Build option to include AArch32 registers in cpu context

The system registers that are saved and restored in CPU context include
AArch32 systems registers like SPSR_ABT, SPSR_UND, SPSR_IRQ, SPSR_FIQ,
DACR32_EL2, IFSR32_EL2 and FPEXC32_EL2. Accessing these registers on an
AArch64-only (i.e. on hardware that does not implement AArch32, or at
least not at EL1 and higher ELs) platform leads to an exception. This patch
introduces the build option `CTX_INCLUDE_AARCH32_REGS` to specify whether to
include these AArch32 systems registers in the cpu context or not. By default
this build option is set to 1 to ensure compatibility. AArch64-only platforms
must set it to 0. A runtime check is added in BL1 and BL31 cold boot path to
verify this.

Fixes ARM-software/tf-issues#386

Change-Id: I720cdbd7ed7f7d8516635a2ec80d025f478b95ee

6 files changed, 119 insertions, 67 deletions

diff --git a/Makefile b/Makefile
index b1560a2b..ccb0abc3 100644
--- a/Makefile
+++ b/Makefile
@@ -62,6 +62,9 @@ NS_TIMER_SWITCH			:= 0
 RESET_TO_BL31			:= 0
 # Include FP registers in cpu context
 CTX_INCLUDE_FPREGS		:= 0
+# Build flag to include AArch32 registers in cpu context save and restore
+# during world switch. This flag must be set to 0 for AArch64-only platforms.
+CTX_INCLUDE_AARCH32_REGS	:= 1
 # Determine the version of ARM GIC architecture to use for interrupt management
 # in EL3. The platform port can change this value if needed.
 ARM_GIC_ARCH			:= 2
@@ -392,6 +395,7 @@ $(eval $(call assert_boolean,DEBUG))
 $(eval $(call assert_boolean,NS_TIMER_SWITCH))
 $(eval $(call assert_boolean,RESET_TO_BL31))
 $(eval $(call assert_boolean,CTX_INCLUDE_FPREGS))
+$(eval $(call assert_boolean,CTX_INCLUDE_AARCH32_REGS))
 $(eval $(call assert_boolean,ASM_ASSERTION))
 $(eval $(call assert_boolean,USE_COHERENT_MEM))
 $(eval $(call assert_boolean,DISABLE_PEDANTIC))
@@ -419,6 +423,7 @@ $(eval $(call add_define,SPD_${SPD}))
 $(eval $(call add_define,NS_TIMER_SWITCH))
 $(eval $(call add_define,RESET_TO_BL31))
 $(eval $(call add_define,CTX_INCLUDE_FPREGS))
+$(eval $(call add_define,CTX_INCLUDE_AARCH32_REGS))
 $(eval $(call add_define,ARM_GIC_ARCH))
 $(eval $(call add_define,ARM_CCI_PRODUCT_ID))
 $(eval $(call add_define,ASM_ASSERTION))
diff --git a/bl1/bl1_context_mgmt.c b/bl1/bl1_context_mgmt.c
index bd40608b..972c7f68 100644
--- a/bl1/bl1_context_mgmt.c
+++ b/bl1/bl1_context_mgmt.c
@@ -32,6 +32,7 @@
 #include <assert.h>
 #include <context.h>
 #include <context_mgmt.h>
+#include <debug.h>
 #include <platform.h>
 
 /*
@@ -66,6 +67,19 @@ void bl1_prepare_next_image(unsigned int image_id)
 	image_desc_t *image_desc;
 	entry_point_info_t *next_bl_ep;
 
+#if CTX_INCLUDE_AARCH32_REGS
+	/*
+	 * Ensure that the build flag to save AArch32 system registers in CPU
+	 * context is not set for AArch64-only platforms.
+	 */
+	if (((read_id_aa64pfr0_el1() >> ID_AA64PFR0_EL1_SHIFT)
+			& ID_AA64PFR0_ELX_MASK) == 0x1) {
+		ERROR("EL1 supports AArch64-only. Please set build flag "
+				"CTX_INCLUDE_AARCH32_REGS = 0");
+		panic();
+	}
+#endif
+
 	/* Get the image descriptor. */
 	image_desc = bl1_plat_get_image_desc(image_id);
 	assert(image_desc);
diff --git a/bl31/bl31_main.c b/bl31/bl31_main.c
index 835d41e8..7f04d218 100644
--- a/bl31/bl31_main.c
+++ b/bl31/bl31_main.c
@@ -145,6 +145,19 @@ void bl31_prepare_next_image_entry(void)
 	entry_point_info_t *next_image_info;
 	uint32_t image_type;
 
+#if CTX_INCLUDE_AARCH32_REGS
+	/*
+	 * Ensure that the build flag to save AArch32 system registers in CPU
+	 * context is not set for AArch64-only platforms.
+	 */
+	if (((read_id_aa64pfr0_el1() >> ID_AA64PFR0_EL1_SHIFT)
+			& ID_AA64PFR0_ELX_MASK) == 0x1) {
+		ERROR("EL1 supports AArch64-only. Please set build flag "
+				"CTX_INCLUDE_AARCH32_REGS = 0");
+		panic();
+	}
+#endif
+
 	/* Determine which image to execute next */
 	image_type = bl31_get_next_image_type();
 
diff --git a/common/aarch64/context.S b/common/aarch64/context.S
index 0baa9b2f..d51daa78 100644
--- a/common/aarch64/context.S
+++ b/common/aarch64/context.S
@@ -57,14 +57,6 @@ func el1_sysregs_context_save
 	mrs	x10, elr_el1
 	stp	x9, x10, [x0, #CTX_SPSR_EL1]
 
-	mrs	x11, spsr_abt
-	mrs	x12, spsr_und
-	stp	x11, x12, [x0, #CTX_SPSR_ABT]
-
-	mrs	x13, spsr_irq
-	mrs	x14, spsr_fiq
-	stp	x13, x14, [x0, #CTX_SPSR_IRQ]
-
 	mrs	x15, sctlr_el1
 	mrs	x16, actlr_el1
 	stp	x15, x16, [x0, #CTX_SCTLR_EL1]
@@ -93,10 +85,6 @@ func el1_sysregs_context_save
 	mrs	x10, tpidrro_el0
 	stp	x9, x10, [x0, #CTX_TPIDR_EL0]
 
-	mrs	x11, dacr32_el2
-	mrs	x12, ifsr32_el2
-	stp	x11, x12, [x0, #CTX_DACR32_EL2]
-
 	mrs	x13, par_el1
 	mrs	x14, far_el1
 	stp	x13, x14, [x0, #CTX_PAR_EL1]
@@ -109,6 +97,24 @@ func el1_sysregs_context_save
 	mrs	x9, vbar_el1
 	stp	x17, x9, [x0, #CTX_CONTEXTIDR_EL1]
 
+	/* Save AArch32 system registers if the build has instructed so */
+#if CTX_INCLUDE_AARCH32_REGS
+	mrs	x11, spsr_abt
+	mrs	x12, spsr_und
+	stp	x11, x12, [x0, #CTX_SPSR_ABT]
+
+	mrs	x13, spsr_irq
+	mrs	x14, spsr_fiq
+	stp	x13, x14, [x0, #CTX_SPSR_IRQ]
+
+	mrs	x15, dacr32_el2
+	mrs	x16, ifsr32_el2
+	stp	x15, x16, [x0, #CTX_DACR32_EL2]
+
+	mrs	x17, fpexc32_el2
+	str	x17, [x0, #CTX_FP_FPEXC32_EL2]
+#endif
+
 	/* Save NS timer registers if the build has instructed so */
 #if NS_TIMER_SWITCH
 	mrs	x10, cntp_ctl_el0
@@ -123,9 +129,6 @@ func el1_sysregs_context_save
 	str	x14, [x0, #CTX_CNTKCTL_EL1]
 #endif
 
-	mrs	x15, fpexc32_el2
-	str	x15, [x0, #CTX_FP_FPEXC32_EL2]
-
 	ret
 endfunc el1_sysregs_context_save
 
@@ -143,14 +146,6 @@ func el1_sysregs_context_restore
 	msr	spsr_el1, x9
 	msr	elr_el1, x10
 
