linux-hardening - [PATCH 03/15] objtool: Add ASM_STACK_FRAME_NON

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Date:   Fri, 16 Apr 2021 13:38:32 -0700
From:   Sami Tolvanen <samitolvanen@...gle.com>
To:     x86@...nel.org
Cc:     Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Sedat Dilek <sedat.dilek@...il.com>,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Sami Tolvanen <samitolvanen@...gle.com>
Subject: [PATCH 03/15] objtool: Add ASM_STACK_FRAME_NON_STANDARD

To use the STACK_FRAME_NON_STANDARD macro for a static symbol
defined in inline assembly, we need a C declaration that implies
global visibility. This type mismatch confuses the compiler with
CONFIG_CFI_CLANG. This change adds an inline assembly version of
the macro to avoid the issue.

Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
---
 include/linux/objtool.h       | 5 +++++
 tools/include/linux/objtool.h | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/objtool.h b/include/linux/objtool.h
index 7e72d975cb76..2f29ce48ab5f 100644
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -66,6 +66,11 @@ struct unwind_hint {
 	static void __used __section(".discard.func_stack_frame_non_standard") \
 		*__func_stack_frame_non_standard_##func = func
 
+#define ASM_STACK_FRAME_NON_STANDARD(func)				\
+	".pushsection .discard.func_stack_frame_non_standard, \"aw\"\n"	\
+	".long " __stringify(func) " - .\n"				\
+	".popsection\n"
+
 #else /* __ASSEMBLY__ */
 
 /*
diff --git a/tools/include/linux/objtool.h b/tools/include/linux/objtool.h
index 7e72d975cb76..2f29ce48ab5f 100644
--- a/tools/include/linux/objtool.h
+++ b/tools/include/linux/objtool.h
@@ -66,6 +66,11 @@ struct unwind_hint {
 	static void __used __section(".discard.func_stack_frame_non_standard") \
 		*__func_stack_frame_non_standard_##func = func
 
+#define ASM_STACK_FRAME_NON_STANDARD(func)				\
+	".pushsection .discard.func_stack_frame_non_standard, \"aw\"\n"	\
+	".long " __stringify(func) " - .\n"				\
+	".popsection\n"
+
 #else /* __ASSEMBLY__ */
 
 /*
-- 
2.31.1.368.gbe11c130af-goog