bootwrapper: Drop now-obsolete SMC interface support

Now that the kernel supports simply being started in Hyp mode,
we don't need to maintain the obsolete SMC interface for setting
HVBAR and switching to NS mode. Drop monitor.S in favour of a
much simpler special-purpose bit of code in boot.S which passes
briefly through Monitor mode to set up HVBAR and drop into
NS state. We also disable SMC in NS mode, so that inadvertent
use of it will UNDEF rather than leaping back into the boot
wrapper later on.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

4 files changed, 41 insertions, 119 deletions

diff --git a/Makefile b/Makefile
index f8fc841..0997dcf 100644
--- a/Makefile
+++ b/Makefile
@@ -15,9 +15,8 @@ endif
 
 LIBFDTOBJS      = libfdt/fdt.o libfdt/fdt_ro.o libfdt/fdt_wip.o \
 		  libfdt/fdt_sw.o libfdt/fdt_rw.o libfdt/fdt_strerror.o
-MONITOR		= monitor.S
 BOOTLOADER	= boot.S
-OBJS 		= boot.o c_start.o monitor.o semihosting.o string.o semi_loader.o $(LIBFDTOBJS)
+OBJS 		= boot.o c_start.o semihosting.o string.o semi_loader.o $(LIBFDTOBJS)
 KERNEL		= uImage
 
 IMAGE		= linux-system.axf
@@ -53,9 +52,6 @@ $(SEMIIMG): $(OBJS) modelsemi.lds
 boot.o: $(BOOTLOADER)
 	$(CC) $(CPPFLAGS) -DKCMD='$(KCMD)' -c -o $@ $<
 
-monitor.o: $(MONITOR)
-	$(CC) $(CPPFLAGS) -c -o $@ $<
-
 %.o: %.c
 	$(CC) $(CPPFLAGS) -O2 -ffreestanding -I. -Ilibfdt -c -o $@ $<
 
diff --git a/boot.S b/boot.S
index 1e24b0e..727119a 100644
--- a/boot.S
+++ b/boot.S
@@ -13,20 +13,30 @@
 	.text
 
 .macro enter_hyp
-	@ We can't call hvc from secure mode, so drop down first.
-	mov	r7, #0xffffffff
-	smc	#0				@ Change to NS-mode
-
-	@ This is how we enter hyp mode, for booting the next stage.
+	@ We assume we're entered in Secure Supervisor mode. To
+	@ get to Hyp mode we have to pass through Monitor mode
+	@ and NS-Supervisor mode. Note that there is no way to
+	@ return to the Secure world once we've done this.
+	@
+	@ This will trash r10 and r11.
+	ldr	r10, =vectors
+	mcr	p15, 0, r10, c12, c0, 1		@ Monitor vector base address
+	@ Switch to monitor mode, which will set up the HVBAR and
+	@ then return to us in NS-SVC
+	smc	#0
+	@ Now we're in NS-SVC, make a Hyp call to get into Hyp mode
 	hvc	#0
+	@ We will end up here in NS-Hyp.
 .endm
 
 .align 5
-/* Once we get rid of monitor.S, use these smc vectors too! */
-hyp_vectors:
+/* We use the same vector table for Hyp and Monitor mode, since
+ * we will only use each once and they don't overlap.
+ */
+vectors:
 	.word 0	/* reset */
 	.word 0	/* undef */
-	.word 0 /* svc */
+	b	2f /* smc */
 	.word 0 /* pabt */
 	.word 0 /* dabt */
 	b	1f
@@ -37,6 +47,28 @@ hyp_vectors:
 1:	mrs	lr, elr_hyp
 	mov	pc, lr
 
+/* In monitor mode, set up HVBAR and SCR then return to caller in NS-SVC. */
+2:
+	@ Set up HVBAR
+	mrc	p15, 0, r10, c1, c1, 0		@ SCR
+	@ Set SCR.NS=1 (needed for setting HVBAR and also returning to NS state)
+	@        .IRQ,FIQ,EA=0 (don't take aborts/exceptions to Monitor mode)
+	@        .FW,AW=1 (CPSR.A,F modifiable in NS state)
+	@        .nET=0 (early termination OK)
+	@        .SCD=1 (SMC in NS mode is UNDEF, so accidental SMCs don't
+	@                cause us to leap back into this code confusingly)
+	@        .HCE=1 (HVC does Hyp call)
+	bic	r10, r10, #0x07f
+	ldr	r11, =0x1b1
+	orr	r10, r10, r11
+	mcr	p15, 0, r11, c1, c1, 0
+	isb
+	ldr	r11, =vectors
+	mcr	p15, 4, r11, c12, c0, 0		@ set HVBAR
+	@ ...and return to calling code in NS state
+	movs	pc, lr
+
+
 	.globl	start
 start:
 #ifdef SMP
@@ -87,15 +119,6 @@ start:
 	orr	r0, r0, r1
 	mcr	p15, 0, r0, c1, c1, 2
 
