linux-kernel - [PATCH v2 47/59] x86/asm: Provide ALTERNATIVE

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Date:   Fri, 02 Sep 2022 15:07:12 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org, x86@...nel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
        Johannes Wikner <kwikner@...z.ch>,
        Alyssa Milburn <alyssa.milburn@...ux.intel.com>,
        Jann Horn <jannh@...gle.com>, "H.J. Lu" <hjl.tools@...il.com>,
        Joao Moreira <joao.moreira@...el.com>,
        Joseph Nuzman <joseph.nuzman@...el.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Juergen Gross <jgross@...e.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        K Prateek Nayak <kprateek.nayak@....com>,
        Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 47/59] x86/asm: Provide ALTERNATIVE_3

From: Peter Zijlstra <peterz@...radead.org>

Fairly straight forward adaptation/extention of ALTERNATIVE_2.

Required for call depth tracking.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/include/asm/alternative.h |   33 ++++++++++++++++++++++++++++++---
 1 file changed, 30 insertions(+), 3 deletions(-)

--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -364,6 +364,7 @@ static inline int alternatives_text_rese
 #define old_len			141b-140b
 #define new_len1		144f-143f
 #define new_len2		145f-144f
+#define new_len3		146f-145f
 
 /*
  * gas compatible max based on the idea from:
@@ -371,7 +372,8 @@ static inline int alternatives_text_rese
  *
  * The additional "-" is needed because gas uses a "true" value of -1.
  */
-#define alt_max_short(a, b)	((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
+#define alt_max_2(a, b)		((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
+#define alt_max_3(a, b, c)	(alt_max_2(alt_max_2(a, b), c))
 
 
 /*
@@ -383,8 +385,8 @@ static inline int alternatives_text_rese
 140:
 	\oldinstr
 141:
-	.skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
-		(alt_max_short(new_len1, new_len2) - (old_len)),0x90
+	.skip -((alt_max_2(new_len1, new_len2) - (old_len)) > 0) * \
+		(alt_max_2(new_len1, new_len2) - (old_len)),0x90
 142:
 
 	.pushsection .altinstructions,"a"
@@ -401,6 +403,31 @@ static inline int alternatives_text_rese
 	.popsection
 .endm
 
+.macro ALTERNATIVE_3 oldinstr, newinstr1, feature1, newinstr2, feature2, newinstr3, feature3
+140:
+	\oldinstr
+141:
+	.skip -((alt_max_3(new_len1, new_len2, new_len3) - (old_len)) > 0) * \
+		(alt_max_3(new_len1, new_len2, new_len3) - (old_len)),0x90
+142:
+
+	.pushsection .altinstructions,"a"
+	altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f
+	altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f
+	altinstruction_entry 140b,145f,\feature3,142b-140b,146f-145f
+	.popsection
+
+	.pushsection .altinstr_replacement,"ax"
+143:
+	\newinstr1
+144:
+	\newinstr2
+145:
+	\newinstr3
+146:
+	.popsection
+.endm
+
 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */
 #define ALTERNATIVE_TERNARY(oldinstr, feature, newinstr_yes, newinstr_no) \
 	ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS,	\