linux-kernel - [patch 30/38] x86/retbleed: Add SKL call thunk

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Message-ID: <20220716230954.470918864@linutronix.de>
Date:   Sun, 17 Jul 2022 01:17:58 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     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>
Subject: [patch 30/38] x86/retbleed: Add SKL call thunk

Add the actual SKL call thunk for call depth accounting.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/callthunks.c |   24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -52,6 +52,24 @@ struct thunk_desc {
 
 static struct thunk_desc callthunk_desc __ro_after_init;
 
+asm (
+	".pushsection .rodata				\n"
+	".global skl_call_thunk_template		\n"
+	"skl_call_thunk_template:			\n"
+		__stringify(INCREMENT_CALL_DEPTH)"	\n"
+	".global skl_call_thunk_tail			\n"
+	"skl_call_thunk_tail:				\n"
+	".popsection					\n"
+);
+
+extern u8 skl_call_thunk_template[];
+extern u8 skl_call_thunk_tail[];
+
+#define SKL_TMPL_SIZE \
+	((unsigned int)(skl_call_thunk_tail - skl_call_thunk_template))
+#define SKL_CALLTHUNK_CODE_SIZE	(SKL_TMPL_SIZE + JMP32_INSN_SIZE + INT3_INSN_SIZE)
+#define SKL_CALLTHUNK_SIZE	roundup_pow_of_two(SKL_CALLTHUNK_CODE_SIZE)
+
 struct thunk_mem {
 	void			*base;
 	unsigned int		size;
@@ -447,6 +465,12 @@ static __init noinline void callthunks_i
 {
 	int ret;
 
+	if (cpu_feature_enabled(X86_FEATURE_CALL_DEPTH)) {
+		callthunk_desc.template = skl_call_thunk_template;
+		callthunk_desc.template_size = SKL_TMPL_SIZE;
+		callthunk_desc.thunk_size = SKL_CALLTHUNK_SIZE;
+	}
+
 	if (!callthunk_desc.template)
 		return;