bug#41982: [PATCH] grub-core: Build fixes for i386

[Jan Nieuwenhuizen]

Hi!

When cross-compiling Grub-2.04 from i386-linux-gnu to i586-pc-hurd on
GNU Guix, I got this error

--8<---------------cut here---------------start------------->8---
i586-pc-gnu-gcc -DHAVE_CONFIG_H -I. -I..  -Wall -W  -DGRUB_MACHINE_PCBIOS=1 
-DGRUB_MACHINE=I386_PC -m32 -nostdinc -isystem 
/gnu/store/5s0ldm31100d9ix15d1lmbsvi0aa77pq-gcc-cross-i586-pc-gnu-7.5.0-lib/lib/gcc/i586-pc-gnu/7.5.0/include
 -I../include -I../include -DGRUB_FILE=\"lib/cmos_datetime.c\" -I. -I. -I.. 
-I.. -I../include -I../include -I../grub-core/lib/libgcrypt-grub/src/    
-D_FILE_OFFSET_BITS=64 -Os -Wall -W -Wshadow -Wpointer-arith -Wundef 
-Wchar-subscripts -Wcomment -Wdeprecated-declarations -Wdisabled-optimization 
-Wdiv-by-zero -Wfloat-equal -Wformat-extra-args -Wformat-security -Wformat-y2k 
-Wimplicit -Wimplicit-function-declaration -Wimplicit-int -Wmain 
-Wmissing-braces -Wmissing-format-attribute -Wmultichar -Wparentheses 
-Wreturn-type -Wsequence-point -Wshadow -Wsign-compare -Wswitch -Wtrigraphs 
-Wunknown-pragmas -Wunused -Wunused-function -Wunused-label -Wunused-parameter 
-Wunused-value  -Wunused-variable -Wwrite-strings -Wnested-externs 
-Wstrict-prototypes -g -Wredundant-decls -Wmissing-prototypes 
-Wmissing-declarations  -Wextra -Wattributes -Wendif-labels -Winit-self 
-Wint-to-pointer-cast -Winvalid-pch -Wmissing-field-initializers -Wnonnull 
-Woverflow -Wvla -Wpointer-to-int-cast -Wstrict-aliasing -Wvariadic-macros 
-Wvolatile-register-var -Wpointer-sign -Wmissing-include-dirs 
-Wmissing-prototypes -Wmissing-declarations -Wformat=2 -march=i386 -m32 -mrtd 
-mregparm=3 -falign-jumps=1 -falign-loops=1 -falign-functions=1 
-freg-struct-return -mno-mmx -mno-sse -mno-sse2 -mno-sse3 -mno-3dnow 
-msoft-float -fno-dwarf2-cfi-asm -mno-stack-arg-probe 
-fno-asynchronous-unwind-tables -fno-unwind-tables -fno-stack-protector 
-Wtrampolines -Werror   -ffreestanding   -MT 
lib/datetime_module-cmos_datetime.o -MD -MP -MF 
lib/.deps-core/datetime_module-cmos_datetime.Tpo -c -o 
lib/datetime_module-cmos_datetime.o `test -f 'lib/cmos_datetime.c' || echo 
'./'`lib/cmos_datetime.c
lib/i386/relocator64.S: Assembler messages:
lib/i386/relocator64.S:66: Error: unknown pseudo-op: `.code64'
lib/i386/relocator64.S:74: Error: bad register name `%rax'
lib/i386/relocator64.S:98: Error: bad register name `%rax'
lib/i386/relocator64.S:132: Error: bad register name `%rip)'
make[3]: *** [Makefile:32165: lib/i386/relocator_module-relocator64.o] Error 1
make[3]: *** Waiting for unfinished jobs....
mv -f lib/i386/.deps-core/relocator_module-relocator_common_c.Tpo 
lib/i386/.deps-core/relocator_module-relocator_common_c.Po
mv -f lib/i386/.deps-core/relocator_module-relocator.Tpo 
lib/i386/.deps-core/relocator_module-relocator.Po
mv -f kern/.deps-core/elf_module-elf.Tpo kern/.deps-core/elf_module-elf.Po
mv -f lib/.deps-core/datetime_module-cmos_datetime.Tpo 
lib/.deps-core/datetime_module-cmos_datetime.Po
mv -f fs/.deps-core/xfs_module-xfs.Tpo fs/.deps-core/xfs_module-xfs.Po
mv -f lib/.deps-core/crypto_module-crypto.Tpo 
lib/.deps-core/crypto_module-crypto.Po
mv -f lib/.deps-core/relocator_module-relocator.Tpo 
lib/.deps-core/relocator_module-relocator.Po
make[3]: Leaving directory 
'/tmp/guix-build-grub-minimal-2.04.drv-0/grub-2.04/grub-core'
make[2]: *** [Makefile:26403: all] Error 2
make[2]: Leaving directory 
'/tmp/guix-build-grub-minimal-2.04.drv-0/grub-2.04/grub-core'
make[1]: *** [Makefile:11304: all-recursive] Error 1
make[1]: Leaving directory '/tmp/guix-build-grub-minimal-2.04.drv-0/grub-2.04'
make: *** [Makefile:3343: all] Error 2
command "make" "-j" "8" failed with status 2
--8<---------------cut here---------------end--------------->8---

