[glibc/release/2.31/master] Improve IFUNC check [BZ #25506]

[Aurelien Jarno]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f2d95cf030ff57a7cc067f770d2afbb4e85aa26b

commit f2d95cf030ff57a7cc067f770d2afbb4e85aa26b
Author: Fangrui Song <maskray@google.com>
Date:   Tue Feb 4 21:55:44 2020 -0800

    Improve IFUNC check [BZ #25506]
    
    GNU ld's RISCV port does not support IFUNC. ld -no-pie produces no
    relocation and the test passed incorrectly. Be more rigid by testing
    IRELATIVE explicitly.
    
    Tested-by: Aurelien Jarno <aurelien@aurel32.net>
    Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
    (cherry picked from commit 87a698a21646b7ee620923ef5ffa9735471a8ddd)

Diff:
---
 configure    | 2 +-
 configure.ac | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/configure b/configure
index b959d2d988..3b98ec312f 100755
--- a/configure
+++ b/configure
@@ -4035,7 +4035,7 @@ if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS \
 	    -o conftest conftest.S 1>&5 2>&5; then
   # Do a link to see if the backend supports IFUNC relocs.
   $READELF -r conftest 1>&5
-  LC_ALL=C $READELF -r conftest | grep 'no relocations' >/dev/null || {
+  LC_ALL=C $READELF -Wr conftest | grep -q 'IRELATIVE\|R_SPARC_JMP_IREL' && {
     libc_cv_ld_gnu_indirect_function=yes
   }
 fi
diff --git a/configure.ac b/configure.ac
index 49b900c1ed..e20034f301 100644
--- a/configure.ac
+++ b/configure.ac
@@ -649,7 +649,7 @@ if ${CC-cc} $CFLAGS $CPPFLAGS $LDFLAGS \
 	    -o conftest conftest.S 1>&AS_MESSAGE_LOG_FD 2>&AS_MESSAGE_LOG_FD; then
   # Do a link to see if the backend supports IFUNC relocs.
   $READELF -r conftest 1>&AS_MESSAGE_LOG_FD
-  LC_ALL=C $READELF -r conftest | grep 'no relocations' >/dev/null || {
+  LC_ALL=C $READELF -Wr conftest | grep -q 'IRELATIVE\|R_SPARC_JMP_IREL' && {
     libc_cv_ld_gnu_indirect_function=yes
   }
 fi