Date:	Tue, 18 Oct 2011 22:38:36 -0500
From:	Richard Kuo <rkuo@...eaurora.org>
To:	linux-arch@...r.kernel.org, linux-hexagon@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v5 20/36] Hexagon: Provide basic debugging and system trap support.

Signed-off-by: Richard Kuo <rkuo@...eaurora.org>
Signed-off-by: Linas Vepstas <linas@...eaurora.org>
Acked-by: Arnd Bergmann <arnd@...db.de>
---
 arch/hexagon/include/asm/traps.h |   29 +++
 arch/hexagon/kernel/traps.c      |  454 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 483 insertions(+), 0 deletions(-)
 create mode 100644 arch/hexagon/include/asm/traps.h
 create mode 100644 arch/hexagon/kernel/traps.c

diff --git a/arch/hexagon/include/asm/traps.h b/arch/hexagon/include/asm/traps.h
new file mode 100644
index 0000000..6a407f6
--- /dev/null
+++ b/arch/hexagon/include/asm/traps.h
@@ -0,0 +1,29 @@
+/*
+ * Trap support for Hexagon
+ *
+ * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#ifndef _ASM_HEXAGON_TRAPS_H
+#define _ASM_HEXAGON_TRAPS_H
+
+#include <asm/registers.h>
+
+extern int die(const char *str, struct pt_regs *regs, long err);
+extern int die_if_kernel(char *str, struct pt_regs *regs, long err);
+
+#endif /* _ASM_HEXAGON_TRAPS_H */
diff --git a/arch/hexagon/kernel/traps.c b/arch/hexagon/kernel/traps.c
new file mode 100644
index 0000000..f08857d
--- /dev/null
+++ b/arch/hexagon/kernel/traps.c
@@ -0,0 +1,454 @@
+/*
+ * Kernel traps/events for Hexagon processor
+ *
+ * Copyright (c) 2010-2011, Code Aurora Forum. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/module.h>
+#include <linux/kallsyms.h>
+#include <linux/kdebug.h>
+#include <linux/syscalls.h>
+#include <linux/signal.h>
+#include <linux/tracehook.h>
+#include <asm/traps.h>
+#include <asm/vm_fault.h>
+#include <asm/syscall.h>
+#include <asm/registers.h>
+#include <asm/unistd.h>
+#include <asm/sections.h>
+#ifdef CONFIG_KGDB
+# include <linux/kgdb.h>
+#endif
+
+#define TRAP_SYSCALL	1
+#define TRAP_DEBUG	0xdb
+
+void __init trap_init(void)
+{
+}
+
+#ifdef CONFIG_GENERIC_BUG
+/* Maybe should resemble arch/sh/kernel/traps.c ?? */
+int is_valid_bugaddr(unsigned long addr)
+{
+	return 1;
+}
+#endif /* CONFIG_GENERIC_BUG */
+
+static const char *ex_name(int ex)
+{
+	switch (ex) {
+	case HVM_GE_C_XPROT:
+	case HVM_GE_C_XUSER:
+		return "Execute protection fault";
+	case HVM_GE_C_RPROT:
+	case HVM_GE_C_RUSER:
+		return "Read protection fault";
+	case HVM_GE_C_WPROT:
+	case HVM_GE_C_WUSER:
+		return "Write protection fault";
+	case HVM_GE_C_XMAL:
+		return "Misaligned instruction";
+	case HVM_GE_C_RMAL:
+		return "Misaligned data load";
+	case HVM_GE_C_WMAL:
+		return "Misaligned data store";
+	case HVM_GE_C_INVI:
+	case HVM_GE_C_PRIVI:
+		return "Illegal instruction";
+	case HVM_GE_C_BUS:
+		return "Precise bus error";
+	case HVM_GE_C_CACHE:
+		return "Cache error";
+
+	case 0xdb:
+		return "Debugger trap";
+
+	default:
+		return "Unrecognized exception";
+	}
+}
+
+static void do_show_stack(struct task_struct *task, unsigned long *fp,
+			  unsigned long ip)
+{
+	int kstack_depth_to_print = 24;
+	unsigned long offset, size;
+	const char *name = NULL;
+	unsigned long *newfp;
+	unsigned long low, high;
+	char tmpstr[128];
+	char *modname;
+	int i;
+
+	if (task == NULL)
+		task = current;
+
+	printk(KERN_INFO "CPU#%d, %s/%d, Call Trace:\n",
+	       raw_smp_processor_id(), task->comm,
+	       task_pid_nr(task));
+
+	if (fp == NULL) {
+		if (task == current) {
+			asm("%0 = r30" : "=r" (fp));
+		} else {
