linux-kernel - [PATCH v4 13/13] x86/retpoline: Exclude objtool with retpoline

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Date:   Fri,  5 Jan 2018 02:01:09 +0000
From:   David Woodhouse <dwmw@...zon.co.uk>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     Paul Turner <pjt@...gle.com>, LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>, tglx@...utronix.de,
        Kees Cook <keescook@...gle.com>,
        Rik van Riel <riel@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        Jiri Kosina <jikos@...nel.org>, gnomes@...rguk.ukuu.org.uk
Subject: [PATCH v4 13/13] x86/retpoline: Exclude objtool with retpoline

From: Andi Kleen <ak@...ux.intel.com>

objtool's assembler nanny currently cannot deal with the code generated
by the retpoline compiler and throws hundreds of warnings, mostly
because it sees calls that don't have a symbolic target.

Exclude all the options that rely on objtool when RETPOLINE is active.

This mainly means that we use the frame pointer unwinder and livepatch
is not supported.

Eventually objtool can be fixed to handle this.

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
---
 arch/x86/Kconfig       | 4 ++--
 arch/x86/Kconfig.debug | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1009d1a..439633a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -172,8 +172,8 @@ config X86
 	select HAVE_PERF_USER_STACK_DUMP
 	select HAVE_RCU_TABLE_FREE
 	select HAVE_REGS_AND_STACK_ACCESS_API
-	select HAVE_RELIABLE_STACKTRACE		if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION
-	select HAVE_STACK_VALIDATION		if X86_64
+	select HAVE_RELIABLE_STACKTRACE		if X86_64 && UNWINDER_FRAME_POINTER && STACK_VALIDATION && !RETPOLINE
+	select HAVE_STACK_VALIDATION		if X86_64 && !RETPOLINE
 	select HAVE_SYSCALL_TRACEPOINTS
 	select HAVE_UNSTABLE_SCHED_CLOCK
 	select HAVE_USER_RETURN_NOTIFIER
diff --git a/arch/x86/Kconfig.debug b/arch/x86/Kconfig.debug
index 672441c..f169d88 100644
--- a/arch/x86/Kconfig.debug
+++ b/arch/x86/Kconfig.debug
@@ -359,8 +359,8 @@ config PUNIT_ATOM_DEBUG
 
 choice
 	prompt "Choose kernel unwinder"
-	default UNWINDER_ORC if X86_64
-	default UNWINDER_FRAME_POINTER if X86_32
+	default UNWINDER_ORC if X86_64 && !RETPOLINE
+	default UNWINDER_FRAME_POINTER if X86_32 || RETPOLINE
 	---help---
 	  This determines which method will be used for unwinding kernel stack
 	  traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
@@ -368,7 +368,7 @@ choice
 
 config UNWINDER_ORC
 	bool "ORC unwinder"
-	depends on X86_64
+	depends on X86_64 && !RETPOLINE
 	select STACK_VALIDATION
 	---help---
 	  This option enables the ORC (Oops Rewind Capability) unwinder for
-- 
2.7.4