From f484427d10a5ff6c2437c2f7c671e9e552ad6766 Mon Sep 17 00:00:00 2001
From: Ard Biesheuvel <ardb@kernel.org>
Date: Sun, 26 Mar 2023 10:58:35 +0200
Subject: [PATCH] ArmPkg, BaseTools AARCH64: Add BTI ELF note to .hii objects

The ELF based toolchains use objcopy to create HII object files, which
contain only a single .hii section. This means no GNU note is inserted
that describes the object as compatible with BTI, even though the lack
of executable code in such an object makes the distinction irrelevant.
However, the linker will not add the note globally to the resulting ELF
executable, and this breaks BTI compatibility.

So let's insert a GNU BTI-compatible ELF note by hand when generating
such object files.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com>
Reviewed-by: Oliver Smith-Denny <osd@smith-denny.com>
---
 ArmPkg/Library/GnuNoteBti.bin     | Bin 0 -> 32 bytes
 BaseTools/Conf/tools_def.template |   5 +++--
 2 files changed, 3 insertions(+), 2 deletions(-)
 create mode 100644 ArmPkg/Library/GnuNoteBti.bin

diff --git a/ArmPkg/Library/GnuNoteBti.bin b/ArmPkg/Library/GnuNoteBti.bin
new file mode 100644
index 0000000000000000000000000000000000000000..339567b4e89943c610b44767ddad5f631229ed3b
GIT binary patch
literal 32
dcmZQ!U|<jcVpbq__X`D*3<p?%1S5zA1OOf&0m%RW

literal 0
HcmV?d00001

diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
index 471eb67c0c..ae43101853 100755
--- a/BaseTools/Conf/tools_def.template
+++ b/BaseTools/Conf/tools_def.template
@@ -1880,6 +1880,7 @@ DEFINE GCC_IA32_RC_FLAGS           = -I binary -O elf32-i386          -B i386
 DEFINE GCC_X64_RC_FLAGS            = -I binary -O elf64-x86-64        -B i386        --rename-section .data=.hii
 DEFINE GCC_ARM_RC_FLAGS            = -I binary -O elf32-littlearm     -B arm         --rename-section .data=.hii
 DEFINE GCC_AARCH64_RC_FLAGS        = -I binary -O elf64-littleaarch64 -B aarch64     --rename-section .data=.hii
+DEFINE GCC_AARCH64_RC_BTI_FLAGS    = --add-section .note.gnu.property=$(WORKSPACE)/ArmPkg/Library/GnuNoteBti.bin --set-section-flags .note.gnu.property=alloc,readonly
 DEFINE GCC_RISCV64_RC_FLAGS        = -I binary -O elf64-littleriscv   -B riscv       --rename-section .data=.hii
 DEFINE GCC_LOONGARCH64_RC_FLAGS    = -I binary -O elf64-loongarch     -B loongarch64 --rename-section .data=.hii
 
@@ -2400,7 +2401,7 @@ RELEASE_GCC5_ARM_DLINK_FLAGS     = DEF(GCC5_ARM_DLINK_FLAGS) -flto -Os -L$(WORKS
 *_GCC5_AARCH64_DTCPP_FLAGS       = DEF(GCC_DTCPP_FLAGS)
 *_GCC5_AARCH64_PLATFORM_FLAGS    =
 *_GCC5_AARCH64_PP_FLAGS          = $(PLATFORM_FLAGS) DEF(GCC_PP_FLAGS)
-*_GCC5_AARCH64_RC_FLAGS          = DEF(GCC_AARCH64_RC_FLAGS)
+*_GCC5_AARCH64_RC_FLAGS          = DEF(GCC_AARCH64_RC_FLAGS) DEF(GCC_AARCH64_RC_BTI_FLAGS)
 *_GCC5_AARCH64_VFRPP_FLAGS       = $(PLATFORM_FLAGS) DEF(GCC_VFRPP_FLAGS)
 *_GCC5_AARCH64_CC_XIPFLAGS       = DEF(GCC5_AARCH64_CC_XIPFLAGS)
 
@@ -2735,7 +2736,7 @@ DEFINE CLANG38_AARCH64_DLINK_FLAGS  = DEF(CLANG38_AARCH64_TARGET) DEF(GCC_AARCH6
 *_CLANG38_AARCH64_DLINK2_FLAGS   = DEF(GCC_DLINK2_FLAGS_COMMON) -Wl,--defsym=PECOFF_HEADER_SIZE=0x228
 *_CLANG38_AARCH64_PLATFORM_FLAGS =
 *_CLANG38_AARCH64_PP_FLAGS       = DEF(GCC_PP_FLAGS) DEF(CLANG38_AARCH64_TARGET) $(PLATFORM_FLAGS)
-*_CLANG38_AARCH64_RC_FLAGS       = DEF(GCC_AARCH64_RC_FLAGS)
+*_CLANG38_AARCH64_RC_FLAGS       = DEF(GCC_AARCH64_RC_FLAGS) DEF(GCC_AARCH64_RC_BTI_FLAGS)
 *_CLANG38_AARCH64_VFRPP_FLAGS    = DEF(GCC_VFRPP_FLAGS) DEF(CLANG38_AARCH64_TARGET) $(PLATFORM_FLAGS)
 *_CLANG38_AARCH64_ASLPP_FLAGS    = DEF(GCC_ASLPP_FLAGS) DEF(CLANG38_AARCH64_TARGET)
 *_CLANG38_AARCH64_CC_XIPFLAGS    = DEF(GCC_AARCH64_CC_XIPFLAGS)