[PATCH v2] gcc: Use ld -r when checking for HAVE_LD_RO_RW_SECTION_MIXING

[PATCH v2] gcc: Use ld -r when checking for HAVE_LD_RO_RW_SECTION_MIXING

[Joakim Nohlgård]

Fall back to ld -r if ld -shared fails during configure. The check for
HAVE_LD_RO_RW_SECTION_MIXING can fail on targets where ld does not
support shared objects, even though the answer to the test should be
'read-write'. One such target is riscv64-unknown-elf. Failing this test
results in a libgcc crtbegin.o which has a writable .eh_frame section
leading to the default linker scripts placing the .eh_frame section in a
writable memory segment, or a linker warning when using ld scripts that
place .eh_frame unconditionally in ROM.

gcc/ChangeLog:

	* configure: Regenerate.
	* configure.ac: Use ld -r in the check for HAVE_LD_RO_RW_SECTION_MIXING

Signed-off-by: Joakim Nohlgård <joakim@nohlgard.se>
---
 gcc/configure.ac | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/gcc/configure.ac b/gcc/configure.ac
index 7c55bff6cb0..500829ceb1d 100644
--- a/gcc/configure.ac
+++ b/gcc/configure.ac
@@ -3152,16 +3152,19 @@ elif test x$gcc_cv_as != x -a x$gcc_cv_ld != x -a x$gcc_cv_objdump != x ; then
   echo '.byte 0' >> conftest3.s
   if $gcc_cv_as -o conftest1.o conftest1.s > /dev/null 2>&1 \
      && $gcc_cv_as -o conftest2.o conftest2.s > /dev/null 2>&1 \
-     && $gcc_cv_as -o conftest3.o conftest3.s > /dev/null 2>&1 \
-     && $gcc_cv_ld -shared -o conftest1.so conftest1.o \
-	conftest2.o conftest3.o > /dev/null 2>&1; then
-    gcc_cv_ld_ro_rw_mix=`$gcc_cv_objdump -h conftest1.so \
-			 | sed -e '/myfoosect/!d' -e N`
-    if echo "$gcc_cv_ld_ro_rw_mix" | grep CONTENTS > /dev/null; then
-      if echo "$gcc_cv_ld_ro_rw_mix" | grep READONLY > /dev/null; then
-	gcc_cv_ld_ro_rw_mix=read-only
-      else
-	gcc_cv_ld_ro_rw_mix=read-write
+     && $gcc_cv_as -o conftest3.o conftest3.s > /dev/null 2>&1; then
+    if $gcc_cv_ld -shared -o conftest1.so conftest1.o \
+       conftest2.o conftest3.o > /dev/null 2>&1 \
+       || $gcc_cv_ld -r -o conftest1.so conftest1.o \
+	  conftest2.o conftest3.o > /dev/null 2>&1; then
+      gcc_cv_ld_ro_rw_mix=`$gcc_cv_objdump -h conftest1.so \
+			   | sed -e '/myfoosect/!d' -e N`
+      if echo "$gcc_cv_ld_ro_rw_mix" | grep CONTENTS > /dev/null; then
+	if echo "$gcc_cv_ld_ro_rw_mix" | grep READONLY > /dev/null; then
+	  gcc_cv_ld_ro_rw_mix=read-only
+	else
+	  gcc_cv_ld_ro_rw_mix=read-write
+	fi
       fi
     fi
   fi
-- 
2.38.1

Re: [PATCH v2] gcc: Use ld -r when checking for HAVE_LD_RO_RW_SECTION_MIXING

[Jeff Law]

On 12/5/22 06:43, Joakim Nohlgård wrote:
> Fall back to ld -r if ld -shared fails during configure. The check for
> HAVE_LD_RO_RW_SECTION_MIXING can fail on targets where ld does not
> support shared objects, even though the answer to the test should be
> 'read-write'. One such target is riscv64-unknown-elf. Failing this test
> results in a libgcc crtbegin.o which has a writable .eh_frame section
> leading to the default linker scripts placing the .eh_frame section in a
> writable memory segment, or a linker warning when using ld scripts that
> place .eh_frame unconditionally in ROM.
> 
> gcc/ChangeLog:
> 
> 	* configure: Regenerate.
> 	* configure.ac: Use ld -r in the check for HAVE_LD_RO_RW_SECTION_MIXING
Thanks.  I've pushed this to the trunk.
jeff