Re: [uml-devel] [PATCH] Fix UML build on i386 Ubuntu Dapper

[Nishanth Aravamudan <nacc@us.ibm.com>]

On 27.06.2006 [16:56:13 +0200], Blaisorblade wrote:
> On Tuesday 27 June 2006 00:02, Nishanth Aravamudan wrote:
> > Hi Jeff,
> >
> > I run an x86_64 kernel with i386 userspace (Ubuntu Dapper) and decided
> > to try out UML today. I found that UML wasn't quite aware of biarch
> > compilers (which Ubuntu i386 ships). A fix similar to what was done for
> > x86_64 should probably be committed (see
> > http://marc.theaimsgroup.com/?l=linux-kernel&m=113425940204010&w=2).
> 
> Ok, it seemed strange but I understand the stuff... that's very
> interesting as this is the setup I'd wished to have since ages. I'll
> switch to it ASAP...

Indeed :)

> > Without the FLAGS changes, the build will fail at a number of places and
> > without the LINK change, the final link will fail.
> >
> > Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
> 
> The first hunk (#undef i386) should be unnecessary given you specify
> -m64 (add it to CPPFLAGS too). Also it can/could be problematic for
> i386 kernels.  However, if UML builds and runs on already supported
> configurations, the patch is almost ok - but the original comment must
> be added for the #undef: /* in case the preprocessor is a 32bit one */

Ah yes, sorry, I'll add the comment. I found if I did not add the
#undef, I got a broken build (the "1:x86_64" issue in the above thread,
when it should be "i386:x86_64"):

  LD      .tmp_vmlinux1
/usr/bin/ld:arch/um/kernel/vmlinux.lds:251: syntax error
collect2: ld returned 1 exit status
  KSYM    .tmp_kallsyms1.S
nm: '.tmp_vmlinux1': No such file
No valid symbol.

After discovering SUBARCH, I rebuilt my tree as an i386 UML and it
successfully completed with this patch. If someone could test a native
i386 build as well, just to be sure?

Updated patch follows.

I run an x86_64 kernel with i386 userspace (Ubuntu Dapper) and decided
to try out UML today. I found that UML wasn't quite aware of biarch
compilers (which Ubuntu i386 ships). A fix similar to what was done for
x86_64 should probably be committed (see
http://marc.theaimsgroup.com/?l=linux-kernel&m=113425940204010&w=2).
Without the FLAGS changes, the build will fail at a number of places and
without the LINK change, the final link will fail. Compile- and
boot-tested with SUBARCH=x86_64 (native) and compile-tested and
boot-tested with SUBARCH=i386.

Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>

diff -urpN 2.6.17/arch/um/kernel/vmlinux.lds.S 2.6.17-dev/arch/um/kernel/vmlinux.lds.S
--- 2.6.17/arch/um/kernel/vmlinux.lds.S	2006-06-17 18:49:35.000000000 -0700
+++ 2.6.17-dev/arch/um/kernel/vmlinux.lds.S	2006-06-27 08:03:43.000000000 -0700
@@ -1,4 +1,6 @@
 #include <linux/config.h>
+/* in case the preprocessor is a 32bit one */
+#undef i386
 #ifdef CONFIG_LD_SCRIPT_STATIC
 #include "uml.lds.S"
 #else
diff -urpN 2.6.17/arch/um/Makefile-x86_64 2.6.17-dev/arch/um/Makefile-x86_64
--- 2.6.17/arch/um/Makefile-x86_64	2006-06-17 18:49:35.000000000 -0700
+++ 2.6.17-dev/arch/um/Makefile-x86_64	2006-06-26 14:49:01.000000000 -0700
@@ -6,9 +6,11 @@ START := 0x60000000
 
 #We #undef __x86_64__ for kernelspace, not for userspace where
 #it's needed for headers to work!
-CFLAGS += -U__$(SUBARCH)__ -fno-builtin
-USER_CFLAGS += -fno-builtin
+CFLAGS += -U__$(SUBARCH)__ -fno-builtin -m64
+USER_CFLAGS += -fno-builtin -m64
 CHECKFLAGS  += -m64
+AFLAGS += -m64
+LDFLAGS += -m elf_x86_64
 
 ELF_ARCH := i386:x86-64
 ELF_FORMAT := elf64-x86-64
@@ -16,3 +18,4 @@ ELF_FORMAT := elf64-x86-64
 # Not on all 64-bit distros /lib is a symlink to /lib64. PLD is an example.
 
 LINK-$(CONFIG_LD_SCRIPT_DYN) += -Wl,-rpath,/lib64
+LINK-y += -m64

-- 
Nishanth Aravamudan <nacc@us.ibm.com>
IBM Linux Technology Center

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