[PATCH v2 9/9] riscv: Update alignment for some sections in linker scripts
Michal Simek
monstr at monstr.eu
Wed Feb 14 12:15:47 CET 2024
Hi Bin,
čt 13. 4. 2023 v 8:21 odesílatel Bin Meng <bmeng at tinylab.org> napsal:
> Some sections in the linker scripts are aligned to 4 bytes, which
> may cause misaligned exception on some platforms, e.g.: clearing
> the bss section on 64-bit hardware if __bss_start does not start
> from a naturally 8 bytes aligned address.
>
> Signed-off-by: Bin Meng <bmeng at tinylab.org>
>
> ---
>
> (no changes since v1)
>
> arch/riscv/cpu/u-boot-spl.lds | 2 +-
> arch/riscv/cpu/u-boot.lds | 6 +++---
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/cpu/u-boot-spl.lds b/arch/riscv/cpu/u-boot-spl.lds
> index c3b4907905..d1113a59aa 100644
> --- a/arch/riscv/cpu/u-boot-spl.lds
> +++ b/arch/riscv/cpu/u-boot-spl.lds
> @@ -44,7 +44,7 @@ SECTIONS
> __binman_sym_end = .;
> } > .spl_mem
>
> - . = ALIGN(4);
> + . = ALIGN(8);
>
> _end = .;
> _image_binary_end = .;
> diff --git a/arch/riscv/cpu/u-boot.lds b/arch/riscv/cpu/u-boot.lds
> index 1c937aebee..15b5cbc585 100644
> --- a/arch/riscv/cpu/u-boot.lds
> +++ b/arch/riscv/cpu/u-boot.lds
> @@ -57,7 +57,7 @@ SECTIONS
> __efi_runtime_rel_stop = .;
> }
>
> - . = ALIGN(4);
> + . = ALIGN(8);
>
> /DISCARD/ : { *(.rela.plt*) }
> .rela.dyn : {
> @@ -66,7 +66,7 @@ SECTIONS
> __rel_dyn_end = .;
> }
>
> - . = ALIGN(4);
> + . = ALIGN(8);
>
> .dynsym : {
> __dyn_sym_start = .;
> @@ -74,7 +74,7 @@ SECTIONS
> __dyn_sym_end = .;
> }
>
> - . = ALIGN(4);
> + . = ALIGN(8);
>
> _end = .;
>
This change has actually a side effect on SPL and its behavior. You are
enforcing here that symbols _end
or _image_binary_end are 8byte aligned but if previous section are only 4
bytes aligned you are forcing 4byte gap
between the end of u-boot-nodtb.bin binary and symbol reference.
It means when you want to attach dtb behind SPL you have a problem.
DTBs should be 64bit aligned. It means alignment of 8bytes is fine but you
need to also make sure that
spl/u-boot-nodtb.bin is 8byte aligned.
Pretty much talking about change like below but it would require to change
all u-boot-spl.lds to make sure that end symbols are
8byte aligned that appended DTB is 8byte aligned all the time.
Thanks,
Michal
diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl
index 407fc52376a5..486360f10176 100644
--- a/scripts/Makefile.spl
+++ b/scripts/Makefile.spl
@@ -320,7 +320,7 @@ endif
endif
ifneq ($(build_dtb),)
-$(obj)/$(SPL_BIN)-dtb.bin: $(obj)/$(SPL_BIN)-nodtb.bin \
+$(obj)/$(SPL_BIN)-dtb.bin: $(obj)/$(SPL_BIN)-nodtb-align.bin \
$(if
$(CONFIG_$(SPL_TPL_)SEPARATE_BSS),,$(obj)/$(SPL_BIN)-pad.bin) \
$(FINAL_DTB_CONTAINER) FORCE
$(call if_changed,cat)
@@ -328,7 +328,7 @@ $(obj)/$(SPL_BIN)-dtb.bin: $(obj)/$(SPL_BIN)-nodtb.bin \
$(obj)/$(SPL_BIN).bin: $(obj)/$(SPL_BIN)-dtb.bin FORCE
$(call if_changed,copy)
else
-$(obj)/$(SPL_BIN).bin: $(obj)/$(SPL_BIN)-nodtb.bin FORCE
+$(obj)/$(SPL_BIN).bin: $(obj)/$(SPL_BIN)-nodtb-align.bin FORCE
$(call if_changed,copy)
endif
@@ -390,6 +390,9 @@ OBJCOPYFLAGS_$(SPL_BIN)-nodtb.bin = $(SPL_OBJCFLAGS) -O
binary \
$(obj)/$(SPL_BIN)-nodtb.bin: $(obj)/$(SPL_BIN) FORCE
$(call if_changed,objcopy)
+$(obj)/$(SPL_BIN)-nodtb-align.bin: $(obj)/$(SPL_BIN)-nodtb.bin
+ @dd if=$< of=$@ conv=block,sync bs=8 2>/dev/null;
+
OBJCOPYFLAGS_u-boot-x86-start16-spl.bin := -O binary -j .start16
$(obj)/u-boot-x86-start16-spl.bin: $(obj)/u-boot-spl FORCE
$(call if_changed,objcopy)
Thanks,
Michal
--
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Xilinx Microblaze
Maintainer of Linux kernel - Xilinx Zynq ARM and ZynqMP ARM64 SoCs
U-Boot custodian - Xilinx Microblaze/Zynq/ZynqMP/Versal SoCs
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