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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 <ard.biesheuvel@linaro.org>
Acked-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Ard Biesheuvel 2017-03-31 09:22:56 +01:00
parent af8388059a
commit c2d56a894b
1 changed files with 1 additions and 1 deletions
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BaseTools/Conf/tools_def.template
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@ -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