linux-kernel - [PATCH] kexec_file: Drop pr_err in weak implementations of arch_kexec_apply_relocations[

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Message-Id: <20220425174128.11455-1-naveen.n.rao@linux.vnet.ibm.com>
Date:   Mon, 25 Apr 2022 23:11:28 +0530
From:   "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Eric Biederman <ebiederm@...ssion.com>
Cc:     <linuxppc-dev@...ts.ozlabs.org>, <linux-kernel@...r.kernel.org>,
        kexec@...ts.infradead.org
Subject: [PATCH] kexec_file: Drop pr_err in weak implementations of arch_kexec_apply_relocations[_add]

kexec_load_purgatory() can fail for many reasons - there is no need to
print an error when encountering unsupported relocations.

This solves a build issue on powerpc with binutils v2.36 and newer [1].
Since commit d1bcae833b32f1 ("ELF: Don't generate unused section
symbols") [2], binutils 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. Dropping
pr_err() calls results in these functions being left in .text section,
enabling recordmcount to emit a proper relocation record.

[1] https://github.com/linuxppc/issues/issues/388
[2] https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d1bcae833b32f1

Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
---
 kernel/kexec_file.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index 8347fc158d2b96..55d144c58b5278 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -121,7 +121,6 @@ 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;
 }

@@ -138,7 +137,6 @@ int __weak
 arch_kexec_apply_relocations(struct purgatory_info *pi, Elf_Shdr *section,
 			     const Elf_Shdr *relsec, const Elf_Shdr *symtab)
 {
-	pr_err("REL relocation unsupported.\n");
 	return -ENOEXEC;
 }

base-commit: 83d8a0d166119de813cad27ae7d61f54f9aea707
-- 
2.35.1