-	ldp	x11, x12, [x0, #CTX_SPSR_ABT]
-	msr	spsr_abt, x11
-	msr	spsr_und, x12
-
-	ldp	x13, x14, [x0, #CTX_SPSR_IRQ]
-	msr	spsr_irq, x13
-	msr	spsr_fiq, x14
-
 	ldp	x15, x16, [x0, #CTX_SCTLR_EL1]
 	msr	sctlr_el1, x15
 	msr	actlr_el1, x16
@@ -179,10 +174,6 @@ func el1_sysregs_context_restore
 	msr	tpidr_el0, x9
 	msr	tpidrro_el0, x10
 
-	ldp	x11, x12, [x0, #CTX_DACR32_EL2]
-	msr	dacr32_el2, x11
-	msr	ifsr32_el2, x12
-
 	ldp	x13, x14, [x0, #CTX_PAR_EL1]
 	msr	par_el1, x13
 	msr	far_el1, x14
@@ -195,6 +186,23 @@ func el1_sysregs_context_restore
 	msr	contextidr_el1, x17
 	msr	vbar_el1, x9
 
+	/* Restore AArch32 system registers if the build has instructed so */
+#if CTX_INCLUDE_AARCH32_REGS
+	ldp	x11, x12, [x0, #CTX_SPSR_ABT]
+	msr	spsr_abt, x11
+	msr	spsr_und, x12
+
+	ldp	x13, x14, [x0, #CTX_SPSR_IRQ]
+	msr	spsr_irq, x13
+	msr	spsr_fiq, x14
+
+	ldp	x15, x16, [x0, #CTX_DACR32_EL2]
+	msr	dacr32_el2, x15
+	msr	ifsr32_el2, x16
+
+	ldr	x17, [x0, #CTX_FP_FPEXC32_EL2]
+	msr	fpexc32_el2, x17
+#endif
 	/* Restore NS timer registers if the build has instructed so */
 #if NS_TIMER_SWITCH
 	ldp	x10, x11, [x0, #CTX_CNTP_CTL_EL0]
@@ -209,11 +217,7 @@ func el1_sysregs_context_restore
 	msr	cntkctl_el1, x14
 #endif
 
-	ldr	x15, [x0, #CTX_FP_FPEXC32_EL2]
-	msr	fpexc32_el2, x15
-
 	/* No explict ISB required here as ERET covers it */
-
 	ret
 endfunc el1_sysregs_context_restore
 
diff --git a/docs/user-guide.md b/docs/user-guide.md
index cd9c8c33..0911eb8b 100644
--- a/docs/user-guide.md
+++ b/docs/user-guide.md
@@ -380,6 +380,12 @@ performed.
     any register that is not part of the SBSA generic UART specification.
     Default value is 0 (a full PL011 compliant UART is present).
 
