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Re: [PATCH 5/5] x86: Disallow -mindirect-branch=/-mfunction-return= with -mcmodel=large

From: "H.J. Lu" <hjl dot tools at gmail dot com>
To: Jan Hubicka <hubicka at ucw dot cz>, Uros Bizjak <ubizjak at gmail dot com>
Cc: GCC Patches <gcc-patches at gcc dot gnu dot org>
Date: Sun, 14 Jan 2018 07:14:03 -0800
Subject: Re: [PATCH 5/5] x86: Disallow -mindirect-branch=/-mfunction-return= with -mcmodel=large
Authentication-results: sourceware.org; auth=none
References: <20180114033707.6297-1-hjl.tools@gmail.com> <20180114033707.6297-6-hjl.tools@gmail.com> <20180114104732.GD14673@atrey.karlin.mff.cuni.cz> <CAMe9rOr3kKiNYt55YvkoBs7cjjzoE=Aw=Ks=WzDfdwzev77F=A@mail.gmail.com>

On Sun, Jan 14, 2018 at 4:57 AM, H.J. Lu <hjl.tools@gmail.com> wrote:
> On Sun, Jan 14, 2018 at 2:47 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
>>> Since the thunk function may not be reachable in large code model,
>>> -mcmodel=large is incompatible with -mindirect-branch=thunk,
>>> -mindirect-branch=thunk-extern, -mfunction-return=thunk and
>>> -mfunction-return=thunk-extern.  Issue an error when they are used with
>>> -mcmodel=large.
>>>
>>> gcc/
>>>
>>>       * config/i386/i386.c (ix86_set_indirect_branch_type): Disallow
>>>       -mcmodel=large with -mindirect-branch=thunk,
>>>       -mindirect-branch=thunk-extern, -mfunction-return=thunk and
>>>       -mfunction-return=thunk-extern.
>>>       * doc/invoke.texi: Document -mcmodel=large is incompatible with
>>>       -mindirect-branch=thunk, -mindirect-branch=thunk-extern,
>>>       -mfunction-return=thunk and -mfunction-return=thunk-extern.
>>>
>>> gcc/testsuite/
>>>
>>>       * gcc.target/i386/indirect-thunk-10.c: New test.
>>>       * gcc.target/i386/indirect-thunk-8.c: Likewise.
>>>       * gcc.target/i386/indirect-thunk-9.c: Likewise.
>>>       * gcc.target/i386/indirect-thunk-attr-10.c: Likewise.
>>>       * gcc.target/i386/indirect-thunk-attr-11.c: Likewise.
>>>       * gcc.target/i386/indirect-thunk-attr-9.c: Likewise.
>>>       * gcc.target/i386/ret-thunk-17.c: Likewise.
>>>       * gcc.target/i386/ret-thunk-18.c: Likewise.
>>>       * gcc.target/i386/ret-thunk-19.c: Likewise.
>>>       * gcc.target/i386/ret-thunk-20.c: Likewise.
>>>       * gcc.target/i386/ret-thunk-21.c: Likewise.
>>
>> OK.
>> Honza
>
> This is the patch I am checking in to only run tests on LP64 since
> -mcmodel=large doesn't work with -mx32.
>

Here is the backport for GCC 7.  OK for gcc-7-branch?

-- 
H.J.

From 13dce7cceef28026c4fc2e505d724526141fe4c1 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Sat, 13 Jan 2018 18:01:54 -0800
Subject: [PATCH 5/5] x86: Disallow -mindirect-branch=/-mfunction-return= with
 -mcmodel=large

Since the thunk function may not be reachable in large code model,
-mcmodel=large is incompatible with -mindirect-branch=thunk,
-mindirect-branch=thunk-extern, -mfunction-return=thunk and
-mfunction-return=thunk-extern.  Issue an error when they are used with
-mcmodel=large.

gcc/

	Backport from mainline
	* config/i386/i386.c (ix86_set_indirect_branch_type): Disallow
	-mcmodel=large with -mindirect-branch=thunk,
	-mindirect-branch=thunk-extern, -mfunction-return=thunk and
	-mfunction-return=thunk-extern.
	* doc/invoke.texi: Document -mcmodel=large is incompatible with
	-mindirect-branch=thunk, -mindirect-branch=thunk-extern,
	-mfunction-return=thunk and -mfunction-return=thunk-extern.

