For vmlinux linking, no architecture uses the .gnu.version* section,
so remove it via the common DISCARDS macro in preparation for adding
--orphan-handling=warn more widely.
Signed-off-by: Kees Cook <[email protected]>
---
include/asm-generic/vmlinux.lds.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index db600ef218d7..6fbe9ed10cdb 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -934,6 +934,7 @@
*(.discard) \
*(.discard.*) \
*(.modinfo) \
+ *(.gnu.version*) \
}
/**
--
2.25.1
On 2020-06-22, Kees Cook wrote:
>For vmlinux linking, no architecture uses the .gnu.version* section,
>so remove it via the common DISCARDS macro in preparation for adding
>--orphan-handling=warn more widely.
>
>Signed-off-by: Kees Cook <[email protected]>
>---
> include/asm-generic/vmlinux.lds.h | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
>index db600ef218d7..6fbe9ed10cdb 100644
>--- a/include/asm-generic/vmlinux.lds.h
>+++ b/include/asm-generic/vmlinux.lds.h
>@@ -934,6 +934,7 @@
> *(.discard) \
> *(.discard.*) \
> *(.modinfo) \
>+ *(.gnu.version*) \
> }
>
> /**
>--
>2.25.1
I wonder what lead to .gnu.version{,_d,_r} sections in the kernel.
tools/lib/bpf/libbpf_internal.h uses `.symver` directive and
-Wl,--version-script, which may lead to .gnu.version{,_d}, but this only
applies to the userspace libbpf.so
libperf.so has a similar -Wl,--version-script.
Linking vmlinux does not appear to use any symbol versioning.
On Mon, Jun 22, 2020 at 03:00:43PM -0700, Fangrui Song wrote:
> On 2020-06-22, Kees Cook wrote:
> > For vmlinux linking, no architecture uses the .gnu.version* section,
> > so remove it via the common DISCARDS macro in preparation for adding
> > --orphan-handling=warn more widely.
> >
> > Signed-off-by: Kees Cook <[email protected]>
> > ---
> > include/asm-generic/vmlinux.lds.h | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> > index db600ef218d7..6fbe9ed10cdb 100644
> > --- a/include/asm-generic/vmlinux.lds.h
> > +++ b/include/asm-generic/vmlinux.lds.h
> > @@ -934,6 +934,7 @@
> > *(.discard) \
> > *(.discard.*) \
> > *(.modinfo) \
> > + *(.gnu.version*) \
> > }
> >
> > /**
> > --
> > 2.25.1
>
> I wonder what lead to .gnu.version{,_d,_r} sections in the kernel.
This looks like a bug in bfd.ld? There are no versioned symbols in any
of the input files (and no output section either!)
The link command is:
$ ld -m elf_x86_64 --no-ld-generated-unwind-info -z noreloc-overflow -pie \
--no-dynamic-linker --orphan-handling=warn -T \
arch/x86/boot/compressed/vmlinux.lds \
arch/x86/boot/compressed/kernel_info.o \
arch/x86/boot/compressed/head_64.o arch/x86/boot/compressed/misc.o \
arch/x86/boot/compressed/string.o arch/x86/boot/compressed/cmdline.o \
arch/x86/boot/compressed/error.o arch/x86/boot/compressed/piggy.o \
arch/x86/boot/compressed/cpuflags.o \
arch/x86/boot/compressed/early_serial_console.o \
arch/x86/boot/compressed/kaslr.o arch/x86/boot/compressed/kaslr_64.o \
arch/x86/boot/compressed/mem_encrypt.o \
arch/x86/boot/compressed/pgtable_64.o arch/x86/boot/compressed/acpi.o \
-o arch/x86/boot/compressed/vmlinux
None of the inputs have the section:
$ for i in arch/x86/boot/compressed/kernel_info.o \
arch/x86/boot/compressed/head_64.o arch/x86/boot/compressed/misc.o \
arch/x86/boot/compressed/string.o arch/x86/boot/compressed/cmdline.o \
arch/x86/boot/compressed/error.o arch/x86/boot/compressed/piggy.o \
arch/x86/boot/compressed/cpuflags.o \
arch/x86/boot/compressed/early_serial_console.o \
arch/x86/boot/compressed/kaslr.o arch/x86/boot/compressed/kaslr_64.o \
arch/x86/boot/compressed/mem_encrypt.o \
arch/x86/boot/compressed/pgtable_64.o arch/x86/boot/compressed/acpi.o \
; do echo -n $i": "; readelf -Vs $i | grep 'version'; done
arch/x86/boot/compressed/kernel_info.o: No version information found in this file.
