Commit 12ca2c67 authored by Masahiro Yamada's avatar Masahiro Yamada
Browse files

modpost: detect section mismatch for R_ARM_{MOVW_ABS_NC,MOVT_ABS} 



For ARM defconfig (i.e. multi_v7_defconfig), modpost fails to detect
some types of section mismatches.

  [test code]

    #include <linux/init.h>

    int __initdata foo;
    int get_foo(void) { return foo; }

It is apparently a bad reference, but modpost does not report anything.

The test code above produces the following relocations.

  Relocation section '.rel.text' at offset 0x200 contains 2 entries:
   Offset     Info    Type            Sym.Value  Sym. Name
  00000000  0000062b R_ARM_MOVW_ABS_NC 00000000   .LANCHOR0
  00000004  0000062c R_ARM_MOVT_ABS    00000000   .LANCHOR0

Currently, R_ARM_MOVW_ABS_NC and R_ARM_MOVT_ABS are just skipped.

Add code to handle them. I checked arch/arm/kernel/module.c to learn
how the offset is encoded in the instruction.

The referenced symbol in relocation might be a local anchor.
If is_valid_name() returns false, let's search for a better symbol name.

Signed-off-by: default avatarMasahiro Yamada <masahiroy@kernel.org>
parent 56a24b8c

scripts/mod/modpost.c

+9 −2
Original line number Diff line number Diff line
@@ -1078,7 +1078,7 @@ static inline int is_valid_name(struct elf_info *elf, Elf_Sym *sym) 
/**

 * Find symbol based on relocation record info.

 * In some cases the symbol supplied is a valid symbol so

 * return refsym. If st_name != 0 we assume this is a valid symbol.

 * return refsym. If is_valid_name() == true, we assume this is a valid symbol.

 * In other cases the symbol needs to be looked up in the symbol table

 * based on section and address.

 *  **/
@@ -1091,7 +1091,7 @@ static Elf_Sym *find_tosym(struct elf_info *elf, Elf64_Sword addr, 
	Elf64_Sword d;

	unsigned int relsym_secindex;



	if (relsym->st_name != 0)

	if (is_valid_name(elf, relsym))

		return relsym;



	/*
@@ -1297,6 +1297,13 @@ static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) 
		inst = TO_NATIVE(*(uint32_t *)loc);

		r->r_addend = inst + sym->st_value;

		break;

	case R_ARM_MOVW_ABS_NC:

	case R_ARM_MOVT_ABS:

		inst = TO_NATIVE(*(uint32_t *)loc);

		offset = sign_extend32(((inst & 0xf0000) >> 4) | (inst & 0xfff),

				       15);

		r->r_addend = offset + sym->st_value;

		break;

	case R_ARM_PC24:

	case R_ARM_CALL:

	case R_ARM_JUMP24: