1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
4 */
5
6#include <linux/elf.h>
7#include <linux/kernel.h>
8#include <linux/module.h>
9#include <linux/moduleloader.h>
10#include <linux/ftrace.h>
11
12Elf_Addr module_emit_got_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val)
13{
14	struct mod_section *got_sec = &mod->arch.got;
15	int i = got_sec->num_entries;
16	struct got_entry *got = get_got_entry(val, sechdrs, got_sec);
17
18	if (got)
19		return (Elf_Addr)got;
20
21	/* There is no GOT entry for val yet, create a new one. */
22	got = (struct got_entry *)sechdrs[got_sec->shndx].sh_addr;
23	got[i] = emit_got_entry(val);
24
25	got_sec->num_entries++;
26	if (got_sec->num_entries > got_sec->max_entries) {
27		/*
28		 * This may happen when the module contains a GOT_HI20 without
29		 * a paired GOT_LO12. Such a module is broken, reject it.
30		 */
31		pr_err("%s: module contains bad GOT relocation\n", mod->name);
32		return 0;
33	}
34
35	return (Elf_Addr)&got[i];
36}
37
38Elf_Addr module_emit_plt_entry(struct module *mod, Elf_Shdr *sechdrs, Elf_Addr val)
39{
40	int nr;
41	struct mod_section *plt_sec = &mod->arch.plt;
42	struct mod_section *plt_idx_sec = &mod->arch.plt_idx;
43	struct plt_entry *plt = get_plt_entry(val, sechdrs, plt_sec, plt_idx_sec);
44	struct plt_idx_entry *plt_idx;
45
46	if (plt)
47		return (Elf_Addr)plt;
48
49	nr = plt_sec->num_entries;
50
51	/* There is no duplicate entry, create a new one */
52	plt = (struct plt_entry *)sechdrs[plt_sec->shndx].sh_addr;
53	plt[nr] = emit_plt_entry(val);
54	plt_idx = (struct plt_idx_entry *)sechdrs[plt_idx_sec->shndx].sh_addr;
55	plt_idx[nr] = emit_plt_idx_entry(val);
56
57	plt_sec->num_entries++;
58	plt_idx_sec->num_entries++;
59	BUG_ON(plt_sec->num_entries > plt_sec->max_entries);
60
61	return (Elf_Addr)&plt[nr];
62}
63
64static int is_rela_equal(const Elf_Rela *x, const Elf_Rela *y)
65{
66	return x->r_info == y->r_info && x->r_addend == y->r_addend;
67}
68
69static bool duplicate_rela(const Elf_Rela *rela, int idx)
70{
71	int i;
72
73	for (i = 0; i < idx; i++) {
74		if (is_rela_equal(&rela[i], &rela[idx]))
75			return true;
76	}
77
78	return false;
79}
80
81static void count_max_entries(Elf_Rela *relas, int num,
82			      unsigned int *plts, unsigned int *gots)
83{
84	unsigned int i, type;
85
86	for (i = 0; i < num; i++) {
87		type = ELF_R_TYPE(relas[i].r_info);
88		switch (type) {
89		case R_LARCH_SOP_PUSH_PLT_PCREL:
90		case R_LARCH_B26:
91			if (!duplicate_rela(relas, i))
92				(*plts)++;
93			break;
94		case R_LARCH_GOT_PC_HI20:
95			if (!duplicate_rela(relas, i))
96				(*gots)++;
97			break;
98		default:
99			break; /* Do nothing. */
100		}
101	}
102}
103
104int module_frob_arch_sections(Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
105			      char *secstrings, struct module *mod)
106{
107	unsigned int i, num_plts = 0, num_gots = 0;
108	Elf_Shdr *got_sec, *plt_sec, *plt_idx_sec, *tramp = NULL;
109
110	/*
111	 * Find the empty .plt sections.
112	 */
113	for (i = 0; i < ehdr->e_shnum; i++) {
114		if (!strcmp(secstrings + sechdrs[i].sh_name, ".got"))
115			mod->arch.got.shndx = i;
116		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt"))
117			mod->arch.plt.shndx = i;
118		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".plt.idx"))
119			mod->arch.plt_idx.shndx = i;
120		else if (!strcmp(secstrings + sechdrs[i].sh_name, ".ftrace_trampoline"))
121			tramp = sechdrs + i;
122	}
123
124	if (!mod->arch.got.shndx) {
125		pr_err("%s: module GOT section(s) missing\n", mod->name);
126		return -ENOEXEC;
127	}
128	if (!mod->arch.plt.shndx) {
129		pr_err("%s: module PLT section(s) missing\n", mod->name);
130		return -ENOEXEC;
131	}
132	if (!mod->arch.plt_idx.shndx) {
133		pr_err("%s: module PLT.IDX section(s) missing\n", mod->name);
134		return -ENOEXEC;
135	}
136
137	/* Calculate the maxinum number of entries */
138	for (i = 0; i < ehdr->e_shnum; i++) {
139		int num_rela = sechdrs[i].sh_size / sizeof(Elf_Rela);
140		Elf_Rela *relas = (void *)ehdr + sechdrs[i].sh_offset;
141		Elf_Shdr *dst_sec = sechdrs + sechdrs[i].sh_info;
142
143		if (sechdrs[i].sh_type != SHT_RELA)
144			continue;
145
146		/* ignore relocations that operate on non-exec sections */
147		if (!(dst_sec->sh_flags & SHF_EXECINSTR))
148			continue;
149
150		count_max_entries(relas, num_rela, &num_plts, &num_gots);
151	}
152
153	got_sec = sechdrs + mod->arch.got.shndx;
154	got_sec->sh_type = SHT_NOBITS;
155	got_sec->sh_flags = SHF_ALLOC;
156	got_sec->sh_addralign = L1_CACHE_BYTES;
157	got_sec->sh_size = (num_gots + 1) * sizeof(struct got_entry);
158	mod->arch.got.num_entries = 0;
159	mod->arch.got.max_entries = num_gots;
160
161	plt_sec = sechdrs + mod->arch.plt.shndx;
162	plt_sec->sh_type = SHT_NOBITS;
163	plt_sec->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
164	plt_sec->sh_addralign = L1_CACHE_BYTES;
165	plt_sec->sh_size = (num_plts + 1) * sizeof(struct plt_entry);
166	mod->arch.plt.num_entries = 0;
167	mod->arch.plt.max_entries = num_plts;
168
169	plt_idx_sec = sechdrs + mod->arch.plt_idx.shndx;
170	plt_idx_sec->sh_type = SHT_NOBITS;
171	plt_idx_sec->sh_flags = SHF_ALLOC;
172	plt_idx_sec->sh_addralign = L1_CACHE_BYTES;
173	plt_idx_sec->sh_size = (num_plts + 1) * sizeof(struct plt_idx_entry);
174	mod->arch.plt_idx.num_entries = 0;
175	mod->arch.plt_idx.max_entries = num_plts;
176
177	if (tramp) {
178		tramp->sh_type = SHT_NOBITS;
179		tramp->sh_flags = SHF_EXECINSTR | SHF_ALLOC;
180		tramp->sh_addralign = __alignof__(struct plt_entry);
181		tramp->sh_size = NR_FTRACE_PLTS * sizeof(struct plt_entry);
182	}
183
184	return 0;
185}
186