[PATCH 4.9 28/29] kexec_file: drop weak attribute from arch_kexec_apply_relocations[_add]

Greg Kroah-Hartman
2022-06-30T13:49:51Z

From: Naveen N. Rao <naveen.n.rao@linux.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@linux-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@ellerman.id.au>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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