gcc/testsuite/

	Backport from mainline
	* gcc.target/i386/indirect-thunk-10.c: New test.
	* gcc.target/i386/indirect-thunk-8.c: Likewise.
	* gcc.target/i386/indirect-thunk-9.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-10.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-11.c: Likewise.
	* gcc.target/i386/indirect-thunk-attr-9.c: Likewise.
	* gcc.target/i386/ret-thunk-17.c: Likewise.
	* gcc.target/i386/ret-thunk-18.c: Likewise.
	* gcc.target/i386/ret-thunk-19.c: Likewise.
	* gcc.target/i386/ret-thunk-20.c: Likewise.
	* gcc.target/i386/ret-thunk-21.c: Likewise.
---
 gcc/config/i386/i386.c                             | 26 ++++++++++++++++++++++
 gcc/doc/invoke.texi                                | 11 +++++++++
 gcc/testsuite/gcc.target/i386/indirect-thunk-10.c  |  7 ++++++
 gcc/testsuite/gcc.target/i386/indirect-thunk-8.c   |  7 ++++++
 gcc/testsuite/gcc.target/i386/indirect-thunk-9.c   |  7 ++++++
 .../gcc.target/i386/indirect-thunk-attr-10.c       |  9 ++++++++
 .../gcc.target/i386/indirect-thunk-attr-11.c       |  9 ++++++++
 .../gcc.target/i386/indirect-thunk-attr-9.c        |  9 ++++++++
 gcc/testsuite/gcc.target/i386/ret-thunk-17.c       |  7 ++++++
 gcc/testsuite/gcc.target/i386/ret-thunk-18.c       |  8 +++++++
 gcc/testsuite/gcc.target/i386/ret-thunk-19.c       |  8 +++++++
 gcc/testsuite/gcc.target/i386/ret-thunk-20.c       |  9 ++++++++
 gcc/testsuite/gcc.target/i386/ret-thunk-21.c       |  9 ++++++++
 13 files changed, 126 insertions(+)
 create mode 100644 gcc/testsuite/gcc.target/i386/indirect-thunk-10.c
 create mode 100644 gcc/testsuite/gcc.target/i386/indirect-thunk-8.c
 create mode 100644 gcc/testsuite/gcc.target/i386/indirect-thunk-9.c
 create mode 100644 gcc/testsuite/gcc.target/i386/indirect-thunk-attr-10.c
 create mode 100644 gcc/testsuite/gcc.target/i386/indirect-thunk-attr-11.c
 create mode 100644 gcc/testsuite/gcc.target/i386/indirect-thunk-attr-9.c
 create mode 100644 gcc/testsuite/gcc.target/i386/ret-thunk-17.c
 create mode 100644 gcc/testsuite/gcc.target/i386/ret-thunk-18.c
 create mode 100644 gcc/testsuite/gcc.target/i386/ret-thunk-19.c
 create mode 100644 gcc/testsuite/gcc.target/i386/ret-thunk-20.c
 create mode 100644 gcc/testsuite/gcc.target/i386/ret-thunk-21.c

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index e32de13688a..318a71840c9 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -7187,6 +7187,19 @@ ix86_set_indirect_branch_type (tree fndecl)
 	}
       else
 	cfun->machine->indirect_branch_type = ix86_indirect_branch;
+
+      /* -mcmodel=large is not compatible with -mindirect-branch=thunk
+	 nor -mindirect-branch=thunk-extern.  */
+      if ((ix86_cmodel == CM_LARGE || ix86_cmodel == CM_LARGE_PIC)
+	  && ((cfun->machine->indirect_branch_type
+	       == indirect_branch_thunk_extern)
+	      || (cfun->machine->indirect_branch_type
+		  == indirect_branch_thunk)))
+	error ("%<-mindirect-branch=%s%> and %<-mcmodel=large%> are not "
+	       "compatible",
+	       ((cfun->machine->indirect_branch_type
+		 == indirect_branch_thunk_extern)
+		? "thunk-extern" : "thunk"));
     }
 
