1 /*
2 * Copyright (c) 2024 Intel Corporation
3 *
4 * SPDX-License-Identifier: Apache-2.0
5 */
6
7 #include <zephyr/llext/elf.h>
8 #include <zephyr/llext/llext.h>
9 #include <zephyr/llext/llext_internal.h>
10 #include <zephyr/llext/loader.h>
11 #include <zephyr/logging/log.h>
12 #include <zephyr/sys/util.h>
13
14 LOG_MODULE_REGISTER(elf, CONFIG_LLEXT_LOG_LEVEL);
15
16 #define R_ARC_32 4
17 #define R_ARC_B26 5 /* AKA R_ARC_64 */
18 #define R_ARC_S25H_PCREL 16
19 #define R_ARC_S25W_PCREL 17
20 #define R_ARC_32_ME 27
21
22 /* ARCompact insns packed in memory have Middle Endian encoding */
23 #define ME(x) (((x & 0xffff0000) >> 16) | ((x & 0xffff) << 16))
24
25 /**
26 * @brief Architecture specific function for relocating shared elf
27 *
28 * Elf files contain a series of relocations described in multiple sections.
29 * These relocation instructions are architecture specific and each architecture
30 * supporting modules must implement this.
31 *
32 * The relocation codes are well documented:
33 * https://github.com/foss-for-synopsys-dwc-arc-processors/arc-ABI-manual/blob/master/ARCv2_ABI.pdf
34 * https://github.com/zephyrproject-rtos/binutils-gdb
35 */
arch_elf_relocate(struct llext_loader * ldr,struct llext * ext,elf_rela_t * rel,const elf_shdr_t * shdr)36 int arch_elf_relocate(struct llext_loader *ldr, struct llext *ext, elf_rela_t *rel,
37 const elf_shdr_t *shdr)
38 {
39 int ret = 0;
40 uint32_t value;
41 const uintptr_t loc = llext_get_reloc_instruction_location(ldr, ext, shdr->sh_info, rel);
42 uint32_t insn = UNALIGNED_GET((uint32_t *)loc);
43 elf_sym_t sym;
44 uintptr_t sym_base_addr;
45 const char *sym_name;
46
47 ret = llext_read_symbol(ldr, ext, rel, &sym);
48
49 if (ret != 0) {
50 LOG_ERR("Could not read symbol from binary!");
51 return ret;
52 }
53
54 sym_name = llext_symbol_name(ldr, ext, &sym);
55
56 ret = llext_lookup_symbol(ldr, ext, &sym_base_addr, rel, &sym, sym_name, shdr);
57
58 if (ret != 0) {
59 LOG_ERR("Could not find symbol %s!", sym_name);
60 return ret;
61 }
62
63 sym_base_addr += rel->r_addend;
64
65 int reloc_type = ELF32_R_TYPE(rel->r_info);
66
67 switch (reloc_type) {
68 case R_ARC_32:
69 case R_ARC_B26:
70 UNALIGNED_PUT(sym_base_addr, (uint32_t *)loc);
71 break;
72 case R_ARC_S25H_PCREL:
73 /* ((S + A) - P) >> 1
74 * S = symbol address
75 * A = addend
76 * P = relative offset to PCL
77 */
78 value = (sym_base_addr + rel->r_addend - (loc & ~0x3)) >> 1;
79
80 insn = ME(insn);
81
82 /* disp25h */
83 insn = insn & ~0x7feffcf;
84 insn |= ((value >> 0) & 0x03ff) << 17;
85 insn |= ((value >> 10) & 0x03ff) << 6;
86 insn |= ((value >> 20) & 0x000f) << 0;
87
88 insn = ME(insn);
89
90 UNALIGNED_PUT(insn, (uint32_t *)loc);
91 break;
92 case R_ARC_S25W_PCREL:
93 /* ((S + A) - P) >> 2 */
94 value = (sym_base_addr + rel->r_addend - (loc & ~0x3)) >> 2;
95
96 insn = ME(insn);
97
98 /* disp25w */
99 insn = insn & ~0x7fcffcf;
100 insn |= ((value >> 0) & 0x01ff) << 18;
101 insn |= ((value >> 9) & 0x03ff) << 6;
102 insn |= ((value >> 19) & 0x000f) << 0;
103
104 insn = ME(insn);
105
106 UNALIGNED_PUT(insn, (uint32_t *)loc);
107 break;
108 case R_ARC_32_ME:
109 UNALIGNED_PUT(ME(sym_base_addr), (uint32_t *)loc);
110 break;
111 default:
112 LOG_ERR("unknown relocation: %u\n", reloc_type);
113 ret = -ENOEXEC;
114 break;
115 }
116
117 return ret;
118 }
119