ARM: zImage/virt: hyp mode entry support for the zImage loader

The zImage loader needs to turn on the MMU in order to take
advantage of caching while decompressing the zImage.  Running this
in hyp mode would require the LPAE pagetable format to be
supported; to avoid this complexity, this patch switches out of hyp
mode, and returns back to hyp mode just before booting the kernel.

This implementation assumes that the Hyp mode view of memory and the
PL1 view of memory are coherent, providing that the MMU and caches
are off in both, as required by the boot protocol.  The zImage
decompression code must drain the write buffer on completion anyway, and
entry into Hyp mode should flush any prefetch buffer, avoiding hazards
associated with local write buffers and the pipeline.

Signed-off-by: Dave Martin <dave.martin@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

4 files changed, 91 insertions, 8 deletions

diff --git a/arch/arm/boot/compressed/.gitignore b/arch/arm/boot/compressed/.gitignore
index d0d441c429ae..f79a08efe000 100644
--- a/arch/arm/boot/compressed/.gitignore
+++ b/arch/arm/boot/compressed/.gitignore
@@ -1,6 +1,7 @@
 ashldi3.S
 font.c
 lib1funcs.S
+hyp-stub.S
 piggy.gzip
 piggy.lzo
 piggy.lzma
diff --git a/arch/arm/boot/compressed/Makefile b/arch/arm/boot/compressed/Makefile
index bb267562e7ed..a517153a13ea 100644
--- a/arch/arm/boot/compressed/Makefile
+++ b/arch/arm/boot/compressed/Makefile
@@ -30,6 +30,10 @@ FONTC	= $(srctree)/drivers/video/console/font_acorn_8x8.c
 OBJS            += string.o
 CFLAGS_string.o := -Os
 
+ifeq ($(CONFIG_ARM_VIRT_EXT),y)
+OBJS            += hyp-stub.o
+endif
+
 #
 # Architecture dependencies
 #
@@ -126,7 +130,7 @@ KBUILD_CFLAGS = $(subst -pg, , $(ORIG_CFLAGS))
 endif
 
 ccflags-y := -fpic -fno-builtin -I$(obj)
-asflags-y := -Wa,-march=all
+asflags-y := -Wa,-march=all -DZIMAGE
 
 # Supply kernel BSS size to the decompressor via a linker symbol.
 KBSS_SZ = $(shell $(CROSS_COMPILE)size $(obj)/../../../../vmlinux | \
@@ -198,3 +202,6 @@ $(obj)/font.c: $(FONTC)
 
 $(obj)/vmlinux.lds: $(obj)/vmlinux.lds.in arch/arm/boot/Makefile $(KCONFIG_CONFIG)
         @sed "$(SEDFLAGS)" < $< > $@
+
+$(obj)/hyp-stub.S: $(srctree)/arch/$(SRCARCH)/kernel/hyp-stub.S
+        $(call cmd,shipped)
diff --git a/arch/arm/boot/compressed/head.S b/arch/arm/boot/compressed/head.S
index b8c64b80bafc..0749a6184abf 100644
--- a/arch/arm/boot/compressed/head.S
+++ b/arch/arm/boot/compressed/head.S
@@ -9,6 +9,7 @@
  * published by the Free Software Foundation.
  */
 #include <linux/linkage.h>
+#include <asm/assembler.h>
 
 /*
  * Debugging stuff
@@ -132,7 +133,12 @@ start:
                 .word   start                   @ absolute load/run zImage address
                 .word   _edata                  @ zImage end address
  THUMB(         .thumb                  )
-1:              mov     r7, r1                  @ save architecture ID
+1:
+                mrs     r9, cpsr
+#ifdef CONFIG_ARM_VIRT_EXT
+                bl      __hyp_stub_install      @ get into SVC mode, reversibly
+#endif
+                mov     r7, r1                  @ save architecture ID
                 mov     r8, r2                  @ save atags pointer
 
 #ifndef __ARM_ARCH_2__
@@ -148,9 +154,9 @@ start:
  ARM(           swi     0x123456        )       @ angel_SWI_ARM
  THUMB(         svc     0xab            )       @ angel_SWI_THUMB
 not_angel:
-                mrs     r2, cpsr                @ turn off interrupts to
-                orr     r2, r2, #0xc0           @ prevent angel from running
-                msr     cpsr_c, r2
+                safe_svcmode_maskall r0
+                msr     spsr_cxsf, r9           @ Save the CPU boot mode in
+                                                @ SPSR
 #else
                 teqp    pc, #0x0c000003         @ turn off interrupts
 #endif
@@ -350,6 +356,20 @@ dtb_check_done:
                 adr     r5, restart
                 bic     r5, r5, #31
 
