linux-kernel - [PATCH v17 4/9] x86/objtool: Add STACK_FRAME_NON

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Message-Id: <6b5098f327af4dfc11ad9bcdc274b0c8f0e2b2e5.1456331595.git.jpoimboe@redhat.com>
Date:	Wed, 24 Feb 2016 10:36:06 -0600
From:	Josh Poimboeuf <jpoimboe@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org
Cc:	linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
	Michal Marek <mmarek@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Andy Lutomirski <luto@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>,
	Pedro Alves <palves@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Bernd Petrovitsch <bernd@...rovitsch.priv.at>,
	Chris J Arges <chris.j.arges@...onical.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: [PATCH v17 4/9] x86/objtool: Add STACK_FRAME_NON_STANDARD macro

Add a new objtool ignore macro, STACK_FRAME_NON_STANDARD, which can be
used to tell objtool to skip validation of a function.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 MAINTAINERS                   |  1 +
 arch/x86/kernel/vmlinux.lds.S |  5 ++++-
 include/linux/objtool.h       | 22 ++++++++++++++++++++++
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 include/linux/objtool.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 7c7cebd..43a940e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7782,6 +7782,7 @@ OBJTOOL
 M:	Josh Poimboeuf <jpoimboe@...hat.com>
 S:	Supported
 F:	tools/objtool/
+F:	include/linux/objtool.h
 
 OMAP SUPPORT
 M:	Tony Lindgren <tony@...mide.com>
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 92dc211..6038fe0 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -343,7 +343,10 @@ SECTIONS
 
 	/* Sections to be discarded */
 	DISCARDS
-	/DISCARD/ : { *(.eh_frame) }
+	/DISCARD/ : {
+		*(.eh_frame)
+		*(__objtool_ignore_*)
+	}
 }
 
 
diff --git a/include/linux/objtool.h b/include/linux/objtool.h
new file mode 100644
index 0000000..cce9d67
--- /dev/null
+++ b/include/linux/objtool.h
@@ -0,0 +1,22 @@
+#ifndef _LINUX_OBJTOOL_H
+#define _LINUX_OBJTOOL_H
+
+#ifdef CONFIG_STACK_VALIDATION
+/*
+ * This C macro tells objtool to ignore the function when doing stack metadata
+ * validation.  It should only be used in special cases where you're 100% sure
+ * it won't affect the reliability of frame pointers and kernel stack traces.
+ *
+ * For more information, see tools/objtool/Documentation/stack-validation.txt.
+ */
+#define STACK_FRAME_NON_STANDARD(_func) \
+	static void __used __section(__objtool_ignore_func) \
+		*__objtool_ignore_func_##_func = _func
+
+#else /* !CONFIG_STACK_VALIDATION */
+
+#define STACK_FRAME_NON_STANDARD(_func)
+
+#endif /* CONFIG_STACK_VALIDATION */
+
+#endif /* _LINUX_OBJTOOL_H */
-- 
2.4.3