On 22 July 2015 at 21:12, Jordan Justen <[email protected]> wrote: > On 2015-07-22 06:56:45, Ard Biesheuvel wrote: >> After two recent changes have been applied to the ELF conversion >> routines in GenFw, i.e., PE/COFF section alignment based on ELF >> section alignment (54b1b57a59b5 "BaseTools: Update GenFw to support >> 4K alignment"), and removal of the debug section (pending), there is >> no reason anymore to have different GNU ld scripts for GCC/X86 4.4, >> GCC/X86 4.9 and GCC/AARCH64. >> >> So introduce a new unified linker script gcc-base.lds, with overlays >> to force 4 KB or 64 KB alignment (for building DXE runtime drivers >> and/or building AARCH64 code using the small C model) >> >> Notable differences between the original versions: >> - the 4 KB alignment linker script is now a simple overlay rather than a >> complete duplicate of the original with just the alignment changed; > > What do you mean by 'overlay'? Obviously not this: > > https://sourceware.org/binutils/docs/ld/Overlay-Description.html#Overlay-Description >
Nope, sorry, poor choice of words. Let's use 'linker script override', i.e., a script which just sets some additional parameters, but does not duplicate the entire original. > It seems like the new scripts will change GCC44-48 to use 64-byte > section alignment. > Yes, it will. The removal of the .debug section will also reduce the size of the headers to 0x228, which means that 44-48 and 49 and up will both start at 0x240, instead of having 0x260 and 0x280, respectively. So there are up to 3 remaining sections, each of which may use 32 additional bytes due to rounding; subtract the 0x20 and 0x40 we saved above, and the net result is ~0 on average and 64 bytes size increase worst case. What you get in return is identical ELF *and* PE/COFF layouts for all toolchain versions, which is an improvement imo. But indeed, if you prefer to keep the rounding for <4.9 exactly as is, another linker script override could be added for 64 bytes. > What if we defined two linker script variables via tools def. > > GCC:*_*_*_DLINK_LDCFG = $(EDK_TOOLS_PATH)/Scripts/default-cfg.lds > GCC:*_*_*_DLINK_LDSCRIPT = $(EDK_TOOLS_PATH)/Scripts/default.lds > > Then update build_rule to use --script with those two scripts. > > It looks like the LDCFG one might be able to set variables, like a > section_alignment variable that the LDSCRIPT could then use. > Unfortunately, the section ALIGN() value that comes /after/ the colon must be a constant and not an expression. So if that is what we want, we're down to preprocessor magic or whatever EDK2's equivalent is. But being able to set a single value rather than using the override scripts would indeed be quite useful, and I wouldn't mind having generated linker scripts as build artefacts. -- Ard. >> - .rodata has been moved into .text where it belongs; >> - the =90909090 NOP padding has been removed, since the only purpose it >> serves is making it easier for hackers to launch exploits, whereas >> correct code does not rely on these NOPs at all; >> - the .got contents have been moved into .text, but since we do not use >> PIC code, this input section should always be empty anyway. >> >> Contributed-under: TianoCore Contribution Agreement 1.0 >> Signed-off-by: Ard Biesheuvel <[email protected]> >> --- >> BaseTools/Scripts/GCC/gcc-align-4K.lds | 20 +++++++ >> BaseTools/Scripts/GCC/gcc-align-64K.lds | 20 +++++++ >> BaseTools/Scripts/GCC/gcc-base.lds | 62 ++++++++++++++++++++ >> 3 files changed, 102 insertions(+) >> >> diff --git a/BaseTools/Scripts/GCC/gcc-align-4K.lds >> b/BaseTools/Scripts/GCC/gcc-align-4K.lds >> new file mode 100644 >> index 000000000000..bba9fc591767 >> --- /dev/null >> +++ b/BaseTools/Scripts/GCC/gcc-align-4K.lds >> @@ -0,0 +1,20 @@ >> +/** @file >> + >> + Unified linker script for GCC based builds - 4 KB alignment overlay >> + >> + Copyright (c) 2015, Linaro Ltd. All rights reserved.