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V4 [PATCH 04/12] x86/CET: Extend arch_prctl syscall for CET control

From: "H.J. Lu" <hjl dot tools at gmail dot com>
To: Joseph Myers <joseph at codesourcery dot com>
Cc: "Carlos O'Donell" <carlos at redhat dot com>, GNU C Library <libc-alpha at sourceware dot org>
Date: Tue, 24 Jul 2018 09:13:15 -0700
Subject: V4 [PATCH 04/12] x86/CET: Extend arch_prctl syscall for CET control

On Tue, Jul 24, 2018 at 8:56 AM, Joseph Myers <joseph@codesourcery.com> wrote:
> On Tue, 24 Jul 2018, H.J. Lu wrote:
>
>> CET arch_prctl bits should be defined in <asm/prctl.h> from Linux kernel
>> header files.   Here is the updated patch to add x86 <include/asm/prctl.h>.
>>
>> OK for master?
>
> I don't think the relevant condition for removing such a wrapper is "after
> the CET kernel interface has been committed into the public kernel".  It's
> after we require kernel headers recent enough to have that interface,
> which may well be several years away.  Once the interface has been
> committed into the public kernel, the wrapper should be updated to name
> the kernel version that has it and to say it should be removed once we
> require kernel headers at least that recent.

Like this?


-- 
H.J.

From 8244c8532d22976c3d92ec25bcefeb3a7854123f Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Sat, 7 Jul 2018 07:33:04 -0700
Subject: [PATCH] x86/CET: Extend arch_prctl syscall for CET control

CET arch_prctl bits should be defined in <asm/prctl.h> from Linux kernel
header files.  Add x86 <include/asm/prctl.h> for pre-CET kernel header
files.

Note: sysdeps/unix/sysv/linux/x86/include/asm/prctl.h should be removed
if <asm/prctl.h> from the required kernel header files contains CET
arch_prctl bits.

 /* CET features:
    IBT:   GNU_PROPERTY_X86_FEATURE_1_IBT
    SHSTK: GNU_PROPERTY_X86_FEATURE_1_SHSTK
  */

 /* Return CET features in unsigned long long *addr:
      features: addr[0].
      shadow stack base address: addr[1].
      shadow stack size: addr[2].
  */
 # define ARCH_CET_STATUS		0x3001
 /* Disable CET features in unsigned int features.  */
 # define ARCH_CET_DISABLE		0x3002
 /* Lock all CET features.  */
 # define ARCH_CET_LOCK			0x3003
 /* Allocate a new shadow stack with unsigned long long *addr:
      IN: requested shadow stack size: *addr.
      OUT: allocated shadow stack address: *addr.
  */
 # define ARCH_CET_ALLOC_SHSTK		0x3004
 /* Return legacy region bitmap info in unsigned long long *addr:
     address: addr[0].
     size: addr[1].
  */
 # define ARCH_CET_LEGACY_BITMAP	0x3005

	* sysdeps/unix/sysv/linux/x86/include/asm/prctl.h: New file.
	* sysdeps/unix/sysv/linux/x86/cpu-features.c: Include
	<sys/prctl.h> and <asm/prctl.h>.
	(get_cet_status): Call arch_prctl with ARCH_CET_STATUS.
	* sysdeps/unix/sysv/linux/x86/dl-cet.h: Include <sys/prctl.h>
	and <asm/prctl.h>.
	(dl_cet_allocate_legacy_bitmap): Call arch_prctl with
	ARCH_CET_LEGACY_BITMAP.
	(dl_cet_disable_cet): Call arch_prctl with ARCH_CET_DISABLE.
	(dl_cet_lock_cet): Call arch_prctl with ARCH_CET_LOCK.
	* sysdeps/x86/libc-start.c: Include <startup.h>.
---
 sysdeps/unix/sysv/linux/x86/cpu-features.c    |  8 +++++
 sysdeps/unix/sysv/linux/x86/dl-cet.h          | 30 +++++++++++++----
 .../unix/sysv/linux/x86/include/asm/prctl.h   | 32 +++++++++++++++++++
 sysdeps/x86/libc-start.c                      |  3 ++
 4 files changed, 67 insertions(+), 6 deletions(-)
 create mode 100644 sysdeps/unix/sysv/linux/x86/include/asm/prctl.h

diff --git a/sysdeps/unix/sysv/linux/x86/cpu-features.c b/sysdeps/unix/sysv/linux/x86/cpu-features.c
index 7c9df9b794..8566a265b8 100644
--- a/sysdeps/unix/sysv/linux/x86/cpu-features.c
+++ b/sysdeps/unix/sysv/linux/x86/cpu-features.c
@@ -17,9 +17,17 @@
    <http://www.gnu.org/licenses/>.  */
 
