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SubjectRe: [PATCH 5/5] efi/x86: Check for bad relocations
On Thu, 16 Apr 2020 at 00:15, Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> Add relocation checking for x86 as well to catch non-PC-relative
> relocations that require runtime processing, since the EFI stub does not
> do any runtime relocation processing.
>
> This will catch, for example, data relocations created by static
> initializers of pointers.
>
> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
> ---
> drivers/firmware/efi/libstub/Makefile | 10 +++++-----
> 1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 0bb2916eb12b..2aff59812a54 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -96,6 +96,8 @@ STUBCOPY_RELOC-$(CONFIG_ARM) := R_ARM_ABS
> # .bss section here so it's easy to pick out in the linker script.
> #
> STUBCOPY_FLAGS-$(CONFIG_X86) += --rename-section .bss=.bss.efistub,load,alloc
> +STUBCOPY_RELOC-$(CONFIG_X86_32) := 'R_X86_32_(8|16|32)'

This should be R_386_xxx

> +STUBCOPY_RELOC-$(CONFIG_X86_64) := 'R_X86_64_(8|16|32|32S|64)'
>

... and in general, I think we only need the native pointer sized ones, so

R_386_32
R_X86_64_64

> $(obj)/%.stub.o: $(obj)/%.o FORCE
> $(call if_changed,stubcopy)
> @@ -107,16 +109,14 @@ $(obj)/%.stub.o: $(obj)/%.o FORCE
> # this time, use objcopy and leave all sections in place.
> #
>
> -cmd_stubrelocs_check-y = /bin/true
> -
> -cmd_stubrelocs_check-$(CONFIG_EFI_ARMSTUB) = \
> +cmd_stubrelocs_check = \
> $(STRIP) --strip-debug -o $@ $<; \
> - if $(OBJDUMP) -r $@ | grep $(STUBCOPY_RELOC-y); then \
> + if $(OBJDUMP) -r $@ | grep -E $(STUBCOPY_RELOC-y); then \

... which means we don't need to -E either

> echo "$@: absolute symbol references not allowed in the EFI stub" >&2; \
> /bin/false; \
> fi
>
> quiet_cmd_stubcopy = STUBCPY $@
> cmd_stubcopy = \
> - $(cmd_stubrelocs_check-y); \
> + $(cmd_stubrelocs_check); \
> $(OBJCOPY) $(STUBCOPY_FLAGS-y) $< $@
> --
> 2.24.1
>

Could we fold this into the previous x86 patch, and drop the one that
splits off the relocation check from stubcpy?

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