2023-11-24 03:56:38

by WANG Rui

Subject: [PATCH] LoongArch: Apply dynamic relocations for LLD

For the following assembly code:

.text
.global func
func:
nop

.data
var:
.dword func

When linked with `-pie`, GNU LD populates the `var` variable with the
pre-relocated value of `func`. However, LLVM LLD does not exhibit the
same behavior. This issue also arises with the `kernel_entry` in
arch/loongarch/kernel/head.S:

_head:
.word MZ_MAGIC /* "MZ", MS-DOS header */
.org 0x8
.dword kernel_entry /* Kernel entry point */

The correct kernel entry from the MS-DOS header is crucial for jumping
to vmlinux from zboot. This necessity is why the compressed kernel
compiled by Clang encounters difficulties in booting.

To address this problem, it is proposed to apply dynamic relocations to
place with `--apply-dynamic-relocs`.

Link: https://github.com/ClangBuiltLinux/linux/issues/1962
Signed-off-by: WANG Rui <[email protected]>
---
arch/loongarch/Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
index 1f0d74403419..05ab85118212 100644
--- a/arch/loongarch/Makefile
+++ b/arch/loongarch/Makefile
@@ -83,7 +83,7 @@ endif

ifeq ($(CONFIG_RELOCATABLE),y)
KBUILD_CFLAGS_KERNEL += -fPIE
-LDFLAGS_vmlinux += -static -pie --no-dynamic-linker -z notext
+LDFLAGS_vmlinux += -static -pie --no-dynamic-linker -z notext $(call ld-option, --apply-dynamic-relocs)
endif

cflags-y += $(call cc-option, -mno-check-zero-division)
--
2.43.0

2023-11-26 14:20:36

by Huacai Chen

Subject: Re: [PATCH] LoongArch: Apply dynamic relocations for LLD

Queued for loongarch-fixes, thanks.

Huacai

On Fri, Nov 24, 2023 at 11:56 AM WANG Rui <[email protected]> wrote:
>
> For the following assembly code:
>
> .text
> .global func
> func:
> nop
>
> .data
> var:
> .dword func
>
> When linked with `-pie`, GNU LD populates the `var` variable with the
> pre-relocated value of `func`. However, LLVM LLD does not exhibit the
> same behavior. This issue also arises with the `kernel_entry` in
> arch/loongarch/kernel/head.S:
>
> _head:
> .word MZ_MAGIC /* "MZ", MS-DOS header */
> .org 0x8
> .dword kernel_entry /* Kernel entry point */
>
> The correct kernel entry from the MS-DOS header is crucial for jumping
> to vmlinux from zboot. This necessity is why the compressed kernel
> compiled by Clang encounters difficulties in booting.
>
> To address this problem, it is proposed to apply dynamic relocations to
> place with `--apply-dynamic-relocs`.
>
> Link: https://github.com/ClangBuiltLinux/linux/issues/1962
> Signed-off-by: WANG Rui <[email protected]>
> ---
> arch/loongarch/Makefile | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/loongarch/Makefile b/arch/loongarch/Makefile
> index 1f0d74403419..05ab85118212 100644
> --- a/arch/loongarch/Makefile
> +++ b/arch/loongarch/Makefile
> @@ -83,7 +83,7 @@ endif
>
> ifeq ($(CONFIG_RELOCATABLE),y)
> KBUILD_CFLAGS_KERNEL += -fPIE
> -LDFLAGS_vmlinux += -static -pie --no-dynamic-linker -z notext
> +LDFLAGS_vmlinux += -static -pie --no-dynamic-linker -z notext $(call ld-option, --apply-dynamic-relocs)
> endif
>
> cflags-y += $(call cc-option, -mno-check-zero-division)
> --
> 2.43.0
>
>