 #if CET_ENABLED
+# include <sys/prctl.h>
+# include <asm/prctl.h>
+
 static inline int __attribute__ ((always_inline))
 get_cet_status (void)
 {
+  unsigned long long cet_status[3];
+  INTERNAL_SYSCALL_DECL (err);
+  if (INTERNAL_SYSCALL (arch_prctl, err, 2, ARCH_CET_STATUS,
+			cet_status) == 0)
+    return cet_status[0];
   return 0;
 }
 
diff --git a/sysdeps/unix/sysv/linux/x86/dl-cet.h b/sysdeps/unix/sysv/linux/x86/dl-cet.h
index ae81e2f2ca..3fbcfebed5 100644
--- a/sysdeps/unix/sysv/linux/x86/dl-cet.h
+++ b/sysdeps/unix/sysv/linux/x86/dl-cet.h
@@ -15,23 +15,41 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <sys/prctl.h>
+#include <asm/prctl.h>
+
 static inline int __attribute__ ((always_inline))
 dl_cet_allocate_legacy_bitmap (unsigned long *legacy_bitmap)
 {
-  /* FIXME: Need syscall support.  */
-  return -1;
+  /* Allocate legacy bitmap.  */
+  INTERNAL_SYSCALL_DECL (err);
+#ifdef __LP64__
+  return (int) INTERNAL_SYSCALL (arch_prctl, err, 2,
+				 ARCH_CET_LEGACY_BITMAP, legacy_bitmap);
+#else
+  unsigned long long legacy_bitmap_u64[2];
+  int res = INTERNAL_SYSCALL (arch_prctl, err, 2,
+			      ARCH_CET_LEGACY_BITMAP, legacy_bitmap_u64);
+  if (res == 0)
+    {
+      legacy_bitmap[0] = legacy_bitmap_u64[0];
+      legacy_bitmap[1] = legacy_bitmap_u64[1];
+    }
+  return res;
+#endif
 }
 
 static inline int __attribute__ ((always_inline))
 dl_cet_disable_cet (unsigned int cet_feature)
 {
-  /* FIXME: Need syscall support.  */
-  return -1;
+  INTERNAL_SYSCALL_DECL (err);
+  return (int) INTERNAL_SYSCALL (arch_prctl, err, 2, ARCH_CET_DISABLE,
+				 cet_feature);
 }
 
 static inline int __attribute__ ((always_inline))
 dl_cet_lock_cet (void)
 {
-  /* FIXME: Need syscall support.  */
-  return -1;
+  INTERNAL_SYSCALL_DECL (err);
+  return (int) INTERNAL_SYSCALL (arch_prctl, err, 2, ARCH_CET_LOCK, 0);
 }
diff --git a/sysdeps/unix/sysv/linux/x86/include/asm/prctl.h b/sysdeps/unix/sysv/linux/x86/include/asm/prctl.h
new file mode 100644
index 0000000000..f67f3299b9
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86/include/asm/prctl.h
@@ -0,0 +1,32 @@
+/* FIXME: CET arch_prctl bits should come from the kernel header files.
+   This file should be removed if <asm/prctl.h> from the required kernel
+   header files contains CET arch_prctl bits.  */
+
+#include_next <asm/prctl.h>
+
+#ifndef ARCH_CET_STATUS
+/* CET features:
+   IBT:   GNU_PROPERTY_X86_FEATURE_1_IBT
+   SHSTK: GNU_PROPERTY_X86_FEATURE_1_SHSTK
+ */
+/* Return CET features in unsigned long long *addr:
+     features: addr[0].
+     shadow stack base address: addr[1].
+     shadow stack size: addr[2].
+ */
+# define ARCH_CET_STATUS	0x3001
+/* Disable CET features in unsigned int features.  */
+# define ARCH_CET_DISABLE	0x3002
+/* Lock all CET features.  */
+# define ARCH_CET_LOCK		0x3003
+/* Allocate a new shadow stack with unsigned long long *addr:
+     IN: requested shadow stack size: *addr.
+     OUT: allocated shadow stack address: *addr.
+ */
+# define ARCH_CET_ALLOC_SHSTK	0x3004
+/* Return legacy region bitmap info in unsigned long long *addr:
+     address: addr[0].
+     size: addr[1].
+ */
+# define ARCH_CET_LEGACY_BITMAP	0x3005
+#endif /* ARCH_CET_STATUS */
diff --git a/sysdeps/x86/libc-start.c b/sysdeps/x86/libc-start.c
index 43aba9d061..eb5335c154 100644
--- a/sysdeps/x86/libc-start.c
+++ b/sysdeps/x86/libc-start.c
@@ -16,6 +16,9 @@
    <http://www.gnu.org/licenses/>.  */
 
 #ifndef SHARED
+/* Define I386_USE_SYSENTER to support syscall during startup in static
+   PIE.  */
+# include <startup.h>
 # include <ldsodefs.h>
 # include <cpu-features.h>
 # include <cpu-features.c>
-- 
2.17.1

Follow-Ups:
- Re: V4 [PATCH 04/12] x86/CET: Extend arch_prctl syscall for CET control
  - From: Joseph Myers
- Re: V4 [PATCH 04/12] x86/CET: Extend arch_prctl syscall for CET control
  - From: Carlos O'Donell

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