *l->addr;
132			val = ((insn & 0xffff) << 16) + vallo;
133			val += v;
134
135			/*
136			 * Account for the sign extension that will happen in
137			 * the low bits.
138			 */
139			val = ((val >> 16) + ((val & 0x8000) != 0)) & 0xffff;
140
141			insn = (insn & ~0xffff) | val;
142			*l->addr = insn;
143
144			next = l->next;
145			kfree(l);
146			l = next;
147		}
148
149		me->arch.r_mips_hi16_list = NULL;
150	}
151
152	/*
153	 * Ok, we're done with the HI16 relocs.	 Now deal with the LO16.
154	 */
155	val = v + vallo;
156	insnlo = (insnlo & ~0xffff) | (val & 0xffff);
157	*location = insnlo;
158
159	return 0;
160
161out_danger:
162	free_relocation_chain(l);
163	me->arch.r_mips_hi16_list = NULL;
164
165	pr_err("module %s: dangerous R_MIPS_LO16 relocation\n", me->name);
166
167	return -ENOEXEC;
168}
169
170static int apply_r_mips_pc(struct module *me, u32 *location, u32 base,
171			   Elf_Addr v, unsigned int bits)
172{
173	unsigned long mask = GENMASK(bits - 1, 0);
174	unsigned long se_bits;
175	long offset;
176
177	if (v % 4) {
178		pr_err("module %s: dangerous R_MIPS_PC%u relocation\n",
179		       me->name, bits);
180		return -ENOEXEC;
181	}
182
183	/* retrieve & sign extend implicit addend if any */
184	offset = base & mask;
185	offset |= (offset & BIT(bits - 1)) ? ~mask : 0;
186
187	offset += ((long)v - (long)location) >> 2;
188
189	/* check the sign bit onwards are identical - ie. we didn't overflow */
190	se_bits = (offset & BIT(bits - 1)) ? ~0ul : 0;
191	if ((offset & ~mask) != (se_bits & ~mask)) {
192		pr_err("module %s: relocation overflow\n", me->name);
193		return -ENOEXEC;
194	}
195
196	*location = (*location & ~mask) | (offset & mask);
197
198	return 0;
199}
200
201static int apply_r_mips_pc16(struct module *me, u32 *location, u32 base,
202			     Elf_Addr v)
203{
204	return apply_r_mips_pc(me, location, base, v, 16);
205}
206
207static int apply_r_mips_pc21(struct module *me, u32 *location, u32 base,
208			     Elf_Addr v)
209{
210	return apply_r_mips_pc(me, location, base, v, 21);
211}
212
213static int apply_r_mips_pc26(struct module *me, u32 *location, u32 base,
214			     Elf_Addr v)
215{
216	return apply_r_mips_pc(me, location, base, v, 26);
217}
218
219static int apply_r_mips_64(u32 *location, Elf_Addr v, bool rela)
220{
221	if (WARN_ON(!rela))
222		return -EINVAL;
223
224	*(Elf_Addr *)location = v;
225
226	return 0;
227}
228
229static int apply_r_mips_higher(u32 *location, Elf_Addr v, bool rela)
230{
231	if (WARN_ON(!rela))
232		return -EINVAL;
233
234	*location = (*location & 0xffff0000) |
235		    ((((long long)v + 0x80008000LL) >> 32) & 0xffff);
236
237	return 0;
238}
239
240static int apply_r_mips_highest(u32 *location, Elf_Addr v, bool rela)
241{
242	if (WARN_ON(!rela))
243		return -EINVAL;
244
245	*location = (*location & 0xffff0000) |
246		    ((((long long)v + 0x800080008000LL) >> 48) & 0xffff);
247
248	return 0;
249}
250
251/**
252 * reloc_handler() - Apply a particular relocation to a module
253 * @type: type of the relocation to apply
254 * @me: the module to apply the reloc to
255 * @location: the address at which the reloc is to be applied
256 * @base: the existing value at location for REL-style; 0 for RELA-style
257 * @v: the value of the reloc, with addend for RELA-style
258 * @rela: indication of is this a RELA (true) or REL (false) relocation
259 *
260 * Each implemented relocation function applies a particular type of
261 * relocation to the module @me. Relocs that may be found in either REL or RELA
262 * variants can be handled by making use of the @base & @v parameters which are
263 * set to values which abstract the difference away from the particular reloc
264 * implementations.
