kgdb: support for ARCH=arm

This patch adds the ARCH=arm specific a kgdb backend, originally
written by Deepak Saxena <dsaxena@plexity.net> and George Davis
<gdavis@mvista.com>.  Geoff Levand <geoffrey.levand@am.sony.com>,
Nicolas Pitre, Manish Lachwani, and Jason Wessel have contributed
various fixups here as well.

The KGDB patch makes one change to the core ARM architecture such that
the traps are initialized early for use with the debugger or other
subsystems.

[ mingo@elte.hu: small cleanups. ]
[ ben-linux@fluff.org: fixed early_trap_init ]

Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Deepak Saxena <dsaxena@plexity.net>

5 files changed, 210 insertions, 0 deletions

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index c7ad324..d048f68 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -12,6 +12,7 @@ config ARM
 	select RTC_LIB
 	select SYS_SUPPORTS_APM_EMULATION
 	select HAVE_OPROFILE
+	select HAVE_ARCH_KGDB
 	select HAVE_KPROBES if (!XIP_KERNEL)
 	select HAVE_KRETPROBES if (HAVE_KPROBES)
 	select HAVE_FTRACE if (!XIP_KERNEL)
diff --git a/arch/arm/kernel/Makefile b/arch/arm/kernel/Makefile
index eb9092c..1d296fc 100644
--- a/arch/arm/kernel/Makefile
+++ b/arch/arm/kernel/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_KPROBES)		+= kprobes.o kprobes-decode.o
 obj-$(CONFIG_ATAGS_PROC)	+= atags.o
 obj-$(CONFIG_OABI_COMPAT)	+= sys_oabi-compat.o
 obj-$(CONFIG_ARM_THUMBEE)	+= thumbee.o
+obj-$(CONFIG_KGDB)		+= kgdb.o
 
