From c2d56a894b3211bd96a63f388932ea8b38ae3463 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Fri, 31 Mar 2017 09:22:56 +0100 Subject: [PATCH] BaseTools/GCC AARCH64: force disable PIC code generation As a security measure, some distro toolchains now default to PIC code generation, allowing executables (as opposed to shared libraries) using the objects to be built as PIE binaries, which can be loaded at a random virtual offset. However, our ELF to PE/COFF generation code does not deal with the resulting relocation types (i.e., GOT based), and so the use of PIC code leads to GenFw errors. Given that a) our non-PIC PE/COFF executables are already relocatable, b) PIC code leads to all symbol references to be indirected via GOT entries containing absolute addresses, each requiring an entry in the relocation table, c) the AArch64 ISA makes it perfectly feasible to built PIE executables from non-PIC code, there is absolutely no upside to using PIC code for building EDK2 modules, and so we're better off simply disabling it unconditionally. Note that when running under the OS, the GOT has an additional advantage, i.e., that all .text/.rodata pages remain clean and so can be shared between processes. This does not apply to the UEFI environment, however. Contributed-under: TianoCore Contribution Agreement 1.0 Signed-off-by: Ard Biesheuvel Acked-by: Laszlo Ersek --- BaseTools/Conf/tools_def.template | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template index 0aabdeb2d9..2c5cd58089 100755 --- a/BaseTools/Conf/tools_def.template +++ b/BaseTools/Conf/tools_def.template @@ -4341,7 +4341,7 @@ DEFINE GCC_X64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mno-red-zone -Wno-ad DEFINE GCC_IPF_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -minline-int-divide-min-latency DEFINE GCC_ARM_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -mabi=aapcs -fno-short-enums -funsigned-char -ffunction-sections -fdata-sections -fomit-frame-pointer -fno-builtin -Wno-address -mthumb -mfloat-abi=soft DEFINE GCC_ARM_CC_XIPFLAGS = -mno-unaligned-access -DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -fno-builtin -Wno-address -fno-asynchronous-unwind-tables +DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mlittle-endian -fno-short-enums -fverbose-asm -funsigned-char -ffunction-sections -fdata-sections -fno-builtin -Wno-address -fno-asynchronous-unwind-tables -fno-pic DEFINE GCC_AARCH64_CC_XIPFLAGS = -mstrict-align DEFINE GCC_DLINK_FLAGS_COMMON = -nostdlib --pie DEFINE GCC_DLINK2_FLAGS_COMMON = -Wl,--script=$(EDK_TOOLS_PATH)/Scripts/GccBase.lds