On Mon, 27 Mar 2023 at 11:51, Pingfan Liu <kernelfans@xxxxxxxxx> wrote:
>
> Using objcopy to reform vmlinuz.efi.elf to vmlinuz.efi will not convey
> any relocation information. That means vmlinuz.efi is expected to be
> PIC.
>
> At present, vmlinuz.efi is PIC. But it is better to adopt the same
Why is it better?
> solution used by the kernel to resolve the code relocation issue by
> itself. That is to resolve R_AARCH64_RELATIVE at the runtime.
>
This breaks other architectures.
> Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Cc: Kees Cook <keescook@xxxxxxxxxxxx>
> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> Cc: Sami Tolvanen <samitolvanen@xxxxxxxxxx>
> Cc: Huacai Chen <chenhuacai@xxxxxxxxxx>
> To: linux-efi@xxxxxxxxxxxxxxx
> ---
> drivers/firmware/efi/libstub/Makefile | 2 +-
> drivers/firmware/efi/libstub/Makefile.zboot | 2 +-
> drivers/firmware/efi/libstub/zboot-entry.S | 35 +++++++++++++++++++++
> drivers/firmware/efi/libstub/zboot.c | 2 +-
> drivers/firmware/efi/libstub/zboot.lds | 6 ++++
> 5 files changed, 44 insertions(+), 3 deletions(-)
> create mode 100644 drivers/firmware/efi/libstub/zboot-entry.S
>
> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 80d85a5169fb..4447395d7218 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -95,7 +95,7 @@ lib-$(CONFIG_LOONGARCH) += loongarch.o loongarch-stub.o
> CFLAGS_arm32-stub.o := -DTEXT_OFFSET=$(TEXT_OFFSET)
>
> zboot-obj-$(CONFIG_RISCV) := lib-clz_ctz.o lib-ashldi3.o
> -lib-$(CONFIG_EFI_ZBOOT) += zboot.o $(zboot-obj-y)
> +lib-$(CONFIG_EFI_ZBOOT) += zboot-entry.o zboot.o $(zboot-obj-y)
>
> extra-y := $(lib-y)
> lib-y := $(patsubst %.o,%.stub.o,$(lib-y))
> diff --git a/drivers/firmware/efi/libstub/Makefile.zboot b/drivers/firmware/efi/libstub/Makefile.zboot
> index 43e9a4cab9f5..1ed948cee92f 100644
> --- a/drivers/firmware/efi/libstub/Makefile.zboot
> +++ b/drivers/firmware/efi/libstub/Makefile.zboot
> @@ -36,7 +36,7 @@ $(obj)/zboot-header.o: $(srctree)/drivers/firmware/efi/libstub/zboot-header.S FO
>
> ZBOOT_DEPS := $(obj)/zboot-header.o $(objtree)/drivers/firmware/efi/libstub/lib.a
>
> -LDFLAGS_vmlinuz.efi.elf := -T $(srctree)/drivers/firmware/efi/libstub/zboot.lds
> +LDFLAGS_vmlinuz.efi.elf := --no-undefined -X -shared -Bsymbolic -z notext --no-apply-dynamic-relocs -T $(srctree)/drivers/firmware/efi/libstub/zboot.lds
> $(obj)/vmlinuz.efi.elf: $(obj)/vmlinuz.o $(ZBOOT_DEPS) FORCE
> $(call if_changed,ld)
>
> diff --git a/drivers/firmware/efi/libstub/zboot-entry.S b/drivers/firmware/efi/libstub/zboot-entry.S
> new file mode 100644
> index 000000000000..072207f2f6ba
> --- /dev/null
> +++ b/drivers/firmware/efi/libstub/zboot-entry.S
> @@ -0,0 +1,35 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#include <asm/elf.h>
> +#define ZBOOT_HEADER_BASE 0
> +
> + .text
> +/*
> + * x0: efi_handle_t
> + * x1: efi_system_table_t *
> + */
> + .global efi_zboot_entry
> +efi_zboot_entry:
> + adrp x2, efi_zboot_header
> + add x2, x2, :lo12:efi_zboot_header
> + mov x3, ZBOOT_HEADER_BASE
> + sub x3, x2, x3 // delta between actual and linked address
> + adrp x4, _rela_start
> + add x4, x4, :lo12:_rela_start
> + adrp x5, _rela_end
> + add x5, x5, :lo12:_rela_end
> +
> +0: cmp x5, x4
> + b.hs 1f
> + ldp x6, x7, [x4], #24
> + ldr x8, [x4, #-8]
> + cmp w7, #R_AARCH64_RELATIVE
> + b.ne 0b
> + add x8, x8, x3
> + str x8, [x6, x3]
> + b 0b
> +
> +1:
> + dsb ishst
> + ic iallu
> + b efi_zboot_main
> diff --git a/drivers/firmware/efi/libstub/zboot.c b/drivers/firmware/efi/libstub/zboot.c
> index ba234e062a1a..7aa6b2e6d104 100644
> --- a/drivers/firmware/efi/libstub/zboot.c
> +++ b/drivers/firmware/efi/libstub/zboot.c
> @@ -58,7 +58,7 @@ void __weak efi_cache_sync_image(unsigned long image_base,
> }
>
> asmlinkage efi_status_t __efiapi
> -efi_zboot_entry(efi_handle_t handle, efi_system_table_t *systab)
> +efi_zboot_main(efi_handle_t handle, efi_system_table_t *systab)
> {
> unsigned long compressed_size = _gzdata_end - _gzdata_start;
> unsigned long image_base, alloc_size, code_size;
> diff --git a/drivers/firmware/efi/libstub/zboot.lds b/drivers/firmware/efi/libstub/zboot.lds
> index 93d33f68333b..631942604c3f 100644
> --- a/drivers/firmware/efi/libstub/zboot.lds
> +++ b/drivers/firmware/efi/libstub/zboot.lds
> @@ -12,6 +12,12 @@ SECTIONS
> *(.text* .init.text*)
> }
>
> + .rela.dyn : ALIGN(8) {
> + __efistub__rela_start = .;
> + *(.rela .rela*)
> + __efistub__rela_end = .;
> + }
> +
> .rodata : ALIGN(8) {
> __efistub__gzdata_start = .;
> *(.gzdata)
> --
> 2.31.1
>
