* [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS
@ 2020-03-26 19:30 H.J. Lu
2020-03-26 19:30 ` [PATCH 2/2] Discard .note.gnu.property sections in generic NOTES H.J. Lu
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: H.J. Lu @ 2020-03-26 19:30 UTC (permalink / raw)
To: linux-kernel
Cc: Andy Lutomirski, Thomas Gleixner, Kees Cook, Thomas Lendacky,
Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov,
H . Peter Anvin, x86, Arnd Bergmann, linux-arch, Yu-cheng Yu
In x86 kernel, .exit.text and .exit.data sections are discarded at
runtime, not by linker. Add RUNTIME_DISCARD_EXIT to generic DISCARDS
and define it in x86 kernel linker script to keep them.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
arch/x86/kernel/vmlinux.lds.S | 1 +
include/asm-generic/vmlinux.lds.h | 10 ++++++++--
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index e3296aa028fe..7206e1ac23dd 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -21,6 +21,7 @@
#define LOAD_OFFSET __START_KERNEL_map
#endif
+#define RUNTIME_DISCARD_EXIT
#define EMITS_PT_NOTE
#define RO_EXCEPTION_TABLE_ALIGN 16
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index e00f41aa8ec4..6b943fb8c5fd 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -894,10 +894,16 @@
* section definitions so that such archs put those in earlier section
* definitions.
*/
+#ifdef RUNTIME_DISCARD_EXIT
+#define EXIT_DISCARDS
+#else
+#define EXIT_DISCARDS \
+ EXIT_TEXT \
+ EXIT_DATA
+#endif
#define DISCARDS \
/DISCARD/ : { \
- EXIT_TEXT \
- EXIT_DATA \
+ EXIT_DISCARDS \
EXIT_CALL \
*(.discard) \
*(.discard.*) \
--
2.25.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH 2/2] Discard .note.gnu.property sections in generic NOTES
2020-03-26 19:30 [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS H.J. Lu
@ 2020-03-26 19:30 ` H.J. Lu
2020-03-26 20:11 ` [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS Borislav Petkov
2020-03-27 11:07 ` [tip: x86/build] x86, vmlinux.lds: " tip-bot2 for H.J. Lu
2 siblings, 0 replies; 6+ messages in thread
From: H.J. Lu @ 2020-03-26 19:30 UTC (permalink / raw)
To: linux-kernel
Cc: Andy Lutomirski, Thomas Gleixner, Kees Cook, Thomas Lendacky,
Sami Tolvanen, Heiko Carstens, Ingo Molnar, Borislav Petkov,
H . Peter Anvin, x86, Arnd Bergmann, linux-arch, Yu-cheng Yu
With the command-line option, -mx86-used-note=yes, the x86 assembler
in binutils 2.32 and above generates a program property note in a note
section, .note.gnu.property, to encode used x86 ISAs and features. But
kernel linker script only contains a single NOTE segment:
PHDRS {
text PT_LOAD FLAGS(5);
data PT_LOAD FLAGS(6);
percpu PT_LOAD FLAGS(6);
init PT_LOAD FLAGS(7);
note PT_NOTE FLAGS(0);
}
SECTIONS
{
...
.notes : AT(ADDR(.notes) - 0xffffffff80000000) { __start_notes = .; KEEP(*(.not
e.*)) __stop_notes = .; } :text :note
...
}
The NOTE segment generated by kernel linker script is aligned to 4 bytes.
But .note.gnu.property section must be aligned to 8 bytes on x86-64 and
we get
[hjl@gnu-skx-1 linux]$ readelf -n vmlinux
Displaying notes found in: .notes
Owner Data size Description
Xen 0x00000006 Unknown note type: (0x00000006)
description data: 6c 69 6e 75 78 00
Xen 0x00000004 Unknown note type: (0x00000007)
description data: 32 2e 36 00
xen-3.0 0x00000005 Unknown note type: (0x006e6558)
description data: 08 00 00 00 03
readelf: Warning: note with invalid namesz and/or descsz found at offset 0x50
readelf: Warning: type: 0xffffffff, namesize: 0x006e6558, descsize:
0x80000000, alignment: 8
[hjl@gnu-skx-1 linux]$
Since note.gnu.property section in kernel image is never used, this patch
discards .note.gnu.property sections in kernel linker script by adding
/DISCARD/ : {
*(.note.gnu.property)
}
before kernel NOTE segment in generic NOTES.
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
---
include/asm-generic/vmlinux.lds.h | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index 6b943fb8c5fd..6659a7c07c84 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -818,7 +818,14 @@
#define TRACEDATA
#endif
+/*
+ * Discard .note.gnu.property sections which are unused and have
+ * different alignment requirement from kernel note sections.
