From 88bf1c3910e4cf97dcb85c6d32291c23e572a516 Mon Sep 17 00:00:00 2001

From: "H.J. Lu" <hjl.tools@gmail.com>

Date: Wed, 27 Oct 2021 07:48:54 -0700

Subject: [PATCH 1/4] x86: Add -mharden-sls=[none|all|return|indirect-branch]

Add -mharden-sls= to mitigate against straight line speculation (SLS)

for function return and indirect branch by adding an INT3 instruction

after function return and indirect branch.

gcc/

	PR target/102952

	* config/i386/i386-opts.h (harden_sls): New enum.

	* config/i386/i386.c (output_indirect_thunk): Mitigate against

	SLS for function return.

	(ix86_output_function_return): Likewise.

	(ix86_output_jmp_thunk_or_indirect): Mitigate against indirect

	branch.

	(ix86_output_indirect_jmp): Likewise.

	(ix86_output_call_insn): Likewise.

	* config/i386/i386.opt: Add -mharden-sls=.

	* doc/invoke.texi: Document -mharden-sls=.

gcc/testsuite/

	PR target/102952

	* gcc.target/i386/harden-sls-1.c: New test.

	* gcc.target/i386/harden-sls-2.c: Likewise.

	* gcc.target/i386/harden-sls-3.c: Likewise.

	* gcc.target/i386/harden-sls-4.c: Likewise.

	* gcc.target/i386/harden-sls-5.c: Likewise.

(cherry picked from commit 53a643f8568067d7700a9f2facc8ba39974973d3)

---

 gcc/config/i386/i386-opts.h                  |  7 +++++++

 gcc/config/i386/i386.c                       | 22 +++++++++++++++-----

 gcc/config/i386/i386.opt                     | 20 ++++++++++++++++++

 gcc/doc/invoke.texi                          | 10 ++++++++-

 gcc/testsuite/gcc.target/i386/harden-sls-1.c | 14 +++++++++++++

 gcc/testsuite/gcc.target/i386/harden-sls-2.c | 14 +++++++++++++

 gcc/testsuite/gcc.target/i386/harden-sls-3.c | 14 +++++++++++++

 gcc/testsuite/gcc.target/i386/harden-sls-4.c | 16 ++++++++++++++

 gcc/testsuite/gcc.target/i386/harden-sls-5.c | 17 +++++++++++++++

 9 files changed, 128 insertions(+), 6 deletions(-)

 create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-1.c

 create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-2.c

 create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-3.c

 create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-4.c

 create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-5.c

diff --git a/gcc/config/i386/i386-opts.h b/gcc/config/i386/i386-opts.h

index 46366cbfa72..34718b6d52c 100644

--- a/gcc/config/i386/i386-opts.h

+++ b/gcc/config/i386/i386-opts.h

@@ -119,4 +119,11 @@ enum indirect_branch {

   indirect_branch_thunk_extern

 };

+enum harden_sls {

+  harden_sls_none = 0,

+  harden_sls_return = 1 << 0,

+  harden_sls_indirect_branch = 1 << 1,

+  harden_sls_all = harden_sls_return | harden_sls_indirect_branch

+};

+

 #endif

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c

index 31502774ef3..eb9303f8742 100644

--- a/gcc/config/i386/i386.c

+++ b/gcc/config/i386/i386.c

@@ -10977,6 +10977,9 @@ output_indirect_thunk (enum indirect_thunk_prefix need_prefix,

     fputs ("\tbnd ret\n", asm_out_file);

   else

     fputs ("\tret\n", asm_out_file);

+

+  if ((ix86_harden_sls & harden_sls_return))

+    fputs ("\tint3\n", asm_out_file);

 }

 /* Output a funtion with a call and return thunk for indirect branch.

