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RISC-V: Support GOT_HI20/CALL_PLT relocation type in kernel module 

For CALL_PLT, emit the plt entry only when offset is more than 32-bit.

For PCREL_LO12, it uses the location of corresponding HI20 to
get the address of external symbol. It should check the HI20 type
is the PCREL_HI20 or GOT_HI20, because sometime the location will
have two or more relocation types.
For example:
0:   00000797                auipc   a5,0x0
                     0: R_RISCV_ALIGN        *ABS*
                     0: R_RISCV_GOT_HI20     SYMBOL
4:   0007b783                ld      a5,0(a5) # 0 <SYMBOL>
                     4: R_RISCV_PCREL_LO12_I .L0
                     4: R_RISCV_RELAX        *ABS*

Signed-off-by: Zong Li <zong@andestech.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>
This commit is contained in:
Zong Li 2018-03-15 16:50:43 +08:00 committed by Palmer Dabbelt
parent b8bde0ef12
commit da975dd481
No known key found for this signature in database
GPG Key ID: EF4CA1502CCBAB41
1 changed files with 52 additions and 10 deletions
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62
arch/riscv/kernel/module.c
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@ -92,6 +92,28 @@ static int apply_r_riscv_pcrel_lo12_s_rela(struct module *me, u32 *location,
return 0;
}
static int apply_r_riscv_got_hi20_rela(struct module *me, u32 *location,
Elf_Addr v)
{
s64 offset = (void *)v - (void *)location;
s32 hi20;
/* Always emit the got entry */
if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
offset = module_emit_got_entry(me, v);
offset = (void *)offset - (void *)location;
} else {
pr_err(
"%s: can not generate the GOT entry for symbol = %016llx from PC = %p\n",
me->name, v, location);
return -EINVAL;
}
hi20 = (offset + 0x800) & 0xfffff000;
*location = (*location & 0xfff) | hi20;
return 0;
}
static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
Elf_Addr v)
{
@ -100,10 +122,16 @@ static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
u32 hi20, lo12;
if (offset != fill_v) {
pr_err(
"%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
me->name, v, location);
return -EINVAL;
/* Only emit the plt entry if offset over 32-bit range */
if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
offset = module_emit_plt_entry(me, v);
offset = (void *)offset - (void *)location;
} else {
pr_err(
"%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
me->name, v, location);
return -EINVAL;
}
}
hi20 = (offset + 0x800) & 0xfffff000;
@ -127,6 +155,7 @@ static int (*reloc_handlers_rela[]) (struct module *me, u32 *location,
[R_RISCV_PCREL_HI20] = apply_r_riscv_pcrel_hi20_rela,
[R_RISCV_PCREL_LO12_I] = apply_r_riscv_pcrel_lo12_i_rela,
[R_RISCV_PCREL_LO12_S] = apply_r_riscv_pcrel_lo12_s_rela,
[R_RISCV_GOT_HI20] = apply_r_riscv_got_hi20_rela,
[R_RISCV_CALL_PLT] = apply_r_riscv_call_plt_rela,
[R_RISCV_RELAX] = apply_r_riscv_relax_rela,
};
@ -184,25 +213,38 @@ int apply_relocate_add(Elf_Shdr *sechdrs, const char *strtab,
u64 hi20_loc =
sechdrs[sechdrs[relsec].sh_info].sh_addr
+ rel[j].r_offset;
/* Find the corresponding HI20 PC-relative relocation entry */
if (hi20_loc == sym->st_value) {
u32 hi20_type = ELF_RISCV_R_TYPE(rel[j].r_info);
/* Find the corresponding HI20 relocation entry */
if (hi20_loc == sym->st_value
&& (hi20_type == R_RISCV_PCREL_HI20
|| hi20_type == R_RISCV_GOT_HI20)) {
s32 hi20, lo12;
Elf_Sym *hi20_sym =
(Elf_Sym *)sechdrs[symindex].sh_addr
+ ELF_RISCV_R_SYM(rel[j].r_info);
u64 hi20_sym_val =
hi20_sym->st_value
+ rel[j].r_addend;
/* Calculate lo12 */
s64 offset = hi20_sym_val - hi20_loc;
s32 hi20 = (offset + 0x800) & 0xfffff000;
s32 lo12 = offset - hi20;
u64 offset = hi20_sym_val - hi20_loc;
if (IS_ENABLED(CONFIG_MODULE_SECTIONS)
&& hi20_type == R_RISCV_GOT_HI20) {
offset = module_emit_got_entry(
me, hi20_sym_val);
offset = offset - hi20_loc;
}
hi20 = (offset + 0x800) & 0xfffff000;
lo12 = offset - hi20;
v = lo12;
break;
}
}
if (j == sechdrs[relsec].sh_size / sizeof(*rel)) {
pr_err(
"%s: Can not find HI20 PC-relative relocation information\n",
"%s: Can not find HI20 relocation information\n",
me->name);
return -EINVAL;
}