Merge tag 'core-headers-2020-08-03' of git://git.kernel.org/pub/scm/l…

…inux/kernel/git/tip/tip Pull header cleanup from Ingo Molnar: "Separate out the instrumentation_begin()/end() bits from compiler.h" * tag 'core-headers-2020-08-03' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: compiler.h: Move instrumentation_begin()/end() to new <linux/instrumentation.h> header
mariux64 · Aug 3, 2020 · 5ece081 · 5ece081
2 parents c8e6939 + d19e789
commit 5ece081
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diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h
@@ -3,6 +3,7 @@
 #define _ASM_X86_BUG_H
 
 #include <linux/stringify.h>
+#include <linux/instrumentation.h>
 
 /*
  * Despite that some emulators terminate on UD2, we use it for WARN().

diff --git a/include/asm-generic/bug.h b/include/asm-generic/bug.h
@@ -3,6 +3,7 @@
 #define _ASM_GENERIC_BUG_H
 
 #include <linux/compiler.h>
+#include <linux/instrumentation.h>
 
 #define CUT_HERE		"------------[ cut here ]------------\n"
 

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
@@ -120,65 +120,12 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
 /* Annotate a C jump table to allow objtool to follow the code flow */
 #define __annotate_jump_table __section(.rodata..c_jump_table)
 
-#ifdef CONFIG_DEBUG_ENTRY
-/* Begin/end of an instrumentation safe region */
-#define instrumentation_begin() ({					\
-	asm volatile("%c0: nop\n\t"						\
-		     ".pushsection .discard.instr_begin\n\t"		\
-		     ".long %c0b - .\n\t"				\
-		     ".popsection\n\t" : : "i" (__COUNTER__));		\
-})
-
-/*
- * Because instrumentation_{begin,end}() can nest, objtool validation considers
- * _begin() a +1 and _end() a -1 and computes a sum over the instructions.
- * When the value is greater than 0, we consider instrumentation allowed.
- *
- * There is a problem with code like:
- *
- * noinstr void foo()
- * {
- *	instrumentation_begin();
- *	...
- *	if (cond) {
- *		instrumentation_begin();
- *		...
- *		instrumentation_end();
- *	}
- *	bar();
- *	instrumentation_end();
- * }
- *
- * If instrumentation_end() would be an empty label, like all the other
- * annotations, the inner _end(), which is at the end of a conditional block,
- * would land on the instruction after the block.
- *
- * If we then consider the sum of the !cond path, we'll see that the call to
- * bar() is with a 0-value, even though, we meant it to happen with a positive
- * value.
- *
- * To avoid this, have _end() be a NOP instruction, this ensures it will be
- * part of the condition block and does not escape.
- */
-#define instrumentation_end() ({					\
-	asm volatile("%c0: nop\n\t"					\
-		     ".pushsection .discard.instr_end\n\t"		\
-		     ".long %c0b - .\n\t"				\
-		     ".popsection\n\t" : : "i" (__COUNTER__));		\
-})
-#endif /* CONFIG_DEBUG_ENTRY */
-
 #else
 #define annotate_reachable()
 #define annotate_unreachable()
 #define __annotate_jump_table
 #endif
 
-#ifndef instrumentation_begin
-#define instrumentation_begin()		do { } while(0)
-#define instrumentation_end()		do { } while(0)
-#endif
-
 #ifndef ASM_UNREACHABLE
 # define ASM_UNREACHABLE
 #endif

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
@@ -5,6 +5,8 @@
 #include <linux/sched.h>
 #include <linux/vtime.h>
 #include <linux/context_tracking_state.h>
+#include <linux/instrumentation.h>
+
 #include <asm/ptrace.h>
 
 

diff --git a/include/linux/instrumentation.h b/include/linux/instrumentation.h
@@ -0,0 +1,57 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_INSTRUMENTATION_H
+#define __LINUX_INSTRUMENTATION_H
+
+#if defined(CONFIG_DEBUG_ENTRY) && defined(CONFIG_STACK_VALIDATION)
+
+/* Begin/end of an instrumentation safe region */
+#define instrumentation_begin() ({					\
+	asm volatile("%c0: nop\n\t"						\
+		     ".pushsection .discard.instr_begin\n\t"		\
+		     ".long %c0b - .\n\t"				\
+		     ".popsection\n\t" : : "i" (__COUNTER__));		\
+})
+
+/*
+ * Because instrumentation_{begin,end}() can nest, objtool validation considers
+ * _begin() a +1 and _end() a -1 and computes a sum over the instructions.
+ * When the value is greater than 0, we consider instrumentation allowed.
+ *
+ * There is a problem with code like:
+ *
+ * noinstr void foo()
+ * {
+ *	instrumentation_begin();
+ *	...
+ *	if (cond) {
+ *		instrumentation_begin();
+ *		...
+ *		instrumentation_end();
+ *	}
+ *	bar();
+ *	instrumentation_end();
+ * }
+ *
+ * If instrumentation_end() would be an empty label, like all the other
+ * annotations, the inner _end(), which is at the end of a conditional block,
+ * would land on the instruction after the block.
+ *
+ * If we then consider the sum of the !cond path, we'll see that the call to
+ * bar() is with a 0-value, even though, we meant it to happen with a positive
+ * value.
+ *
+ * To avoid this, have _end() be a NOP instruction, this ensures it will be
+ * part of the condition block and does not escape.
+ */
+#define instrumentation_end() ({					\
+	asm volatile("%c0: nop\n\t"					\
+		     ".pushsection .discard.instr_end\n\t"		\
+		     ".long %c0b - .\n\t"				\
+		     ".popsection\n\t" : : "i" (__COUNTER__));		\
+})
+#else
+# define instrumentation_begin()	do { } while(0)
+# define instrumentation_end()		do { } while(0)
+#endif
+
+#endif /* __LINUX_INSTRUMENTATION_H */