[glibc] aarch64: Use build attributes for asm feature marking
Adhemerval Zanella via Glibc-cvs <[email protected]> Fri, 29 May 2026 17:00:44 +0000 (GMT)
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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=b9e893b60ef6bfe3f0add02e9125e1aae58f012c commit b9e893b60ef6bfe3f0add02e9125e1aae58f012c Author: Muhammad Kamran <[email protected]> Date: Thu May 28 09:29:33 2026 +0000 aarch64: Use build attributes for asm feature marking When the compiler defines __ARM_BUILDATTR64_FV, emit AArch64 feature-and-bits build attributes for BTI, PAC, and GCS from sysdep.h instead of a GNU property note. Keep the GNU property note as the fallback for older toolchains. Mirror the same marking logic in elf/tst-asm-helper.h so custom test DSOs and assembly tests that cannot include sysdep.h get consistent feature marking. Reviewed-by: Adhemerval Zanella <[email protected]> Diff: --- elf/tst-asm-helper.h | 37 ++++++++++++++++++++++++++++++------- sysdeps/aarch64/sysdep.h | 32 ++++++++++++++++++++++++++++---- 2 files changed, 58 insertions(+), 11 deletions(-) diff --git a/elf/tst-asm-helper.h b/elf/tst-asm-helper.h index 51d079b94e..aa565dc1c7 100644 --- a/elf/tst-asm-helper.h +++ b/elf/tst-asm-helper.h @@ -1,6 +1,5 @@ -/* Test header that defines macros for GNU properties that need to be - used in some test assembly files where sysdep.h cannot be included - for some reason. +/* Test header that defines feature-marking macros used in some test + assembly files where sysdep.h cannot be included for some reason. Copyright (C) 2024-2026 Free Software Foundation, Inc. This file is part of the GNU C Library. @@ -27,7 +26,6 @@ #define FEATURE_1_PAC 2 #define FEATURE_1_GCS 4 -/* Add a NT_GNU_PROPERTY_TYPE_0 note. */ #define GNU_PROPERTY(type, value) \ .section .note.gnu.property, "a"; \ .p2align 3; \ @@ -41,7 +39,32 @@ .word 0; \ .text -/* Add GNU property note with the supported features to all asm code - where sysdep.h is included. */ -GNU_PROPERTY (FEATURE_1_AND, FEATURE_1_BTI|FEATURE_1_PAC|FEATURE_1_GCS) +#ifdef __ARM_BUILDATTR64_FV +/* Add AArch64 feature bits build attributes. */ +# define FEATURE_1_AND_MARK(value) \ + .aeabi_subsection aeabi_feature_and_bits, optional, ULEB128; \ + .if ((value) & FEATURE_1_BTI); \ + .aeabi_attribute Tag_Feature_BTI, 1; \ + .else; \ + .aeabi_attribute Tag_Feature_BTI, 0; \ + .endif; \ + .if ((value) & FEATURE_1_GCS); \ + .aeabi_attribute Tag_Feature_GCS, 1; \ + .else; \ + .aeabi_attribute Tag_Feature_GCS, 0; \ + .endif; \ + .if ((value) & FEATURE_1_PAC); \ + .aeabi_attribute Tag_Feature_PAC, 1; \ + .else; \ + .aeabi_attribute Tag_Feature_PAC, 0; \ + .endif; \ + .text +#else +/* Add a NT_GNU_PROPERTY_TYPE_0 note. */ +# define FEATURE_1_AND_MARK(value) GNU_PROPERTY (FEATURE_1_AND, value) +#endif /* __ARM_BUILDATTR64_FV */ + +/* Add marking with the supported features to all asm code where this header + is included. */ +FEATURE_1_AND_MARK (FEATURE_1_BTI | FEATURE_1_PAC | FEATURE_1_GCS) #endif diff --git a/sysdeps/aarch64/sysdep.h b/sysdeps/aarch64/sysdep.h index da4b7f3fd3..77e6564d97 100644 --- a/sysdeps/aarch64/sysdep.h +++ b/sysdeps/aarch64/sysdep.h @@ -43,7 +43,6 @@ #define FEATURE_1_PAC 2 #define FEATURE_1_GCS 4 -/* Add a NT_GNU_PROPERTY_TYPE_0 note. */ #define GNU_PROPERTY(type, value) \ .section .note.gnu.property, "a"; \ .p2align 3; \ @@ -57,9 +56,34 @@ .word 0; \ .text -/* Add GNU property note with the supported features to all asm code - where sysdep.h is included. */ -GNU_PROPERTY (FEATURE_1_AND, FEATURE_1_BTI|FEATURE_1_PAC|FEATURE_1_GCS) +#ifdef __ARM_BUILDATTR64_FV +/* Add AArch64 feature bits build attributes. */ +# define FEATURE_1_AND_MARK(value) \ + .aeabi_subsection aeabi_feature_and_bits, optional, ULEB128; \ + .if ((value) & FEATURE_1_BTI); \ + .aeabi_attribute Tag_Feature_BTI, 1; \ + .else; \ + .aeabi_attribute Tag_Feature_BTI, 0; \ + .endif; \ + .if ((value) & FEATURE_1_GCS); \ + .aeabi_attribute Tag_Feature_GCS, 1; \ + .else; \ + .aeabi_attribute Tag_Feature_GCS, 0; \ + .endif; \ + .if ((value) & FEATURE_1_PAC); \ + .aeabi_attribute Tag_Feature_PAC, 1; \ + .else; \ + .aeabi_attribute Tag_Feature_PAC, 0; \ + .endif; \ + .text +#else +/* Add a NT_GNU_PROPERTY_TYPE_0 note. */ +# define FEATURE_1_AND_MARK(value) GNU_PROPERTY (FEATURE_1_AND, value) +#endif /* __ARM_BUILDATTR64_FV */ + +/* Add marking with the supported features to all asm code where sysdep.h + is included. */ +FEATURE_1_AND_MARK (FEATURE_1_BTI | FEATURE_1_PAC | FEATURE_1_GCS) /* Define an entry point visible from C. */ #define ENTRY(name) \