A small number of ARM fixes

- Fix function tracer and unwinder dependencies so that we don't
   end up building kernels that will crash.
 - Fix ARMv7M nommu initialisation (missing register initialisation)
 - Fix EFI decompressor entry (ensuring barrier instructions are
   enabled prior to use.)
 -----BEGIN PGP SIGNATURE-----
 Version: GnuPG v1
 
 iQIVAwUAXMWwyfTnkBvkraxkAQJRZg/+Pf90mhZrEZk54EvxD/asPC/s2B173tjt
 GqV+m7uHhfQRx1GL6zrirmOwx+fNLGc0ktlM7SGwEdljbkZ7juu/+Qbp6xe+uXPE
 4PeI+NdxlQQrZ5Bye/qpINWueW+awDoJyiLuofYgfTYZZbUnHL2kmITAObRgLmmQ
 MM1SrVXAleVw+IZWzPfsNiTJ5ouaSpdXMtUrfxPHU4PkxNAiTT3XJr4Uo9z2aS25
 vgpdq566wq6XneOjrRU9yVvh2g+KFuxv2bJplimcxnMj8C5asC6XuDqIKXp4sLyi
 OYZn5CeWIGuSdWTCaztD6cu8G0gsYL9Nf7SLYCw1YdR7SMawexu9aPE7UmLu/c1i
 +a2Sd1s5eUZpUqelmdxOEIiiFssbKB0c57ntwhAPQ6vj/Gnd5kIvMMJ/sx36Je4G
 7tVRDSPiNm/uU8wTy1MKGe2IOnwBUoRsryHc82Z8qaYGK8FJp3Fg3BVtJRMvZUIr
 toLAm+7l0D085W0DrPCDqYTkVYocBZ7366XQGRegoZ4z5a+oPfP0OBLzotiY3LpV
 KsEkBZUvhzI0IseV5U/s6htMqkgRktCSu80aYSJdHO+HQ67essOddTTV/7mxigEN
 Q/f8sgMMf7/we2bgDA0qZUGl1Q6/CT8HhHO3X2pwscvA+5SWHnDwbiHOpwhHbq9l
 gtR0D2vtdsY=
 =DnoV
 -----END PGP SIGNATURE-----

Merge tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm

Pull ARM fixes from Russell King:
 "A small number of ARM fixes

   - Fix function tracer and unwinder dependencies so that we don't end
     up building kernels that will crash

   - Fix ARMv7M nommu initialisation (missing register initialisation)

   - Fix EFI decompressor entry (ensuring barrier instructions are
     enabled prior to use)"

* tag 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm:
  ARM: 8857/1: efi: enable CP15 DMB instructions before cleaning the cache
  ARM: 8856/1: NOMMU: Fix CCR register faulty initialization when MPU is disabled
  ARM: fix function graph tracer and unwinder dependencies

arch/arm/Kconfig

@@ -73,7 +73,7 @@ config ARM
 	select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU
 	select HAVE_EXIT_THREAD
 	select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL
-	select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL
+	select HAVE_FUNCTION_GRAPH_TRACER if !THUMB2_KERNEL && !CC_IS_CLANG
 	select HAVE_FUNCTION_TRACER if !XIP_KERNEL
 	select HAVE_GCC_PLUGINS
 	select HAVE_HW_BREAKPOINT if PERF_EVENTS && (CPU_V6 || CPU_V6K || CPU_V7)

arch/arm/Kconfig.debug

@@ -47,8 +47,8 @@ config DEBUG_WX
 
 choice
 	prompt "Choose kernel unwinder"
-	default UNWINDER_ARM if AEABI && !FUNCTION_GRAPH_TRACER
-	default UNWINDER_FRAME_POINTER if !AEABI || FUNCTION_GRAPH_TRACER
+	default UNWINDER_ARM if AEABI
+	default UNWINDER_FRAME_POINTER if !AEABI
 	help
 	  This determines which method will be used for unwinding kernel stack
 	  traces for panics, oopses, bugs, warnings, perf, /proc/<pid>/stack,
@@ -65,7 +65,7 @@ config UNWINDER_FRAME_POINTER
 
 config UNWINDER_ARM
 	bool "ARM EABI stack unwinder"
-	depends on AEABI
+	depends on AEABI && !FUNCTION_GRAPH_TRACER
 	select ARM_UNWIND
 	help
 	  This option enables stack unwinding support in the kernel

arch/arm/boot/compressed/head.S

@@ -1438,7 +1438,21 @@ ENTRY(efi_stub_entry)
 
 		@ Preserve return value of efi_entry() in r4
 		mov	r4, r0
-		bl	cache_clean_flush
+
+		@ our cache maintenance code relies on CP15 barrier instructions
+		@ but since we arrived here with the MMU and caches configured
+		@ by UEFI, we must check that the CP15BEN bit is set in SCTLR.
+		@ Note that this bit is RAO/WI on v6 and earlier, so the ISB in
+		@ the enable path will be executed on v7+ only.
+		mrc	p15, 0, r1, c1, c0, 0	@ read SCTLR
+		tst	r1, #(1 << 5)		@ CP15BEN bit set?
+		bne	0f
+		orr	r1, r1, #(1 << 5)	@ CP15 barrier instructions
+		mcr	p15, 0, r1, c1, c0, 0	@ write SCTLR
+ ARM(		.inst	0xf57ff06f		@ v7+ isb	)
+ THUMB(		isb						)
+
+0:		bl	cache_clean_flush
 		bl	cache_off
 
 		@ Set parameters for booting zImage according to boot protocol

arch/arm/kernel/head-nommu.S

@@ -133,9 +133,9 @@ __secondary_data:
  */
 	.text
 __after_proc_init:
-#ifdef CONFIG_ARM_MPU
 M_CLASS(movw	r12, #:lower16:BASEADDR_V7M_SCB)
 M_CLASS(movt	r12, #:upper16:BASEADDR_V7M_SCB)
+#ifdef CONFIG_ARM_MPU
 M_CLASS(ldr	r3, [r12, 0x50])
 AR_CLASS(mrc	p15, 0, r3, c0, c1, 4)          @ Read ID_MMFR0
 	and	r3, r3, #(MMFR0_PMSA)           @ PMSA field