linux-kernel - [PATCH 4.9 28/29] kexec_file: drop weak attribute from arch_kexec_apply_relocations[

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Message-Id: <20220630133232.031674776@linuxfoundation.org>
Date:   Thu, 30 Jun 2022 15:46:28 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Michael Ellerman <mpe@...erman.id.au>,
        "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: [PATCH 4.9 28/29] kexec_file: drop weak attribute from arch_kexec_apply_relocations[_add]

From: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

commit 3e35142ef99fe6b4fe5d834ad43ee13cca10a2dc upstream.

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.
Instead, follow the existing pattern of having architectures #define the
name of the function they want to override in their headers.

[1] https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d1bcae833b32f1

[akpm@...ux-foundation.org: arch/s390/include/asm/kexec.h needs linux/module.h]
Link: https://lkml.kernel.org/r/20220519091237.676736-1-naveen.n.rao@linux.vnet.ibm.com
Signed-off-by: Michael Ellerman <mpe@...erman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 arch/x86/include/asm/kexec.h |    7 +++++++
 include/linux/kexec.h        |   26 ++++++++++++++++++++++----
 kernel/kexec_file.c          |   18 ------------------
 3 files changed, 29 insertions(+), 22 deletions(-)

--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -20,6 +20,7 @@
 #ifndef __ASSEMBLY__
 
 #include <linux/string.h>
+#include <linux/module.h>
 
 #include <asm/page.h>
 #include <asm/ptrace.h>
@@ -206,6 +207,12 @@ struct kexec_entry64_regs {
 	uint64_t r15;
 	uint64_t rip;
 };
+
+#ifdef CONFIG_KEXEC_FILE
+int arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr,
+				     Elf_Shdr *sechdrs, unsigned int relsec);
+#define arch_kexec_apply_relocations_add arch_kexec_apply_relocations_add
+#endif
 #endif
 
 typedef void crash_vmclear_fn(void);
--- a/include/linux/kexec.h
+++ b/include/linux/kexec.h
@@ -148,6 +148,28 @@ struct kexec_file_ops {
 	kexec_verify_sig_t *verify_sig;
 #endif
 };
+
+#ifndef arch_kexec_apply_relocations_add
+/* Apply relocations of type RELA */
+static inline int
+arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr,
+				 Elf_Shdr *sechdrs, unsigned int relsec)
+{
+	pr_err("RELA relocation unsupported.\n");
+	return -ENOEXEC;
+}
+#endif
+
+#ifndef arch_kexec_apply_relocations
+/* Apply relocations of type REL */
+static inline int
+arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
+			     unsigned int relsec)
+{
+	pr_err("REL relocation unsupported.\n");
+	return -ENOEXEC;
+}
+#endif
 #endif
 
 struct kimage {
@@ -320,10 +342,6 @@ void * __weak arch_kexec_kernel_image_lo
 int __weak arch_kimage_file_post_load_cleanup(struct kimage *image);
 int __weak arch_kexec_kernel_verify_sig(struct kimage *image, void *buf,
 					unsigned long buf_len);
-int __weak arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr,
-					Elf_Shdr *sechdrs, unsigned int relsec);
-int __weak arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
-					unsigned int relsec);
 void arch_kexec_protect_crashkres(void);
 void arch_kexec_unprotect_crashkres(void);
 
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -59,24 +59,6 @@ int __weak arch_kexec_kernel_verify_sig(
 }
 #endif
 
-/* Apply relocations of type RELA */
-int __weak
-arch_kexec_apply_relocations_add(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
-				 unsigned int relsec)
-{
-	pr_err("RELA relocation unsupported.\n");
-	return -ENOEXEC;
-}
-
-/* Apply relocations of type REL */
-int __weak
-arch_kexec_apply_relocations(const Elf_Ehdr *ehdr, Elf_Shdr *sechdrs,
-			     unsigned int relsec)
-{
-	pr_err("REL relocation unsupported.\n");
-	return -ENOEXEC;
-}
-
 /*
  * Free up memory used by kernel, initrd, and command line. This is temporary
  * memory allocation which is not needed any more after these buffers have