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

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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: Masahiro Yamada <masahiroy@kernel.org>
This commit is contained in:
Masahiro Yamada 2023-06-01 21:09:57 +09:00
parent 56a24b8ce6
commit 12ca2c67d7
1 changed files with 9 additions and 2 deletions
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11
scripts/mod/modpost.c
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@ -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: