linux-kernel - [patch 34/38] x86/orc: Make it callthunk aware

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Date:   Sun, 17 Jul 2022 01:18:05 +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>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: [patch 34/38] x86/orc: Make it callthunk aware

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

Callthunks addresses on the stack would confuse the ORC unwinder. Handle
them correctly and tell ORC to proceed further down the stack.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>
---
 arch/x86/include/asm/alternative.h |    5 +++++
 arch/x86/kernel/callthunks.c       |    2 +-
 arch/x86/kernel/unwind_orc.c       |   21 ++++++++++++++++++++-
 3 files changed, 26 insertions(+), 2 deletions(-)

--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -94,6 +94,7 @@ extern void callthunks_patch_module_call
 					  struct module *mod);
 extern void callthunks_module_free(struct module *mod);
 extern void *callthunks_translate_call_dest(void *dest);
+extern bool is_callthunk(void *addr);
 #else
 static __always_inline void callthunks_patch_builtin_calls(void) {}
 static __always_inline void
@@ -104,6 +105,10 @@ static __always_inline void *callthunks_
 {
 	return dest;
 }
+static __always_inline bool is_callthunk(void *addr)
+{
+	return false;
+}
 #endif
 
 #ifdef CONFIG_SMP
--- a/arch/x86/kernel/callthunks.c
+++ b/arch/x86/kernel/callthunks.c
@@ -565,7 +565,7 @@ static bool is_module_callthunk(void *ad
 	return ret;
 }
 
-static bool is_callthunk(void *addr)
+bool is_callthunk(void *addr)
 {
 	if (builtin_layout.base <= addr &&
 	    addr < builtin_layout.base + builtin_layout.size)
--- a/arch/x86/kernel/unwind_orc.c
+++ b/arch/x86/kernel/unwind_orc.c
@@ -131,6 +131,21 @@ static struct orc_entry null_orc_entry =
 	.type = UNWIND_HINT_TYPE_CALL
 };
 
+#ifdef CONFIG_CALL_THUNKS
+static struct orc_entry *orc_callthunk_find(unsigned long ip)
+{
+	if (!is_callthunk((void *)ip))
+		return NULL;
+
+	return &null_orc_entry;
+}
+#else
+static struct orc_entry *orc_callthunk_find(unsigned long ip)
+{
+	return NULL;
+}
+#endif
+
 /* Fake frame pointer entry -- used as a fallback for generated code */
 static struct orc_entry orc_fp_entry = {
 	.type		= UNWIND_HINT_TYPE_CALL,
@@ -184,7 +199,11 @@ static struct orc_entry *orc_find(unsign
 	if (orc)
 		return orc;
 
-	return orc_ftrace_find(ip);
+	orc =  orc_ftrace_find(ip);
+	if (orc)
+		return orc;
+
+	return orc_callthunk_find(ip);
 }
 
 #ifdef CONFIG_MODULES