i386: Insert ENDBR to trampoline for -fcf-protection=branch -mibt

When -fcf-protection=branch -mibt are used, we need to insert ENDBR
to trampoline.  TRAMPOLINE_SIZE is creased by 4 bytes to accommodate
4-byte ENDBR instruction.

gcc/

	PR target/85044
	* config/i386/i386.c (ix86_trampoline_init): Insert ENDBR for
	-fcf-protection=branch -mibt.
	* config/i386/i386.h (TRAMPOLINE_SIZE): Increased by 4 bytes.

gcc/testsuite/

	PR target/85044
	* gcc.target/i386/pr85044.c: New test.

From-SVN: r258897

gcc/ChangeLog

+2018-03-27  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/85044
+	* config/i386/i386.c (ix86_trampoline_init): Insert ENDBR for
+	-fcf-protection=branch -mibt.
+	* config/i386/i386.h (TRAMPOLINE_SIZE): Increased by 4 bytes.
+
 2018-03-27  Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
 
 	PR target/81863

gcc/config/i386/i386.c

@@ -30411,6 +30411,7 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
   rtx mem, fnaddr;
   int opcode;
   int offset = 0;
+  bool need_endbr = (flag_cf_protection & CF_BRANCH) && TARGET_IBT;
 
   fnaddr = XEXP (DECL_RTL (fndecl), 0);
 
@@ -30418,6 +30419,14 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
     {
       int size;
 
+      if (need_endbr)
+	{
+	  /* Insert ENDBR64.  */
+	  mem = adjust_address (m_tramp, SImode, offset);
+	  emit_move_insn (mem, gen_int_mode (0xfa1e0ff3, SImode));
+	  offset += 4;
+	}
+
       /* Load the function address to r11.  Try to load address using
 	 the shorter movl instead of movabs.  We may want to support
 	 movq for kernel mode, but kernel does not use trampolines at
@@ -30495,6 +30504,14 @@ ix86_trampoline_init (rtx m_tramp, tree fndecl, rtx chain_value)
       else
 	opcode = 0x68;
 
+      if (need_endbr)
+	{
+	  /* Insert ENDBR32.  */
+	  mem = adjust_address (m_tramp, SImode, offset);
+	  emit_move_insn (mem, gen_int_mode (0xfb1e0ff3, SImode));
+	  offset += 4;
+	}
+
       mem = adjust_address (m_tramp, QImode, offset);
       emit_move_insn (mem, gen_int_mode (opcode, QImode));
 

gcc/config/i386/i386.h

@@ -1716,7 +1716,7 @@ typedef struct ix86_args {
 
 /* Length in units of the trampoline for entering a nested function.  */
 
-#define TRAMPOLINE_SIZE (TARGET_64BIT ? 24 : 10)
+#define TRAMPOLINE_SIZE (TARGET_64BIT ? 28 : 14)
 
 /* Definitions for register eliminations.
 

gcc/testsuite/ChangeLog

+2018-03-27  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR target/85044
+	* gcc.target/i386/pr85044.c: New test.
+
 2018-03-27  Martin Sebor  <msebor@redhat.com>
 
 	PR testsuite/83462

gcc/testsuite/gcc.target/i386/pr85044.c

+/* { dg-do run { target cet } } */
+/* { dg-options "-O2 -fcf-protection=branch -mibt" } */
+
+void callme (void (*callback) (void));
+
+int
+main (void)
+{
+  int ok = 0;
+  void callback (void) { ok = 1; }
+
+  callme (&callback);
+
+  if (!ok)
+   __builtin_abort ();
+  return 0;
+}
+
+__attribute__((noinline, noclone))
+void
+callme (void (*callback) (void))
+{
+  (*callback) ();
+}