arch/x86/boot/compressed/head_64.o: No version information found in this file.
arch/x86/boot/compressed/misc.o: No version information found in this file.
arch/x86/boot/compressed/string.o: No version information found in this file.
arch/x86/boot/compressed/cmdline.o: No version information found in this file.
arch/x86/boot/compressed/error.o: No version information found in this file.
arch/x86/boot/compressed/piggy.o: No version information found in this file.
arch/x86/boot/compressed/cpuflags.o: No version information found in this file.
arch/x86/boot/compressed/early_serial_console.o: No version information found in this file.
arch/x86/boot/compressed/kaslr.o: No version information found in this file.
arch/x86/boot/compressed/kaslr_64.o: No version information found in this file.
arch/x86/boot/compressed/mem_encrypt.o: No version information found in this file.
arch/x86/boot/compressed/pgtable_64.o: No version information found in this file.
arch/x86/boot/compressed/acpi.o: No version information found in this file.
And it's not in the output:
$ readelf -Vs arch/x86/boot/compressed/vmlinux | grep version
No version information found in this file.
So... for the kernel we need to silence it right now.
--
Kees Cook
On Mon, Jun 22, 2020 at 3:57 PM Kees Cook <[email protected]> wrote:
>
> On Mon, Jun 22, 2020 at 03:52:37PM -0700, Fangrui Song wrote:
> > > And it's not in the output:
> > >
> > > $ readelf -Vs arch/x86/boot/compressed/vmlinux | grep version
> > > No version information found in this file.
> > >
> > > So... for the kernel we need to silence it right now.
> >
> > Re-link with -M (or -Map file) to check where .gnu.version{,_d,_r} input
> > sections come from?
>
> It's not reporting it correctly:
>
> .gnu.version_d 0x00000000008966b0 0x0
> .gnu.version_d
> 0x00000000008966b0 0x0 arch/x86/boot/compressed/kernel_info.o
>
> .gnu.version 0x00000000008966b0 0x0
> .gnu.version 0x00000000008966b0 0x0 arch/x86/boot/compressed/kernel_info.o
>
> .gnu.version_r 0x00000000008966b0 0x0
> .gnu.version_r
> 0x00000000008966b0 0x0 arch/x86/boot/compressed/kernel_info.o
>
> it just reports whatever file is listed on the link command line first.
>
> > If it is a bug, we should probably figure out which version of binutils
> > has fixed the bug.
>
> I see this with binutils 2.34...
>
> --
> Kees Cook
:( It deserves a binutils bug
(https://sourceware.org/bugzilla/enter_bug.cgi?product=binutils ) and
a comment..
With the description adjusted to say that this works around a bug
Reviewed-by: Fangrui Song <[email protected]>
On Mon, Jun 22, 2020 at 03:00:43PM -0700, Fangrui Song wrote:
> On 2020-06-22, Kees Cook wrote:
> > For vmlinux linking, no architecture uses the .gnu.version* section,
> > so remove it via the common DISCARDS macro in preparation for adding
> > --orphan-handling=warn more widely.
> >
> > Signed-off-by: Kees Cook <[email protected]>
> > ---
> > include/asm-generic/vmlinux.lds.h | 1 +
> > 1 file changed, 1 insertion(+)
> >
> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> > index db600ef218d7..6fbe9ed10cdb 100644
> > --- a/include/asm-generic/vmlinux.lds.h
> > +++ b/include/asm-generic/vmlinux.lds.h
> > @@ -934,6 +934,7 @@
> > *(.discard) \
> > *(.discard.*) \
> > *(.modinfo) \
> > + *(.gnu.version*) \
> > }
> >
> > /**
> > --
> > 2.25.1
>
> I wonder what lead to .gnu.version{,_d,_r} sections in the kernel.
