Blackfin: add support for the DBGA (debug assert) pseudo insn

A few pseudo debug insns exist to make testing of simulators easier.
Since these don't actually exist in the hardware, we have to have the
exception handler take care of emulating these.  This allows sim test
cases to be executed unmodified under Linux and thus simplify debugging
greatly.

Signed-off-by: Robin Getz <robin.getz@analog.com>
Signed-off-by: Mike Frysinger <vapier@gentoo.org>

arch/blackfin/Kconfig.debug

@@ -264,4 +264,13 @@ config BFIN_ISRAM_SELF_TEST
 	help
 	  Run some self tests of the isram driver code at boot.
 
+config BFIN_PSEUDODBG_INSNS
+	bool "Support pseudo debug instructions"
+	default n
+	help
+	  This option allows the kernel to emulate some pseudo instructions which
+	  allow simulator test cases to be run under Linux with no changes.
+
+	  Most people should say N here.
+
 endmenu

arch/blackfin/include/asm/pseudo_instructions.h

@@ -0,0 +1,17 @@
+/*
+ * header file for pseudo instructions
+ *
+ * Copyright 2010 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2 or later.
+ */
+
+#ifndef _BLACKFIN_PSEUDO_
+#define _BLACKFIN_PSEUDO_
+
+#include <linux/types.h>
+#include <asm/ptrace.h>
+
+extern bool execute_pseudodbg_assert(struct pt_regs *fp, unsigned int opcode);
+
+#endif

arch/blackfin/kernel/Makefile

@@ -31,6 +31,7 @@ obj-$(CONFIG_EARLY_PRINTK)           += early_printk.o
 obj-$(CONFIG_EARLY_PRINTK)           += shadow_console.o
 obj-$(CONFIG_STACKTRACE)             += stacktrace.o
 obj-$(CONFIG_DEBUG_VERBOSE)          += trace.o
+obj-$(CONFIG_BFIN_PSEUDODBG_INSNS)   += pseudodbg.o
 
 # the kgdb test puts code into L2 and without linker
 # relaxation, we need to force long calls to/from it

arch/blackfin/kernel/pseudodbg.c

@@ -0,0 +1,73 @@
+/* The fake debug assert instructions
+ *
+ * Copyright 2010 Analog Devices Inc.
+ *
+ * Licensed under the GPL-2 or later
+ */
+
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/ptrace.h>
+
+#define PseudoDbg_Assert_opcode         0xf0000000
+#define PseudoDbg_Assert_expected_bits  0
+#define PseudoDbg_Assert_expected_mask  0xffff
+#define PseudoDbg_Assert_regtest_bits   16
+#define PseudoDbg_Assert_regtest_mask   0x7
+#define PseudoDbg_Assert_grp_bits       19
+#define PseudoDbg_Assert_grp_mask       0x7
+#define PseudoDbg_Assert_dbgop_bits     22
+#define PseudoDbg_Assert_dbgop_mask     0x3
+#define PseudoDbg_Assert_dontcare_bits  24
+#define PseudoDbg_Assert_dontcare_mask  0x7
+#define PseudoDbg_Assert_code_bits      27
+#define PseudoDbg_Assert_code_mask      0x1f
+
+bool execute_pseudodbg_assert(struct pt_regs *fp, unsigned int opcode)
+{
+	int expected = ((opcode >> PseudoDbg_Assert_expected_bits) & PseudoDbg_Assert_expected_mask);
+	int dbgop    = ((opcode >> (PseudoDbg_Assert_dbgop_bits)) & PseudoDbg_Assert_dbgop_mask);
+	int grp      = ((opcode >> (PseudoDbg_Assert_grp_bits)) & PseudoDbg_Assert_grp_mask);
+	int regtest  = ((opcode >> (PseudoDbg_Assert_regtest_bits)) & PseudoDbg_Assert_regtest_mask);
+	long *value = &fp->r0;
+
+	if ((opcode & 0xFF000000) != PseudoDbg_Assert_opcode)
+		return false;
+
+	/* Only do Dregs and Pregs for now */
+	if (grp > 1)
+		return false;
+
+	/*
+	 * Unfortunately, the pt_regs structure is not laid out the same way as the
+	 * hardware register file, so we need to do some fix ups.
+	 */
+	if (grp == 0 || (grp == 1 && regtest < 6))
+		value -= (regtest + 8 * grp);
+	else if (grp == 1 && regtest == 6)
+		value = &fp->usp;
+	else if (grp == 1 && regtest == 7)
+		value = &fp->fp;
+
+	if (dbgop == 0 || dbgop == 2) {
+		/* DBGA ( regs_lo , uimm16 ) */
+		/* DBGAL ( regs , uimm16 ) */
+		if (expected != (*value & 0xFFFF)) {
+			pr_notice("DBGA (%s%i.L,0x%x) failure, got 0x%x\n", grp ? "P" : "R",
+				regtest, expected, (unsigned int)(*value & 0xFFFF));
+			return false;
+		}
+
+	} else if (dbgop == 1 || dbgop == 3) {
+		/* DBGA ( regs_hi , uimm16 ) */
+		/* DBGAH ( regs , uimm16 ) */
+		if (expected != ((*value >> 16) & 0xFFFF)) {
+			pr_notice("DBGA (%s%i.H,0x%x) failure, got 0x%x\n", grp ? "P" : "R",
+				regtest, expected, (unsigned int)((*value >> 16) & 0xFFFF));
+			return false;
+		}
+	}
+
+	fp->pc += 4;
+	return true;
+}

arch/blackfin/kernel/traps.c

@@ -16,6 +16,7 @@
 #include <linux/irq.h>
 #include <asm/trace.h>
 #include <asm/fixed_code.h>
+#include <asm/pseudo_instructions.h>
 
 #ifdef CONFIG_KGDB
 # include <linux/kgdb.h>
@@ -67,6 +68,9 @@ asmlinkage notrace void trap_c(struct pt_regs *fp)
 {
 #ifdef CONFIG_DEBUG_BFIN_HWTRACE_ON
 	int j;
+#endif
+#ifdef CONFIG_BFIN_PSEUDODBG_INSNS
+	int opcode;
 #endif
 	unsigned int cpu = raw_smp_processor_id();
 	const char *strerror = NULL;
@@ -199,6 +203,17 @@ asmlinkage notrace void trap_c(struct pt_regs *fp)
 				panic("BUG()");
 			}
 		}
+#endif
+#ifdef CONFIG_BFIN_PSEUDODBG_INSNS
+		/*
+		 * Support for the fake instructions, if the instruction fails,
+		 * then just execute a illegal opcode failure (like normal).
+		 * Don't support these instructions inside the kernel
+		 */
+		if (!kernel_mode_regs(fp) && get_instruction(&opcode, (unsigned short *)fp->pc)) {
+			if (execute_pseudodbg_assert(fp, opcode))
+				goto traps_done;
+		}
 #endif
 		info.si_code = ILL_ILLOPC;
 		sig = SIGILL;