Messages in this thread | | | From | Nick Desaulniers <> | Date | Fri, 11 Jan 2019 11:27:31 -0800 | Subject | Re: [PATCH v2] x86_64: Add "-m elf_i386" when linking i386 object files. |
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On Fri, Jan 11, 2019 at 11:14 AM Tri Vo <trong@android.com> wrote: > > From: George Rimar <grimar@accesssoftek.com> > > Linux kernel uses OUTPUT_FORMAT in it's linker scripts. Most of the time > -m option is passed to the linker with correct architecture, but > sometimes (at least for x86_64) the -m option contradicts OUTPUT_FORMAT > directive. Specifically, arch/x86/boot and arch/x86/realmode/rm modules > have i386 object files, but are linked with -m elf_x86_64 linker flag > when building for x86_64. > > "man ld" doesn't explicitly state any tie-breakers between -m and > OUTPUT_FORMAT. BFD and Gold linkers override -m value with > OUTPUT_FORMAT. But LLVM lld has a different behavior. When supplied with > contradicting -m and OUTPUT_FORMAT values it fails with the following > error message: > > ld.lld: error: arch/x86/realmode/rm/header.o is incompatible with elf_x86_64 > > Suggested fix: just add correct -m after incorrect one (it overrides > it), so the linker invocation looks like this: ld -m elf_x86_64 -z > max-page-size=0x200000 -m elf_i386 --emit-relocs -T realmode.lds > header.o trampoline_64.o stack.o reboot.o -o realmode.elf > > This is not a functional change for GNU ld, because (although not > explicitly documented) it already overrides -m EMULATION with > OUTPUT_FORMAT. > > Tested by building x86_64 kernel with GNU gcc/ld toolchain and booting > it in QEMU. > > Suggested-by: Dmitry Golovin <dima@golovin.in> > Signed-off-by: Georgii Rymar <grimar@accesssoftek.com>
misspelled, and you may carry forward my tested by tag from v1.
> Signed-off-by: Tri Vo <trong@android.com> > Tested-by: Tri Vo <trong@android.com> > ---
So when making a change, you can put any text below this `---` delimiter. For LKML, it's common practice to put something like: v1 -> v2: updated commit message That helps code review so reviewers know what to expect "inter-diff" when eyeballing patch files. Internally when using gerrit, it will highlight inter-version diffs (ie. what changed between v2 and v3 of a patch), but since we do things the hard way on LKML, this can help a lot. After `git format-patch ...`, I usually add such a comment to the patch file in vim before sending.
> arch/x86/boot/Makefile | 2 +- > arch/x86/realmode/rm/Makefile | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile > index 9b5adae9cc40..e2839b5c246c 100644 > --- a/arch/x86/boot/Makefile > +++ b/arch/x86/boot/Makefile > @@ -100,7 +100,7 @@ $(obj)/zoffset.h: $(obj)/compressed/vmlinux FORCE > AFLAGS_header.o += -I$(objtree)/$(obj) > $(obj)/header.o: $(obj)/zoffset.h > > -LDFLAGS_setup.elf := -T > +LDFLAGS_setup.elf := -m elf_i386 -T > $(obj)/setup.elf: $(src)/setup.ld $(SETUP_OBJS) FORCE > $(call if_changed,ld) > > diff --git a/arch/x86/realmode/rm/Makefile b/arch/x86/realmode/rm/Makefile > index 4463fa72db94..96cb20de08af 100644 > --- a/arch/x86/realmode/rm/Makefile > +++ b/arch/x86/realmode/rm/Makefile > @@ -47,7 +47,7 @@ $(obj)/pasyms.h: $(REALMODE_OBJS) FORCE > targets += realmode.lds > $(obj)/realmode.lds: $(obj)/pasyms.h > > -LDFLAGS_realmode.elf := --emit-relocs -T > +LDFLAGS_realmode.elf := -m elf_i386 --emit-relocs -T > CPPFLAGS_realmode.lds += -P -C -I$(objtree)/$(obj) > > targets += realmode.elf > -- > 2.20.1.97.g81188d93c3-goog >
-- Thanks, ~Nick Desaulniers
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