Here's where I see it:
ld: warning: orphan section `.gnu.version_d' from `arch/x86/boot/compressed/kernel_info.o' being placed in section `.gnu.version_d'
--
Kees Cook
On 2020-06-22, Kees Cook wrote:
>On Mon, Jun 22, 2020 at 03:00:43PM -0700, Fangrui Song wrote:
>> On 2020-06-22, Kees Cook wrote:
>> > For vmlinux linking, no architecture uses the .gnu.version* section,
>> > so remove it via the common DISCARDS macro in preparation for adding
>> > --orphan-handling=warn more widely.
>> >
>> > Signed-off-by: Kees Cook <[email protected]>
>> > ---
>> > include/asm-generic/vmlinux.lds.h | 1 +
>> > 1 file changed, 1 insertion(+)
>> >
>> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
>> > index db600ef218d7..6fbe9ed10cdb 100644
>> > --- a/include/asm-generic/vmlinux.lds.h
>> > +++ b/include/asm-generic/vmlinux.lds.h
>> > @@ -934,6 +934,7 @@
>> > *(.discard) \
>> > *(.discard.*) \
>> > *(.modinfo) \
>> > + *(.gnu.version*) \
>> > }
>> >
>> > /**
>> > --
>> > 2.25.1
>>
>> I wonder what lead to .gnu.version{,_d,_r} sections in the kernel.
>
>This looks like a bug in bfd.ld? There are no versioned symbols in any
>of the input files (and no output section either!)
>
>The link command is:
>$ ld -m elf_x86_64 --no-ld-generated-unwind-info -z noreloc-overflow -pie \
>--no-dynamic-linker --orphan-handling=warn -T \
>arch/x86/boot/compressed/vmlinux.lds \
>arch/x86/boot/compressed/kernel_info.o \
>arch/x86/boot/compressed/head_64.o arch/x86/boot/compressed/misc.o \
>arch/x86/boot/compressed/string.o arch/x86/boot/compressed/cmdline.o \
>arch/x86/boot/compressed/error.o arch/x86/boot/compressed/piggy.o \
>arch/x86/boot/compressed/cpuflags.o \
>arch/x86/boot/compressed/early_serial_console.o \
>arch/x86/boot/compressed/kaslr.o arch/x86/boot/compressed/kaslr_64.o \
>arch/x86/boot/compressed/mem_encrypt.o \
>arch/x86/boot/compressed/pgtable_64.o arch/x86/boot/compressed/acpi.o \
>-o arch/x86/boot/compressed/vmlinux
>
>None of the inputs have the section:
>
>$ for i in arch/x86/boot/compressed/kernel_info.o \
>arch/x86/boot/compressed/head_64.o arch/x86/boot/compressed/misc.o \
>arch/x86/boot/compressed/string.o arch/x86/boot/compressed/cmdline.o \
>arch/x86/boot/compressed/error.o arch/x86/boot/compressed/piggy.o \
>arch/x86/boot/compressed/cpuflags.o \
>arch/x86/boot/compressed/early_serial_console.o \
>arch/x86/boot/compressed/kaslr.o arch/x86/boot/compressed/kaslr_64.o \
>arch/x86/boot/compressed/mem_encrypt.o \
>arch/x86/boot/compressed/pgtable_64.o arch/x86/boot/compressed/acpi.o \
>; do echo -n $i": "; readelf -Vs $i | grep 'version'; done
>arch/x86/boot/compressed/kernel_info.o: No version information found in this file.
>arch/x86/boot/compressed/head_64.o: No version information found in this file.
>arch/x86/boot/compressed/misc.o: No version information found in this file.
>arch/x86/boot/compressed/string.o: No version information found in this file.
>arch/x86/boot/compressed/cmdline.o: No version information found in this file.
>arch/x86/boot/compressed/error.o: No version information found in this file.
