summaryrefslogtreecommitdiff
path: root/arch/powerpc/kernel/module_32.c
blob: d7134c614c16b1a99f5ce8c2c977840019d0c961 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
// SPDX-License-Identifier: GPL-2.0-or-later
/*  Kernel module help for PPC.
    Copyright (C) 2001 Rusty Russell.

*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/moduleloader.h>
#include <linux/elf.h>
#include <linux/vmalloc.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/ftrace.h>
#include <linux/cache.h>
#include <linux/bug.h>
#include <linux/sort.h>
#include <asm/setup.h>

/* Count how many different relocations (different symbol, different
   addend) */
static unsigned int count_relocs(const Elf32_Rela *rela, unsigned int num)
{
	unsigned int i, r_info, r_addend, _count_relocs;

	_count_relocs = 0;
	r_info = 0;
	r_addend = 0;
	for (i = 0; i < num; i++)
		/* Only count 24-bit relocs, others don't need stubs */
		if (ELF32_R_TYPE(rela[i].r_info) == R_PPC_REL24 &&
		    (r_info != ELF32_R_SYM(rela[i].r_info) ||
		     r_addend != rela[i].r_addend)) {
			_count_relocs++;
			r_info = ELF32_R_SYM(rela[i].r_info);
			r_addend = rela[i].r_addend;
		}

#ifdef CONFIG_DYNAMIC_FTRACE
	_count_relocs++;	/* add one for ftrace_caller */
#endif
	return _count_relocs;
}

static int relacmp(const void *_x, const void *_y)
{
	const Elf32_Rela *x, *y;

	y = (Elf32_Rela *)_x;
	x = (Elf32_Rela *)_y;

	/* Compare the entire r_info (as opposed to ELF32_R_SYM(r_info) only) to
	 * make the comparison cheaper/faster. It won't affect the sorting or
	 * the counting algorithms' performance
	 */
	if (x->r_info < y->r_info)
		return -1;
	else if (x->r_info > y->r_info)
		return 1;
	else if (x->r_addend < y->r_addend)
		return -1;
	else if (x->r_addend > y->r_addend)
		return 1;
	else
		return 0;
}

static void relaswap(void *_x, void *_y, int size)
{
	uint32_t *x, *y, tmp;
	int i;

	y = (uint32_t *)_x;
	x = (uint32_t *)_y;

	for (i = 0; i < sizeof(Elf32_Rela) / sizeof(uint32_t); i++) {
		tmp = x[i];
		x[i] = y[i];
		y[i] = tmp;
	}
}

/* Get the potential trampolines size required of the init and
   non-init sections */
static unsigned long get_plt_size(const Elf32_Ehdr *hdr,
				  const Elf32_Shdr *sechdrs,
				  const char *secstrings,
				  int is_init)
{
	unsigned long ret = 0;
	unsigned i;

	/* Everything marked ALLOC (this includes the exported
           symbols) */
	for (i = 1; i < hdr->e_shnum; i++) {
		/* If it's called *.init*, and we're not init, we're
                   not interested */
		if ((strstr(secstrings + sechdrs[i].sh_name, ".init") != NULL)
		    != is_init)
			continue;

		/* We don't want to look at debug sections. */
		if (strstr(secstrings + sechdrs[i].sh_name, ".debug"))
			continue;

		if (sechdrs[i].sh_type == SHT_RELA) {
			pr_debug("Found relocations in section %u\n", i);
			pr_debug("Ptr: %p.  Number: %u\n",
			       (void *)hdr + sechdrs[i].sh_offset,
			       sechdrs[i].sh_size / sizeof(Elf32_Rela));

			/* Sort the relocation information based on a symbol and
			 * addend key. This is a stable O(n*log n) complexity
			 * alogrithm but it will reduce the complexity of
			 * count_relocs() to linear complexity O(n)
			 */
			sort((void *)hdr + sechdrs[i].sh_offset,
			     sechdrs[i].sh_size / sizeof(Elf32_Rela),
			     sizeof(Elf32_Rela), relacmp, relaswap);

			ret += count_relocs((void *)hdr
					     + sechdrs[i].sh_offset,
					     sechdrs[i].sh_size
					     / sizeof(Elf32_Rela))
				* sizeof(struct ppc_plt_entry);
		}
	}

	return ret;
}

int module_frob_arch_sections(Elf32_Ehdr *hdr,
			      Elf32_Shdr *sechdrs,
			      char *secstrings,
			      struct module *me)
{
	unsigned int i;

	/* Find .plt and .init.plt sections */
	for (i = 0; i < hdr->e_shnum; i++) {
		if (strcmp(secstrings + sechdrs[i].sh_name, ".init.plt") == 0)
			me->arch.init_plt_section = i;
		else if (strcmp(secstrings + sechdrs[i].sh_name, ".plt") == 0)
			me->arch.core_plt_section = i;
	}
	if (!me->arch.core_plt_section || !me->arch.init_plt_section) {
		pr_err("Module doesn't contain .plt or .init.plt sections.\n");
		return -ENOEXEC;
	}

