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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Borislav Petkov <bp@suse.de>,
        Kees Cook <keescook@chromium.org>,
        Nick Desaulniers <ndesaulniers@google.com>
Subject: [PATCH 5.10 144/148] x86: Use -mindirect-branch-cs-prefix for RETPOLINE builds
Date:   Sat, 23 Jul 2022 11:55:56 +0200
Message-Id: <20220723095304.680881838@linuxfoundation.org>
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From: Peter Zijlstra <peterz@infradead.org>

commit 68cf4f2a72ef8786e6b7af6fd9a89f27ac0f520d upstream.

In order to further enable commit:

  bbe2df3f6b6d ("x86/alternative: Try inline spectre_v2=retpoline,amd")

add the new GCC flag -mindirect-branch-cs-prefix:

  https://gcc.gnu.org/g:2196a681d7810ad8b227bf983f38ba716620545e
  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102952
  https://bugs.llvm.org/show_bug.cgi?id=52323

to RETPOLINE=y builds. This should allow fully inlining retpoline,amd
for GCC builds.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lkml.kernel.org/r/20211119165630.276205624@infradead.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 Makefile |    1 +
 1 file changed, 1 insertion(+)

--- a/Makefile
+++ b/Makefile
@@ -672,6 +672,7 @@ endif
 
 ifdef CONFIG_CC_IS_GCC
 RETPOLINE_CFLAGS	:= $(call cc-option,-mindirect-branch=thunk-extern -mindirect-branch-register)
+RETPOLINE_CFLAGS	+= $(call cc-option,-mindirect-branch-cs-prefix)
 RETPOLINE_VDSO_CFLAGS	:= $(call cc-option,-mindirect-branch=thunk-inline -mindirect-branch-register)
 endif
 ifdef CONFIG_CC_IS_CLANG