[PATCH 4.19 04/38] elfcore: fix building with clang

[Greg Kroah-Hartman]

From: Arnd Bergmann <arnd@xxxxxxxx>

commit 6e7b64b9dd6d96537d816ea07ec26b7dedd397b9 upstream.

kernel/elfcore.c only contains weak symbols, which triggers a bug with
clang in combination with recordmcount:

  Cannot find symbol for section 2: .text.
  kernel/elfcore.o: failed

Move the empty stubs into linux/elfcore.h as inline functions.  As only
two architectures use these, just use the architecture specific Kconfig
symbols to key off the declaration.

Link: https://lkml.kernel.org/r/20201204165742.3815221-2-arnd@xxxxxxxxxx
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Nathan Chancellor <natechancellor@xxxxxxxxx>
Cc: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
Cc: Barret Rhoden <brho@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 include/linux/elfcore.h |   22 ++++++++++++++++++++++
 kernel/Makefile         |    1 -
 kernel/elfcore.c        |   26 --------------------------
 3 files changed, 22 insertions(+), 27 deletions(-)
 delete mode 100644 kernel/elfcore.c

--- a/include/linux/elfcore.h
+++ b/include/linux/elfcore.h
@@ -58,6 +58,7 @@ static inline int elf_core_copy_task_xfp
 }
 #endif
 
+#if defined(CONFIG_UM) || defined(CONFIG_IA64)
 /*
  * These functions parameterize elf_core_dump in fs/binfmt_elf.c to write out
  * extra segments containing the gate DSO contents.  Dumping its
@@ -72,5 +73,26 @@ elf_core_write_extra_phdrs(struct coredu
 extern int
 elf_core_write_extra_data(struct coredump_params *cprm);
 extern size_t elf_core_extra_data_size(void);
+#else
+static inline Elf_Half elf_core_extra_phdrs(void)
+{
+	return 0;
+}
+
+static inline int elf_core_write_extra_phdrs(struct coredump_params *cprm, loff_t offset)
+{
+	return 1;
+}
+
+static inline int elf_core_write_extra_data(struct coredump_params *cprm)
+{
+	return 1;
+}
+
+static inline size_t elf_core_extra_data_size(void)
+{
+	return 0;
+}
+#endif
 
 #endif /* _LINUX_ELFCORE_H */
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -92,7 +92,6 @@ obj-$(CONFIG_TASK_DELAY_ACCT) += delayac
 obj-$(CONFIG_TASKSTATS) += taskstats.o tsacct.o
 obj-$(CONFIG_TRACEPOINTS) += tracepoint.o
 obj-$(CONFIG_LATENCYTOP) += latencytop.o
-obj-$(CONFIG_ELFCORE) += elfcore.o
 obj-$(CONFIG_FUNCTION_TRACER) += trace/
 obj-$(CONFIG_TRACING) += trace/
 obj-$(CONFIG_TRACE_CLOCK) += trace/
--- a/kernel/elfcore.c
+++ /dev/null
@@ -1,26 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-#include <linux/elf.h>
-#include <linux/fs.h>
-#include <linux/mm.h>
-#include <linux/binfmts.h>
-#include <linux/elfcore.h>
-
-Elf_Half __weak elf_core_extra_phdrs(void)
-{
-	return 0;
-}
-
-int __weak elf_core_write_extra_phdrs(struct coredump_params *cprm, loff_t offset)
-{
-	return 1;
-}
-
-int __weak elf_core_write_extra_data(struct coredump_params *cprm)
-{
-	return 1;
-}
-
-size_t __weak elf_core_extra_data_size(void)
-{
-	return 0;
-}