Quoting a post of a ipxe related developer that did a nice check realizing that e.g. disassembly always lists pushq (and opcode stays the same) - thanks to Valentine for these checks!:
AFAIU, segment registers are 16-bit long, however, "pushl" and "pushq" should also be valid and produce the same opcode. Quite interesting that obdump -S always shows "pushq" even when "push" or "pushl" is used in the original source. Please, take a look at the following log: user@ubuntu19.10:/tmp$ cat push.S push %gs push %fs user@ubuntu19.10:/tmp$ as --64 push.S -o push.out user@ubuntu19.10:/tmp$ objdump -S push.out push.out: file format elf64-x86-64 Disassembly of section .text: 0000000000000000 <.text>: 0: 0f a8 pushq %gs 2: 0f a0 pushq %fs user@ubuntu19.10:/tmp$ cat pushl.S pushl %gs pushl %fs user@ubuntu19.10:/tmp$ as --64 pushl.S -o pushl.out user@ubuntu19.10:/tmp$ objdump -S pushl.out pushl.out: file format elf64-x86-64 Disassembly of section .text: 0000000000000000 <.text>: 0: 0f a8 pushq %gs 2: 0f a0 pushq %fs user@ubuntu19.10:/tmp$ cat pushq.S pushq %gs pushq %fs user@ubuntu19.10:/tmp$ as --64 pushq.S -o pushq.out pushq.S: Assembler messages: pushq.S:1: Error: operand type mismatch for `push' pushq.S:2: Error: operand type mismatch for `push' -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to binutils in Ubuntu. https://bugs.launchpad.net/bugs/1843394 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 To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/binutils/+bug/1843394/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
