Re-sending as plain text. Sorry.
On Mon, Jan 7, 2019 at 3:11 PM Tri Vo <tr...@android.com> wrote: > > Hello, hope everyone's had great holidays. > Could someone review at this patch? > > On Tue, Dec 18, 2018 at 3:39 AM George Rimar <gri...@accesssoftek.com> wrote: >> >> Added Rui, an LLD code owner. >> >> This patch contains the approach we discussed earlier during LLD development >> when >> faced this issue first time (and as a result of the discussion, >> the same fix was suggested: >> https://bugzilla.kernel.org/show_bug.cgi?id=194091#c0), >> so I think it is fine. >> >> Best regards, >> George | Developer | Access Softek, Inc >> >> ________________________________________ >> От: Tri Vo <tr...@android.com> >> Отправлено: 12 декабря 2018 г. 22:48 >> Кому: Nick Desaulniers >> Копия: b...@alien8.de; x...@kernel.org; t...@linutronix.de; >> mi...@redhat.com; George Rimar; Dmitry Golovin; Bill Wendling; >> h...@zytor.com; linux-kernel@vger.kernel.org >> Тема: Re: [RFC PATCH] x86_64: Add "-m elf_i386" when linking i386 object >> files. >> >> CAUTION: This email originated from outside of the organization. Do not >> click links or open attachments unless you recognize the sender and know the >> content is safe. >> >> Adding appropriate people, lists. >> On Tue, Dec 11, 2018 at 1:07 PM Nick Desaulniers >> <ndesaulni...@google.com> wrote: >> > >> > On Mon, Dec 10, 2018 at 2:50 PM Nick Desaulniers >> > <ndesaulni...@google.com> wrote: >> > > >> > > On Mon, Dec 10, 2018 at 2:26 PM Tri Vo <tr...@android.com> wrote: >> > > > >> > > > From: George Rimar <gri...@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. >> > > > >> > > > BFD and Gold linkers are OK with this, but lld fails: >> > > > 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 (it will also >> > > > work with GNU ld, because it supports OUTPUT_FORMAT and just ignores -m >> > > > options if this directive is in the linker script). >> > > > >> > > > Tested by building x86_64 kernel with GNU gcc/ld toolchain and booting >> > > > it in QEMU. >> > > > >> > > > Suggested-by: Dmitry Golovin <d...@golovin.in> >> > > > Signed-off-by: Tri Vo <tr...@android.com> >> > > > Tested-by: Tri Vo <tr...@android.com> >> > > >> > > This fixes the following linkage error I observe when linking an x86 >> > > kernel with LLD: >> > > >> > > ``` >> > > LD arch/x86/realmode/rm/realmode.elf >> > > ld.lld: error: arch/x86/realmode/rm/header.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/trampoline_64.o is incompatible >> > > with elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/stack.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/reboot.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/wakeup_asm.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/wakemain.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/video-mode.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/copy.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/bioscall.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/regs.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/video-vga.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/video-vesa.o is incompatible with >> > > elf_x86_64 >> > > ld.lld: error: arch/x86/realmode/rm/video-bios.o is incompatible with >> > > elf_x86_64 >> > > arch/x86/realmode/rm/Makefile:55: recipe for target >> > > 'arch/x86/realmode/rm/realmode.elf' failed >> > > ``` >> > > Tested-by: Nick Desaulniers <ndesaulni...@google.com> >> > > >> > > Looks like we still have a few other (unrelated) issues to track down >> > > with LLD, but this gets us one step closer. >> > > >> > > Thanks for sending this, Tri! >> > >> > Just some additional thoughts on this: >> > >> > The kernel is adding -m elf_x86_64 to the linker command line >> > parameters, but then relying on binutils tie-breaking-behavior by >> > specifying a different architecture via linker script. So it's >> > ambiguous which arch the kernel is trying to link for, and the kernel >> > gets lucky/relies on the way ld.bfd happens to resolve this ambiguity >> > without warning. An alternative fix may be to just filter out/remove >> > the -m elf_x86_64 for this target's linker flags. >> > >> > > >> > > > --- >> > > > 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 >> > > > -- >> > > > 2.20.0.rc2.403.gdbc3b29805-goog >> > > > >> > > >> > > >> > > -- >> > > Thanks, >> > > ~Nick Desaulniers >> > >> > >> > >> > -- >> > Thanks, >> > ~Nick Desaulniers
