1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*  Kernel module help for Alpha.
3     Copyright (C) 2002 Richard Henderson.
4 
5 */
6 #include <linux/moduleloader.h>
7 #include <linux/elf.h>
8 #include <linux/vmalloc.h>
9 #include <linux/fs.h>
10 #include <linux/string.h>
11 #include <linux/kernel.h>
12 #include <linux/slab.h>
13 
14 #if 0
15 #define DEBUGP printk
16 #else
17 #define DEBUGP(fmt...)
18 #endif
19 
20 /* Allocate the GOT at the end of the core sections.  */
21 
22 struct got_entry {
23 	struct got_entry *next;
24 	Elf64_Sxword r_addend;
25 	int got_offset;
26 };
27 
28 static inline void
process_reloc_for_got(Elf64_Rela * rela,struct got_entry * chains,Elf64_Xword * poffset)29 process_reloc_for_got(Elf64_Rela *rela,
30 		      struct got_entry *chains, Elf64_Xword *poffset)
31 {
32 	unsigned long r_sym = ELF64_R_SYM (rela->r_info);
33 	unsigned long r_type = ELF64_R_TYPE (rela->r_info);
34 	Elf64_Sxword r_addend = rela->r_addend;
35 	struct got_entry *g;
36 
37 	if (r_type != R_ALPHA_LITERAL)
38 		return;
39 
40 	for (g = chains + r_sym; g ; g = g->next)
41 		if (g->r_addend == r_addend) {
42 			if (g->got_offset == 0) {
43 				g->got_offset = *poffset;
44 				*poffset += 8;
45 			}
46 			goto found_entry;
47 		}
48 
49 	g = kmalloc (sizeof (*g), GFP_KERNEL);
50 	g->next = chains[r_sym].next;
51 	g->r_addend = r_addend;
52 	g->got_offset = *poffset;
53 	*poffset += 8;
54 	chains[r_sym].next = g;
55 
56  found_entry:
57 	/* Trick: most of the ELF64_R_TYPE field is unused.  There are
58 	   42 valid relocation types, and a 32-bit field.  Co-opt the
59 	   bits above 256 to store the got offset for this reloc.  */
60 	rela->r_info |= g->got_offset << 8;
61 }
62 
63 int
module_frob_arch_sections(Elf64_Ehdr * hdr,Elf64_Shdr * sechdrs,char * secstrings,struct module * me)64 module_frob_arch_sections(Elf64_Ehdr *hdr, Elf64_Shdr *sechdrs,
65 			  char *secstrings, struct module *me)
66 {
67 	struct got_entry *chains;
68 	Elf64_Rela *rela;
69 	Elf64_Shdr *esechdrs, *symtab, *s, *got;
70 	unsigned long nsyms, nrela, i;
71 
72 	esechdrs = sechdrs + hdr->e_shnum;
73 	symtab = got = NULL;
74 
75 	/* Find out how large the symbol table is.  Allocate one got_entry
76 	   head per symbol.  Normally this will be enough, but not always.
77 	   We'll chain different offsets for the symbol down each head.  */
78 	for (s = sechdrs; s < esechdrs; ++s)
79 		if (s->sh_type == SHT_SYMTAB)
80 			symtab = s;
81 		else if (!strcmp(".got", secstrings + s->sh_name)) {
82 			got = s;
83 			me->arch.gotsecindex = s - sechdrs;
84 		}
85 
86 	if (!symtab) {
87 		printk(KERN_ERR "module %s: no symbol table\n", me->name);
88 		return -ENOEXEC;
89 	}
90 	if (!got) {
91 		printk(KERN_ERR "module %s: no got section\n", me->name);
92 		return -ENOEXEC;
93 	}
94 
95 	nsyms = symtab->sh_size / sizeof(Elf64_Sym);
96 	chains = kcalloc(nsyms, sizeof(struct got_entry), GFP_KERNEL);
97 	if (!chains) {
98 		printk(KERN_ERR
99 		       "module %s: no memory for symbol chain buffer\n",
100 		       me->name);
101 		return -ENOMEM;
102 	}
103 
104 	got->sh_size = 0;
105 	got->sh_addralign = 8;
106 	got->sh_type = SHT_NOBITS;
107 
108 	/* Examine all LITERAL relocations to find out what GOT entries
109 	   are required.  This sizes the GOT section as well.  */
110 	for (s = sechdrs; s < esechdrs; ++s)
111 		if (s->sh_type == SHT_RELA) {
112 			nrela = s->sh_size / sizeof(Elf64_Rela);
113 			rela = (void *)hdr + s->sh_offset;
114 			for (i = 0; i < nrela; ++i)
115 				process_reloc_for_got(rela+i, chains,
116 						      &got->sh_size);
117 		}
118 
119 	/* Free the memory we allocated.  */
120 	for (i = 0; i < nsyms; ++i) {
121 		struct got_entry *g, *n;
122 		for (g = chains[i].next; g ; g = n) {
123 			n = g->next;
124 			kfree(g);
125 		}
126 	}
127 	kfree(chains);
128 
129 	return 0;
130 }
131 
132 int
apply_relocate_add(Elf64_Shdr * sechdrs,const char * strtab,unsigned int symindex,unsigned int relsec,struct module * me)133 apply_relocate_add(Elf64_Shdr *sechdrs, const char *strtab,
134 		   unsigned int symindex, unsigned int relsec,
135 		   struct module *me)
136 {