+			fp = (unsigned long *)
+			     ((struct hexagon_switch_stack *)
+			     task->thread.switch_sp)->fp;
+		}
+	}
+
+	if ((((unsigned long) fp) & 0x3) || ((unsigned long) fp < 0x1000)) {
+		printk(KERN_INFO "-- Corrupt frame pointer %p\n", fp);
+		return;
+	}
+
+	/* Saved link reg is one word above FP */
+	if (!ip)
+		ip = *(fp+1);
+
+	/* Expect kernel stack to be in-bounds */
+	low = (unsigned long)task_stack_page(task);
+	high = low + THREAD_SIZE - 8;
+	low += sizeof(struct thread_info);
+
+	for (i = 0; i < kstack_depth_to_print; i++) {
+
+		name = kallsyms_lookup(ip, &size, &offset, &modname, tmpstr);
+
+		printk(KERN_INFO "[%p] 0x%lx: %s + 0x%lx", fp, ip, name,
+			offset);
+		if (((unsigned long) fp < low) || (high < (unsigned long) fp))
+			printk(KERN_CONT " (FP out of bounds!)");
+		if (modname)
+			printk(KERN_CONT " [%s] ", modname);
+		printk(KERN_CONT "\n");
+
+		newfp = (unsigned long *) *fp;
+
+		if (((unsigned long) newfp) & 0x3) {
+			printk(KERN_INFO "-- Corrupt frame pointer %p\n",
+				newfp);
+			break;
+		}
+
+		/* Attempt to continue past exception. */
+		if (0 == newfp) {
+			struct pt_regs *regs = (struct pt_regs *) (((void *)fp)
+						+ 8);
+
+			if (regs->syscall_nr != -1) {
+				printk(KERN_INFO "-- trap0 -- syscall_nr: %ld",
+					regs->syscall_nr);
+				printk(KERN_CONT "  psp: %lx  elr: %lx\n",
+					 pt_psp(regs), pt_elr(regs));
+				break;
+			} else {
+				/* really want to see more ... */
+				kstack_depth_to_print += 6;
+				printk(KERN_INFO "-- %s (0x%lx)  badva: %lx\n",
+					ex_name(pt_cause(regs)), pt_cause(regs),
+					pt_badva(regs));
+			}
+
+			newfp = (unsigned long *) regs->r30;
+			ip = pt_elr(regs);
+		} else {
+			ip = *(newfp + 1);
+		}
+
+		/* If link reg is null, we are done. */
+		if (ip == 0x0)
+			break;
+
+		/* If newfp isn't larger, we're tracing garbage. */
+		if (newfp > fp)
+			fp = newfp;
+		else
+			break;
+	}
+}
+
+void show_stack(struct task_struct *task, unsigned long *fp)
+{
+	/* Saved link reg is one word above FP */
+	do_show_stack(task, fp, 0);
+}
+
+void dump_stack(void)
+{
+	unsigned long *fp;
+	asm("%0 = r30" : "=r" (fp));
+	show_stack(current, fp);
+}
+EXPORT_SYMBOL(dump_stack);
+
+int die(const char *str, struct pt_regs *regs, long err)
+{
+	static struct {
+		spinlock_t lock;
+		int counter;
+	} die = {
+		.lock = __SPIN_LOCK_UNLOCKED(die.lock),
+		.counter = 0
+	};
+
+	console_verbose();
+	oops_enter();
+
+	spin_lock_irq(&die.lock);
+	bust_spinlocks(1);
+	printk(KERN_EMERG "Oops: %s[#%d]:\n", str, ++die.counter);
+
+	if (notify_die(DIE_OOPS, str, regs, err, pt_cause(regs), SIGSEGV) ==
+	    NOTIFY_STOP)
+		return 1;
+
+	print_modules();
+	show_regs(regs);
+	do_show_stack(current, &regs->r30, pt_elr(regs));
+
+	bust_spinlocks(0);
+	add_taint(TAINT_DIE);
+
+	spin_unlock_irq(&die.lock);
+
+	if (in_interrupt())
+		panic("Fatal exception in interrupt");
+
+	if (panic_on_oops)
+		panic("Fatal exception");
+
+	oops_exit();
+	do_exit(err);
+	return 0;
+}
+
+int die_if_kernel(char *str, struct pt_regs *regs, long err)
+{
+	if (!user_mode(regs))
+		return die(str, regs, err);
+	else
+		return 0;
+}
+
+/*
+ * It's not clear that misaligned fetches are ever recoverable.
+ */
+static void misaligned_instruction(struct pt_regs *regs)
+{
+	die_if_kernel("Misaligned Instruction", regs, 0);
+	force_sig(SIGBUS, current);
+}
+
+/*
+ * Misaligned loads and stores, on the other hand, can be
+ * emulated, and probably should be, some day.  But for now
+ * they will be considered fatal.