265 *
266 * Return: 0 upon success, else -ERRNO
267 */
268static int reloc_handler(u32 type, struct module *me, u32 *location, u32 base,
269			 Elf_Addr v, bool rela)
270{
271	switch (type) {
272	case R_MIPS_NONE:
273		break;
274	case R_MIPS_32:
275		apply_r_mips_32(location, base, v);
276		break;
277	case R_MIPS_26:
278		return apply_r_mips_26(me, location, base, v);
279	case R_MIPS_HI16:
280		return apply_r_mips_hi16(me, location, v, rela);
281	case R_MIPS_LO16:
282		return apply_r_mips_lo16(me, location, base, v, rela);
283	case R_MIPS_PC16:
284		return apply_r_mips_pc16(me, location, base, v);
285	case R_MIPS_PC21_S2:
286		return apply_r_mips_pc21(me, location, base, v);
287	case R_MIPS_PC26_S2:
288		return apply_r_mips_pc26(me, location, base, v);
289	case R_MIPS_64:
290		return apply_r_mips_64(location, v, rela);
291	case R_MIPS_HIGHER:
292		return apply_r_mips_higher(location, v, rela);
293	case R_MIPS_HIGHEST:
294		return apply_r_mips_highest(location, v, rela);
295	default:
296		pr_err("%s: Unknown relocation type %u\n", me->name, type);
297		return -EINVAL;
298	}
299
300	return 0;
301}
302
303static int __apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
304			    unsigned int symindex, unsigned int relsec,
305			    struct module *me, bool rela)
306{
307	union {
308		Elf_Mips_Rel *rel;
309		Elf_Mips_Rela *rela;
310	} r;
311	Elf_Sym *sym;
312	u32 *location, base;
313	unsigned int i, type;
314	Elf_Addr v;
315	int err = 0;
316	size_t reloc_sz;
317
318	pr_debug("Applying relocate section %u to %u\n", relsec,
319	       sechdrs[relsec].sh_info);
320
321	r.rel = (void *)sechdrs[relsec].sh_addr;
322	reloc_sz = rela ? sizeof(*r.rela) : sizeof(*r.rel);
323	me->arch.r_mips_hi16_list = NULL;
324	for (i = 0; i < sechdrs[relsec].sh_size / reloc_sz; i++) {
325		/* This is where to make the change */
326		location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
327			+ r.rel->r_offset;
328		/* This is the symbol it is referring to */
329		sym = (Elf_Sym *)sechdrs[symindex].sh_addr
330			+ ELF_MIPS_R_SYM(*r.rel);
331		if (sym->st_value >= -MAX_ERRNO) {
332			/* Ignore unresolved weak symbol */
333			if (ELF_ST_BIND(sym->st_info) == STB_WEAK)
334				continue;
335			pr_warn("%s: Unknown symbol %s\n",
336				me->name, strtab + sym->st_name);
337			err = -ENOENT;
338			goto out;
339		}
340
341		type = ELF_MIPS_R_TYPE(*r.rel);
342
343		if (rela) {
344			v = sym->st_value + r.rela->r_addend;
345			base = 0;
346			r.rela = &r.rela[1];
347		} else {
348			v = sym->st_value;
349			base = *location;
350			r.rel = &r.rel[1];
351		}
352
353		err = reloc_handler(type, me, location, base, v, rela);
354		if (err)
355			goto out;
356	}
357
358out:
359	/*
360	 * Normally the hi16 list should be deallocated at this point. A
361	 * malformed binary however could contain a series of R_MIPS_HI16
362	 * relocations not followed by a R_MIPS_LO16 relocation, or if we hit
363	 * an error processing a reloc we might have gotten here before
364	 * reaching the R_MIPS_LO16. In either case, free up the list and
365	 * return an error.
366	 */
367	if (me->arch.r_mips_hi16_list) {
368		free_relocation_chain(me->arch.r_mips_hi16_list);
369		me->arch.r_mips_hi16_list = NULL;
370		err = err ?: -ENOEXEC;
371	}
372
373	return err;
374}
375
376int apply_relocate(Elf_Shdr *sechdrs, const char *strtab,
377		   unsigned int symindex, unsigned int relsec,
378		   struct module *me)
379{
380	return __apply_relocate(sechdrs, strtab, symindex, relsec, me, false);
381}
382
383#ifdef CONFIG_MODULES_USE_ELF_RELA
384int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
385		       unsigned int symindex, unsigned int relsec,
386		       struct module *me)
387{
388	return __apply_relocate(sechdrs, strtab, symindex, relsec, me, true);
389}
390#endif /* CONFIG_MODULES_USE_ELF_RELA */
391
392/* Given an address, look for it in the module exception tables. */
393const struct exception_table_entry *search_module_dbetables(unsigned long addr)
394{
395	unsigned long flags;
396	const struct exception_table_entry *e = NULL;
397	struct mod_arch_specific *dbe;
398
399	spin_lock_irqsave(&dbe_lock, flags);
400	list_for_each_entry(dbe, &dbe_list, dbe_list) {
401		e = search_extable(dbe->dbe_start,
402				   dbe->dbe_end - dbe->dbe_start, addr);
403		if (e)
404			break;
405	}
406	spin_unlock_irqrestore(&dbe_lock, flags);
407
408	/* Now, if we found one, we are running inside it now, hence
409	   we cannot unload the module, hence no refcnt needed. */
410	return e;
411}
412
413/* Put in dbe list if necessary. */
414int module_finalize(const Elf_Ehdr *hdr,
415		    const Elf_Shdr *sechdrs,
416		    struct module *me)
417{
418	const Elf_Shdr *s;
419	char *secstrings = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
420
421	if (IS_ENABLED(CONFIG_JUMP_LABEL))
422		jump_label_apply_nops(me);
423
424	INIT_LIST_HEAD(&me->arch.dbe_list);
425	for (s = sechdrs; s < sechdrs + hdr->e_shnum; s++) {
426		if (strcmp("__dbe_table", secstrings + s->sh_name) != 0)
427			continue;
428		me->arch.dbe_start = (void *)s->sh_addr;
429		me->arch.dbe_end = (void *)s->sh_addr + s->sh_size;
430		spin_lock_irq(&dbe_lock);
431		list_add(&me->arch.dbe_list, &dbe_list);
432		spin_unlock_irq(&dbe_lock);
433	}
434	return 0;
435}
436
437void module_arch_cleanup(struct module *mod)
438{
439	spin_lock_irq(&dbe_lock);
440	list_del(&mod->arch.dbe_list);
441	spin_unlock_irq(&dbe_lock);
442}
443