[edk2,v3,9/9] BaseTools/tools_def: switch GCC/X64 to the PIE small model

Message ID 1468751686-28047-10-git-send-email-ard.biesheuvel@linaro.org
State Accepted
Commit f49513f666ed25d24bdf3a02a1fdb5d18ae081c0
Headers show

Commit Message

Ard Biesheuvel July 17, 2016, 10:34 a.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 PIE 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 'protected' 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>

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

-- 
1.9.1

_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel

Patch

diff --git a/BaseTools/Conf/tools_def.template b/BaseTools/Conf/tools_def.template
index a7da6741611d..f9b26fad44de 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 -fpie -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
 DEFINE GCC44_IA32_X64_DLINK_FLAGS    = DEF(GCC44_IA32_X64_DLINK_COMMON) --entry $(IMAGE_ENTRY_POINT) -u $(IMAGE_ENTRY_POINT) -Map $(DEST_DIR_DEBUG)/$(BASE_NAME).map