+ */
#define NOTES \
+ /DISCARD/ : { \
+ *(.note.gnu.property) \
+ } \
.notes : AT(ADDR(.notes) - LOAD_OFFSET) { \
__start_notes = .; \
KEEP(*(.note.*)) \
--
2.25.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS
2020-03-26 19:30 [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS H.J. Lu
2020-03-26 19:30 ` [PATCH 2/2] Discard .note.gnu.property sections in generic NOTES H.J. Lu
@ 2020-03-26 20:11 ` Borislav Petkov
2020-03-26 20:39 ` Kees Cook
2020-03-27 11:07 ` [tip: x86/build] x86, vmlinux.lds: " tip-bot2 for H.J. Lu
2 siblings, 1 reply; 6+ messages in thread
From: Borislav Petkov @ 2020-03-26 20:11 UTC (permalink / raw)
To: Kees Cook
Cc: H.J. Lu, linux-kernel, Andy Lutomirski, Thomas Gleixner,
Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar,
H . Peter Anvin, x86, Arnd Bergmann, linux-arch, Yu-cheng Yu
On Thu, Mar 26, 2020 at 12:30:20PM -0700, H.J. Lu wrote:
> In x86 kernel, .exit.text and .exit.data sections are discarded at
> runtime, not by linker. Add RUNTIME_DISCARD_EXIT to generic DISCARDS
> and define it in x86 kernel linker script to keep them.
>
> Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> ---
> arch/x86/kernel/vmlinux.lds.S | 1 +
> include/asm-generic/vmlinux.lds.h | 10 ++++++++--
> 2 files changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
> index e3296aa028fe..7206e1ac23dd 100644
> --- a/arch/x86/kernel/vmlinux.lds.S
> +++ b/arch/x86/kernel/vmlinux.lds.S
> @@ -21,6 +21,7 @@
> #define LOAD_OFFSET __START_KERNEL_map
> #endif
>
> +#define RUNTIME_DISCARD_EXIT
> #define EMITS_PT_NOTE
> #define RO_EXCEPTION_TABLE_ALIGN 16
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index e00f41aa8ec4..6b943fb8c5fd 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -894,10 +894,16 @@
> * section definitions so that such archs put those in earlier section
> * definitions.
> */
> +#ifdef RUNTIME_DISCARD_EXIT
> +#define EXIT_DISCARDS
> +#else
> +#define EXIT_DISCARDS \
> + EXIT_TEXT \
> + EXIT_DATA
> +#endif
/me goes back and reads the old thread on this...
Kees, do you expect other arches to actually need this
RUNTIME_DISCARD_EXIT thing or was that a hypothetical thing?
/me searches more...
oh, there's a patchset from you
https://lkml.kernel.org/r/20200228002244.15240-1-keescook@chromium.org
which already contains this patch *and* an ARM64 patch which defines
RUNTIME_DISCARD_EXIT so I'm guessing ARM64 wants to discard at runtime
too.
Which leaves the question why is H.J. sending that patch separate and
you carry it in a patchset about orphan section warning? Seems like it
wants to be in your patchset?
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS
2020-03-26 20:11 ` [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS Borislav Petkov
@ 2020-03-26 20:39 ` Kees Cook
0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2020-03-26 20:39 UTC (permalink / raw)
To: Borislav Petkov
Cc: H.J. Lu, linux-kernel, Andy Lutomirski, Thomas Gleixner,
Thomas Lendacky, Sami Tolvanen, Heiko Carstens, Ingo Molnar,
H . Peter Anvin, x86, Arnd Bergmann, linux-arch, Yu-cheng Yu
On Thu, Mar 26, 2020 at 09:11:42PM +0100, Borislav Petkov wrote:
> On Thu, Mar 26, 2020 at 12:30:20PM -0700, H.J. Lu wrote:
> > In x86 kernel, .exit.text and .exit.data sections are discarded at
> > runtime, not by linker. Add RUNTIME_DISCARD_EXIT to generic DISCARDS
> > and define it in x86 kernel linker script to keep them.
> >
> > Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> > ---
> > arch/x86/kernel/vmlinux.lds.S | 1 +
> > include/asm-generic/vmlinux.lds.h | 10 ++++++++--
> > 2 files changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
> > index e3296aa028fe..7206e1ac23dd 100644
> > --- a/arch/x86/kernel/vmlinux.lds.S
> > +++ b/arch/x86/kernel/vmlinux.lds.S
> > @@ -21,6 +21,7 @@
> > #define LOAD_OFFSET __START_KERNEL_map
> > #endif
> >
> > +#define RUNTIME_DISCARD_EXIT
> > #define EMITS_PT_NOTE
> > #define RO_EXCEPTION_TABLE_ALIGN 16
> >
> > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> > index e00f41aa8ec4..6b943fb8c5fd 100644
> > --- a/include/asm-generic/vmlinux.lds.h
> > +++ b/include/asm-generic/vmlinux.lds.h
> > @@ -894,10 +894,16 @@
> > * section definitions so that such archs put those in earlier section
> > * definitions.
> > */
> > +#ifdef RUNTIME_DISCARD_EXIT
> > +#define EXIT_DISCARDS
> > +#else
> > +#define EXIT_DISCARDS \
> > + EXIT_TEXT \
> > + EXIT_DATA
> > +#endif
>
> /me goes back and reads the old thread on this...
>
> Kees, do you expect other arches to actually need this
> RUNTIME_DISCARD_EXIT thing or was that a hypothetical thing?
