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Re: [PATCH][aarch64] Enable ifunc resolver attribute by default
- From: Steve Ellcey <sellcey at cavium dot com>
- To: Szabolcs Nagy <szabolcs dot nagy at arm dot com>, gcc-patches at gcc dot gnu dot org
- Cc: nd at arm dot com
- Date: Tue, 05 Sep 2017 10:09:33 -0700
- Subject: Re: [PATCH][aarch64] Enable ifunc resolver attribute by default
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On Mon, 2017-09-04 at 15:40 +0100, Szabolcs Nagy wrote:
> this is not the right default for bionic, uclibc and musl
>
> (gcc does not distinguish between supporting ifunc in the
> compiler vs runtime, so when ifunc is enabled it is assumed
> the c runtime will have support too, hence libatomic and
> libgcc starts using ifuncs which breaks at runtime)
>
> so don't change the default if target matches
> *-*-*android*|*-*-*uclibc*|*-*-*musl*)
>
> (i think the default should be kept "no" for these targets
> independently of cpu arch, so the current logic that is
> repeated many places in config.gcc is suboptimal.
I cleaned up config.gcc so default_gnu_indirect_function is set in a
single place now and has the right defaults for android/uclibc/musl.
> and i think the attribute syntax should be always supported
> and this setting should only mean that ifunc use is allowed
> in the runtime libraries.)
I think that might be a reasonable thing to do but should be a
separate patch from this change, so I have not done anything
with that.
I retested on aarch64 but I did not test any of the other platforms
where I moved the setting of default_gnu_indirect_function, but I
don't think I changed any defaults.
Steve Ellcey
sellcey@cavium.com
2017-09-05 Steve Ellcey <sellcey@cavium.com>
* config.gcc: Add new case statement to set
default_gnu_indirect_function. Remove it from x86_64-*-linux*,
i[34567]86-*, powerpc*-*-linux*spe*, powerpc*-*-linux*, s390-*-linux*,
s390x-*-linux* case statements. Added aarch64 to the list of
supported architectures.
diff --git a/gcc/config.gcc b/gcc/config.gcc
index cc56c57..1a1b2fe 100644
--- a/gcc/config.gcc
+++ b/gcc/config.gcc
@@ -1516,14 +1516,6 @@ i[34567]86-*-linux* | i[34567]86-*-kfreebsd*-gnu | i[34567]86-*-gnu* | i[34567]8
i[34567]86-*-linux*)
tm_file="${tm_file} linux.h linux-android.h"
extra_options="${extra_options} linux-android.opt"
- # Assume modern glibc if not targeting Android nor uclibc.
- case ${target} in
- *-*-*android*|*-*-*uclibc*|*-*-*musl*)
- ;;
- *)
- default_gnu_indirect_function=yes
- ;;
- esac
if test x$enable_targets = xall; then
tm_file="${tm_file} i386/x86-64.h i386/gnu-user-common.h i386/gnu-user64.h i386/linux-common.h i386/linux64.h"
tm_defines="${tm_defines} TARGET_BI_ARCH=1"
@@ -1582,14 +1574,6 @@ x86_64-*-linux* | x86_64-*-kfreebsd*-gnu)
x86_64-*-linux*)
tm_file="${tm_file} linux.h linux-android.h i386/linux-common.h i386/linux64.h"
extra_options="${extra_options} linux-android.opt"
- # Assume modern glibc if not targeting Android nor uclibc.
- case ${target} in
- *-*-*android*|*-*-*uclibc*|*-*-*musl*)
- ;;
- *)
- default_gnu_indirect_function=yes
- ;;
- esac
;;
x86_64-*-kfreebsd*-gnu)
tm_file="${tm_file} kfreebsd-gnu.h i386/kfreebsd-gnu64.h"
@@ -2455,7 +2439,6 @@ powerpc*-*-linux*spe*)
tm_file="${tm_file} powerpcspe/linux.h glibc-stdint.h"
tmake_file="${tmake_file} powerpcspe/t-ppcos powerpcspe/t-linux"
tm_file="${tm_file} powerpcspe/linuxspe.h powerpcspe/e500.h"
- default_gnu_indirect_function=yes
;;
powerpc*-*-linux*)
tm_file="${tm_file} dbxelf.h elfos.h gnu-user.h freebsd-spec.h rs6000/sysv4.h"
@@ -2535,14 +2518,6 @@ powerpc*-*-linux*)
if test x${enable_secureplt} = xyes; then
tm_file="rs6000/secureplt.h ${tm_file}"
fi
- # Assume modern glibc if not targeting Android nor uclibc.
- case ${target} in
- *-*-*android*|*-*-*uclibc*|*-*-*musl*)
- ;;
- *)
- default_gnu_indirect_function=yes
- ;;
- esac
;;
powerpc-wrs-vxworksspe)
tm_file="${tm_file} elfos.h freebsd-spec.h powerpcspe/sysv4.h"
@@ -2664,7 +2639,6 @@ rx-*-elf*)
tmake_file="${tmake_file} rx/t-rx"
;;
s390-*-linux*)
- default_gnu_indirect_function=yes
tm_file="s390/s390.h dbxelf.h elfos.h gnu-user.h linux.h glibc-stdint.h s390/linux.h"
c_target_objs="${c_target_objs} s390-c.o"
cxx_target_objs="${cxx_target_objs} s390-c.o"
@@ -2674,7 +2648,6 @@ s390-*-linux*)
tmake_file="${tmake_file} s390/t-s390"
;;
s390x-*-linux*)
- default_gnu_indirect_function=yes
tm_file="s390/s390x.h s390/s390.h dbxelf.h elfos.h gnu-user.h linux.h glibc-stdint.h s390/linux.h"
tm_p_file="linux-protos.h s390/s390-protos.h"
c_target_objs="${c_target_objs} s390-c.o"
@@ -3120,6 +3093,20 @@ case ${target} in
;;
esac
+# Assume the existence of indirect function support and allow the use of the
+# resolver attribute.
+case ${target} in
+*-*-linux*android*|*-*-linux*uclibc*|*-*-linux*musl*)
+ ;;
+*-*-linux*)
+ case ${target} in
+ aarch64*-* | i[34567]86-* | powerpc*-* | s390*-* | x86_64-*)
+ default_gnu_indirect_function=yes
+ ;;
+ esac
+ ;;
+esac
+
# Build mkoffload tool
case ${target} in
*-intelmic-* | *-intelmicemul-*)