<BR> >> + >> + This program and the accompanying materials are licensed and made >> available under >> + the terms and conditions of the BSD License that accompanies this >> distribution. >> + The full text of the license may be found at >> + http://opensource.org/licenses/bsd-license.php. >> + >> + THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, >> + WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR >> IMPLIED. >> + >> +**/ >> + >> +SECTIONS { >> + .text : ALIGN(0x1000) { } >> + .data : ALIGN(0x1000) { } >> +} >> diff --git a/BaseTools/Scripts/GCC/gcc-align-64K.lds >> b/BaseTools/Scripts/GCC/gcc-align-64K.lds >> new file mode 100644 >> index 000000000000..b115faa8fcbe >> --- /dev/null >> +++ b/BaseTools/Scripts/GCC/gcc-align-64K.lds >> @@ -0,0 +1,20 @@ >> +/** @file >> + >> + Unified linker script for GCC based builds - 64 KB alignment overlay >> + >> + Copyright (c) 2015, Linaro Ltd. All rights reserved.<BR> >> + >> + This program and the accompanying materials are licensed and made >> available under >> + the terms and conditions of the BSD License that accompanies this >> distribution. >> + The full text of the license may be found at >> + http://opensource.org/licenses/bsd-license.php. >> + >> + THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, >> + WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR >> IMPLIED. >> + >> +**/ >> + >> +SECTIONS { >> + .text : ALIGN(0x10000) { } >> + .data : ALIGN(0x10000) { } >> +} >> diff --git a/BaseTools/Scripts/GCC/gcc-base.lds >> b/BaseTools/Scripts/GCC/gcc-base.lds >> new file mode 100644 >> index 000000000000..a40640542484 >> --- /dev/null >> +++ b/BaseTools/Scripts/GCC/gcc-base.lds >> @@ -0,0 +1,62 @@ >> +/** @file >> + >> + Unified linker script for GCC based builds >> + >> + Copyright (c) 2015, Linaro Ltd. All rights reserved.<BR> >> + >> + This program and the accompanying materials are licensed and made >> available under >> + the terms and conditions of the BSD License that accompanies this >> distribution. >> + The full text of the license may be found at >> + http://opensource.org/licenses/bsd-license.php. >> + >> + THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, >> + WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR >> IMPLIED. >> + >> +**/ >> + >> +SECTIONS { >> + >> + /* >> + * The PE/COFF binary consists of DOS and PE/COFF headers, and a sequence >> of >> + * section headers adding up to 0x228 bytes at the most. So choose 0x228 >> as >> + * the start address: the actual start of the .text section will be >> rounded >> + * up based on its actual alignment. >> + */ >> + . = 0x228; >> + >> + .text : ALIGN(0x40) { >> + *(.text .text.* .stub .gnu.linkonce.t.*) >> + *(.rodata .rodata.* .gnu.linkonce.r.*) >> + *(.got .got.*) >> + } >> + >> + /* >> + * The alignment of the .data section should be less than or equal to the >> + * alignment of the .text section. This ensures that the relative offset >> + * between these sections is the same in the ELF and the PE/COFF versions >> of >> + * this binary. >> + */ >> + .data ALIGN(ALIGNOF(.text)) : { >> + *(.data .data.* .gnu.linkonce.d.*) >> + *(.bss .bss.* *COM*) >> + } >> + >> + .eh_frame ALIGN(0x20) : { >> + KEEP (*(.eh_frame)) >> + } >> + >> + .rela ALIGN(0x20) : { >> + *(.rela .rela.*) >> + } >> + >> + /DISCARD/ : { >> + *(.note.GNU-stack) >> + *(.gnu_debuglink) >> + *(.interp) >> + *(.dynsym) >> + *(.dynstr) >> + *(.dynamic) >> + *(.hash) >> + *(.comment) >> + } >> +} >> -- >> 1.9.1 >> _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