-	@ Leave monitor.S trap in place for the transition...
-	mov	r0, #0xf0000000
-	mcr	p15, 0, r0, c12, c0, 1		@ Monitor vector base address
-
-	@ Set up hvbar so hvc comes back here.
-	ldr	r0, =hyp_vectors
-	mov	r7, #0xfffffff0
-	smc	#0				@ Set HVBAR
-
 	@ Check CPU nr again
 	mrc	p15, 0, r0, c0, c0, 5		@ MPIDR (ARMv7 only)
 	and	r0, r0, #15			@ CPU number
diff --git a/model.lds.S b/model.lds.S
index 07fae8c..793df89 100644
--- a/model.lds.S
+++ b/model.lds.S
@@ -47,8 +47,6 @@ SECTIONS
 
 
  . = MON_OFFSET;
- .monitor : { monitor.o }
-
  /* Put most of the actual boot loader code up in high memory
   * where it won't get overwritten by kernel, initrd or atags.
   */
diff --git a/monitor.S b/monitor.S
deleted file mode 100644
index dea8551..0000000
--- a/monitor.S
+++ /dev/null
@@ -1,95 +0,0 @@
-/*
- * monitor.S - simple monitor code to switch to NS state before executing kernel
- *
- * Copyright (C) 2011 Columbia University. All rights reserved.
- * 		      Christoffer Dall <cdall@cs.columbia.edu>
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE.txt file.
- */
-
-#.syntax	unified
-	.section monitor, "x"
-
-	.word 0
-	.word 0
-	b	1f
-	.word 0
-	.word 0
-	.word 0
-	.word 0
-	.word 0
-
-	@
-	@ Secure Monitor Call
-	@
-1:
-	ldr	sp, =_monitor_stack
-	push	{r10-r12}
-
-	cmp	r7, #0xffffffff
-	beq	_non_sec
-
-	@ Check smc number and VMID
-	bic	r12, r7, #0xf
-	cmp	r12, #0xfffffff0
-	movnes	pc, lr
-	and	r12, r7, #0xf
-	cmp	r12, #0x0
-	popgt   {r10-r12}
-	movgts	pc, lr
-
-	@ Check the VMID is 0
-	mrc	p15, 0, r10, c1, c1, 0		@ SCR
-	orr	r11, r10, #1			@ SCR.NS = 1
-	mcr	p15, 0, r11, c1, c1, 0
-	isb
-	mrrc	p15, 6, r12, r11, c2
-	mcr	p15, 0, r10, c1, c1, 0		@ Restore SCR
-	lsr	r11, r11, #16
-	and	r11, r11, #0xff
-	cmp	r11, #0
-	popne	{r10-r12}
-	movnes	pc, lr
-
-	@ Jump to the right function
-	and	r12, r7, #0xf
-	adr	r11, _hyp_funcs
-	add	r11, r11, r12, lsl #2
-	ldr	pc, [r11]
-
-	@
-	@ Jump table for the SMC hypervisor API calls
-	@
-_hyp_funcs:
-	.long	_write_hvbar
-
-	@
-	@ Switch to non-secure mode
-	@
-_non_sec:
-	mrc	p15, 0, r12, c1, c1, 0		@ Secure configuration register
-	bic	r12, r12, #0x07f
-	ldr	r11, =0x131
-	orr	r12, r12, r11
-	mcr	p15, 0, r12, c1, c1, 0
-	pop	{r10-r12}
-	movs	pc, lr
-
-	@
-	@ Read/Write HVBAR
-	@
-_write_hvbar:
-	orr	r11, r10, #1			@ SCR.NS = 1 (r10 already = SCR)
-	mcr	p15, 0, r11, c1, c1, 0
-	isb
-	mcr	p15, 4, r0, c12, c0, 0
-	mcr	p15, 0, r10, c1, c1, 0		@ Restore SCR
-	pop	{r10-r12}
-	movs	pc, lr
-
-	.ltorg
-
-	/* A bit of stack space for monitor mode */
-	.align	12
-_monitor_stack: