[edk2,v2,5/5] BaseTools/tools_def: switch GCC/X64 to the PIC small model

Message ID 1468620971-5960-6-git-send-email-ard.biesheuvel@linaro.org
State Superseded
Headers show

Commit Message

Ard Biesheuvel July 15, 2016, 10:16 p.m.
The ordinary small code model for x86_64 cannot be used in UEFI, since
it assumes the executable is loaded in the first 2 GB of memory.
Therefore, we use the large model instead, which can execute anywhere,
but uses absolute 64-bit wide quantities for all symbol references,
which is costly in terms of code size.

So switch to the PIC small code model, this uses 32-bit relative
references where possible, but does not make any assumptions about the
load address (i.e., all absolute symbol references are 64-bits wide).
Note that, due to the 'hidden' visibility pragma introduced in an
earlier patch, there is no need for the EDK2 build system to deal with
GOT related ELF relocation types.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Tested-by: Laszlo Ersek <lersek@redhat.com>

 BaseTools/Conf/tools_def.template | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


edk2-devel mailing list


diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
index a7da6741611d..17f2207680d3 100644
--- a/BaseTools/Conf/tools_def.template
+++ b/BaseTools/Conf/tools_def.template
@@ -4353,7 +4353,7 @@  DEFINE GCC_AARCH64_RC_FLAGS        = -I binary -O elf64-littleaarch64 -B aarch64
 DEFINE GCC44_ALL_CC_FLAGS            = -g -fshort-wchar -fno-strict-aliasing -Wall -Werror -Wno-array-bounds -ffunction-sections -fdata-sections -c -include AutoGen.h -fno-common -DSTRING_ARRAY_NAME=$(BASE_NAME)Strings
 DEFINE GCC44_IA32_CC_FLAGS           = DEF(GCC44_ALL_CC_FLAGS) -m32 -march=i586 -malign-double -fno-stack-protector -D EFI32 -fno-asynchronous-unwind-tables
-DEFINE GCC44_X64_CC_FLAGS            = DEF(GCC44_ALL_CC_FLAGS) -m64 -fno-stack-protector "-DEFIAPI=__attribute__((ms_abi))" -Os -maccumulate-outgoing-args -mno-red-zone -Wno-address -mcmodel=large -fno-asynchronous-unwind-tables
+DEFINE GCC44_X64_CC_FLAGS            = DEF(GCC44_ALL_CC_FLAGS) -m64 -fno-stack-protector "-DEFIAPI=__attribute__((ms_abi))" -Os -maccumulate-outgoing-args -mno-red-zone -Wno-address -mcmodel=small -fpic -fno-asynchronous-unwind-tables
 DEFINE GCC44_IA32_X64_DLINK_COMMON   = -nostdlib -n -q --gc-sections -z common-page-size=0x20
 DEFINE GCC44_IA32_X64_ASLDLINK_FLAGS = DEF(GCC44_IA32_X64_DLINK_COMMON) --entry ReferenceAcpiTable -u ReferenceAcpiTable