On Fri, Jul 15, 2022 at 1:44 AM H.J. Lu via Gcc-patches
<gcc-patches@gcc.gnu.org> wrote:
>
> When shadow stack is enabled, function with indirect_return attribute
> may return via indirect jump. In this case, we need to disable sibcall
> if caller doesn't have indirect_return attribute and indirect branch
> tracking is enabled since compiler won't generate ENDBR when calling the
> caller.
>
LGTM.
> gcc/
>
> PR target/85620
> * config/i386/i386.cc (ix86_function_ok_for_sibcall): Return
> false if callee has indirect_return attribute and caller
> doesn't.
>
> gcc/testsuite/
>
> PR target/85620
> * gcc.target/i386/pr85620-2.c: Updated.
> * gcc.target/i386/pr85620-5.c: New test.
> * gcc.target/i386/pr85620-6.c: Likewise.
> * gcc.target/i386/pr85620-7.c: Likewise.
> ---
> gcc/config/i386/i386.cc | 10 ++++++++++
> gcc/testsuite/gcc.target/i386/pr85620-2.c | 3 ++-
> gcc/testsuite/gcc.target/i386/pr85620-5.c | 13 +++++++++++++
> gcc/testsuite/gcc.target/i386/pr85620-6.c | 14 ++++++++++++++
> gcc/testsuite/gcc.target/i386/pr85620-7.c | 14 ++++++++++++++
> 5 files changed, 53 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/gcc.target/i386/pr85620-5.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr85620-6.c
> create mode 100644 gcc/testsuite/gcc.target/i386/pr85620-7.c
>
> diff --git a/gcc/config/i386/i386.cc b/gcc/config/i386/i386.cc
> index 3a3c7299eb4..e03f86d4a23 100644
> --- a/gcc/config/i386/i386.cc
> +++ b/gcc/config/i386/i386.cc
> @@ -1024,6 +1024,16 @@ ix86_function_ok_for_sibcall (tree decl, tree exp)
> return false;
> }
>
> + /* Disable sibcall if callee has indirect_return attribute and
> + caller doesn't since callee will return to the caller's caller
> + via an indirect jump. */
> + if (((flag_cf_protection & (CF_RETURN | CF_BRANCH))
> + == (CF_RETURN | CF_BRANCH))
> + && lookup_attribute ("indirect_return", TYPE_ATTRIBUTES (type))
> + && !lookup_attribute ("indirect_return",
> + TYPE_ATTRIBUTES (TREE_TYPE (cfun->decl))))
> + return false;
> +
> /* Otherwise okay. That also includes certain types of indirect calls. */
> return true;
> }
> diff --git a/gcc/testsuite/gcc.target/i386/pr85620-2.c
> b/gcc/testsuite/gcc.target/i386/pr85620-2.c
> index b2e680fa1fe..14ce0ffd1e1 100644
> --- a/gcc/testsuite/gcc.target/i386/pr85620-2.c
> +++ b/gcc/testsuite/gcc.target/i386/pr85620-2.c
> @@ -1,6 +1,7 @@
> /* { dg-do compile } */
> /* { dg-options "-O2 -fcf-protection" } */
> -/* { dg-final { scan-assembler-times {\mendbr} 1 } } */
> +/* { dg-final { scan-assembler-times {\mendbr} 2 } } */
> +/* { dg-final { scan-assembler-not "jmp" } } */
>
> struct ucontext;
>
> diff --git a/gcc/testsuite/gcc.target/i386/pr85620-5.c
> b/gcc/testsuite/gcc.target/i386/pr85620-5.c
> new file mode 100644
> index 00000000000..04537702d09
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr85620-5.c
> @@ -0,0 +1,13 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fcf-protection" } */
> +/* { dg-final { scan-assembler-not "jmp" } } */
> +
> +struct ucontext;
> +
> +extern int (*bar) (struct ucontext *) __attribute__((__indirect_return__));
> +
> +int
> +foo (struct ucontext *oucp)
> +{
> + return bar (oucp);
> +}
> diff --git a/gcc/testsuite/gcc.target/i386/pr85620-6.c
> b/gcc/testsuite/gcc.target/i386/pr85620-6.c
> new file mode 100644
> index 00000000000..0b6a64e8454
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr85620-6.c
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fcf-protection" } */
> +/* { dg-final { scan-assembler "jmp" } } */
> +
> +struct ucontext;
> +
> +extern int bar (struct ucontext *) __attribute__((__indirect_return__));
> +
> +__attribute__((__indirect_return__))
> +int
> +foo (struct ucontext *oucp)
> +{
> + return bar (oucp);
> +}
> diff --git a/gcc/testsuite/gcc.target/i386/pr85620-7.c
> b/gcc/testsuite/gcc.target/i386/pr85620-7.c
> new file mode 100644
> index 00000000000..fa62d56decf
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/i386/pr85620-7.c
> @@ -0,0 +1,14 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O2 -fcf-protection" } */
> +/* { dg-final { scan-assembler "jmp" } } */
> +
> +struct ucontext;
> +
> +extern int (*bar) (struct ucontext *) __attribute__((__indirect_return__));
> +extern int foo (struct ucontext *) __attribute__((__indirect_return__));
> +
> +int
> +foo (struct ucontext *oucp)
> +{
> + return bar (oucp);
> +}
> --
> 2.36.1
>
--
BR,
Hongtao
