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 <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
---
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
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 <[email protected]>
> Reviewed-by: Kees Cook <[email protected]>
> ---
> 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/[email protected]
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
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 <[email protected]>
> > Reviewed-by: Kees Cook <[email protected]>
> > ---
> > 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/[email protected]
>
> 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
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 <[email protected]>
AuthorDate: Thu, 26 Mar 2020 12:30:20 -07:00
Committer: Borislav Petkov <[email protected]>
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 <[email protected]>
Signed-off-by: Borislav Petkov <[email protected]>
Reviewed-by: Kees Cook <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
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.*) \
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