From e4f4094de8ddcbe6d5ff1cdf782d2b89e0563903 Mon Sep 17 00:00:00 2001 From: Khem Raj Date: Wed, 30 Apr 2025 19:51:19 -0700 Subject: [PATCH] libunwind: Use +gcs instead of gcs target attribute __attribute__((target("gcs"))) does not work with gcc GCC-15 has added gcs intrinsics [1] but the syntax for enabling it is slightly different. This syntax works with clang too. With gcc15 compiler libunwind's check for this macros is succeeding and it ends up enabling 'gcs' by using function attribute, this works with clang but not with gcc but '+gcs' works with both We can see this in rust compiler bootstrap for aarch64/musl when system uses gcc15, it ends up with these errors Building libunwind.a for aarch64-poky-linux-musl cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:191:1: error: arch extension 'gcs' should be prefixed by '+' cargo:warning= 191 | unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) { cargo:warning= | ^~~~~~~~~~~~~ cargo:warning=/mnt/b/yoe/master/sources/poky/build/tmp/work/cortexa57-poky-linux-musl/rust/1.85.1/rustc-1.85.1-src/src/llvm-project/libunwind/src/UnwindLevel1.c:337:22: error: arch extension 'gcs' should be prefixed by '+' cargo:warning= 337 | _Unwind_Stop_Fn stop, void *stop_parameter) { cargo:warning= | ^~~~~~~~~~~~~~~ [1] https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=5a6af707f0af Upstream-Status: Submitted [https://github.com/llvm/llvm-project/pull/138077] Signed-off-by: Khem Raj --- src/llvm-project/libunwind/src/UnwindLevel1.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/src/llvm-project/libunwind/src/UnwindLevel1.c +++ b/src/llvm-project/libunwind/src/UnwindLevel1.c @@ -185,7 +185,7 @@ extern int __unw_step_stage2(unw_cursor_ #if defined(_LIBUNWIND_USE_GCS) // Enable the GCS target feature to permit gcspop instructions to be used. -__attribute__((target("gcs"))) +__attribute__((target("+gcs"))) #endif static _Unwind_Reason_Code unwind_phase2(unw_context_t *uc, unw_cursor_t *cursor, _Unwind_Exception *exception_object) { @@ -329,7 +329,7 @@ unwind_phase2(unw_context_t *uc, unw_cur #if defined(_LIBUNWIND_USE_GCS) // Enable the GCS target feature to permit gcspop instructions to be used. -__attribute__((target("gcs"))) +__attribute__((target("+gcs"))) #endif static _Unwind_Reason_Code unwind_phase2_forced(unw_context_t *uc, unw_cursor_t *cursor, --- a/src/llvm-project/libunwind/src/cet_unwind.h +++ b/src/llvm-project/libunwind/src/cet_unwind.h @@ -42,7 +42,8 @@ #include // We can only use GCS if arm_acle.h defines the GCS intrinsics. -#ifdef _CHKFEAT_GCS +// Enable gcs with clang for now, gcc does not build unwindlevel1.c correctly +#if defined(_CHKFEAT_GCS) && defined(__clang__) #define _LIBUNWIND_USE_GCS 1 #endif