+/* Relocate the hyp vector base if necessary */
+#ifdef CONFIG_ARM_VIRT_EXT
+                mrs     r0, spsr
+                and     r0, r0, #MODE_MASK
+                cmp     r0, #HYP_MODE
+                bne     1f
+
+                bl      __hyp_get_vectors
+                sub     r0, r0, r5
+                add     r0, r0, r10
+                bl      __hyp_set_vectors
+1:
+#endif
+
                 sub     r9, r6, r5              @ size to copy
                 add     r9, r9, #31             @ rounded up to a multiple
                 bic     r9, r9, #31             @ ... of 32 bytes
@@ -458,11 +478,29 @@ not_relocated:	mov	r0, #0
                 bl      decompress_kernel
                 bl      cache_clean_flush
                 bl      cache_off
-                mov     r0, #0                  @ must be zero
                 mov     r1, r7                  @ restore architecture number
                 mov     r2, r8                  @ restore atags pointer
- ARM(           mov     pc, r4  )               @ call kernel
- THUMB(         bx      r4      )               @ entry point is always ARM
+
+#ifdef CONFIG_ARM_VIRT_EXT
+                mrs     r0, spsr                @ Get saved CPU boot mode
+                and     r0, r0, #MODE_MASK
+                cmp     r0, #HYP_MODE           @ if not booted in HYP mode...
+                bne     __enter_kernel          @ boot kernel directly
+
+                adr     r12, .L__hyp_reentry_vectors_offset
+                ldr     r0, [r12]
+                add     r0, r0, r12
+
+                bl      __hyp_set_vectors
+                __HVC(0)                        @ otherwise bounce to hyp mode
+
+                b       .                       @ should never be reached
+
+                .align  2
+.L__hyp_reentry_vectors_offset: .long   __hyp_reentry_vectors - .
+#else
+                b       __enter_kernel
+#endif
 
                 .align  2
                 .type   LC0, #object
@@ -1191,6 +1229,25 @@ memdump:	mov	r12, r0
 #endif
 
                 .ltorg
+
+#ifdef CONFIG_ARM_VIRT_EXT
+.align 5
+__hyp_reentry_vectors:
+                W(b)    .                       @ reset
+                W(b)    .                       @ undef
+                W(b)    .                       @ svc
+                W(b)    .                       @ pabort
+                W(b)    .                       @ dabort
+                W(b)    __enter_kernel          @ hyp
+                W(b)    .                       @ irq
+                W(b)    .                       @ fiq
+#endif /* CONFIG_ARM_VIRT_EXT */
+
+__enter_kernel:
+                mov     r0, #0                  @ must be 0
+ ARM(           mov     pc, r4  )               @ call kernel
+ THUMB(         bx      r4      )               @ entry point is always ARM
+
 reloc_code_end:
 
                 .align
diff --git a/arch/arm/kernel/hyp-stub.S b/arch/arm/kernel/hyp-stub.S
index b03e9244e5ad..70609417deaf 100644
--- a/arch/arm/kernel/hyp-stub.S
+++ b/arch/arm/kernel/hyp-stub.S
@@ -21,6 +21,7 @@
 #include <asm/assembler.h>
 #include <asm/virt.h>
 
+#ifndef ZIMAGE
 /*
  * For the kernel proper, we need to find out the CPU boot mode long after
  * boot, so we need to store it in a writable variable.
@@ -59,6 +60,21 @@ ENTRY(__boot_cpu_mode)
         strne   r7, [r5, r6]            @ record what happened and give up
         .endm
 
+#else   /* ZIMAGE */
+
+        .macro  store_primary_cpu_mode  reg1:req, reg2:req, reg3:req
+        .endm
+
+/*
+ * The zImage loader only runs on one CPU, so we don't bother with mult-CPU
+ * consistency checking:
+ */
+        .macro  compare_cpu_mode_with_primary mode, reg1, reg2, reg3
+        cmp     \mode, \mode
+        .endm
+
+#endif /* ZIMAGE */
+
 /*
  * Hypervisor stub installation functions.
  *
@@ -174,9 +190,11 @@ ENTRY(__hyp_set_vectors)
         bx      lr
 ENDPROC(__hyp_set_vectors)
 
+#ifndef ZIMAGE
 .align 2
 .L__boot_cpu_mode_offset:
         .long   __boot_cpu_mode - .
+#endif
 
 .align 5
 __hyp_stub_vectors: