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

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

	* 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>.

3 files changed, 64 insertions, 6 deletions

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 */