   if (cfun->machine->function_return_type == indirect_branch_unset)
@@ -7212,6 +7225,19 @@ ix86_set_indirect_branch_type (tree fndecl)
 	}
       else
 	cfun->machine->function_return_type = ix86_function_return;
+
+      /* -mcmodel=large is not compatible with -mfunction-return=thunk
+	 nor -mfunction-return=thunk-extern.  */
+      if ((ix86_cmodel == CM_LARGE || ix86_cmodel == CM_LARGE_PIC)
+	  && ((cfun->machine->function_return_type
+	       == indirect_branch_thunk_extern)
+	      || (cfun->machine->function_return_type
+		  == indirect_branch_thunk)))
+	error ("%<-mfunction-return=%s%> and %<-mcmodel=large%> are not "
+	       "compatible",
+	       ((cfun->machine->function_return_type
+		 == indirect_branch_thunk_extern)
+		? "thunk-extern" : "thunk"));
     }
 }
 
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 1e572b1f9a2..6f3c344476c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -25699,6 +25699,11 @@ to external call and return thunk provided in a separate object file.
 You can control this behavior for a specific function by using the
 function attribute @code{indirect_branch}.  @xref{Function Attributes}.
 
+Note that @option{-mcmodel=large} is incompatible with
+@option{-mindirect-branch=thunk} nor
+@option{-mindirect-branch=thunk-extern} since the thunk function may
+not be reachable in large code model.
+
 @item -mfunction-return=@var{choice}
 @opindex -mfunction-return
 Convert function return with @var{choice}.  The default is @samp{keep},
@@ -25710,6 +25715,12 @@ 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{-mcmodel=large} is incompatible with
+@option{-mfunction-return=thunk} nor
+@option{-mfunction-return=thunk-extern} since the thunk function may
+not be reachable in large code model.
+
+
 @item -mindirect-branch-register
 @opindex -mindirect-branch-register
 Force indirect call and jump via register.
diff --git a/gcc/testsuite/gcc.target/i386/indirect-thunk-10.c b/gcc/testsuite/gcc.target/i386/indirect-thunk-10.c
new file mode 100644
index 00000000000..a0674bd2363
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-10.c
@@ -0,0 +1,7 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mindirect-branch=thunk-inline -mfunction-return=keep -mcmodel=large" } */
+
+void
+bar (void)
+{
+}
diff --git a/gcc/testsuite/gcc.target/i386/indirect-thunk-8.c b/gcc/testsuite/gcc.target/i386/indirect-thunk-8.c
new file mode 100644
index 00000000000..7a80a8986e8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-8.c
@@ -0,0 +1,7 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mindirect-branch=thunk -mfunction-return=keep -mcmodel=large" } */
+
+void
+bar (void)
+{ /* { dg-error "'-mindirect-branch=thunk' and '-mcmodel=large' are not compatible" } */
+}
diff --git a/gcc/testsuite/gcc.target/i386/indirect-thunk-9.c b/gcc/testsuite/gcc.target/i386/indirect-thunk-9.c
new file mode 100644
index 00000000000..d4d45c5114d
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-9.c
@@ -0,0 +1,7 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mindirect-branch=thunk-extern -mfunction-return=keep -mcmodel=large" } */
+
+void
+bar (void)
+{ /* { dg-error "'-mindirect-branch=thunk-extern' and '-mcmodel=large' are not compatible" } */
+}
diff --git a/gcc/testsuite/gcc.target/i386/indirect-thunk-attr-10.c b/gcc/testsuite/gcc.target/i386/indirect-thunk-attr-10.c
new file mode 100644
index 00000000000..3a2aeaddbc5
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-attr-10.c
@@ -0,0 +1,9 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mindirect-branch=keep -mfunction-return=keep -mcmodel=large" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+
+__attribute__ ((indirect_branch("thunk-extern")))
+void
+bar (void)
+{ /* { dg-error "'-mindirect-branch=thunk-extern' and '-mcmodel=large' are not compatible" } */
+}
diff --git a/gcc/testsuite/gcc.target/i386/indirect-thunk-attr-11.c b/gcc/testsuite/gcc.target/i386/indirect-thunk-attr-11.c
new file mode 100644
