From: H.J. Lu <hjl.tools@gmail.com>
Date: Tue, 19 Dec 2017 10:45:16 +0000 (-0800)
Subject: x86: Add feature_1 to tcbhead_t [BZ #22563]
X-Git-Tag: glibc-2.27~248
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cba595c350e52194e10c0006732e1991e3d0803b;p=thirdparty%2Fglibc.git

x86: Add feature_1 to tcbhead_t [BZ #22563]

On x86, padding in struct __jmp_buf_tag is used for shadow stack pointer
to support Shadow Stack in Intel Control-flow Enforcemen Technology.
cancel_jmp_buf has been updated to include saved_mask so that it is as
large as struct __jmp_buf_tag.  We must suport the old cancel_jmp_buf
in existing binaries.  Since symbol versioning doesn't work on
cancel_jmp_buf, feature_1 is added to tcbhead_t so that setjmp and
longjmp can check if shadow stack is enabled.  NB: Shadow stack is
enabled only if all modules are shadow stack enabled.

	[BZ #22563]
	* sysdeps/i386/nptl/tcb-offsets.sym (FEATURE_1_OFFSET): New.
	* sysdeps/i386/nptl/tls.h (tcbhead_t): Add feature_1.
	* sysdeps/x86_64/nptl/tcb-offsets.sym (FEATURE_1_OFFSET): New.
	* sysdeps/x86_64/nptl/tls.h (tcbhead_t): Rename __glibc_unused1
	to feature_1.
---

diff --git a/ChangeLog b/ChangeLog
index 73dea64520f..c408eb23508 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+2017-12-19  H.J. Lu  <hongjiu.lu@intel.com>
+
+	[BZ #22563]
+	* sysdeps/i386/nptl/tcb-offsets.sym (FEATURE_1_OFFSET): New.
+	* sysdeps/i386/nptl/tls.h (tcbhead_t): Add feature_1.
+	* sysdeps/x86_64/nptl/tcb-offsets.sym (FEATURE_1_OFFSET): New.
+	* sysdeps/x86_64/nptl/tls.h (tcbhead_t): Rename __glibc_unused1
+	to feature_1.
+
 2017-12-19  H.J. Lu  <hongjiu.lu@intel.com>
 
 	[BZ #22563]
diff --git a/sysdeps/i386/nptl/tcb-offsets.sym b/sysdeps/i386/nptl/tcb-offsets.sym
index 695a8103863..250f1a6e13e 100644
--- a/sysdeps/i386/nptl/tcb-offsets.sym
+++ b/sysdeps/i386/nptl/tcb-offsets.sym
@@ -15,3 +15,4 @@ POINTER_GUARD		offsetof (tcbhead_t, pointer_guard)
 #ifndef __ASSUME_PRIVATE_FUTEX
 PRIVATE_FUTEX		offsetof (tcbhead_t, private_futex)
 #endif
+FEATURE_1_OFFSET	offsetof (tcbhead_t, feature_1)
diff --git a/sysdeps/i386/nptl/tls.h b/sysdeps/i386/nptl/tls.h
index f9a6b11ecf3..7d4b18c16ad 100644
--- a/sysdeps/i386/nptl/tls.h
+++ b/sysdeps/i386/nptl/tls.h
@@ -50,6 +50,10 @@ typedef struct
   void *__private_tm[4];
   /* GCC split stack support.  */
   void *__private_ss;
+  /* Bit 0: IBT.
+     Bit 1: SHSTK.
+   */
+  unsigned int feature_1;
 } tcbhead_t;
 
 # define TLS_MULTIPLE_THREADS_IN_TCB 1
diff --git a/sysdeps/x86_64/nptl/tcb-offsets.sym b/sysdeps/x86_64/nptl/tcb-offsets.sym
index 8a25c482cb0..03b6dba5c3e 100644
--- a/sysdeps/x86_64/nptl/tcb-offsets.sym
+++ b/sysdeps/x86_64/nptl/tcb-offsets.sym
@@ -15,6 +15,7 @@ VGETCPU_CACHE_OFFSET	offsetof (tcbhead_t, vgetcpu_cache)
 #ifndef __ASSUME_PRIVATE_FUTEX
 PRIVATE_FUTEX		offsetof (tcbhead_t, private_futex)
 #endif
+FEATURE_1_OFFSET	offsetof (tcbhead_t, feature_1)
 
 -- Not strictly offsets, but these values are also used in the TCB.
 TCB_CANCELSTATE_BITMASK	 CANCELSTATE_BITMASK
diff --git a/sysdeps/x86_64/nptl/tls.h b/sysdeps/x86_64/nptl/tls.h
index 9b8ad82550f..cec864f231d 100644
--- a/sysdeps/x86_64/nptl/tls.h
+++ b/sysdeps/x86_64/nptl/tls.h
@@ -56,7 +56,10 @@ typedef struct
 # else
   int __glibc_reserved1;
 # endif
-  int __glibc_unused1;
+  /* Bit 0: IBT.
+     Bit 1: SHSTK.
+   */
+  unsigned int feature_1;
   /* Reservation of some values for the TM ABI.  */
   void *__private_tm[4];
   /* GCC split stack support.  */