[gcc(refs/vendors/ibm/heads/gcc-9-branch)] x86: Allow -fcf-protection with external thunk

[Peter Bergner]

https://gcc.gnu.org/g:a03efb266fcbf4a01285fff871a5bfe5caac4944

commit a03efb266fcbf4a01285fff871a5bfe5caac4944
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Wed Apr 29 04:52:46 2020 -0700

    x86: Allow -fcf-protection with external thunk
    
    Allow -fcf-protection with external thunk since the external thunk can be
    made compatible with -fcf-protection.
    
    gcc/
    
            Backport from master
            PR target/93654
            * config/i386/i386-options.c (ix86_set_indirect_branch_type):
            Allow -fcf-protection with -mindirect-branch=thunk-extern and
            -mfunction-return=thunk-extern.
            * doc/invoke.texi: Update notes for -fcf-protection=branch with
            -mindirect-branch=thunk-extern and -mindirect-return=thunk-extern.
    
    gcc/testsuite/
    
            Backport from master
            PR target/93654
            * gcc.target/i386/pr93654.c: New test.
    
    (cherry picked from commit 9be3bb2c0a258fd6a7d3d05d232a21930c757d3c)

Diff:
---
 gcc/ChangeLog                           | 12 ++++++++++++
 gcc/config/i386/i386.c                  |  4 ++++
 gcc/doc/invoke.texi                     | 10 +++++++---
 gcc/testsuite/ChangeLog                 |  8 ++++++++
 gcc/testsuite/gcc.target/i386/pr93654.c |  9 +++++++++
 5 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 4cb1497a61f..c0d72cbbdf5 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,15 @@
+2020-04-29  H.J. Lu  <hongjiu.lu@intel.com>
+
+	Backport from master
+	2020-04-29  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/93654
+	* config/i386/i386.c (ix86_set_indirect_branch_type): Allow
+	-fcf-protection with -mindirect-branch=thunk-extern and
+	-mfunction-return=thunk-extern.
+	* doc/invoke.texi: Update notes for -fcf-protection=branch with
+	-mindirect-branch=thunk-extern and -mindirect-return=thunk-extern.
+
 2020-04-21  Martin Jambor  <mjambor@suse.cz>
 
 	Backport from master
diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index efe32f3975e..ae5046ee6a0 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -5807,6 +5807,8 @@ ix86_set_indirect_branch_type (tree fndecl)
 		? "thunk-extern" : "thunk"));
 
       if (cfun->machine->indirect_branch_type != indirect_branch_keep
+	  && (cfun->machine->indirect_branch_type
+	      != indirect_branch_thunk_extern)
 	  && (flag_cf_protection & CF_RETURN))
 	error ("%<-mindirect-branch%> and %<-fcf-protection%> are not "
 	       "compatible");
@@ -5850,6 +5852,8 @@ ix86_set_indirect_branch_type (tree fndecl)
 		? "thunk-extern" : "thunk"));
 
       if (cfun->machine->function_return_type != indirect_branch_keep
+	  && (cfun->machine->function_return_type
+	      != indirect_branch_thunk_extern)
 	  && (flag_cf_protection & CF_RETURN))
 	error ("%<-mfunction-return%> and %<-fcf-protection%> are not "
 	       "compatible");
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b18e9124b4e..5e6d240dc5d 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -28735,9 +28735,9 @@ Note that @option{-mcmodel=large} is incompatible with
 @option{-mindirect-branch=thunk-extern} since the thunk function may
 not be reachable in the large code model.
 
-Note that @option{-mindirect-branch=thunk-extern} is incompatible with
-@option{-fcf-protection=branch} since the external thunk cannot be modified
-to disable control-flow check.
+Note that @option{-mindirect-branch=thunk-extern} is compatible with
+@option{-fcf-protection=branch} since the external thunk can be made
+to enable control-flow check.
 
 @item -mfunction-return=@var{choice}
 @opindex mfunction-return
@@ -28750,6 +28750,10 @@ object file.  You can control this behavior for a specific function by
 using the function attribute @code{function_return}.
 @xref{Function Attributes}.
 
+Note that @option{-mindirect-return=thunk-extern} is compatible with
+@option{-fcf-protection=branch} since the external thunk can be made
+to enable control-flow check.
+
 Note that @option{-mcmodel=large} is incompatible with
 @option{-mfunction-return=thunk} and
 @option{-mfunction-return=thunk-extern} since the thunk function may
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index ec3b39c1dbd..49e8d899e5e 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,11 @@
+2020-04-29  H.J. Lu  <hongjiu.lu@intel.com>
+
+	Backport from master
+	2020-04-29  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/93654
+	* gcc.target/i386/pr93654.c: New test.
+
 2020-04-24  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	Backport from trunk
diff --git a/gcc/testsuite/gcc.target/i386/pr93654.c b/gcc/testsuite/gcc.target/i386/pr93654.c
new file mode 100644
index 00000000000..ec5bdce86a6
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr93654.c
@@ -0,0 +1,9 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fcf-protection -mfunction-return=thunk-extern -mindirect-branch=thunk-extern" } */
+
+int
+bar (void (*foo) (void))
+{
+  foo (); 
+  return 0;
+}