@@ -28728,6 +28731,8 @@ ix86_output_jmp_thunk_or_indirect (const char *thunk_name,

 	fprintf (asm_out_file, "\tjmp\t");

       assemble_name (asm_out_file, thunk_name);

       putc ('\n', asm_out_file);

+      if ((ix86_harden_sls & harden_sls_indirect_branch))

+	fputs ("\tint3\n", asm_out_file);

     }

   else

     output_indirect_thunk (need_prefix, regno);

@@ -28973,10 +28978,10 @@ ix86_output_indirect_jmp (rtx call_op)

 	gcc_unreachable ();

       ix86_output_indirect_branch (call_op, "%0", true);

-      return "";

     }

   else

-    return "%!jmp\t%A0";

+    output_asm_insn ("%!jmp\t%A0", &call_op);

+  return (ix86_harden_sls & harden_sls_indirect_branch) ? "int3" : "";

 }

 /* Output function return.  CALL_OP is the jump target.  Add a REP

@@ -29018,9 +29023,11 @@ ix86_output_function_return (bool long_p)

     }

   if (!long_p || ix86_bnd_prefixed_insn_p (current_output_insn))

-    return "%!ret";

+    output_asm_insn ("%!ret", NULL);

+  else

+    output_asm_insn ("rep%; ret", NULL);

-  return "rep%; ret";

+  return (ix86_harden_sls & harden_sls_return) ? "int3" : "";

 }

 /* Output indirect function return.  RET_OP is the function return

@@ -29158,7 +29165,12 @@ ix86_output_call_insn (rtx_insn *insn, rtx call_op)

       if (output_indirect_p && !direct_p)

 	ix86_output_indirect_branch (call_op, xasm, true);

       else

-	output_asm_insn (xasm, &call_op);

+	{

+	  output_asm_insn (xasm, &call_op);

+	  if (!direct_p

+	      && (ix86_harden_sls & harden_sls_indirect_branch))

+	    return "int3";

+	}

       return "";

     }

diff --git a/gcc/config/i386/i386.opt b/gcc/config/i386/i386.opt

index d9bd909a885..3ae48609e25 100644

--- a/gcc/config/i386/i386.opt

+++ b/gcc/config/i386/i386.opt

@@ -1055,3 +1055,23 @@ Support MOVDIRI built-in functions and code generation.

 mmovdir64b

 Target Report Mask(ISA_MOVDIR64B) Var(ix86_isa_flags2) Save

 Support MOVDIR64B built-in functions and code generation.

+

+mharden-sls=

+Target RejectNegative Joined Enum(harden_sls) Var(ix86_harden_sls) Init(harden_sls_none)

+Generate code to mitigate against straight line speculation.

+

+Enum

+Name(harden_sls) Type(enum harden_sls)

+Known choices for mitigation against straight line speculation with -mharden-sls=:

+

+EnumValue

+Enum(harden_sls) String(none) Value(harden_sls_none)

+

+EnumValue

+Enum(harden_sls) String(return) Value(harden_sls_return)

+

+EnumValue

+Enum(harden_sls) String(indirect-branch) Value(harden_sls_indirect_branch)

+

+EnumValue

+Enum(harden_sls) String(all) Value(harden_sls_all)

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi

index 78ca7738df2..1e20efd6969 100644

--- a/gcc/doc/invoke.texi

+++ b/gcc/doc/invoke.texi

@@ -1284,7 +1284,7 @@ See RS/6000 and PowerPC Options.

 -mstack-protector-guard-symbol=@var{symbol} -mmitigate-rop @gol

 -mgeneral-regs-only -mcall-ms2sysv-xlogues @gol

 -mindirect-branch=@var{choice} -mfunction-return=@var{choice} @gol

--mindirect-branch-register}

+-mindirect-branch-register -mharden-sls=@var{choice}}

 @emph{x86 Windows Options}

 @gccoptlist{-mconsole  -mcygwin  -mno-cygwin  -mdll @gol

@@ -28036,6 +28036,14 @@ not be reachable in the large code model.

 @opindex -mindirect-branch-register

 Force indirect call and jump via register.

+@item -mharden-sls=@var{choice}

+@opindex mharden-sls

+Generate code to mitigate against straight line speculation (SLS) with

+@var{choice}.  The default is @samp{none} which disables all SLS

+hardening.  @samp{return} enables SLS hardening for function return.

+@samp{indirect-branch} enables SLS hardening for indirect branch.

+@samp{all} enables all SLS hardening.

