Rework BL3-1 unhandled exception handling and reporting

This patch implements the register reporting when unhandled exceptions are
taken in BL3-1. Unhandled exceptions will result in a dump of registers
to the console, before halting execution by that CPU. The Crash Stack,
previously called the Exception Stack, is used for this activity.
This stack is used to preserve the CPU context and runtime stack
contents for debugging and analysis.

This also introduces the per_cpu_ptr_cache, referenced by tpidr_el3,
to provide easy access to some of BL3-1 per-cpu data structures.
Initially, this is used to provide a pointer to the Crash stack.

panic() now prints the the error file and line number in Debug mode
and prints the PC value in release mode.

The Exception Stack is renamed to Crash Stack with this patch.
The original intention of exception stack is no longer valid
since we intend to support several valid exceptions like IRQ
and FIQ in the trusted firmware context. This stack is now
utilized for dumping and reporting the system state when a
crash happens and hence the rename.

Fixes ARM-software/tf-issues#79 Improve reporting of unhandled exception

Change-Id: I260791dc05536b78547412d147193cdccae7811a

4 files changed, 25 insertions, 48 deletions

diff --git a/include/bl31/cm_macros.S b/include/bl31/cm_macros.S
index e82f3a3..f12f8c3 100644
--- a/include/bl31/cm_macros.S
+++ b/include/bl31/cm_macros.S
@@ -30,12 +30,6 @@
 #include <arch.h>
 #include <context.h>
 
-	.macro	switch_to_exception_stack reg1 reg2
-	mov     \reg1 , sp
-	ldr	\reg2, [\reg1, #CTX_EL3STATE_OFFSET + CTX_EXCEPTION_SP]
-	mov	sp, \reg2
-	.endm
-
 	/* -----------------------------------------------------
 	 * Handle SMC exceptions seperately from other sync.
 	 * exceptions.
@@ -54,45 +48,10 @@
 
 	/* -----------------------------------------------------
 	 * The following code handles any synchronous exception
-	 * that is not an SMC. SP_EL3 is pointing to a context
-	 * structure where all the scratch registers are saved.
-	 * An exception stack is also retrieved from the context
-	 * Currently, a register dump is printed since BL31 does
-	 * not expect any such exceptions.
+	 * that is not an SMC.
 	 * -----------------------------------------------------
 	 */
-	bl	save_gp_registers
-	switch_to_exception_stack x0 x1
-
-	/* Save the core_context pointer for handled faults */
-	stp	x0, xzr, [sp, #-0x10]!
-	bl	fault_handler
-	ldp	x0, xzr, [sp], #0x10
-
-	mov	sp, x0
-	bl	restore_gp_registers
-	ldr	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
-	eret
-	.endm
-
-	/* -----------------------------------------------------
-	 * Use a platform defined mechanism to report an async.
-	 * exception.
-	 * -----------------------------------------------------
-	 */
-	.macro	handle_async_exception type
-	str	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
-	bl	save_gp_registers
-	switch_to_exception_stack x0 x1
-
-	/* Save the core_context pointer */
-	stp	x0, xzr, [sp, #-0x10]!
-	mov	x0, \type
-	bl	plat_report_exception
-	ldp	x0, xzr, [sp], #0x10
 
-	mov	sp, x0
-	bl	restore_gp_registers
-	ldr	x30, [sp, #CTX_GPREGS_OFFSET + CTX_GPREG_LR]
+	bl	dump_state_and_die
 	.endm
 
diff --git a/include/bl31/context.h b/include/bl31/context.h
index 549fa21..59c61da 100644
--- a/include/bl31/context.h
+++ b/include/bl31/context.h
@@ -76,7 +76,7 @@
  * 32-bits wide but are stored as 64-bit values for convenience
  ******************************************************************************/
 #define CTX_EL3STATE_OFFSET	(CTX_GPREGS_OFFSET + CTX_GPREGS_END)
-#define CTX_EXCEPTION_SP	0x0
+#define CTX_VBAR_EL3	0x0		/* Currently unused */
 #define CTX_RUNTIME_SP		0x8
 #define CTX_SPSR_EL3		0x10
 #define CTX_ELR_EL3		0x18
@@ -89,7 +89,7 @@
 #define CTX_TCR_EL3		0x50
 #define CTX_TTBR0_EL3		0x58
 #define CTX_DAIF_EL3		0x60
-#define CTX_VBAR_EL3		0x68	/* Currently unused */
+/* Unused space to honour alignment requirements */
 #define CTX_EL3STATE_END	0x70
 
 /*******************************************************************************
@@ -176,6 +176,11 @@
 #define CTX_FP_FPCR		0x208
 #define CTX_FPREGS_END		0x210
 
+/******************************************************************************
+ * Offsets for the per cpu cache implementation
+ ******************************************************************************/
+#define PTR_CACHE_CRASH_STACK_OFFSET 0x0
+
 #ifndef __ASSEMBLY__
 
 #include <cassert.h>
@@ -316,6 +321,18 @@ void el1_sysregs_context_restore(el1_sys_regs_t *regs);
 void fpregs_context_save(fp_regs_t *regs);
 void fpregs_context_restore(fp_regs_t *regs);
 
+
+/* Per-CPU pointer cache of recently used pointers and also the crash stack
+ * TODO: Add other commonly used variables to this (tf_issues#90)
+ */
+typedef struct per_cpu_ptr_cache {
+	uint64_t crash_stack;
+} per_cpu_ptr_cache_t;
+
+CASSERT(PTR_CACHE_CRASH_STACK_OFFSET == __builtin_offsetof\
+	(per_cpu_ptr_cache_t, crash_stack), \
+	assert_per_cpu_ptr_cache_crash_stack_offset_mismatch);
+
 #undef CTX_SYSREG_ALL
 #undef CTX_FP_ALL
 #undef CTX_GPREG_ALL
diff --git a/include/bl31/context_mgmt.h b/include/bl31/context_mgmt.h
index efcdcd2..d2598ee 100644
--- a/include/bl31/context_mgmt.h
+++ b/include/bl31/context_mgmt.h
@@ -49,6 +49,8 @@ extern void cm_set_el3_eret_context(uint32_t security_state, uint64_t entrypoint
 		uint32_t spsr, uint32_t scr);
 extern void cm_set_el3_elr(uint32_t security_state, uint64_t entrypoint);
 extern void cm_set_next_eret_context(uint32_t security_state);
-extern void cm_init_exception_stack(uint64_t mpidr, uint32_t security_state);
+extern void cm_init_pcpu_ptr_cache();
+extern void cm_set_pcpu_ptr_cache(const void *pcpu_ptr);
+extern void *cm_get_pcpu_ptr_cache(void);
 
 #endif /* __CM_H__ */
diff --git a/include/bl31/runtime_svc.h b/include/bl31/runtime_svc.h
index 12b5db8..6d70896 100644
--- a/include/bl31/runtime_svc.h
+++ b/include/bl31/runtime_svc.h
@@ -262,8 +262,7 @@ CASSERT(RT_SVC_DESC_HANDLE == __builtin_offsetof(rt_svc_desc_t, handle), \
 extern void runtime_svc_init();
 extern uint64_t __RT_SVC_DESCS_START__;
 extern uint64_t __RT_SVC_DESCS_END__;
-extern uint64_t get_exception_stack(uint64_t mpidr);
+extern uint64_t get_crash_stack(uint64_t mpidr);
 extern void runtime_exceptions(void);
-extern void fault_handler(void *handle);
 #endif /*__ASSEMBLY__*/
 #endif /* __RUNTIME_SVC_H__ */