137 	Elf64_Rela *rela = (void *)sechdrs[relsec].sh_addr;
138 	unsigned long i, n = sechdrs[relsec].sh_size / sizeof(*rela);
139 	Elf64_Sym *symtab, *sym;
140 	void *base, *location;
141 	unsigned long got, gp;
142 
143 	DEBUGP("Applying relocate section %u to %u\n", relsec,
144 	       sechdrs[relsec].sh_info);
145 
146 	base = (void *)sechdrs[sechdrs[relsec].sh_info].sh_addr;
147 	symtab = (Elf64_Sym *)sechdrs[symindex].sh_addr;
148 
149 	got = sechdrs[me->arch.gotsecindex].sh_addr;
150 	gp = got + 0x8000;
151 
152 	for (i = 0; i < n; i++) {
153 		unsigned long r_sym = ELF64_R_SYM (rela[i].r_info);
154 		unsigned long r_type = ELF64_R_TYPE (rela[i].r_info);
155 		unsigned long r_got_offset = r_type >> 8;
156 		unsigned long value, hi, lo;
157 		r_type &= 0xff;
158 
159 		/* This is where to make the change.  */
160 		location = base + rela[i].r_offset;
161 
162 		/* This is the symbol it is referring to.  Note that all
163 		   unresolved symbols have been resolved.  */
164 		sym = symtab + r_sym;
165 		value = sym->st_value + rela[i].r_addend;
166 
167 		switch (r_type) {
168 		case R_ALPHA_NONE:
169 			break;
170 		case R_ALPHA_REFLONG:
171 			*(u32 *)location = value;
172 			break;
173 		case R_ALPHA_REFQUAD:
174 			/* BUG() can produce misaligned relocations. */
175 			((u32 *)location)[0] = value;
176 			((u32 *)location)[1] = value >> 32;
177 			break;
178 		case R_ALPHA_GPREL32:
179 			value -= gp;
180 			if ((int)value != value)
181 				goto reloc_overflow;
182 			*(u32 *)location = value;
183 			break;
184 		case R_ALPHA_LITERAL:
185 			hi = got + r_got_offset;
186 			lo = hi - gp;
187 			if ((short)lo != lo)
188 				goto reloc_overflow;
189 			*(u16 *)location = lo;
190 			*(u64 *)hi = value;
191 			break;
192 		case R_ALPHA_LITUSE:
193 			break;
194 		case R_ALPHA_GPDISP:
195 			value = gp - (u64)location;
196 			lo = (short)value;
197 			hi = (int)(value - lo);
198 			if (hi + lo != value)
199 				goto reloc_overflow;
200 			*(u16 *)location = hi >> 16;
201 			*(u16 *)(location + rela[i].r_addend) = lo;
202 			break;
203 		case R_ALPHA_BRSGP:
204 			/* BRSGP is only allowed to bind to local symbols.
205 			   If the section is undef, this means that the
206 			   value was resolved from somewhere else.  */
207 			if (sym->st_shndx == SHN_UNDEF)
208 				goto reloc_overflow;
209 			if ((sym->st_other & STO_ALPHA_STD_GPLOAD) ==
210 			    STO_ALPHA_STD_GPLOAD)
211 				/* Omit the prologue. */
212 				value += 8;
213 			fallthrough;
214 		case R_ALPHA_BRADDR:
215 			value -= (u64)location + 4;
216 			if (value & 3)
217 				goto reloc_overflow;
218 			value = (long)value >> 2;
219 			if (value + (1<<21) >= 1<<22)
220 				goto reloc_overflow;
221 			value &= 0x1fffff;
222 			value |= *(u32 *)location & ~0x1fffff;
223 			*(u32 *)location = value;
224 			break;
225 		case R_ALPHA_HINT:
226 			break;
227 		case R_ALPHA_SREL32:
228 			value -= (u64)location;
229 			if ((int)value != value)
230 				goto reloc_overflow;
231 			*(u32 *)location = value;
232 			break;
233 		case R_ALPHA_SREL64:
234 			value -= (u64)location;
235 			*(u64 *)location = value;
236 			break;
237 		case R_ALPHA_GPRELHIGH:
238 			value = (long)(value - gp + 0x8000) >> 16;
239 			if ((short) value != value)
240 				goto reloc_overflow;
241 			*(u16 *)location = value;
242 			break;
243 		case R_ALPHA_GPRELLOW:
244 			value -= gp;
245 			*(u16 *)location = value;
246 			break;
247 		case R_ALPHA_GPREL16:
248 			value -= gp;
249 			if ((short) value != value)
250 				goto reloc_overflow;
251 			*(u16 *)location = value;
252 			break;
253 		default:
254 			printk(KERN_ERR "module %s: Unknown relocation: %lu\n",
255 			       me->name, r_type);
256 			return -ENOEXEC;
257 		reloc_overflow:
258 			if (ELF64_ST_TYPE (sym->st_info) == STT_SECTION)
259 			  printk(KERN_ERR
260 			         "module %s: Relocation (type %lu) overflow vs section %d\n",
261 			         me->name, r_type, sym->st_shndx);
262 			else
263 			  printk(KERN_ERR
264 			         "module %s: Relocation (type %lu) overflow vs %s\n",
265 			         me->name, r_type, strtab + sym->st_name);
266 			return -ENOEXEC;
267 		}
268 	}
269 
270 	return 0;
271 }
272