[Bug 1843394] Re: FTBFS in Eoan - Error: operand type mismatch for `push' - gcc 9.2.1 / binutils 2.32.51.20190905-0ubuntu1

[Christian Ehrhardt ]

Note: given that this went into the archive in early July and that nothing but this section in IPXE broke I lean toward assuming that the ipxe code is broken or at least (while it worked in the past) not implemented the way it should be for the assembly to work.
Yet I'm not feeling experienced enough to really feel confident about my suggested fix without further upstream feedback or other people backing me up.

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Title:
  FTBFS in Eoan - Error: operand type mismatch for `push' - gcc 9.2.1 /
  binutils 2.32.51.20190905-0ubuntu1

Status in binutils package in Ubuntu:
  New
Status in ipxe package in Ubuntu:
  New

Bug description:
  This might be due to new gcc-9 being more strict, but the build that
  worked before now fails with:

  arch/x86_64/core/gdbidt.S: Assembler messages:
  arch/x86_64/core/gdbidt.S:109: Error: operand type mismatch for `push'
  arch/x86_64/core/gdbidt.S:110: Error: operand type mismatch for `push'
  arch/x86_64/core/gdbidt.S:161: Error: operand type mismatch for `pop'
  arch/x86_64/core/gdbidt.S:162: Error: operand type mismatch for `pop'
  make[2]: *** [Makefile.housekeeping:937: bin-x86_64-efi/gdbidt.o] Error 1

  Full log at: https://launchpadlibrarian.net/441262285/buildlog_ubuntu-
  eoan-amd64.ipxe_1.0.0+git-20190109.133f4c4-0ubuntu2_BUILDING.txt.gz

  Now all of this is about push/pop of %fs and %gs.
  That needs to match the size of the registers which depend on the current running mode.

  In this particular case in ./src/arch/x86_64/core/gdbidt.S
  The failing file is in ".code64" mode.
  In that I'd expect %gs/%fs to be 64 bit.

  
  Usually we see push/pop "w" in .code16 (word), l in .code32 (long) but in that sense here q (quad word) seems right at first (should be what correctly matches the .code64).
  That matches what I see throughout the ipxe code but also throughout the archive https://codesearch.debian.net/search?q=pop%5Ba-z%5D.*%25fs&literal=0&page=2

  Maybe I misread the mode it is in, or it is actually a false positives.
  Or the sizes of FS/GS do not change - haven't touched them in a loooong time.
  Was it that segment registers didn't change size?
  I'll need to do a few checks to first see what the compiler would expect there and from there need to understand this.

  The command used also points to AS being in 64 bit mode when this happens:
  gcc -E  -DARCH=x86_64 -DPLATFORM=efi -DSECUREBOOT=0 -fstrength-reduce -fomit-frame-pointer -falign-jumps=1 -falign-loops=1 -falign-functions=1 -m64 -mno-mmx -mno-sse -fshort-wchar -Ui386 -Ulinux -DNVALGRIND -fpie -mno-red-zone -Iinclude -I. -Iarch/x86/include -Iarch/x86_64/include -Iarch/x86_64/include/efi -Os -g -ffreestanding -Wall -W -Wformat-nonliteral  -fno-stack-protector -fno-dwarf2-cfi-asm -fno-exceptions  -fno-unwind-tables -fno-asynchronous-unwind-tables -Wno-address -Wno-stringop-truncation   -ffunction-sections -fdata-sections -include include/compiler.h -DASM_TCHAR='@' -DASM_TCHAR_OPS='@' -DASSEMBLY  -DOBJECT=gdbidt arch/x86_64/core/gdbidt.S | as  --64    -o bin-x86_64-efi/gdbidt.o

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