index 00000000000..8e52f032b6c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-attr-11.c
@@ -0,0 +1,9 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mindirect-branch=keep -mfunction-return=keep -mcmodel=large" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+
+__attribute__ ((indirect_branch("thunk-inline")))
+void
+bar (void)
+{
+}
diff --git a/gcc/testsuite/gcc.target/i386/indirect-thunk-attr-9.c b/gcc/testsuite/gcc.target/i386/indirect-thunk-attr-9.c
new file mode 100644
index 00000000000..bdaa4f6911b
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/indirect-thunk-attr-9.c
@@ -0,0 +1,9 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mindirect-branch=keep -mfunction-return=keep -mcmodel=large" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+
+__attribute__ ((indirect_branch("thunk")))
+void
+bar (void)
+{ /* { dg-error "'-mindirect-branch=thunk' and '-mcmodel=large' are not compatible" } */
+}
diff --git a/gcc/testsuite/gcc.target/i386/ret-thunk-17.c b/gcc/testsuite/gcc.target/i386/ret-thunk-17.c
new file mode 100644
index 00000000000..0605e2c6542
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/ret-thunk-17.c
@@ -0,0 +1,7 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mfunction-return=thunk -mindirect-branch=keep -mcmodel=large" } */
+
+void
+bar (void)
+{ /* { dg-error "'-mfunction-return=thunk' and '-mcmodel=large' are not compatible" } */
+}
diff --git a/gcc/testsuite/gcc.target/i386/ret-thunk-18.c b/gcc/testsuite/gcc.target/i386/ret-thunk-18.c
new file mode 100644
index 00000000000..307019dc242
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/ret-thunk-18.c
@@ -0,0 +1,8 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mfunction-return=thunk-extern -mindirect-branch=keep -mcmodel=large" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+
+void
+bar (void)
+{ /* { dg-error "'-mfunction-return=thunk-extern' and '-mcmodel=large' are not compatible" } */
+}
diff --git a/gcc/testsuite/gcc.target/i386/ret-thunk-19.c b/gcc/testsuite/gcc.target/i386/ret-thunk-19.c
new file mode 100644
index 00000000000..772617f4010
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/ret-thunk-19.c
@@ -0,0 +1,8 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mfunction-return=keep -mindirect-branch=keep -mcmodel=large" } */
+
+__attribute__ ((function_return("thunk")))
+void
+bar (void)
+{ /* { dg-error "'-mfunction-return=thunk' and '-mcmodel=large' are not compatible" } */
+}
diff --git a/gcc/testsuite/gcc.target/i386/ret-thunk-20.c b/gcc/testsuite/gcc.target/i386/ret-thunk-20.c
new file mode 100644
index 00000000000..1e9f9bd5a66
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/ret-thunk-20.c
@@ -0,0 +1,9 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mfunction-return=keep -mindirect-branch=keep -mcmodel=large" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+
+__attribute__ ((function_return("thunk-extern")))
+void
+bar (void)
+{ /* { dg-error "'-mfunction-return=thunk-extern' and '-mcmodel=large' are not compatible" } */
+}
diff --git a/gcc/testsuite/gcc.target/i386/ret-thunk-21.c b/gcc/testsuite/gcc.target/i386/ret-thunk-21.c
new file mode 100644
index 00000000000..eea07f7abe1
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/ret-thunk-21.c
@@ -0,0 +1,9 @@
+/* { dg-do compile { target { lp64 } } } */
+/* { dg-options "-O2 -mfunction-return=keep -mindirect-branch=keep -mcmodel=large" } */
+/* { dg-additional-options "-fPIC" { target fpic } } */
+
+__attribute__ ((function_return("thunk-inline")))
+void
+bar (void)
+{
+}
-- 
2.14.3

References:
- [PATCH 0/5] x86: CVE-2017-5715, aka Spectre
  - From: H.J. Lu
- [PATCH 5/5] x86: Disallow -mindirect-branch=/-mfunction-return= with -mcmodel=large
  - From: H.J. Lu
- Re: [PATCH 5/5] x86: Disallow -mindirect-branch=/-mfunction-return= with -mcmodel=large
  - From: Jan Hubicka
- Re: [PATCH 5/5] x86: Disallow -mindirect-branch=/-mfunction-return= with -mcmodel=large
  - From: H.J. Lu

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