linux-kernel - [PATCH v2 50/59] x86/retbleed: Add SKL call thunk

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Date:   Fri, 02 Sep 2022 15:07:15 +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 50/59] x86/retbleed: Add SKL call thunk

From: Thomas Gleixner <tglx@...utronix.de>

Add the actual SKL call thunk for call depth accounting.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/kernel/callthunks.c |   25 ++++++++++++++++++++-----
 1 file changed, 20 insertions(+), 5 deletions(-)

--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -7,6 +7,7 @@
 #include <linux/moduleloader.h>
 
 #include <asm/alternative.h>
+#include <asm/asm-offsets.h>
 #include <asm/cpu.h>
 #include <asm/ftrace.h>
 #include <asm/insn.h>
@@ -55,7 +56,21 @@ static const struct core_text builtin_co
 	.name = "builtin",
 };
 
-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))
 
 extern void error_entry(void);
 extern void xen_error_entry(void);
@@ -157,11 +172,11 @@ static const u8 nops[] = {
 
 static __init_or_module void *patch_dest(void *dest, bool direct)
 {
-	unsigned int tsize = callthunk_desc.template_size;
+	unsigned int tsize = SKL_TMPL_SIZE;
 	u8 *pad = dest - tsize;
 
 	/* Already patched? */
-	if (!bcmp(pad, callthunk_desc.template, tsize))
+	if (!bcmp(pad, skl_call_thunk_template, tsize))
 		return pad;
 
 	/* Ensure there are nops */
@@ -171,9 +186,9 @@ static __init_or_module void *patch_dest
 	}
 
 	if (direct)
-		memcpy(pad, callthunk_desc.template, tsize);
+		memcpy(pad, skl_call_thunk_template, tsize);
 	else
-		text_poke_copy_locked(pad, callthunk_desc.template, tsize, true);
+		text_poke_copy_locked(pad, skl_call_thunk_template, tsize, true);
 	return pad;
 }