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Unverified Commit da975dd4 authored by Zong Li's avatar Zong Li Committed by Palmer Dabbelt
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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: default avatarZong Li <zong@andestech.com>
Signed-off-by: default avatarPalmer Dabbelt <palmer@sifive.com>
parent b8bde0ef

arch/riscv/kernel/module.c

+52 −10
Original line number Diff line number Diff line
@@ -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)

{
@@ -100,11 +122,17 @@ static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location, 
	u32 hi20, lo12;



	if (offset != fill_v) {

		/* 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;

	lo12 = (offset - hi20) & 0xfff;
@@ -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;

			}