arch/riscv/include/asm/module.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /* Copyright (C) 2017 Andes Technology Corporation */
   3
   4 #ifndef _ASM_RISCV_MODULE_H
   5 #define _ASM_RISCV_MODULE_H
   6
   7 #include <asm-generic/module.h>
   8 #include <linux/elf.h>
   9
  10 struct module;
  11 unsigned long module_emit_got_entry(struct module *mod, unsigned long val);
  12 unsigned long module_emit_plt_entry(struct module *mod, unsigned long val);
  13
  14 #ifdef CONFIG_MODULE_SECTIONS
  15 struct mod_section {
  16         Elf_Shdr *shdr;
  17         int num_entries;
  18         int max_entries;
  19 };
  20
  21 struct mod_arch_specific {
  22         struct mod_section got;
  23         struct mod_section plt;
  24         struct mod_section got_plt;
  25 };
  26
  27 struct got_entry {
  28         unsigned long symbol_addr;      /* the real variable address */
  29 };
  30
  31 static inline struct got_entry emit_got_entry(unsigned long val)
  32 {
  33         return (struct got_entry) {val};
  34 }
  35
  36 static inline struct got_entry *get_got_entry(unsigned long val,
  37                                               const struct mod_section *sec)
  38 {
  39         struct got_entry *got = (struct got_entry *)(sec->shdr->sh_addr);
  40         int i;
  41         for (i = 0; i < sec->num_entries; i++) {
  42                 if (got[i].symbol_addr == val)
  43                         return &got[i];
  44         }
  45         return NULL;
  46 }
  47
  48 struct plt_entry {
  49         /*
  50          * Trampoline code to real target address. The return address
  51          * should be the original (pc+4) before entring plt entry.
  52          */
  53         u32 insn_auipc;         /* auipc t0, 0x0                       */
  54         u32 insn_ld;            /* ld    t1, 0x10(t0)                  */
  55         u32 insn_jr;            /* jr    t1                            */
  56 };
  57
  58 #define OPC_AUIPC  0x0017
  59 #define OPC_LD     0x3003
  60 #define OPC_JALR   0x0067
  61 #define REG_T0     0x5
  62 #define REG_T1     0x6
  63
  64 static inline struct plt_entry emit_plt_entry(unsigned long val,
  65                                               unsigned long plt,
  66                                               unsigned long got_plt)
  67 {
  68         /*
  69          * U-Type encoding:
  70          * +------------+----------+----------+
  71          * | imm[31:12] | rd[11:7] | opc[6:0] |
  72          * +------------+----------+----------+
  73          *
  74          * I-Type encoding:
  75          * +------------+------------+--------+----------+----------+
  76          * | imm[31:20] | rs1[19:15] | funct3 | rd[11:7] | opc[6:0] |
  77          * +------------+------------+--------+----------+----------+
  78          *
  79          */
  80         unsigned long offset = got_plt - plt;
  81         u32 hi20 = (offset + 0x800) & 0xfffff000;
  82         u32 lo12 = (offset - hi20);
  83         return (struct plt_entry) {
  84                 OPC_AUIPC | (REG_T0 << 7) | hi20,
  85                 OPC_LD | (lo12 << 20) | (REG_T0 << 15) | (REG_T1 << 7),
  86                 OPC_JALR | (REG_T1 << 15)
  87         };
  88 }
  89
  90 static inline int get_got_plt_idx(unsigned long val, const struct mod_section *sec)
  91 {
  92         struct got_entry *got_plt = (struct got_entry *)sec->shdr->sh_addr;
  93         int i;
  94         for (i = 0; i < sec->num_entries; i++) {
  95                 if (got_plt[i].symbol_addr == val)
  96                         return i;
  97         }
  98         return -1;
  99 }
 100
 101 static inline struct plt_entry *get_plt_entry(unsigned long val,
 102                                               const struct mod_section *sec_plt,
 103                                               const struct mod_section *sec_got_plt)
 104 {
 105         struct plt_entry *plt = (struct plt_entry *)sec_plt->shdr->sh_addr;
 106         int got_plt_idx = get_got_plt_idx(val, sec_got_plt);
 107         if (got_plt_idx >= 0)
 108                 return plt + got_plt_idx;
 109         else
 110                 return NULL;
 111 }
 112
 113 #endif /* CONFIG_MODULE_SECTIONS */
 114
 115 static inline const Elf_Shdr *find_section(const Elf_Ehdr *hdr,
 116                                            const Elf_Shdr *sechdrs,
 117                                            const char *name)
 118 {
 119         const Elf_Shdr *s, *se;
 120         const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
 121
 122         for (s = sechdrs, se = sechdrs + hdr->e_shnum; s < se; s++) {
 123                 if (strcmp(name, secstrs + s->sh_name) == 0)
 124                         return s;
 125         }
 126
 127         return NULL;
 128 }
 129
 130 #endif /* _ASM_RISCV_MODULE_H */