From: Rob Landley <rob@landley.net>
To: linux-kernel@vger.kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>,Ingo Molnar <mingo@redhat.com>,Borislav Petkov <bp@alien8.de>,Dave Hansen <dave.hansen@linux.intel.com>,x86@kernel.org,H. Peter Anvin <hpa@zytor.com>
Date: Mon, 4 Jul 2022 23:51:05 -0500
Subject: [PATCH 2/5] X86-64 should not uniquely require a third ELF package to
 build.

x86-64 is the only architecture that can't compile without an extra
ELF library installed on the host. (The kernel already has multiple ELF
parse implementations built-in, so requiring another one is questionable
at best.) You can switch it back on in menuconfig if you want to, this
just stops it being mandatory.

See https://lkml.iu.edu/hypermail/linux/kernel/2110.3/00402.html
and https://lkml.iu.edu/hypermail/linux/kernel/2110.3/00278.html

Signed-off-by: Rob Landley <rob@landley.net>
---

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 53bab123a8ee..5b2866ef30d2 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -245,7 +245,7 @@ config X86
 	select HAVE_NOINSTR_HACK		if HAVE_OBJTOOL
 	select HAVE_NMI
 	select HAVE_NOINSTR_VALIDATION		if HAVE_OBJTOOL
-	select HAVE_OBJTOOL			if X86_64
+	select HAVE_OBJTOOL			if X86_64 && !UNWINDER_FRAME_POINTER
 	select HAVE_OPTPROBES
 	select HAVE_PCSPKR_PLATFORM
 	select HAVE_PERF_EVENTS
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index f31e286c2977..d9074767a5b5 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -84,6 +84,12 @@
  * with them due to bugs in both AMD and Intel CPUs.
  */
 
+#ifndef CONFIG_HAVE_RELIABLE_STACK_TRACE
+#define UNWIND_HINT_ENTRY
+#define UNWIND_HINT_IRET_ENTRY
+#define validate_unret_begin
+#endif
+
 SYM_CODE_START(entry_SYSCALL_64)
 	UNWIND_HINT_ENTRY
 	ENDBR
@@ -386,11 +392,10 @@ SYM_CODE_END(xen_error_entry)
 .macro idtentry vector asmsym cfunc has_error_code:req
 SYM_CODE_START(\asmsym)
 
+	UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8
 	.if \vector == X86_TRAP_BP
 		/* #BP advances %rip to the next instruction */
-		UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8 signal=0
-	.else
-		UNWIND_HINT_IRET_ENTRY offset=\has_error_code*8
+		UNWIND_HINT_IRET_ENTRY signal=0
 	.endif
 
 	ENDBR