In Guix we are now using the patch attached, which seems to fix this for
us.  We are not entirely sure if this is the proper fix though, see
<https://bugs.gnu.org/41982>.

Paraphrasing the questions raised there: why does this seem to compile
on i386?  Is that because the non-cross 32-bit ‘as’ supports ‘.code64’?
Is the Guix's cross-assembler ‘i586-pc-gnu-as’ configured wrong and
should it support this?

(FWIW, this is not specific for the Hurd, cross compiling from
i686-linux-gnu to i686-linux-gnu show the same error.  The use case for
that may be a bit thin to warrant a bug report.)

Ideas welcome!

Greetings,
Janneke

>From 270667540146f8ef9ea7a44258a71b3837a7af4a Mon Sep 17 00:00:00 2001
From: "Jan (janneke) Nieuwenhuizen" <janneke@gnu.org>
Date: Sun, 21 Jun 2020 15:10:40 +0200
Subject: [PATCH] grub-core: Build fixes for i386

* grub-core/lib/i386/relocator64.S: Avoid x86_64 instructions on i386.
---
 grub-core/lib/i386/relocator64.S | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/grub-core/lib/i386/relocator64.S b/grub-core/lib/i386/relocator64.S
index 148f38adb..45fed9444 100644
--- a/grub-core/lib/i386/relocator64.S
+++ b/grub-core/lib/i386/relocator64.S
@@ -63,7 +63,9 @@ VARIABLE(grub_relocator64_cr3)
        movq    %rax, %cr3
 #endif
 
+#ifdef __x86_64__
        .code64
+#endif
 
        /* mov imm64, %rax */
        .byte   0x48
@@ -71,7 +73,14 @@ VARIABLE(grub_relocator64_cr3)
 VARIABLE(grub_relocator64_rsp)
        .quad   0
 
+#ifndef __x86_64__
+       /* movq %rax, %rsp */
+       .byte   0x48
+       .byte   0x89
+       .byte   0xc4
+#else
        movq    %rax, %rsp
+#endif
 
 #ifdef GRUB_MACHINE_EFI
        jmp     LOCAL(skip_efi_stack_align)
@@ -95,8 +104,15 @@ LOCAL(skip_efi_stack_align):
 VARIABLE(grub_relocator64_rsi)
        .quad   0
 
+#ifndef        __x86_64__
+       /* movq %rax, %rsi */
+       .byte   0x48
+       .byte   0x89
+       .byte   0xc6
+#else
        movq    %rax, %rsi
-       
+#endif
+
        /* mov imm64, %rax */
        .byte   0x48
        .byte   0xb8
@@ -128,6 +144,14 @@ VARIABLE(grub_relocator64_rdx)
 #ifdef __APPLE__
        .byte 0xff, 0x25
        .quad 0
+#elif !defined (__x86_64__)
+       /* jmp *LOCAL(jump_addr) (%rip) */
+       .byte 0xff
+        .byte 0x25
+       .byte 0
+       .byte 0
+       .byte 0
+       .byte 0
 #else
        jmp *LOCAL(jump_addr) (%rip)
 #endif
-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
Freelance IT http://JoyofSource.com | Avatar® http://AvatarAcademy.com

-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
Freelance IT http://JoyofSource.com | Avatar® http://AvatarAcademy.com