linux-kernel - Re: [PATCH v2 04/12] objtool: Convert instrumentation

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Message-ID: <20241116100610.GN22801@noisy.programming.kicks-ass.net>
Date: Sat, 16 Nov 2024 11:06:10 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: seanjc@...gle.com, pbonzini@...hat.com, tglx@...utronix.de,
	linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
	jthoughton@...gle.com
Subject: Re: [PATCH v2 04/12] objtool: Convert instrumentation_{begin,end}()
 to ANNOTATE

On Fri, Nov 15, 2024 at 10:40:08AM -0800, Josh Poimboeuf wrote:
> On Mon, Nov 11, 2024 at 12:59:39PM +0100, Peter Zijlstra wrote:
> > +++ b/include/linux/objtool.h
> > @@ -51,13 +51,16 @@
> >  	".long 998b\n\t"						\
> >  	".popsection\n\t"
> >  
> > -#define ASM_ANNOTATE(x)						\
> > -	"911:\n\t"						\
> > +#define __ASM_ANNOTATE(s, x)					\
> >  	".pushsection .discard.annotate,\"M\",@progbits,8\n\t"	\
> > -	".long 911b - .\n\t"					\
> > +	".long " __stringify(s) "b - .\n\t"			\
> 
> It would probably be better for __ASM_ANNOTATE's callers to pass in the
> full label name (e.g. '911b') since they know where the label is?  It
> could even be a named label.

This seems to work.

--- a/include/linux/instrumentation.h
+++ b/include/linux/instrumentation.h
@@ -6,11 +6,12 @@
 
 #include <linux/objtool.h>
 #include <linux/stringify.h>
+#include <linux/args.h>
 
 /* Begin/end of an instrumentation safe region */
 #define __instrumentation_begin(c) ({					\
 	asm volatile(__stringify(c) ": nop\n\t"				\
-		     __ASM_ANNOTATE(c, ANNOTYPE_INSTR_BEGIN)		\
+		     __ASM_ANNOTATE(CONCATENATE(c, b), ANNOTYPE_INSTR_BEGIN)	\
 		     : : "i" (c));					\
 })
 #define instrumentation_begin() __instrumentation_begin(__COUNTER__)
@@ -48,7 +49,7 @@
  */
 #define __instrumentation_end(c) ({					\
 	asm volatile(__stringify(c) ": nop\n\t"				\
-		     __ASM_ANNOTATE(c, ANNOTYPE_INSTR_END)		\
+		     __ASM_ANNOTATE(CONCATENATE(c, b), ANNOTYPE_INSTR_END)		\
 		     : : "i" (c));					\
 })
 #define instrumentation_end() __instrumentation_end(__COUNTER__)
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -53,13 +53,13 @@
 
 #define __ASM_ANNOTATE(s, x)					\
 	".pushsection .discard.annotate,\"M\",@progbits,8\n\t"	\
-	".long " __stringify(s) "b - .\n\t"			\
+	".long " __stringify(s) " - .\n\t"			\
 	".long " __stringify(x) "\n\t"				\
 	".popsection\n\t"
 
 #define ASM_ANNOTATE(x)						\
 	"911:\n\t"						\
-	__ASM_ANNOTATE(911, x)
+	__ASM_ANNOTATE(911b, x)
 
 #define ANNOTATE_NOENDBR	ASM_ANNOTATE(ANNOTYPE_NOENDBR)