	/* Override their sizes */
	sechdrs[me->arch.core_plt_section].sh_size
		= get_plt_size(hdr, sechdrs, secstrings, 0);
	sechdrs[me->arch.init_plt_section].sh_size
		= get_plt_size(hdr, sechdrs, secstrings, 1);
	return 0;
}

static inline int entry_matches(struct ppc_plt_entry *entry, Elf32_Addr val)
{
	if (entry->jump[0] != (PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val)))
		return 0;
	if (entry->jump[1] != (PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) |
			       PPC_LO(val)))
		return 0;
	return 1;
}

/* Set up a trampoline in the PLT to bounce us to the distant function */
static uint32_t do_plt_call(void *location,
			    Elf32_Addr val,
			    const Elf32_Shdr *sechdrs,
			    struct module *mod)
{
	struct ppc_plt_entry *entry;

	pr_debug("Doing plt for call to 0x%x at 0x%x\n", val, (unsigned int)location);
	/* Init, or core PLT? */
	if (location >= mod->core_layout.base
	    && location < mod->core_layout.base + mod->core_layout.size)
		entry = (void *)sechdrs[mod->arch.core_plt_section].sh_addr;
	else
		entry = (void *)sechdrs[mod->arch.init_plt_section].sh_addr;

	/* Find this entry, or if that fails, the next avail. entry */
	while (entry->jump[0]) {
		if (entry_matches(entry, val)) return (uint32_t)entry;
		entry++;
	}

	/*
	 * lis r12, sym@ha
	 * addi r12, r12, sym@l
	 * mtctr r12
	 * bctr
	 */
	entry->jump[0] = PPC_INST_ADDIS | __PPC_RT(R12) | PPC_HA(val);
	entry->jump[1] = PPC_INST_ADDI | __PPC_RT(R12) | __PPC_RA(R12) | PPC_LO(val);
	entry->jump[2] = PPC_INST_MTCTR | __PPC_RS(R12);
	entry->jump[3] = PPC_INST_BCTR;

	pr_debug("Initialized plt for 0x%x at %p\n", val, entry);
	return (uint32_t)entry;
}

int apply_relocate_add(Elf32_Shdr *sechdrs,
		       const char *strtab,
		       unsigned int symindex,
		       unsigned int relsec,
		       struct module *module)
{
	unsigned int i;
	Elf32_Rela *rela = (void *)sechdrs[relsec].sh_addr;
	Elf32_Sym *sym;
	uint32_t *location;
	uint32_t value;

	pr_debug("Applying ADD relocate section %u to %u\n", relsec,
	       sechdrs[relsec].sh_info);
	for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rela); i++) {
		/* This is where to make the change */
		location = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr
			+ rela[i].r_offset;
		/* This is the symbol it is referring to.  Note that all
		   undefined symbols have been resolved.  */
		sym = (Elf32_Sym *)sechdrs[symindex].sh_addr
			+ ELF32_R_SYM(rela[i].r_info);
		/* `Everything is relative'. */
		value = sym->st_value + rela[i].r_addend;

		switch (ELF32_R_TYPE(rela[i].r_info)) {
		case R_PPC_ADDR32:
			/* Simply set it */
			*(uint32_t *)location = value;
			break;

		case R_PPC_ADDR16_LO:
			/* Low half of the symbol */
			*(uint16_t *)location = value;
			break;

		case R_PPC_ADDR16_HI:
			/* Higher half of the symbol */
			*(uint16_t *)location = (value >> 16);
			break;

		case R_PPC_ADDR16_HA:
			/* Sign-adjusted lower 16 bits: PPC ELF ABI says:
			   (((x >> 16) + ((x & 0x8000) ? 1 : 0))) & 0xFFFF.
			   This is the same, only sane.
			 */
			*(uint16_t *)location = (value + 0x8000) >> 16;
			break;

		case R_PPC_REL24:
			if ((int)(value - (uint32_t)location) < -0x02000000
			    || (int)(value - (uint32_t)location) >= 0x02000000)
				value = do_plt_call(location, value,
						    sechdrs, module);

			/* Only replace bits 2 through 26 */
			pr_debug("REL24 value = %08X. location = %08X\n",
			       value, (uint32_t)location);
			pr_debug("Location before: %08X.\n",
			       *(uint32_t *)location);
			*(uint32_t *)location
				= (*(uint32_t *)location & ~0x03fffffc)
				| ((value - (uint32_t)location)
				   & 0x03fffffc);
			pr_debug("Location after: %08X.\n",
			       *(uint32_t *)location);
			pr_debug("ie. jump to %08X+%08X = %08X\n",
			       *(uint32_t *)location & 0x03fffffc,
			       (uint32_t)location,
			       (*(uint32_t *)location & 0x03fffffc)
			       + (uint32_t)location);
			break;

		case R_PPC_REL32:
			/* 32-bit relative jump. */
			*(uint32_t *)location = value - (uint32_t)location;
			break;

		default:
			pr_err("%s: unknown ADD relocation: %u\n",
			       module->name,
			       ELF32_R_TYPE(rela[i].r_info));
			return -ENOEXEC;
		}
	}

	return 0;
}

#ifdef CONFIG_DYNAMIC_FTRACE
int module_finalize_ftrace(struct module *module, const Elf_Shdr *sechdrs)
{
	module->arch.tramp = do_plt_call(module->core_layout.base,
					 (unsigned long)ftrace_caller,
					 sechdrs, module);
	if (!module->arch.tramp)
		return -ENOENT;

	return 0;
}
#endif