[glibc/maskray/lld] x86: Set header.feature_1 in TCB for always-on CET [BZ #27177]

[glibc/maskray/lld] x86: Set header.feature_1 in TCB for always-on CET [BZ #27177]

[Fangrui Song]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=2ef23b520597f4ea1790a669b83e608f24f4cf12

commit 2ef23b520597f4ea1790a669b83e608f24f4cf12
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Tue Jan 12 19:00:13 2021 -0800

    x86: Set header.feature_1 in TCB for always-on CET [BZ #27177]
    
    Update dl_cet_check() to set header.feature_1 in TCB when both IBT and
    SHSTK are always on.

Diff:
---
 sysdeps/x86/Makefile         | 6 ++++++
 sysdeps/x86/dl-cet.c         | 5 ++++-
 sysdeps/x86/tst-setjmp-cet.c | 1 +
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/sysdeps/x86/Makefile b/sysdeps/x86/Makefile
index c814d5a195..adaa2a92cd 100644
--- a/sysdeps/x86/Makefile
+++ b/sysdeps/x86/Makefile
@@ -48,6 +48,12 @@ endif # $(subdir) == math
 ifeq ($(subdir),setjmp)
 gen-as-const-headers += jmp_buf-ssp.sym
 sysdep_routines += __longjmp_cancel
+ifneq ($(enable-cet),no)
+ifneq ($(have-tunables),no)
+tests += tst-setjmp-cet
+tst-setjmp-cet-ENV = GLIBC_TUNABLES=glibc.cpu.x86_ibt=on:glibc.cpu.x86_shstk=on
+endif
+endif
 endif
 
 ifeq ($(subdir),string)
diff --git a/sysdeps/x86/dl-cet.c b/sysdeps/x86/dl-cet.c
index ed7fd6d10d..a63b9c7164 100644
--- a/sysdeps/x86/dl-cet.c
+++ b/sysdeps/x86/dl-cet.c
@@ -47,7 +47,10 @@ dl_cet_check (struct link_map *m, const char *program)
   /* No legacy object check if both IBT and SHSTK are always on.  */
   if (enable_ibt_type == cet_always_on
       && enable_shstk_type == cet_always_on)
-    return;
+    {
+      THREAD_SETMEM (THREAD_SELF, header.feature_1, GL(dl_x86_feature_1));
+      return;
+    }
 
   /* Check if IBT is enabled by kernel.  */
   bool ibt_enabled
diff --git a/sysdeps/x86/tst-setjmp-cet.c b/sysdeps/x86/tst-setjmp-cet.c
new file mode 100644
index 0000000000..42c795d2a8
--- /dev/null
+++ b/sysdeps/x86/tst-setjmp-cet.c
@@ -0,0 +1 @@
+#include <setjmp/tst-setjmp.c>