| 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: <87ee0q7b92.fsf@email.froward.int.ebiederm.org>
Date: Wed, 18 May 2022 16:59:37 -0500
From: "Eric W. Biederman" <ebiederm@...ssion.com>
To: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@...erman.id.au>,
<linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
kexec@...ts.infradead.org,
Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] kexec_file: Drop weak attribute from
arch_kexec_apply_relocations[_add]
"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com> writes:
> Since commit d1bcae833b32f1 ("ELF: Don't generate unused section
> symbols") [1], binutils (v2.36+) started dropping section symbols that
> it thought were unused. This isn't an issue in general, but with
> kexec_file.c, gcc is placing kexec_arch_apply_relocations[_add] into a
> separate .text.unlikely section and the section symbol ".text.unlikely"
> is being dropped. Due to this, recordmcount is unable to find a non-weak
> symbol in .text.unlikely to generate a relocation record against.
>
> Address this by dropping the weak attribute from these functions:
> - arch_kexec_apply_relocations() is not overridden by any architecture
> today, so just drop the weak attribute.
> - arch_kexec_apply_relocations_add() is only overridden by x86 and s390.
> Retain the function prototype for those and move the weak
> implementation into the header as a static inline for other
> architectures.
>
> [1] https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d1bcae833b32f1
Any chance you can also get machine_kexec_post_load,
crash_free_reserved_phys_range, arch_kexec_protect_protect_crashkres,
arch_kexec_unprotect_crashkres, arch_kexec_kernel_image_probe,
arch_kexec_kernel_image_probe, arch_kimage_file_post_load_cleanup,
arch_kexec_kernel_verify_sig, and arch_kexec_locate_mem_hole as well.
That is everything in kexec that uses a __weak symbol. If we can't
count on them working we might as well just get rid of the rest
preemptively.
Could you also address Andrews concerns by using a Kconfig symbol that
the architectures that implement the symbol can select.
I don't want to ask too much of a volunteer but if you are willing
addressing both of those would be a great help.
Eric
> Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
> ---
> include/linux/kexec.h | 28 ++++++++++++++++++++++++----
> kernel/kexec_file.c | 19 +------------------
> 2 files changed, 25 insertions(+), 22 deletions(-)
>
> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
> index 58d1b58a971e34..e656f981f43a73 100644
> --- a/include/linux/kexec.h
> +++ b/include/linux/kexec.h
> @@ -193,10 +193,6 @@ void *kexec_purgatory_get_symbol_addr(struct kimage *image, const char *name);
> int arch_kexec_kernel_image_probe(struct kimage *image, void *buf,
> unsigned long buf_len);
> void *arch_kexec_kernel_image_load(struct kimage *image);
> -int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
> - Elf_Shdr *section,
> - const Elf_Shdr *relsec,
> - const Elf_Shdr *symtab);
> int arch_kexec_apply_relocations(struct purgatory_info *pi,
> Elf_Shdr *section,
> const Elf_Shdr *relsec,
> @@ -229,6 +225,30 @@ extern int crash_exclude_mem_range(struct crash_mem *mem,
> unsigned long long mend);
> extern int crash_prepare_elf64_headers(struct crash_mem *mem, int kernel_map,
> void **addr, unsigned long *sz);
> +
> +#if defined(CONFIG_X86_64) || defined(CONFIG_S390)
> +int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
> + Elf_Shdr *section,
> + const Elf_Shdr *relsec,
> + const Elf_Shdr *symtab);
> +#else
> +/*
> + * arch_kexec_apply_relocations_add - apply relocations of type RELA
> + * @pi: Purgatory to be relocated.
> + * @section: Section relocations applying to.
> + * @relsec: Section containing RELAs.
> + * @symtab: Corresponding symtab.
> + *
> + * Return: 0 on success, negative errno on error.
> + */
> +static inline int
> +arch_kexec_apply_relocations_add(struct purgatory_info *pi, Elf_Shdr *section,
> + const Elf_Shdr *relsec, const Elf_Shdr *symtab)
> +{
> + pr_err("RELA relocation unsupported.\n");
> + return -ENOEXEC;
> +}
> +#endif /* CONFIG_X86_64 || CONFIG_S390 */
> #endif /* CONFIG_KEXEC_FILE */
>
> #ifdef CONFIG_KEXEC_ELF
> diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
> index 8347fc158d2b96..6bae253b4d315e 100644
> --- a/kernel/kexec_file.c
> +++ b/kernel/kexec_file.c
> @@ -108,23 +108,6 @@ int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
> }
> #endif
>
> -/*
> - * arch_kexec_apply_relocations_add - apply relocations of type RELA
> - * @pi: Purgatory to be relocated.
> - * @section: Section relocations applying to.
> - * @relsec: Section containing RELAs.
> - * @symtab: Corresponding symtab.
> - *
> - * Return: 0 on success, negative errno on error.
> - */
> -int __weak
> -arch_kexec_apply_relocations_add(struct purgatory_info *pi, Elf_Shdr *section,
> - const Elf_Shdr *relsec, const Elf_Shdr *symtab)
> -{
> - pr_err("RELA relocation unsupported.\n");
> - return -ENOEXEC;
> -}
> -
> /*
> * arch_kexec_apply_relocations - apply relocations of type REL
> * @pi: Purgatory to be relocated.
> @@ -134,7 +117,7 @@ arch_kexec_apply_relocations_add(struct purgatory_info *pi, Elf_Shdr *section,
> *
> * Return: 0 on success, negative errno on error.
> */
> -int __weak
> +int
> arch_kexec_apply_relocations(struct purgatory_info *pi, Elf_Shdr *section,
> const Elf_Shdr *relsec, const Elf_Shdr *symtab)
> {
>
> base-commit: ef1302160bfb19f804451d0e919266703501c875
Powered by blists - more mailing lists