Linux Virtualization - Dec 2019 - [PATCH v10 00/11] x86: PIE support to extend KASLR randomization

Minor changes based on feedback and rebase from v9.

Splitting the previous serie in two. This part contains assembly code
changes required for PIE but without any direct dependencies with the
rest of the patchset.

Changes:
 - patch v10 (assembly):
   - Swap rax for rdx on entry/64 changes based on feedback.
   - Addressed feedback from Borislav Petkov on boot, paravirt, alternatives
     and globally.
   - Rebased the patchset and ensure it works with large kaslr (not included).
 - patch v9 (assembly):
   - Moved to relative reference for sync_core based on feedback.
   - x86/crypto had multiple algorithms deleted, removed PIE changes to them.
   - fix typo on comment end line.
 - patch v8 (assembly):
   - Fix issues in crypto changes (thanks to Eric Biggers).
   - Remove unnecessary jump table change.
   - Change author and signoff to chromium email address.
 - patch v7 (assembly):
   - Split patchset and reorder changes.
 - patch v6:
   - Rebase on latest changes in jump tables and crypto.
   - Fix wording on couple commits.
   - Revisit checkpatch warnings.
   - Moving to @chromium.org.
 - patch v5:
   - Adapt new crypto modules for PIE.
   - Improve per-cpu commit message.
   - Fix xen 32-bit build error with .quad.
   - Remove extra code for ftrace.
 - patch v4:
   - Simplify early boot by removing global variables.
   - Modify the mcount location script for __mcount_loc intead of the address
     read in the ftrace implementation.
   - Edit commit description to explain better where the kernel can be located.
   - Streamlined the testing done on each patch proposal. Always testing
     hibernation, suspend, ftrace and kprobe to ensure no regressions.
 - patch v3:
   - Update on message to describe longer term PIE goal.
   - Minor change on ftrace if condition.
   - Changed code using xchgq.
 - patch v2:
   - Adapt patch to work post KPTI and compiler changes
   - Redo all performance testing with latest configs and compilers
   - Simplify mov macro on PIE (MOVABS now)
   - Reduce GOT footprint
 - patch v1:
   - Simplify ftrace implementation.
   - Use gcc mstack-protector-guard-reg=%gs with PIE when possible.
 - rfc v3:
   - Use --emit-relocs instead of -pie to reduce dynamic relocation space on
     mapped memory. It also simplifies the relocation process.
   - Move the start the module section next to the kernel. Remove the need for
     -mcmodel=large on modules. Extends module space from 1 to 2G maximum.
   - Support for XEN PVH as 32-bit relocations can be ignored with
     --emit-relocs.
   - Support for GOT relocations previously done automatically with -pie.
   - Remove need for dynamic PLT in modules.
   - Support dymamic GOT for modules.
 - rfc v2:
   - Add support for global stack cookie while compiler default to fs without
     mcmodel=kernel
   - Change patch 7 to correctly jump out of the identity mapping on kexec load
     preserve.

These patches make some of the changes necessary to build the kernel as
Position Independent Executable (PIE) on x86_64. Another patchset will
add the PIE option and larger architecture changes. PIE allows the kernel to be
placed below the 0xffffffff80000000 increasing the range of KASLR.

The patches:
 - 1, 3-11: Change in assembly code to be PIE compliant.
 - 2: Add a new _ASM_MOVABS macro to fetch a symbol address generically.

diffstat:
 crypto/aegis128-aesni-asm.S         |    6 +-
 crypto/aesni-intel_asm.S            |    8 +--
 crypto/aesni-intel_avx-x86_64.S     |    3 -
 crypto/camellia-aesni-avx-asm_64.S  |   42 +++++++--------
 crypto/camellia-aesni-avx2-asm_64.S |   44 ++++++++--------
 crypto/camellia-x86_64-asm_64.S     |    8 +--
 crypto/cast5-avx-x86_64-asm_64.S    |   50 ++++++++++--------
 crypto/cast6-avx-x86_64-asm_64.S    |   44 +++++++++-------
 crypto/des3_ede-asm_64.S            |   96 ++++++++++++++++++++++++------------
 crypto/ghash-clmulni-intel_asm.S    |    4 -
 crypto/glue_helper-asm-avx.S        |    4 -
 crypto/glue_helper-asm-avx2.S       |    6 +-
 crypto/sha256-avx2-asm.S            |   18 ++++--
 entry/entry_64.S                    |   16 ++++--
 include/asm/alternative.h           |    6 +-
 include/asm/asm.h                   |    1 
 include/asm/paravirt_types.h        |   32 ++++++++++--
 include/asm/pm-trace.h              |    2 
 include/asm/processor.h             |    6 +-
 kernel/acpi/wakeup_64.S             |   31 ++++++-----
 kernel/head_64.S                    |   15 +++--
 kernel/relocate_kernel_64.S         |    2 
 power/hibernate_asm_64.S            |    4 -
 23 files changed, 267 insertions(+), 181 deletions(-)

Patchset is based on next-20191203.

If PIE is enabled, switch the paravirt assembly constraints to be
compatible. The %c/i constrains generate smaller code so is kept by
default.

Position Independent Executable (PIE) support will allow to extend the
KASLR randomization range below 0xffffffff80000000.

Signed-off-by: Thomas Garnier <thgarnie at chromium.org>
Acked-by: Juergen Gross <jgross at suse.com>
---
 arch/x86/include/asm/paravirt_types.h | 32 +++++++++++++++++++++++----
 1 file changed, 28 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/paravirt_types.h
b/arch/x86/include/asm/paravirt_types.h
index 84812964d3dd..82f7ca22e0ae 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -336,9 +336,32 @@ extern struct paravirt_patch_template pv_ops;
 #define PARAVIRT_PATCH(x)					\
 	(offsetof(struct paravirt_patch_template, x) / sizeof(void *))
 
+#ifdef CONFIG_X86_PIE
+#define paravirt_opptr_call "a"
+#define paravirt_opptr_type "p"
+
+/*
+ * Alternative patching requires a maximum of 7 bytes but the relative call is
+ * only 6 bytes. If PIE is enabled, add an additional nop to the call
+ * instruction to ensure patching is possible.
+ *
+ * Without PIE, the call is reg/mem64:
+ * ff 14 25 68 37 02 82    callq  *0xffffffff82023768
+ *
+ * With PIE, it is relative to %rip and take 1-less byte:
+ * ff 15 fa d9 ff 00       callq  *0xffd9fa(%rip) # <pv_ops+0x30>
+ *
+ */
+#define PARAVIRT_CALL_POST  "nop;"
+#else
+#define paravirt_opptr_call "c"
+#define paravirt_opptr_type "i"
+#define PARAVIRT_CALL_POST  ""
+#endif
+
 #define paravirt_type(op)				\
 	[paravirt_typenum] "i" (PARAVIRT_PATCH(op)),	\
-	[paravirt_opptr] "i" (&(pv_ops.op))
+	[paravirt_opptr] paravirt_opptr_type (&(pv_ops.op))
 #define paravirt_clobber(clobber)		\
 	[paravirt_clobber] "i" (clobber)
 
@@ -377,9 +400,10 @@ int paravirt_disable_iospace(void);
  * offset into the paravirt_patch_template structure, and can therefore be
  * freely converted back into a structure offset.
  */
-#define PARAVIRT_CALL					\
-	ANNOTATE_RETPOLINE_SAFE				\
-	"call *%c[paravirt_opptr];"
+#define PARAVIRT_CALL						\
+	ANNOTATE_RETPOLINE_SAFE					\
+	"call *%" paravirt_opptr_call "[paravirt_opptr];"	\
+	PARAVIRT_CALL_POST
 
 /*
  * These macros are intended to wrap calls through one of the paravirt
-- 
2.24.0.393.g34dc348eaf-goog

On Wed, Dec 04, 2019 at 04:09:37PM -0800, Thomas Garnier
wrote:
> Minor changes based on feedback and rebase from v9.
> 
> Splitting the previous serie in two. This part contains assembly code
> changes required for PIE but without any direct dependencies with the
> rest of the patchset.
ISTR suggestion you add an objtool pass that verifies there are no
absolute text references left. Otherwise we'll forever be chasing that
last one..

On Thu, Dec 19, 2019 at 5:35 AM Peter Zijlstra <peterz at infradead.org>
wrote:
>
> On Wed, Dec 04, 2019 at 04:09:37PM -0800, Thomas Garnier wrote:
> > Minor changes based on feedback and rebase from v9.
> >
> > Splitting the previous serie in two. This part contains assembly code
> > changes required for PIE but without any direct dependencies with the
> > rest of the patchset.
>
> ISTR suggestion you add an objtool pass that verifies there are no
> absolute text references left. Otherwise we'll forever be chasing that
> last one..
Correct, I have a reference in the changelog saying I will tackle in
the next patchset because we still have non-pie references in other
places but the fix is a bit more complex (for exemple per-cpu) and not
included in this phase. I will add a better explanation in the next
message for patch v11.

On Wed, Dec 04, 2019 at 04:09:47PM -0800, Thomas Garnier
wrote:
> If PIE is enabled, switch the paravirt assembly constraints to be
> compatible. The %c/i constrains generate smaller code so is kept by
> default.
> 
> Position Independent Executable (PIE) support will allow to extend the
> KASLR randomization range below 0xffffffff80000000.
> 
> Signed-off-by: Thomas Garnier <thgarnie at chromium.org>
> Acked-by: Juergen Gross <jgross at suse.com>
> ---
>  arch/x86/include/asm/paravirt_types.h | 32 +++++++++++++++++++++++----
>  1 file changed, 28 insertions(+), 4 deletions(-)
More missed feedback:

https://lkml.kernel.org/r/CAJcbSZG-JhBC9b1JMv1zq2r5uRQipYLtkNjM67sd7=eqy_iOaA at
mail.gmail.com

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

On Wed, Dec 04, 2019 at 04:09:37PM -0800, Thomas Garnier
wrote:
> Minor changes based on feedback and rebase from v9.
> 
> Splitting the previous serie in two. This part contains assembly code
> changes required for PIE but without any direct dependencies with the
> rest of the patchset.
Ok, modulo the minor commit message and comments fixup, this looks ok
and passes testing here.

I'm going to queue patches 2-11 of the next version unless someone
complains.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

On Tue, Dec 24, 2019 at 02:03:10PM +0100, Borislav Petkov
wrote:
> On Wed, Dec 04, 2019 at 04:09:37PM -0800, Thomas Garnier wrote:
> > Minor changes based on feedback and rebase from v9.
> > 
> > Splitting the previous serie in two. This part contains assembly code
> > changes required for PIE but without any direct dependencies with the
> > rest of the patchset.
> 
> Ok, modulo the minor commit message and comments fixup, this looks ok
> and passes testing here.
> 
> I'm going to queue patches 2-11 of the next version unless someone
> complains.
Great! Thanks very much for the reviews. :)

-- 
Kees Cook