On 24 June 2015 at 17:21, Cohen, Eugene <eug...@hp.com> wrote: >> + * Since some AArch64 code is aligned to 0x800 (i.e., the vector table), >> we >> + * need to use at least this alignment for .text. > > >From what I can see the vector table code uses .align directives to increase > >the alignment size which is propagated into the resulting ELF. The PE-COFF > >conversion respects this so I don't believe it is necessary to impose this > >alignment requirement. > > We are very sensitive to code size in SEC and PEI which are typically > uncompressed and XIP so I would ask that we keep the alignment padding to a > minimum (see Andrew's email about this topic). >
Indeed. If we end up agreeing that using the small C model has its merits, we would ideally implement it in the following way: - use 'large' C model for SEC and PEI, with the smallest alignment that we can support - use 'small' C model for boot time modules, using the linker script in this patch - use 'small' C model and 64 KB alignment (with an alternative linker script) for runtime modules, so that we can benefit from the Properties Table feature, which allows code regions to be mapped R-X and data regions to be mapped RW- I know this is a it of a jumble of related but not entirely similar issues. I was just triggered by your patch, and decided to experiment and come up with something that addresses all these issues. -- Ard. > -----Original Message----- > From: Ard Biesheuvel [mailto:ard.biesheu...@linaro.org] > Sent: Tuesday, June 23, 2015 9:31 AM > To: edk2-devel@lists.sourceforge.net; olivier.mar...@arm.com; > leif.lindh...@linaro.org > Subject: [edk2] [RFC PATCH 2/4] BaseTools: AArch64: use an explicit linker > script > > Instead of relying on the builtin linker script of GNU ld, which may vary > based on binutils version (which is not tightly coupled to the GCC version) > and linker command line options, introduce a linker script for AArch64 to be > used by all GCC/binutils versions. > > The script is laid out such that both the file and memory layout are > identical between the ELF intermediate file and the final PE/COFF file. This > should prevent problems with debuggers and other tooling that are ELF based. > It also places the .text section such that, provided that the entire image is > loaded at a 4 KB aligned offset, the build time and runtime relative > alignment with respect to the nearest 4 KB boundary is the same. This allows > the 'small' GCC C model to be used. > > Contributed-under: TianoCore Contribution Agreement 1.0 > Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org> > --- > BaseTools/Conf/tools_def.template | 23 +++++++++++++---------- > BaseTools/Scripts/gcc-aarch64-ld-script | 33 > +++++++++++++++++++++++++++++++++ > 2 files changed, 46 insertions(+), 10 deletions(-) > > diff --git a/BaseTools/Conf/tools_def.template > b/BaseTools/Conf/tools_def.template > index fd7b4b55e8ba..9ba8d38a1791 100644 > --- a/BaseTools/Conf/tools_def.template > +++ b/BaseTools/Conf/tools_def.template > @@ -3821,9 +3821,12 @@ DEFINE GCC_ARM_CC_FLAGS = > DEF(GCC_ALL_CC_FLAGS) -mword-relocations -m > DEFINE GCC_AARCH64_CC_FLAGS = DEF(GCC_ALL_CC_FLAGS) -mcmodel=large > -mlittle-endian -fno-short-enums -save-temps -fverbose-asm -fsigned-char > -ffunction-sections -fdata-sections -fomit-frame-pointer -fno-builtin > -Wno-address > DEFINE GCC_DLINK_FLAGS_COMMON = -nostdlib --pie > DEFINE GCC_IA32_X64_DLINK_COMMON = DEF(GCC_DLINK_FLAGS_COMMON) > --gc-sections > -DEFINE GCC_ARM_AARCH64_DLINK_COMMON= -Ttext=0x0 --emit-relocs -nostdlib > --gc-sections -u $(IMAGE_ENTRY_POINT) -e $(IMAGE_ENTRY_POINT) -Map > $(DEST_DIR_DEBUG)/$(BASE_NAME).map > +DEFINE GCC_ARM_AARCH64_DLINK_COMMON= --emit-relocs -nostdlib --gc-sections > -u $(IMAGE_ENTRY_POINT) -e $(IMAGE_ENTRY_POINT) -Map > $(DEST_DIR_DEBUG)/$(BASE_NAME).map > +DEFINE GCC_ARM_DLINK_FLAGS = DEF(GCC_ARM_AARCH64_DLINK_COMMON) > -Ttext=0x0 > +DEFINE GCC_AARCH64_DLINK_FLAGS = DEF(GCC_ARM_AARCH64_DLINK_COMMON) > --script=$(EDK_TOOLS_PATH)/Scripts/gcc-aarch64-ld-script > DEFINE GCC_IA32_X64_ASLDLINK_FLAGS = DEF(GCC_IA32_X64_DLINK_COMMON) --entry > _ReferenceAcpiTable -u $(IMAGE_ENTRY_POINT) -DEFINE > GCC_ARM_AARCH64_ASLDLINK_FLAGS = DEF(GCC_ARM_AARCH64_DLINK_COMMON) --entry > ReferenceAcpiTable -u $(IMAGE_ENTRY_POINT) > +DEFINE GCC_ARM_ASLDLINK_FLAGS = DEF(GCC_ARM_DLINK_FLAGS) --entry > ReferenceAcpiTable -u $(IMAGE_ENTRY_POINT) > +DEFINE GCC_AARCH64_ASLDLINK_FLAGS = DEF(GCC_AARCH64_DLINK_FLAGS) > +--entry ReferenceAcpiTable -u $(IMAGE_ENTRY_POINT) > DEFINE GCC_IA32_X64_DLINK_FLAGS = DEF(GCC_IA32_X64_DLINK_COMMON) --entry > _$(IMAGE_ENTRY_POINT) --file-alignment 0x20 --section-alignment 0x20 -Map > $(DEST_DIR_DEBUG)/$(BASE_NAME).map > DEFINE GCC_IPF_DLINK_FLAGS = -nostdlib -O2 --gc-sections --dll > -static --entry $(IMAGE_ENTRY_POINT) --undefined $(IMAGE_ENTRY_POINT) -Map > $(DEST_DIR_DEBUG)/$(BASE_NAME).map > DEFINE GCC_IPF_OBJCOPY_FLAGS = -I elf64-ia64-little -O efi-bsdrv-ia64 > @@ -3866,8 +3869,8 @@ DEFINE GCC46_X64_DLINK_FLAGS = > DEF(GCC45_X64_DLINK_FLAGS) > DEFINE GCC46_ASM_FLAGS = DEF(GCC45_ASM_FLAGS) > DEFINE GCC46_ARM_ASM_FLAGS = $(ARCHASM_FLAGS) $(PLATFORM_FLAGS) > DEF(GCC_ASM_FLAGS) -mlittle-endian > DEFINE GCC46_ARM_CC_FLAGS = $(ARCHCC_FLAGS) $(PLATFORM_FLAGS) > DEF(GCC44_ALL_CC_FLAGS) DEF(GCC_ARM_CC_FLAGS) -fstack-protector > -DEFINE GCC46_ARM_DLINK_FLAGS = DEF(GCC_ARM_AARCH64_DLINK_COMMON) > --oformat=elf32-littlearm > -DEFINE GCC46_ARM_ASLDLINK_FLAGS = DEF(GCC_ARM_AARCH64_ASLDLINK_FLAGS) > --oformat=elf32-littlearm > +DEFINE GCC46_ARM_DLINK_FLAGS = DEF(GCC_ARM_DLINK_FLAGS) > --oformat=elf32-littlearm > +DEFINE GCC46_ARM_ASLDLINK_FLAGS = DEF(GCC_ARM_ASLDLINK_FLAGS) > --oformat=elf32-littlearm > > DEFINE GCC47_IA32_CC_FLAGS = DEF(GCC46_IA32_CC_FLAGS) > DEFINE GCC47_X64_CC_FLAGS = DEF(GCC46_X64_CC_FLAGS) > @@ -3881,9 +3884,9 @@ DEFINE GCC47_AARCH64_ASM_FLAGS = $(ARCHASM_FLAGS) > $(PLATFORM_FLAGS) DEF(GC > DEFINE GCC47_ARM_CC_FLAGS = DEF(GCC46_ARM_CC_FLAGS) > -mno-unaligned-access > DEFINE GCC47_AARCH64_CC_FLAGS = $(ARCHCC_FLAGS) $(PLATFORM_FLAGS) > DEF(GCC44_ALL_CC_FLAGS) DEF(GCC_AARCH64_CC_FLAGS) > DEFINE GCC47_ARM_DLINK_FLAGS = DEF(GCC46_ARM_DLINK_FLAGS) > -DEFINE GCC47_AARCH64_DLINK_FLAGS = DEF(GCC_ARM_AARCH64_DLINK_COMMON) > +DEFINE GCC47_AARCH64_DLINK_FLAGS = DEF(GCC_AARCH64_DLINK_FLAGS) > DEFINE GCC47_ARM_ASLDLINK_FLAGS = DEF(GCC46_ARM_ASLDLINK_FLAGS) > -DEFINE GCC47_AARCH64_ASLDLINK_FLAGS = DEF(GCC_ARM_AARCH64_ASLDLINK_FLAGS) > +DEFINE GCC47_AARCH64_ASLDLINK_FLAGS = DEF(GCC_AARCH64_ASLDLINK_FLAGS) > > DEFINE GCC48_IA32_CC_FLAGS = DEF(GCC47_IA32_CC_FLAGS) > DEFINE GCC48_X64_CC_FLAGS = DEF(GCC47_X64_CC_FLAGS) > @@ -3897,9 +3900,9 @@ DEFINE GCC48_AARCH64_ASM_FLAGS = > DEF(GCC47_AARCH64_ASM_FLAGS) > DEFINE GCC48_ARM_CC_FLAGS = DEF(GCC47_ARM_CC_FLAGS) > DEFINE GCC48_AARCH64_CC_FLAGS = DEF(GCC47_AARCH64_CC_FLAGS) > DEFINE GCC48_ARM_DLINK_FLAGS = DEF(GCC47_ARM_DLINK_FLAGS) > -DEFINE GCC48_AARCH64_DLINK_FLAGS = DEF(GCC_ARM_AARCH64_DLINK_COMMON) > +DEFINE GCC48_AARCH64_DLINK_FLAGS = DEF(GCC47_AARCH64_DLINK_FLAGS) > DEFINE GCC48_ARM_ASLDLINK_FLAGS = DEF(GCC47_ARM_ASLDLINK_FLAGS) > -DEFINE GCC48_AARCH64_ASLDLINK_FLAGS = DEF(GCC_ARM_AARCH64_ASLDLINK_FLAGS) > +DEFINE GCC48_AARCH64_ASLDLINK_FLAGS = > +DEF(GCC47_AARCH64_ASLDLINK_FLAGS) > > DEFINE GCC49_IA32_CC_FLAGS = DEF(GCC48_IA32_CC_FLAGS) > DEFINE GCC49_X64_CC_FLAGS = DEF(GCC48_X64_CC_FLAGS) > @@ -3913,9 +3916,9 @@ DEFINE GCC49_AARCH64_ASM_FLAGS = > DEF(GCC48_AARCH64_ASM_FLAGS) > DEFINE GCC49_ARM_CC_FLAGS = DEF(GCC48_ARM_CC_FLAGS) > DEFINE GCC49_AARCH64_CC_FLAGS = DEF(GCC48_AARCH64_CC_FLAGS) > DEFINE GCC49_ARM_DLINK_FLAGS = DEF(GCC48_ARM_DLINK_FLAGS) > -DEFINE GCC49_AARCH64_DLINK_FLAGS = DEF(GCC_ARM_AARCH64_DLINK_COMMON) > +DEFINE GCC49_AARCH64_DLINK_FLAGS = DEF(GCC48_AARCH64_DLINK_FLAGS) > DEFINE GCC49_ARM_ASLDLINK_FLAGS = DEF(GCC48_ARM_ASLDLINK_FLAGS) > -DEFINE GCC49_AARCH64_ASLDLINK_FLAGS = DEF(GCC_ARM_AARCH64_ASLDLINK_FLAGS) > +DEFINE GCC49_AARCH64_ASLDLINK_FLAGS = > +DEF(GCC48_AARCH64_ASLDLINK_FLAGS) > > > #################################################################################### > # > diff --git a/BaseTools/Scripts/gcc-aarch64-ld-script > b/BaseTools/Scripts/gcc-aarch64-ld-script > new file mode 100644 > index 000000000000..cf09b63d916f > --- /dev/null > +++ b/BaseTools/Scripts/gcc-aarch64-ld-script > @@ -0,0 +1,33 @@ > +SECTIONS { > + > + /* > + * By positioning the .text section at 0x800, and aligning it at 0x800, it > + * is guaranteed to end up at 0x800 offset in the resulting PE/COFF image > as > + * well. This allows us to use GCC's 'small' C model, which uses PC > relative > + * ADRP/ADD and ADRP/LDR pairs to reference global symbols, instead of > 64-bit > + * absolute addresses. > + * Since some AArch64 code is aligned to 0x800 (i.e., the vector table), we > + * need to use at least this alignment for .text. The actual PE/COFF > headers > + * are only around 0x260 bytes in size, so we are wasting around 1.5 KB > here. > + */ > + .text 0x800 : ALIGN(0x800) { > + *(.text .text.* .rodata .rodata.*) > + } > + .data : ALIGN(0x40) { > + *(.data .data.*) > + *(.bss .bss.* *COM*) > + } > + .rela ALIGN(0x20) : { > + *(.rela .rela.*) > + } > + > + /DISCARD/ : { > + *(.note.GNU-stack) > + *(.interp) > + *(.dynsym) > + *(.dynstr) > + *(.dynamic) > + *(.hash) > + *(.comment) > + } > +} > -- > 1.9.1 > > > ------------------------------------------------------------------------------ > Monitor 25 network devices or servers for free with OpManager! > OpManager is web-based network management software that monitors > network devices and physical & virtual servers, alerts via email & sms > for fault. Monitor 25 devices for free with no restriction. Download now > http://ad.doubleclick.net/ddm/clk/292181274;119417398;o > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/edk2-devel > > ------------------------------------------------------------------------------ > Monitor 25 network devices or servers for free with OpManager! > OpManager is web-based network management software that monitors > network devices and physical & virtual servers, alerts via email & sms > for fault. Monitor 25 devices for free with no restriction. Download now > http://ad.doubleclick.net/ddm/clk/292181274;119417398;o > _______________________________________________ > edk2-devel mailing list > edk2-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/edk2-devel ------------------------------------------------------------------------------ Monitor 25 network devices or servers for free with OpManager! OpManager is web-based network management software that monitors network devices and physical & virtual servers, alerts via email & sms for fault. Monitor 25 devices for free with no restriction. Download now http://ad.doubleclick.net/ddm/clk/292181274;119417398;o _______________________________________________ edk2-devel mailing list edk2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/edk2-devel