>
> /me searches more...
>
> oh, there's a patchset from you
>
> https://lkml.kernel.org/r/20200228002244.15240-1-keescook@chromium.org
>
> which already contains this patch *and* an ARM64 patch which defines
> RUNTIME_DISCARD_EXIT so I'm guessing ARM64 wants to discard at runtime
> too.
Correct.
> Which leaves the question why is H.J. sending that patch separate and
> you carry it in a patchset about orphan section warning? Seems like it
> wants to be in your patchset?
I had needed the same clean up for the orphan section handling, and
since it hadn't been picked up yet, I included it in my series. I'm
still stuck addressing several review comments, so there's no reason to
wait for me: I can easily rebase once these patches land somewhere. I'd
be happy to see them in -tip.
Thanks!
-Kees
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread
* [tip: x86/build] x86, vmlinux.lds: Add RUNTIME_DISCARD_EXIT to generic DISCARDS
2020-03-26 19:30 [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS H.J. Lu
2020-03-26 19:30 ` [PATCH 2/2] Discard .note.gnu.property sections in generic NOTES H.J. Lu
2020-03-26 20:11 ` [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS Borislav Petkov
@ 2020-03-27 11:07 ` tip-bot2 for H.J. Lu
2020-03-27 17:43 ` Kees Cook
2 siblings, 1 reply; 6+ messages in thread
From: tip-bot2 for H.J. Lu @ 2020-03-27 11:07 UTC (permalink / raw)
To: linux-tip-commits; +Cc: H.J. Lu, Borislav Petkov, Kees Cook, x86, LKML
The following commit has been merged into the x86/build branch of tip:
Commit-ID: 84d5f77fc2ee4e010c2c037750e32f06e55224b0
Gitweb: https://git.kernel.org/tip/84d5f77fc2ee4e010c2c037750e32f06e55224b0
Author: H.J. Lu <hjl.tools@gmail.com>
AuthorDate: Thu, 26 Mar 2020 12:30:20 -07:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Fri, 27 Mar 2020 11:52:11 +01:00
x86, vmlinux.lds: Add RUNTIME_DISCARD_EXIT to generic DISCARDS
In the x86 kernel, .exit.text and .exit.data sections are discarded at
runtime, not by the linker. Add RUNTIME_DISCARD_EXIT to generic DISCARDS
and define it in the x86 kernel linker script to keep them.
The sections are added before the DISCARD directive so document here
only the situation explicitly as this change doesn't have any effect on
the generated kernel. Also, other architectures like ARM64 will use it
too so generalize the approach with the RUNTIME_DISCARD_EXIT define.
[ bp: Massage and extend commit message. ]
Signed-off-by: H.J. Lu <hjl.tools@gmail.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20200326193021.255002-1-hjl.tools@gmail.com
---
arch/x86/kernel/vmlinux.lds.S | 1 +
include/asm-generic/vmlinux.lds.h | 11 +++++++++--
2 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index e3296aa..7206e1a 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -21,6 +21,7 @@
#define LOAD_OFFSET __START_KERNEL_map
#endif
+#define RUNTIME_DISCARD_EXIT
#define EMITS_PT_NOTE
#define RO_EXCEPTION_TABLE_ALIGN 16
diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index e00f41a..2444336 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -894,10 +894,17 @@
* section definitions so that such archs put those in earlier section
* definitions.
*/
+#ifdef RUNTIME_DISCARD_EXIT
+#define EXIT_DISCARDS
+#else
+#define EXIT_DISCARDS \
+ EXIT_TEXT \
+ EXIT_DATA
+#endif
+
#define DISCARDS \
/DISCARD/ : { \
- EXIT_TEXT \
- EXIT_DATA \
+ EXIT_DISCARDS \
EXIT_CALL \
*(.discard) \
*(.discard.*) \
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [tip: x86/build] x86, vmlinux.lds: Add RUNTIME_DISCARD_EXIT to generic DISCARDS
2020-03-27 11:07 ` [tip: x86/build] x86, vmlinux.lds: " tip-bot2 for H.J. Lu
@ 2020-03-27 17:43 ` Kees Cook
0 siblings, 0 replies; 6+ messages in thread
From: Kees Cook @ 2020-03-27 17:43 UTC (permalink / raw)
To: linux-kernel; +Cc: linux-tip-commits, H.J. Lu, Borislav Petkov, x86
On Fri, Mar 27, 2020 at 11:07:55AM -0000, tip-bot2 for H.J. Lu wrote:
> The following commit has been merged into the x86/build branch of tip:
> [...]
> x86, vmlinux.lds: Add RUNTIME_DISCARD_EXIT to generic DISCARDS
Thanks! And just for note, I'll likely wait for -rc2 to resend the
orphan series -- I now depend on _three_ trees. ;) x86/boot, x86/build,
and arm. Heh
--
Kees Cook
^ permalink raw reply [flat|nested] 6+ messages in thread
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2020-03-26 19:30 [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS H.J. Lu
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2020-03-26 20:11 ` [PATCH 1/2] Add RUNTIME_DISCARD_EXIT to generic DISCARDS Borislav Petkov
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