[glibc] linux: Constify rfv variable in dl_vdso_vsym

[Alan Modra <amodra@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=30afd8c44d6a0a8b0eddbadecb02c9b9dad3facf

commit 30afd8c44d6a0a8b0eddbadecb02c9b9dad3facf
Author: Alan Modra <amodra@gmail.com>
Date:   Sat Jan 22 13:32:39 2022 +1030

    linux: Constify rfv variable in dl_vdso_vsym
    
    Compilers may decide to put the rfv variable in .data rather than on
    the stack.  It's slightly better to put it in .data.rel.ro.local
    instead.  Regardles of that, making it const may enable further
    optimisations.  Found when examining relative relocations (GOT ones
    in particular) as part of enabling static-pie for PowerPC64.

Diff:
---
 sysdeps/unix/sysv/linux/dl-vdso.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sysdeps/unix/sysv/linux/dl-vdso.h b/sysdeps/unix/sysv/linux/dl-vdso.h
index bfefce8f35..8611488acc 100644
--- a/sysdeps/unix/sysv/linux/dl-vdso.h
+++ b/sysdeps/unix/sysv/linux/dl-vdso.h
@@ -45,7 +45,7 @@ dl_vdso_vsym (const char *name)
   ElfW (Sym) wsym = { 0 };
   wsym.st_info = (unsigned char) ELFW (ST_INFO (STB_WEAK, STT_NOTYPE));
 
-  struct r_found_version rfv = { VDSO_NAME, VDSO_HASH, 1, NULL };
+  const struct r_found_version rfv = { VDSO_NAME, VDSO_HASH, 1, NULL };
 
   /* Search the scope of the vdso map.  */
   const ElfW (Sym) *ref = &wsym;