 obj-$(CONFIG_CRUNCH)		+= crunch.o crunch-bits.o
 AFLAGS_crunch-bits.o		:= -Wa,-mcpu=ep9312
diff --git a/arch/arm/kernel/kgdb.c b/arch/arm/kernel/kgdb.c
new file mode 100644
index 0000000..aaffaec
--- /dev/null
+++ b/arch/arm/kernel/kgdb.c
@@ -0,0 +1,201 @@
+/*
+ * arch/arm/kernel/kgdb.c
+ *
+ * ARM KGDB support
+ *
+ * Copyright (c) 2002-2004 MontaVista Software, Inc
+ * Copyright (c) 2008 Wind River Systems, Inc.
+ *
+ * Authors:  George Davis <davis_g@mvista.com>
+ *           Deepak Saxena <dsaxena@plexity.net>
+ */
+#include <linux/kgdb.h>
+#include <asm/traps.h>
+
+/* Make a local copy of the registers passed into the handler (bletch) */
+void pt_regs_to_gdb_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
+{
+	int regno;
+
+	/* Initialize all to zero. */
+	for (regno = 0; regno < GDB_MAX_REGS; regno++)
+		gdb_regs[regno] = 0;
+
+	gdb_regs[_R0]		= kernel_regs->ARM_r0;
+	gdb_regs[_R1]		= kernel_regs->ARM_r1;
+	gdb_regs[_R2]		= kernel_regs->ARM_r2;
+	gdb_regs[_R3]		= kernel_regs->ARM_r3;
+	gdb_regs[_R4]		= kernel_regs->ARM_r4;
+	gdb_regs[_R5]		= kernel_regs->ARM_r5;
+	gdb_regs[_R6]		= kernel_regs->ARM_r6;
+	gdb_regs[_R7]		= kernel_regs->ARM_r7;
+	gdb_regs[_R8]		= kernel_regs->ARM_r8;
+	gdb_regs[_R9]		= kernel_regs->ARM_r9;
+	gdb_regs[_R10]		= kernel_regs->ARM_r10;
+	gdb_regs[_FP]		= kernel_regs->ARM_fp;
+	gdb_regs[_IP]		= kernel_regs->ARM_ip;
+	gdb_regs[_SPT]		= kernel_regs->ARM_sp;
+	gdb_regs[_LR]		= kernel_regs->ARM_lr;
+	gdb_regs[_PC]		= kernel_regs->ARM_pc;
+	gdb_regs[_CPSR]		= kernel_regs->ARM_cpsr;
+}
+
+/* Copy local gdb registers back to kgdb regs, for later copy to kernel */
+void gdb_regs_to_pt_regs(unsigned long *gdb_regs, struct pt_regs *kernel_regs)
+{
+	kernel_regs->ARM_r0	= gdb_regs[_R0];
+	kernel_regs->ARM_r1	= gdb_regs[_R1];
+	kernel_regs->ARM_r2	= gdb_regs[_R2];
+	kernel_regs->ARM_r3	= gdb_regs[_R3];
+	kernel_regs->ARM_r4	= gdb_regs[_R4];
+	kernel_regs->ARM_r5	= gdb_regs[_R5];
+	kernel_regs->ARM_r6	= gdb_regs[_R6];
+	kernel_regs->ARM_r7	= gdb_regs[_R7];
+	kernel_regs->ARM_r8	= gdb_regs[_R8];
+	kernel_regs->ARM_r9	= gdb_regs[_R9];
+	kernel_regs->ARM_r10	= gdb_regs[_R10];
+	kernel_regs->ARM_fp	= gdb_regs[_FP];
+	kernel_regs->ARM_ip	= gdb_regs[_IP];
+	kernel_regs->ARM_sp	= gdb_regs[_SPT];
+	kernel_regs->ARM_lr	= gdb_regs[_LR];
+	kernel_regs->ARM_pc	= gdb_regs[_PC];
+	kernel_regs->ARM_cpsr	= gdb_regs[_CPSR];
+}
+
+void
+sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
+{
+	struct pt_regs *thread_regs;
+	int regno;
+
+	/* Just making sure... */
+	if (task == NULL)
+		return;
+
+	/* Initialize to zero */
+	for (regno = 0; regno < GDB_MAX_REGS; regno++)
+		gdb_regs[regno] = 0;
+
+	/* Otherwise, we have only some registers from switch_to() */
+	thread_regs		= task_pt_regs(task);
+	gdb_regs[_R0]		= thread_regs->ARM_r0;
+	gdb_regs[_R1]		= thread_regs->ARM_r1;
+	gdb_regs[_R2]		= thread_regs->ARM_r2;
+	gdb_regs[_R3]		= thread_regs->ARM_r3;
+	gdb_regs[_R4]		= thread_regs->ARM_r4;
+	gdb_regs[_R5]		= thread_regs->ARM_r5;
+	gdb_regs[_R6]		= thread_regs->ARM_r6;
+	gdb_regs[_R7]		= thread_regs->ARM_r7;
+	gdb_regs[_R8]		= thread_regs->ARM_r8;
+	gdb_regs[_R9]		= thread_regs->ARM_r9;
+	gdb_regs[_R10]		= thread_regs->ARM_r10;
+	gdb_regs[_FP]		= thread_regs->ARM_fp;
+	gdb_regs[_IP]		= thread_regs->ARM_ip;
+	gdb_regs[_SPT]		= thread_regs->ARM_sp;
+	gdb_regs[_LR]		= thread_regs->ARM_lr;
