linux-kernel - [PATCH v2 54/59] x86/orc: Make it callthunk aware

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Date:   Fri, 02 Sep 2022 15:07:19 +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 54/59] 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.

Cc: Josh Poimboeuf <jpoimboe@...nel.org>
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 |    5 +++++
 arch/x86/kernel/callthunks.c       |   13 +++++++++++++
 arch/x86/kernel/unwind_orc.c       |   21 ++++++++++++++++++++-
 3 files changed, 38 insertions(+), 1 deletion(-)

--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -92,6 +92,7 @@ extern void callthunks_patch_builtin_cal
 extern void callthunks_patch_module_calls(struct callthunk_sites *sites,
 					  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
@@ -101,6 +102,10 @@ 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
@@ -292,6 +292,19 @@ void *callthunks_translate_call_dest(voi
 	return target ? : dest;
 }
 
+bool is_callthunk(void *addr)
+{
+	unsigned int tmpl_size = SKL_TMPL_SIZE;
+	void *tmpl = skl_call_thunk_template;
+	unsigned long dest;
+
+	dest = roundup((unsigned long)addr, CONFIG_FUNCTION_ALIGNMENT);
+	if (!thunks_initialized || skip_addr((void *)dest))
+		return false;
+
+	return !bcmp((void *)(dest - tmpl_size), tmpl, tmpl_size);
+}
+
 #ifdef CONFIG_MODULES
 void noinline callthunks_patch_module_calls(struct callthunk_sites *cs,
 					    struct module *mod)
--- 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