>arch/x86/boot/compressed/piggy.o: No version information found in this file.
>arch/x86/boot/compressed/cpuflags.o: No version information found in this file.
>arch/x86/boot/compressed/early_serial_console.o: No version information found in this file.
>arch/x86/boot/compressed/kaslr.o: No version information found in this file.
>arch/x86/boot/compressed/kaslr_64.o: No version information found in this file.
>arch/x86/boot/compressed/mem_encrypt.o: No version information found in this file.
>arch/x86/boot/compressed/pgtable_64.o: No version information found in this file.
>arch/x86/boot/compressed/acpi.o: No version information found in this file.
>
>And it's not in the output:
>
>$ readelf -Vs arch/x86/boot/compressed/vmlinux | grep version
>No version information found in this file.
>
>So... for the kernel we need to silence it right now.
Re-link with -M (or -Map file) to check where .gnu.version{,_d,_r} input
sections come from?
If it is a bug, we should probably figure out which version of binutils
has fixed the bug.
On Mon, Jun 22, 2020 at 03:52:37PM -0700, Fangrui Song wrote:
> > And it's not in the output:
> >
> > $ readelf -Vs arch/x86/boot/compressed/vmlinux | grep version
> > No version information found in this file.
> >
> > So... for the kernel we need to silence it right now.
>
> Re-link with -M (or -Map file) to check where .gnu.version{,_d,_r} input
> sections come from?
It's not reporting it correctly:
.gnu.version_d 0x00000000008966b0 0x0
.gnu.version_d
0x00000000008966b0 0x0 arch/x86/boot/compressed/kernel_info.o
.gnu.version 0x00000000008966b0 0x0
.gnu.version 0x00000000008966b0 0x0 arch/x86/boot/compressed/kernel_info.o
.gnu.version_r 0x00000000008966b0 0x0
.gnu.version_r
0x00000000008966b0 0x0 arch/x86/boot/compressed/kernel_info.o
it just reports whatever file is listed on the link command line first.
> If it is a bug, we should probably figure out which version of binutils
> has fixed the bug.
I see this with binutils 2.34...
--
Kees Cook
On Mon, Jun 22, 2020 at 04:04:40PM -0700, Fāng-ruì Sòng wrote:
> On Mon, Jun 22, 2020 at 3:57 PM Kees Cook <[email protected]> wrote:
> >
> > On Mon, Jun 22, 2020 at 03:52:37PM -0700, Fangrui Song wrote:
> > > > And it's not in the output:
> > > >
> > > > $ readelf -Vs arch/x86/boot/compressed/vmlinux | grep version
> > > > No version information found in this file.
> > > >
> > > > So... for the kernel we need to silence it right now.
> > >
> > > Re-link with -M (or -Map file) to check where .gnu.version{,_d,_r} input
> > > sections come from?
> >
> > It's not reporting it correctly:
> >
> > .gnu.version_d 0x00000000008966b0 0x0
> > .gnu.version_d
> > 0x00000000008966b0 0x0 arch/x86/boot/compressed/kernel_info.o
> >
> > .gnu.version 0x00000000008966b0 0x0
> > .gnu.version 0x00000000008966b0 0x0 arch/x86/boot/compressed/kernel_info.o
> >
> > .gnu.version_r 0x00000000008966b0 0x0
> > .gnu.version_r
> > 0x00000000008966b0 0x0 arch/x86/boot/compressed/kernel_info.o
> >
> > it just reports whatever file is listed on the link command line first.
> >
> > > If it is a bug, we should probably figure out which version of binutils
> > > has fixed the bug.
> >
> > I see this with binutils 2.34...
> >
> > --
> > Kees Cook
>
> :( It deserves a binutils bug
> (https://sourceware.org/bugzilla/enter_bug.cgi?product=binutils ) and
> a comment..
https://sourceware.org/bugzilla/show_bug.cgi?id=26153
> With the description adjusted to say that this works around a bug
>
> Reviewed-by: Fangrui Song <[email protected]>
Adjusted, and thanks!
--
Kees Cook