+*   `CTX_INCLUDE_AARCH32_REGS` : Boolean option that, when set to 1, will cause
+    the AArch32 system registers to be included when saving and restoring the
+    CPU context. The option must be set to 0 for AArch64-only platforms (that
+    is on hardware that does not implement AArch32, or at least not at EL1 and
+    higher ELs). Default value is 1.
+
 *   `CTX_INCLUDE_FPREGS`: Boolean option that, when set to 1, will cause the FP
     registers to be included when saving and restoring the CPU context. Default
     is 0.
diff --git a/include/common/context.h b/include/common/context.h
index 0dfebe0b..ec47f2ad 100644
--- a/include/common/context.h
+++ b/include/common/context.h
@@ -91,48 +91,58 @@
 #define CTX_SYSREGS_OFFSET	(CTX_EL3STATE_OFFSET + CTX_EL3STATE_END)
 #define CTX_SPSR_EL1		0x0
 #define CTX_ELR_EL1		0x8
-#define CTX_SPSR_ABT		0x10
-#define CTX_SPSR_UND		0x18
-#define CTX_SPSR_IRQ		0x20
-#define CTX_SPSR_FIQ		0x28
-#define CTX_SCTLR_EL1		0x30
-#define CTX_ACTLR_EL1		0x38
-#define CTX_CPACR_EL1		0x40
-#define CTX_CSSELR_EL1		0x48
-#define CTX_SP_EL1		0x50
-#define CTX_ESR_EL1		0x58
-#define CTX_TTBR0_EL1		0x60
-#define CTX_TTBR1_EL1		0x68
-#define CTX_MAIR_EL1		0x70
-#define CTX_AMAIR_EL1		0x78
-#define CTX_TCR_EL1		0x80
-#define CTX_TPIDR_EL1		0x88
-#define CTX_TPIDR_EL0		0x90
-#define CTX_TPIDRRO_EL0		0x98
-#define CTX_DACR32_EL2		0xa0
-#define CTX_IFSR32_EL2		0xa8
-#define CTX_PAR_EL1		0xb0
-#define CTX_FAR_EL1		0xb8
-#define CTX_AFSR0_EL1		0xc0
-#define CTX_AFSR1_EL1		0xc8
-#define CTX_CONTEXTIDR_EL1	0xd0
-#define CTX_VBAR_EL1		0xd8
+#define CTX_SCTLR_EL1		0x10
+#define CTX_ACTLR_EL1		0x18
+#define CTX_CPACR_EL1		0x20
+#define CTX_CSSELR_EL1		0x28
+#define CTX_SP_EL1		0x30
+#define CTX_ESR_EL1		0x38
+#define CTX_TTBR0_EL1		0x40
+#define CTX_TTBR1_EL1		0x48
+#define CTX_MAIR_EL1		0x50
+#define CTX_AMAIR_EL1		0x58
+#define CTX_TCR_EL1		0x60
+#define CTX_TPIDR_EL1		0x68
+#define CTX_TPIDR_EL0		0x70
+#define CTX_TPIDRRO_EL0		0x78
+#define CTX_PAR_EL1		0x80
+#define CTX_FAR_EL1		0x88
+#define CTX_AFSR0_EL1		0x90
+#define CTX_AFSR1_EL1		0x98
+#define CTX_CONTEXTIDR_EL1	0xa0
+#define CTX_VBAR_EL1		0xa8
+
+/*
+ * If the platform is AArch64-only, there is no need to save and restore these
+ * AArch32 registers.
+ */
+#if CTX_INCLUDE_AARCH32_REGS
+#define CTX_SPSR_ABT		0xb0
+#define CTX_SPSR_UND		0xb8
+#define CTX_SPSR_IRQ		0xc0
+#define CTX_SPSR_FIQ		0xc8
+#define CTX_DACR32_EL2		0xd0
+#define CTX_IFSR32_EL2		0xd8
+#define CTX_FP_FPEXC32_EL2	0xe0
+#define CTX_TIMER_SYSREGS_OFF		0xf0 /* Align to the next 16 byte boundary */
+#else
+#define CTX_TIMER_SYSREGS_OFF		0xb0
+#endif /* __CTX_INCLUDE_AARCH32_REGS__ */
+
 /*
  * If the timer registers aren't saved and restored, we don't have to reserve
  * space for them in the context
  */
 #if NS_TIMER_SWITCH
-#define CTX_CNTP_CTL_EL0	0xe0
-#define CTX_CNTP_CVAL_EL0	0xe8
-#define CTX_CNTV_CTL_EL0	0xf0
-#define CTX_CNTV_CVAL_EL0	0xf8
-#define CTX_CNTKCTL_EL1		0x100
-#define CTX_FP_FPEXC32_EL2	0x108
-#define CTX_SYSREGS_END		0x110
+#define CTX_CNTP_CTL_EL0	(CTX_TIMER_SYSREGS_OFF + 0x0)
+#define CTX_CNTP_CVAL_EL0	(CTX_TIMER_SYSREGS_OFF + 0x8)
+#define CTX_CNTV_CTL_EL0	(CTX_TIMER_SYSREGS_OFF + 0x10)
+#define CTX_CNTV_CVAL_EL0	(CTX_TIMER_SYSREGS_OFF + 0x18)
+#define CTX_CNTKCTL_EL1		(CTX_TIMER_SYSREGS_OFF + 0x20)
+#define CTX_SYSREGS_END		(CTX_TIMER_SYSREGS_OFF + 0x30) /* Align to the next 16 byte boundary */
 #else
-#define CTX_FP_FPEXC32_EL2	0xe0
-#define CTX_SYSREGS_END		0xf0
-#endif
+#define CTX_SYSREGS_END		CTX_TIMER_SYSREGS_OFF
+#endif /* __NS_TIMER_SWITCH__ */
 
 /*******************************************************************************
  * Constants that allow assembler code to access members of and the 'fp_regs'