+

 @end table

 These @samp{-m} switches are supported in addition to the above

diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-1.c b/gcc/testsuite/gcc.target/i386/harden-sls-1.c

new file mode 100644

index 00000000000..6f70dc94a23

--- /dev/null

+++ b/gcc/testsuite/gcc.target/i386/harden-sls-1.c

@@ -0,0 +1,14 @@

+/* { dg-do compile } */

+/* { dg-options "-O2 -mindirect-branch=thunk-extern -mharden-sls=all" } */

+/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */

+

+extern void foo (void);

+

+void

+bar (void)

+{

+  foo ();

+}

+

+/* { dg-final { scan-assembler "jmp\[ \t\]+_?foo" } } */

+/* { dg-final { scan-assembler-not {int3} } } */

diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-2.c b/gcc/testsuite/gcc.target/i386/harden-sls-2.c

new file mode 100644

index 00000000000..a7c59078d03

--- /dev/null

+++ b/gcc/testsuite/gcc.target/i386/harden-sls-2.c

@@ -0,0 +1,14 @@

+/* { dg-do compile } */

+/* { dg-options "-O2 -mindirect-branch=thunk-extern -mharden-sls=all" } */

+/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */

+

+extern void (*fptr) (void);

+

+void

+foo (void)

+{

+  fptr ();

+}

+

+/* { dg-final { scan-assembler "jmp\[ \t\]+_?__x86_indirect_thunk_(r|e)ax" } } */

+/* { dg-final { scan-assembler-times "int3" 1 } } */

diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-3.c b/gcc/testsuite/gcc.target/i386/harden-sls-3.c

new file mode 100644

index 00000000000..1a6056b6d7b

--- /dev/null

+++ b/gcc/testsuite/gcc.target/i386/harden-sls-3.c

@@ -0,0 +1,14 @@

+/* { dg-do compile } */

+/* { dg-options "-O2 -mindirect-branch=thunk -mharden-sls=all" } */

+/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */

+

+extern void (*fptr) (void);

+

+void

+foo (void)

+{

+  fptr ();

+}

+

+/* { dg-final { scan-assembler "jmp\[ \t\]+_?__x86_indirect_thunk_(r|e)ax" } } */

+/* { dg-final { scan-assembler-times "int3" 2 } } */

diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-4.c b/gcc/testsuite/gcc.target/i386/harden-sls-4.c

new file mode 100644

index 00000000000..f70dd1379d3

--- /dev/null

+++ b/gcc/testsuite/gcc.target/i386/harden-sls-4.c

@@ -0,0 +1,16 @@

+/* { dg-do compile } */

+/* { dg-options "-O2 -mindirect-branch=keep -mharden-sls=all" } */

+/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */

+

+extern void (*fptr) (void);

+

+void

+foo (void)

+{

+  fptr ();

+}

+

+/* { dg-final { scan-assembler "jmp\[ \t\]+\\*_?fptr" { target { ! x32 } } } } */

+/* { dg-final { scan-assembler "movl\[ \t\]+fptr\\(%rip\\), %eax" { target x32 } } } */

+/* { dg-final { scan-assembler "jmp\[ \t\]+\\*%rax" { target x32 } } } */

+/* { dg-final { scan-assembler-times "int3" 1 } } */

diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-5.c b/gcc/testsuite/gcc.target/i386/harden-sls-5.c

new file mode 100644

index 00000000000..613c44c6f82

--- /dev/null

+++ b/gcc/testsuite/gcc.target/i386/harden-sls-5.c

@@ -0,0 +1,17 @@

+/* { dg-do compile } */

+/* { dg-options "-O2 -mno-indirect-branch-register -mfunction-return=keep -mindirect-branch=thunk-extern -mharden-sls=return" } */

+/* { dg-additional-options "-fno-pic" { target { ! *-*-darwin* } } } */

+

+typedef void (*dispatch_t)(long offset);

+

+dispatch_t dispatch;

+

+int

+male_indirect_jump (long offset)

+{

+  dispatch(offset);

+  return 0;

+}

+

+/* { dg-final { scan-assembler-times "ret" 1 } } */

+/* { dg-final { scan-assembler-times "int3" 1 } } */

-- 

2.36.1