From: Paolo Bonzini <pbonzini@redhat.com>
To: Roman Bolshakov <r.bolshakov@yadro.com>, Thomas Huth <thuth@redhat.com>
Cc: kvm@vger.kernel.org
Subject: Re: [kvm-unit-tests PATCH v2 10/10] travis.yml: Add x86 build with clang 10
Date: Tue, 22 Sep 2020 16:51:18 +0200 [thread overview]
Message-ID: <788b7191-6987-9399-f352-2e661255157e@redhat.com> (raw)
In-Reply-To: <20200915155959.GF52559@SPB-NB-133.local>
On 15/09/20 17:59, Roman Bolshakov wrote:
> So, a workaround for that could be adding '-Wl,--build-id=none' to the
> makefile rule for realmode.elf. Then multiboot magic is placed properly
> at 0x4000 instead of 0x4030. Unfortunately it doesn't help with the
> test :-)
Heh, weird. I also tried adding
/DISCARD/ : { *(.note.gnu.build-id) }
to the linker script and I got a very helpful (not) linker warning:
/usr/bin/ld: warning: .note.gnu.build-id section discarded, --build-id ignored.
... except that the --build-id was placed not by me but rather by gcc.
So we should probably simplify things doing this:
diff --git a/x86/Makefile.common b/x86/Makefile.common
index 090ce22..10c8a42 100644
--- a/x86/Makefile.common
+++ b/x86/Makefile.common
@@ -69,8 +69,8 @@ test_cases: $(tests-common) $(tests)
$(TEST_DIR)/%.o: CFLAGS += -std=gnu99 -ffreestanding -I $(SRCDIR)/lib -I $(SRCDIR)/lib/x86 -I lib
$(TEST_DIR)/realmode.elf: $(TEST_DIR)/realmode.o
- $(CC) -m32 -nostdlib -o $@ -Wl,-m,elf_i386 \
- -Wl,-T,$(SRCDIR)/$(TEST_DIR)/realmode.lds $^
+ $(LD) -o $@ -m elf_i386 \
+ -T $(SRCDIR)/$(TEST_DIR)/realmode.lds $^
$(TEST_DIR)/realmode.o: bits = 32
diff --git a/x86/realmode.lds b/x86/realmode.lds
index 0ed3063..3220c19 100644
--- a/x86/realmode.lds
+++ b/x86/realmode.lds
@@ -1,5 +1,6 @@
SECTIONS
{
+ /DISCARD/ : { *(.note.gnu.build-id) }
. = 16K;
stext = .;
.text : { *(.init) *(.text) }
which I will squash in your patch 3.
But the main issue is that clang does not support .code16gcc so it
writes 32-bit code that is run in 16-bit mode. It'd be a start to
use -m16 instead of -m32, but then I think it still miscompiles the
(32-bit) code between "start" and the .code16gcc label.
Paolo
next prev parent reply other threads:[~2020-09-22 14:51 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-01 8:50 [kvm-unit-tests PATCH v2 00/10] Add support for generic ELF cross-compiler Roman Bolshakov
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 01/10] x86: Makefile: Allow division on x86_64-elf binutils Roman Bolshakov
2020-09-03 15:19 ` Thomas Huth
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 02/10] x86: Replace instruction prefixes with spaces Roman Bolshakov
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 03/10] x86: Makefile: Fix linkage of realmode on x86_64-elf binutils Roman Bolshakov
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 04/10] lib: Bundle debugreg.h from the kernel Roman Bolshakov
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 05/10] lib: x86: Use portable format macros for uint32_t Roman Bolshakov
2020-09-04 13:47 ` Thomas Huth
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 06/10] configure: Add an option to specify getopt Roman Bolshakov
2020-09-04 13:50 ` Thomas Huth
2020-09-22 13:53 ` Paolo Bonzini
2020-09-22 21:51 ` Roman Bolshakov
2020-09-23 2:41 ` Paolo Bonzini
2020-09-23 5:14 ` Thomas Huth
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 07/10] README: Update build instructions for macOS Roman Bolshakov
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 08/10] travis.yml: Add CI " Roman Bolshakov
2020-09-04 13:53 ` Thomas Huth
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 09/10] travis.yml: Change matrix keyword to jobs Roman Bolshakov
2020-09-04 14:20 ` Thomas Huth
2020-09-01 8:50 ` [kvm-unit-tests PATCH v2 10/10] travis.yml: Add x86 build with clang 10 Roman Bolshakov
2020-09-04 14:31 ` Thomas Huth
2020-09-14 14:45 ` Roman Bolshakov
2020-09-14 16:37 ` Thomas Huth
2020-09-15 15:59 ` Roman Bolshakov
2020-09-22 14:51 ` Paolo Bonzini [this message]
2020-09-22 21:25 ` Roman Bolshakov
2020-09-23 2:37 ` Paolo Bonzini
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