+	gdb_regs[_PC]		= thread_regs->ARM_pc;
+	gdb_regs[_CPSR]		= thread_regs->ARM_cpsr;
+}
+
+static int compiled_break;
+
+int kgdb_arch_handle_exception(int exception_vector, int signo,
+			       int err_code, char *remcom_in_buffer,
+			       char *remcom_out_buffer,
+			       struct pt_regs *linux_regs)
+{
+	unsigned long addr;
+	char *ptr;
+
+	switch (remcom_in_buffer[0]) {
+	case 'D':
+	case 'k':
+	case 'c':
+		kgdb_contthread = NULL;
+
+		/*
+		 * Try to read optional parameter, pc unchanged if no parm.
+		 * If this was a compiled breakpoint, we need to move
+		 * to the next instruction or we will just breakpoint
+		 * over and over again.
+		 */
+		ptr = &remcom_in_buffer[1];
+		if (kgdb_hex2long(&ptr, &addr))
+			linux_regs->ARM_pc = addr;
+		else if (compiled_break == 1)
+			linux_regs->ARM_pc += 4;
+
+		compiled_break = 0;
+
+		return 0;
+	}
+
+	return -1;
+}
+
+static int kgdb_brk_fn(struct pt_regs *regs, unsigned int instr)
+{
+	kgdb_handle_exception(1, SIGTRAP, 0, regs);
+
+	return 0;
+}
+
+static int kgdb_compiled_brk_fn(struct pt_regs *regs, unsigned int instr)
+{
+	compiled_break = 1;
+	kgdb_handle_exception(1, SIGTRAP, 0, regs);
+
+	return 0;
+}
+
+static struct undef_hook kgdb_brkpt_hook = {
+	.instr_mask		= 0xffffffff,
+	.instr_val		= KGDB_BREAKINST,
+	.fn			= kgdb_brk_fn
+};
+
+static struct undef_hook kgdb_compiled_brkpt_hook = {
+	.instr_mask		= 0xffffffff,
+	.instr_val		= KGDB_COMPILED_BREAK,
+	.fn			= kgdb_compiled_brk_fn
+};
+
+/**
+ *	kgdb_arch_init - Perform any architecture specific initalization.
+ *
+ *	This function will handle the initalization of any architecture
+ *	specific callbacks.
+ */
+int kgdb_arch_init(void)
+{
+	register_undef_hook(&kgdb_brkpt_hook);
+	register_undef_hook(&kgdb_compiled_brkpt_hook);
+
+	return 0;
+}
+
+/**
+ *	kgdb_arch_exit - Perform any architecture specific uninitalization.
+ *
+ *	This function will handle the uninitalization of any architecture
+ *	specific callbacks, for dynamic registration and unregistration.
+ */
+void kgdb_arch_exit(void)
+{
+	unregister_undef_hook(&kgdb_brkpt_hook);
+	unregister_undef_hook(&kgdb_compiled_brkpt_hook);
+}
+
+/*
+ * Register our undef instruction hooks with ARM undef core.
+ * We regsiter a hook specifically looking for the KGB break inst
+ * and we handle the normal undef case within the do_undefinstr
+ * handler.
+ */
+struct kgdb_arch arch_kgdb_ops = {
+#ifndef __ARMEB__
+	.gdb_bpt_instr		= {0xfe, 0xde, 0xff, 0xe7}
+#else /* ! __ARMEB__ */
+	.gdb_bpt_instr		= {0xe7, 0xff, 0xde, 0xfe}
+#endif
+};
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index b7b0720..38f0e79 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -36,6 +36,7 @@
 #include <asm/mach/arch.h>
 #include <asm/mach/irq.h>
 #include <asm/mach/time.h>
+#include <asm/traps.h>
 
 #include "compat.h"
 #include "atags.h"
@@ -853,6 +854,7 @@ void __init setup_arch(char **cmdline_p)
 	conswitchp = &dummy_con;
 #endif
 #endif
+	early_trap_init();
 }
 
 
diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 5595fdd..7277aef 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -708,6 +708,11 @@ EXPORT_SYMBOL(abort);
 
 void __init trap_init(void)
 {
+	return;
+}
+
+void __init early_trap_init(void)
+{
 	unsigned long vectors = CONFIG_VECTORS_BASE;
 	extern char __stubs_start[], __stubs_end[];
 	extern char __vectors_start[], __vectors_end[];