On Sun, May 14, 2023 at 5:54 PM Masahiro Yamada <masahiroy@xxxxxxxxxx> wrote:
>
> The section mismatch check does not show proper warning messages for ARM.
>
> Here, very simple test code.
>
> #include <linux/init.h>
>
> static int __initdata foo;
>
> void set_foo(int x)
> {
> foo = x;
> }
>
> int get_foo(int x)
> {
> return foo;
> }
>
> If I compile it for ARM, modpost does not show the symbol name.
>
> WARNING: modpost: vmlinux.o: section mismatch in reference: set_foo (section: .text) -> (unknown) (section: .init.data)
> WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> (unknown) (section: .init.data)
>
> If I compile it for other architectures, modpost shows the correct symbol name.
>
> WARNING: modpost: vmlinux.o: section mismatch in reference: set_foo (section: .text) -> foo (section: .init.data)
> WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> foo (section: .init.data)
>
> For R_ARM_ABS32, addend_arm_rel() sets r->r_addend to a wrong value.
>
> arch/arm/kernel/module.c handles R_ARM_ABS32 as follows:
>
> case R_ARM_ABS32:
> case R_ARM_TARGET1:
> *(u32 *)loc += sym->st_value;
>
> I just mimicked it in modpost.
>
> Fixes: 56a974fa2d59 ("kbuild: make better section mismatch reports on arm")
> Signed-off-by: Masahiro Yamada <masahiroy@xxxxxxxxxx>
> ---
>
> scripts/mod/modpost.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
> index d4531d09984d..c93780d93caf 100644
> --- a/scripts/mod/modpost.c
> +++ b/scripts/mod/modpost.c
> @@ -1460,12 +1460,13 @@ static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
> static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r)
> {
> unsigned int r_typ = ELF_R_TYPE(r->r_info);
> + unsigned int *location = reloc_location(elf, sechdr, r);
If `location` is only used in one case of the switch, consider
computing `location` only in that case.
> + Elf_Sym *sym;
>
> switch (r_typ) {
> case R_ARM_ABS32:
> - /* From ARM ABI: (S + A) | T */
> - r->r_addend = (int)(long)
> - (elf->symtab_start + ELF_R_SYM(r->r_info));
> + sym = elf->symtab_start + ELF_R_SYM(r->r_info);
> + r->r_addend = TO_NATIVE(*location) + sym->st_value;
> break;
> case R_ARM_PC24:
> case R_ARM_CALL:
> --
> 2.39.2
>
--
Thanks,
~Nick Desaulniers
