From: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org,
Eric Biederman <ebiederm@xmission.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kexec_file: Drop weak attribute from arch_kexec_apply_relocations[_add]
Date: Thu, 19 May 2022 14:43:38 +0530 [thread overview]
Message-ID: <1652950421.sq10xtycz9.naveen@linux.ibm.com> (raw)
In-Reply-To: <20220518134705.7ae186d5419b24d689a38ccc@linux-foundation.org>
Andrew Morton wrote:
> On Wed, 18 May 2022 23:48:28 +0530 "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> wrote:
>
>> 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.
>>
>> ...
>>
>
> Sigh. This patch demonstrates why I like __weak :<
>
>> --- a/include/linux/kexec.h
>> +++ b/include/linux/kexec.h
>> @@ -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)
>
> Let's avoid listing the architectures here? Better to add
>
> select ARCH_HAVE_ARCH_KEXEC_APPLY_RELOCATIONS_ADD
>
> to arch/<arch>/Kconfig?
I followed the approach used in commit 6e7b64b9dd6d96 ("elfcore: fix
building with clang") since here again, it was overridden on only two
architectures. I also wanted to avoid touching the architecture headers
so as to make it simpler to backport.
But, as Michael points out, using a #ifdef isn't too much of a change
either. I also confirmed that those changes still apply cleanly all the
way back to v5.10. I've posted a v2 which takes this approach.
>
> Please cc me on any additional work on this.
I've copied you on the v2 patch. Thanks!
- Naveen
next prev parent reply other threads:[~2022-05-19 9:14 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-18 18:18 [PATCH] kexec_file: Drop weak attribute from arch_kexec_apply_relocations[_add] Naveen N. Rao
2022-05-18 20:47 ` Andrew Morton
2022-05-19 9:13 ` Naveen N. Rao [this message]
2022-05-18 21:59 ` Eric W. Biederman
2022-05-19 2:58 ` Baoquan He
2022-05-19 9:28 ` Naveen N. Rao
2022-05-19 17:59 ` Eric W. Biederman
2022-05-20 10:46 ` Baoquan He
2022-05-20 19:25 ` Eric W. Biederman
2022-05-25 19:56 ` Andrew Morton
2022-05-26 11:00 ` Naveen N. Rao
2022-05-19 5:41 ` Michael Ellerman
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