[PATCH] x86: Generate INT3 for __builtin_eh_return

[PATCH] x86: Generate INT3 for __builtin_eh_return

[H.J. Lu]

Generate INT3 after indirect jmp in exception return for -fcf-protection
with -mharden-sls=indirect-jmp.

gcc/

	PR target/103925
	* config/i386/i386.c (ix86_output_indirect_function_return):
	Generate INT3 after indirect jmp for -mharden-sls=indirect-jmp.

gcc/testsuite/

	PR target/103925
	* gcc.target/i386/harden-sls-6.c: New test.
---
 gcc/config/i386/i386.c                       |  9 ++++++---
 gcc/testsuite/gcc.target/i386/harden-sls-6.c | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-6.c

diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
index 835ec2cafcb..35fb5adf2ef 100644
--- a/gcc/config/i386/i386.c
+++ b/gcc/config/i386/i386.c
@@ -16367,11 +16367,14 @@ ix86_output_indirect_function_return (rtx ret_op)
 	}
       else
 	output_indirect_thunk (regno);
-
-      return "";
     }
   else
-    return "%!jmp\t%A0";
+    {
+      output_asm_insn ("%!jmp\t%A0", &ret_op);
+      if (ix86_harden_sls & harden_sls_indirect_jmp)
+	fputs ("\tint3\n", asm_out_file);
+    }
+  return "";
 }
 
 /* Output the assembly for a call instruction.  */
diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-6.c b/gcc/testsuite/gcc.target/i386/harden-sls-6.c
new file mode 100644
index 00000000000..9068eb64008
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/harden-sls-6.c
@@ -0,0 +1,18 @@
+/* { dg-do compile { target { ! ia32 } } } */
+/* { dg-options "-O2 -fcf-protection -mharden-sls=indirect-jmp" } */
+
+struct _Unwind_Context _Unwind_Resume_or_Rethrow_this_context;
+
+void offset (int);
+
+struct _Unwind_Context {
+  void *reg[7];
+} _Unwind_Resume_or_Rethrow() {
+  struct _Unwind_Context cur_contextcur_context =
+      _Unwind_Resume_or_Rethrow_this_context;
+  offset(0);
+  __builtin_eh_return ((long) offset, 0);
+}
+
+/* { dg-final { scan-assembler "jmp\[ \t\]+\\*%rcx" } } */
+/* { dg-final { scan-assembler-times "int3" 1 } } */
-- 
2.33.1

Re: [PATCH] x86: Generate INT3 for __builtin_eh_return

[Uros Bizjak]

On Thu, Jan 6, 2022 at 7:58 PM H.J. Lu <hjl.tools@gmail.com> wrote:
>
> Generate INT3 after indirect jmp in exception return for -fcf-protection
> with -mharden-sls=indirect-jmp.
>
> gcc/
>
>         PR target/103925
>         * config/i386/i386.c (ix86_output_indirect_function_return):
>         Generate INT3 after indirect jmp for -mharden-sls=indirect-jmp.
>
> gcc/testsuite/
>
>         PR target/103925
>         * gcc.target/i386/harden-sls-6.c: New test.

OK.

Thanks,
Uros.

> ---
>  gcc/config/i386/i386.c                       |  9 ++++++---
>  gcc/testsuite/gcc.target/i386/harden-sls-6.c | 18 ++++++++++++++++++
>  2 files changed, 24 insertions(+), 3 deletions(-)
>  create mode 100644 gcc/testsuite/gcc.target/i386/harden-sls-6.c
>
> diff --git a/gcc/config/i386/i386.c b/gcc/config/i386/i386.c
> index 835ec2cafcb..35fb5adf2ef 100644
> --- a/gcc/config/i386/i386.c
> +++ b/gcc/config/i386/i386.c
> @@ -16367,11 +16367,14 @@ ix86_output_indirect_function_return (rtx ret_op)
>         }
>        else
>         output_indirect_thunk (regno);
> -
> -      return "";
>      }
>    else
> -    return "%!jmp\t%A0";
> +    {
> +      output_asm_insn ("%!jmp\t%A0", &ret_op);
> +      if (ix86_harden_sls & harden_sls_indirect_jmp)
> +       fputs ("\tint3\n", asm_out_file);
> +    }
> +  return "";
>  }
>
>  /* Output the assembly for a call instruction.  */
> diff --git a/gcc/testsuite/gcc.target/i386/harden-sls-6.c b/gcc/testsuite/gcc.target/i386/harden-sls-6.c
> new file mode 100644
> index 00000000000..9068eb64008
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/harden-sls-6.c
> @@ -0,0 +1,18 @@
> +/* { dg-do compile { target { ! ia32 } } } */
> +/* { dg-options "-O2 -fcf-protection -mharden-sls=indirect-jmp" } */
> +
> +struct _Unwind_Context _Unwind_Resume_or_Rethrow_this_context;
> +
> +void offset (int);
> +
> +struct _Unwind_Context {
> +  void *reg[7];
> +} _Unwind_Resume_or_Rethrow() {
> +  struct _Unwind_Context cur_contextcur_context =
> +      _Unwind_Resume_or_Rethrow_this_context;
> +  offset(0);
> +  __builtin_eh_return ((long) offset, 0);
> +}
> +
> +/* { dg-final { scan-assembler "jmp\[ \t\]+\\*%rcx" } } */
> +/* { dg-final { scan-assembler-times "int3" 1 } } */
> --
> 2.33.1
>