elfnote: always use the "a" flag for .note.* sections

GNU as allows specifying different flags when constructing sections, for
example when the second occurrence has empty flags. But clang may not be so
permissive:
    $ cat test.s
    .pushsection .note.Linux, "a", @note ;
    .pushsection .note.Linux, "", @note ;
    $ as test.s
    $ clang-11 -cc1as -triple x86_64-pc-linux-gnu test.s
    test.s:2:1: error: changed section flags for .note.Linux

The kernel reaches this case when both ELFNOTE_START and ELFNOTE add data
to the same section, because the former is used exclusively with the "a"
flag and the latter always uses empty flags.

In vmlinux, the combined .notes section is marked as SHF_ALLOC, so use
the "a" flag for all these macros.

Link: ClangBuiltLinux#913
Signed-off-by: Ilie Halip <[email protected]>

arch/arm64/kernel/vdso/note.S

@@ -13,7 +13,7 @@
 #include <linux/elfnote.h>
 #include <linux/build-salt.h>
 
-ELFNOTE_START(Linux, 0, "a")
+ELFNOTE_START(Linux, 0)
 	.long LINUX_VERSION_CODE
 ELFNOTE_END
 

arch/mips/vdso/elf.S

@@ -11,7 +11,7 @@
 #include <linux/elfnote.h>
 #include <linux/version.h>
 
-ELFNOTE_START(Linux, 0, "a")
+ELFNOTE_START(Linux, 0)
 	.long LINUX_VERSION_CODE
 ELFNOTE_END
 

arch/nds32/kernel/vdso/note.S

@@ -6,6 +6,6 @@
 #include <linux/version.h>
 #include <linux/elfnote.h>
 
-ELFNOTE_START(Linux, 0, "a")
+ELFNOTE_START(Linux, 0)
 	.long LINUX_VERSION_CODE
 ELFNOTE_END

arch/s390/kernel/vdso64/note.S

@@ -8,6 +8,6 @@
 #include <linux/version.h>
 #include <linux/elfnote.h>
 
-ELFNOTE_START(Linux, 0, "a")
+ELFNOTE_START(Linux, 0)
 	.long LINUX_VERSION_CODE
 ELFNOTE_END

arch/sparc/vdso/vdso-note.S

@@ -7,6 +7,6 @@
 #include <linux/version.h>
 #include <linux/elfnote.h>
 
-ELFNOTE_START(Linux, 0, "a")
+ELFNOTE_START(Linux, 0)
 	.long LINUX_VERSION_CODE
 ELFNOTE_END

arch/sparc/vdso/vdso32/vdso-note.S

@@ -7,6 +7,6 @@
 #include <linux/version.h>
 #include <linux/elfnote.h>
 
-ELFNOTE_START(Linux, 0, "a")
+ELFNOTE_START(Linux, 0)
 	.long	LINUX_VERSION_CODE
 ELFNOTE_END

arch/x86/entry/vdso/vdso-note.S

@@ -8,7 +8,7 @@
 #include <linux/version.h>
 #include <linux/elfnote.h>
 
-ELFNOTE_START(Linux, 0, "a")
+ELFNOTE_START(Linux, 0)
 	.long LINUX_VERSION_CODE
 ELFNOTE_END
 

arch/x86/entry/vdso/vdso32/note.S

@@ -11,7 +11,7 @@
 /* Ideally this would use UTS_NAME, but using a quoted string here
    doesn't work. Remember to change this when changing the
    kernel's name. */
-ELFNOTE_START(Linux, 0, "a")
+ELFNOTE_START(Linux, 0)
 	.long LINUX_VERSION_CODE
 ELFNOTE_END
 
@@ -39,7 +39,7 @@ BUILD_SALT
 
 #include "../../xen/vdso.h"	/* Defines VDSO_NOTE_NONEGSEG_BIT.  */
 
-ELFNOTE_START(GNU, 2, "a")
+ELFNOTE_START(GNU, 2)
 	.long 1			/* ncaps */
 VDSO32_NOTE_MASK:		/* Symbol used by arch/x86/xen/setup.c */
 	.long 0			/* mask */

arch/x86/um/vdso/vdso-note.S

@@ -7,6 +7,6 @@
 #include <linux/version.h>
 #include <linux/elfnote.h>
 
-ELFNOTE_START(Linux, 0, "a")
+ELFNOTE_START(Linux, 0)
 	.long LINUX_VERSION_CODE
 ELFNOTE_END

include/linux/elfnote.h

@@ -39,8 +39,8 @@
  * e.g. ELFNOTE(XYZCo, 42, .asciz, "forty-two")
  *      ELFNOTE(XYZCo, 12, .long, 0xdeadbeef)
  */
-#define ELFNOTE_START(name, type, flags)	\
-.pushsection .note.name, flags,@note	;	\
+#define ELFNOTE_START(name, type)		\
+.pushsection .note.name, "a",@note	;	\
   .balign 4				;	\
   .long 2f - 1f		/* namesz */	;	\
   .long 4484f - 3f	/* descsz */	;	\
@@ -54,7 +54,7 @@
 .popsection				;
 
 #define ELFNOTE(name, type, desc)		\
-	ELFNOTE_START(name, type, "")		\
+	ELFNOTE_START(name, type)		\
 		desc			;	\
 	ELFNOTE_END