linux-kernel - [PATCH v15 08/25] x86/stacktool: Add ignore macros

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Message-Id: <cd7778181d2a5251c3dc21811fdbcaa2c16c98c3.1450442274.git.jpoimboe@redhat.com>
Date:	Fri, 18 Dec 2015 06:39:22 -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 v15 08/25] x86/stacktool: Add ignore macros

Add new stacktool ignore macros: STACKTOOL_IGNORE_INSN and
STACKTOOL_IGNORE_FUNC.  These can be used to tell stacktool to skip
validation of an instruction or a function, respectively.

Signed-off-by: Josh Poimboeuf <jpoimboe@...hat.com>
---
 arch/x86/include/asm/stacktool.h | 45 ++++++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/vmlinux.lds.S    |  5 ++++-
 include/linux/stacktool.h        | 29 ++++++++++++++++++++++++++
 3 files changed, 78 insertions(+), 1 deletion(-)
 create mode 100644 arch/x86/include/asm/stacktool.h
 create mode 100644 include/linux/stacktool.h

diff --git a/arch/x86/include/asm/stacktool.h b/arch/x86/include/asm/stacktool.h
new file mode 100644
index 0000000..250a37e
--- /dev/null
+++ b/arch/x86/include/asm/stacktool.h
@@ -0,0 +1,45 @@
+#ifndef _ASM_X86_STACKTOOL_H
+#define _ASM_X86_STACKTOOL_H
+
+#include <asm/asm.h>
+
+#ifdef __ASSEMBLY__
+
+/*
+ * This asm macro tells stacktool to ignore the instruction immediately after
+ * the macro 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/stacktool/Documentation/stack-validation.txt.
+ */
+.macro STACKTOOL_IGNORE_INSN
+#ifdef CONFIG_STACK_VALIDATION
+	.Lstacktool_ignore_\@:
+	.pushsection __stacktool_ignore_insn, "a"
+	_ASM_ALIGN
+	.long .Lstacktool_ignore_\@ - .
+	.popsection
+#endif
+.endm
+
+#else /* !__ASSEMBLY__ */
+
+#ifdef CONFIG_STACK_VALIDATION
+
+#define STACKTOOL_IGNORE_INSN				\
+	"1:\n"							\
+	".pushsection __stacktool_ignore_insn, \"a\"\n"	\
+	_ASM_ALIGN "\n"						\
+	".long 1b - .\n"					\
+	".popsection\n"
+
+#else /* !CONFIG_STACK_VALIDATION */
+
+#define STACKTOOL_IGNORE_INSN ""
+
+#endif /* CONFIG_STACK_VALIDATION */
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_X86_STACKTOOL_H */
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 4f19942..c08c283c 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -333,7 +333,10 @@ SECTIONS
 
 	/* Sections to be discarded */
 	DISCARDS
-	/DISCARD/ : { *(.eh_frame) }
+	/DISCARD/ : {
+		*(.eh_frame)
+		*(__stacktool_ignore_*)
+	}
 }
 
 
diff --git a/include/linux/stacktool.h b/include/linux/stacktool.h
new file mode 100644
index 0000000..c1e151b
--- /dev/null
+++ b/include/linux/stacktool.h
@@ -0,0 +1,29 @@
+#ifndef _LINUX_STACKTOOL_H
+#define _LINUX_STACKTOOL_H
+
+#include <asm/stacktool.h>
+
+#ifndef __ASSEMBLY__
+
+#ifdef CONFIG_STACK_VALIDATION
+/*
+ * This C macro tells stacktool 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/stacktool/Documentation/stack-validation.txt.
+ */
+#define STACKTOOL_IGNORE_FUNC(_func) \
+	static void __used __section(__stacktool_ignore_func) \
+		*__stacktool_ignore_func_##_func = _func
+
+#else /* !CONFIG_STACK_VALIDATION */
+
+#define STACKTOOL_IGNORE_FUNC(_func)
+
+#endif /* CONFIG_STACK_VALIDATION */
+
+#endif /* !__ASSEMBLY__ */
+
+#endif /* _LINUX_STACKTOOL_H */
-- 
2.4.3

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