| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <CAAhV-H6K7SXtXpv9Udo8md0sdn+40TGPTCdSPeM1HmbJqrhboQ@mail.gmail.com>
Date: Sat, 6 Jul 2024 18:29:24 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Xi Ruoyao <xry111@...111.site>
Cc: WANG Xuerui <kernel@...0n.name>, Jinyang He <hejinyang@...ngson.cn>,
Youling Tang <tangyouling@...inos.cn>, Tiezhu Yang <yangtiezhu@...ngson.cn>,
Fangrui Song <maskray@...gle.com>, Nathan Chancellor <nathan@...nel.org>,
Nick Desaulniers <ndesaulniers@...gle.com>, loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH 2/2] LoongArch: Add support for relocating the kernel with
RELR relocation
Hi, Ruoyao,
On Sat, Jul 6, 2024 at 3:39 PM Xi Ruoyao <xry111@...111.site> wrote:
>
> RELR as a relocation packing format for relative relocations for
> reducing the size of relative relocation records. In a position
> independent executable there are often many relative relocation
> records, and our vmlinux is a PIE.
>
> The LLD linker (since 17.0.0) and the BFD linker (since 2.43) supports
> packing the relocations in the RELR format for LoongArch, with the flag
> -z pack-relative-relocs.
>
> Commits 5cf896fb6be3
> ("arm64: Add support for relocating the kernel with RELR relocations")
> and ccb2d173b983
> ("Makefile: use -z pack-relative-relocs") have already added the
> framework to use RELR. We just need to wire it up and process the RELR
> relocation records in relocate_relative() in addition to the RELA
> relocation records.
>
> A ".p2align 3" directive is added to la_abs macro or the BFD linker
> cannot pack the relocation records against the .la_abs section (the
> ". = ALIGN(8);" directive in vmlinux.lds.S is too late in the linking
> process).
>
> With defconfig and CONFIG_RELR vmlinux.efi is 2.1 MiB (6%) smaller, and
> vmlinuz.efi (using gzip compression) is 384 KiB (2.8%) smaller.
>
> Link: https://groups.google.com/d/topic/generic-abi/bX460iggiKg
> Link: https://reviews.llvm.org/D138135#4531389
> Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d89ecf33ab6d
> Signed-off-by: Xi Ruoyao <xry111@...111.site>
> ---
> arch/loongarch/Kconfig | 1 +
> arch/loongarch/include/asm/asmmacro.h | 1 +
> arch/loongarch/include/asm/setup.h | 5 +++++
> arch/loongarch/kernel/relocate.c | 18 ++++++++++++++++++
> arch/loongarch/kernel/vmlinux.lds.S | 8 ++++++++
> 5 files changed, 33 insertions(+)
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index ddc042895d01..03b3ef5edd24 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -607,6 +607,7 @@ config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
>
> config RELOCATABLE
> bool "Relocatable kernel"
> + select ARCH_HAS_RELR
Why is this selection under RELOCATABLE? I know ARM64 is the same, but why?
Huacai
> help
> This builds the kernel as a Position Independent Executable (PIE),
> which retains all relocation metadata required, so as to relocate
> diff --git a/arch/loongarch/include/asm/asmmacro.h b/arch/loongarch/include/asm/asmmacro.h
> index 655db7d7a427..8d7f501b0a12 100644
> --- a/arch/loongarch/include/asm/asmmacro.h
> +++ b/arch/loongarch/include/asm/asmmacro.h
> @@ -609,6 +609,7 @@
> lu32i.d \reg, 0
> lu52i.d \reg, \reg, 0
> .pushsection ".la_abs", "aw", %progbits
> + .p2align 3
> .dword 766b
> .dword \sym
> .popsection
> diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/include/asm/setup.h
> index ee52fb1e9963..3c2fb16b11b6 100644
> --- a/arch/loongarch/include/asm/setup.h
> +++ b/arch/loongarch/include/asm/setup.h
> @@ -34,6 +34,11 @@ extern long __la_abs_end;
> extern long __rela_dyn_begin;
> extern long __rela_dyn_end;
>
> +#ifdef CONFIG_RELR
> +extern long __relr_dyn_begin;
> +extern long __relr_dyn_end;
> +#endif
> +
> extern unsigned long __init relocate_kernel(void);
>
> #endif
> diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
> index 69d73dc7326a..6abb9c91b255 100644
> --- a/arch/loongarch/kernel/relocate.c
> +++ b/arch/loongarch/kernel/relocate.c
> @@ -37,6 +37,24 @@ static inline void __init relocate_relative(void)
> relocated_addr = (Elf64_Addr)RELOCATED(relocated_addr);
> *(Elf64_Addr *)RELOCATED(addr) = relocated_addr;
> }
> +
> +#ifdef CONFIG_RELR
> + u64 *relr = (u64 *)&__relr_dyn_begin;
> + u64 *relr_end = (u64 *)&__relr_dyn_end;
> + u64 *addr = NULL;
> +
> + for ( ; relr < relr_end; relr++) {
> + if ((*relr & 1) == 0) {
> + addr = (u64 *)(*relr + reloc_offset);
> + *addr++ += reloc_offset;
> + } else {
> + for (u64 *p = addr, r = *relr >> 1; r; p++, r >>= 1)
> + if (r & 1)
> + *p += reloc_offset;
> + addr += 63;
> + }
> + }
> +#endif
> }
>
> static inline void __init relocate_absolute(long random_offset)
> diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
> index 3c7595342730..08ea921cdec1 100644
> --- a/arch/loongarch/kernel/vmlinux.lds.S
> +++ b/arch/loongarch/kernel/vmlinux.lds.S
> @@ -113,6 +113,14 @@ SECTIONS
> __rela_dyn_end = .;
> }
>
> +#ifdef CONFIG_RELR
> + .relr.dyn : ALIGN(8) {
> + __relr_dyn_begin = .;
> + *(.relr.dyn)
> + __relr_dyn_end = .;
> + }
> +#endif
> +
> .data.rel : { *(.data.rel*) }
>
> #ifdef CONFIG_RELOCATABLE
> --
> 2.45.2
>
Powered by blists - more mailing lists