+ */
+static void misaligned_data_load(struct pt_regs *regs)
+{
+	die_if_kernel("Misaligned Data Load", regs, 0);
+	force_sig(SIGBUS, current);
+}
+
+static void misaligned_data_store(struct pt_regs *regs)
+{
+	die_if_kernel("Misaligned Data Store", regs, 0);
+	force_sig(SIGBUS, current);
+}
+
+static void illegal_instruction(struct pt_regs *regs)
+{
+	die_if_kernel("Illegal Instruction", regs, 0);
+	force_sig(SIGILL, current);
+}
+
+/*
+ * Precise bus errors may be recoverable with a a retry,
+ * but for now, treat them as irrecoverable.
+ */
+static void precise_bus_error(struct pt_regs *regs)
+{
+	die_if_kernel("Precise Bus Error", regs, 0);
+	force_sig(SIGBUS, current);
+}
+
+/*
+ * If anything is to be done here other than panic,
+ * it will probably be complex and migrate to another
+ * source module.  For now, just die.
+ */
+static void cache_error(struct pt_regs *regs)
+{
+	die("Cache Error", regs, 0);
+}
+
+/*
+ * General exception handler
+ */
+void do_genex(struct pt_regs *regs)
+{
+	/*
+	 * Decode Cause and Dispatch
+	 */
+	switch (pt_cause(regs)) {
+	case HVM_GE_C_XPROT:
+	case HVM_GE_C_XUSER:
+		execute_protection_fault(regs);
+		break;
+	case HVM_GE_C_RPROT:
+	case HVM_GE_C_RUSER:
+		read_protection_fault(regs);
+		break;
+	case HVM_GE_C_WPROT:
+	case HVM_GE_C_WUSER:
+		write_protection_fault(regs);
+		break;
+	case HVM_GE_C_XMAL:
+		misaligned_instruction(regs);
+		break;
+	case HVM_GE_C_RMAL:
+		misaligned_data_load(regs);
+		break;
+	case HVM_GE_C_WMAL:
+		misaligned_data_store(regs);
+		break;
+	case HVM_GE_C_INVI:
+	case HVM_GE_C_PRIVI:
+		illegal_instruction(regs);
+		break;
+	case HVM_GE_C_BUS:
+		precise_bus_error(regs);
+		break;
+	case HVM_GE_C_CACHE:
+		cache_error(regs);
+		break;
+	default:
+		/* Halt and catch fire */
+		panic("Unrecognized exception 0x%lx\n", pt_cause(regs));
+		break;
+	}
+}
+
+/* Indirect system call dispatch */
+long sys_syscall(void)
+{
+	printk(KERN_ERR "sys_syscall invoked!\n");
+	return -ENOSYS;
+}
+
+void do_trap0(struct pt_regs *regs)
+{
+	unsigned long syscallret = 0;
+	syscall_fn syscall;
+
+	switch (pt_cause(regs)) {
+	case TRAP_SYSCALL:
+		/* System call is trap0 #1 */
+
+		/* allow strace to catch syscall args  */
+		if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE) &&
+			tracehook_report_syscall_entry(regs)))
+			return;  /*  return -ENOSYS somewhere?  */
+
+		/* Interrupts should be re-enabled for syscall processing */
+		__vmsetie(VM_INT_ENABLE);
+
+		/*
+		 * System call number is in r6, arguments in r0..r5.
+		 * Fortunately, no Linux syscall has more than 6 arguments,
+		 * and Hexagon ABI passes first 6 arguments in registers.
+		 * 64-bit arguments are passed in odd/even register pairs.
+		 * Fortunately, we have no system calls that take more
+		 * than three arguments with more than one 64-bit value.
+		 * Should that change, we'd need to redesign to copy
+		 * between user and kernel stacks.
+		 */
+		regs->syscall_nr = regs->r06;
+
+		/*
+		 * GPR R0 carries the first parameter, and is also used
+		 * to report the return value.  We need a backup of
+		 * the user's value in case we need to do a late restart
+		 * of the system call.
+		 */
+		regs->restart_r0 = regs->r00;
+
+		if ((unsigned long) regs->syscall_nr >= __NR_syscalls) {
+			regs->r00 = -1;
+		} else {
+			syscall = (syscall_fn)
+				  (sys_call_table[regs->syscall_nr]);
+			syscallret = syscall(regs->r00, regs->r01,
+				   regs->r02, regs->r03,
+				   regs->r04, regs->r05);
+		}
+
+		/*
+		 * If it was a sigreturn system call, don't overwrite
+		 * r0 value in stack frame with return value.
+		 *
+		 * __NR_sigreturn doesn't seem to exist in new unistd.h
+		 */
+
+		if (regs->syscall_nr != __NR_rt_sigreturn)
+			regs->r00 = syscallret;
+
+		/* allow strace to get the syscall return state  */
+		if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE)))
+			tracehook_report_syscall_exit(regs, 0);
+
+		break;
+	case TRAP_DEBUG:
+		/* Trap0 0xdb is debug breakpoint */
+		if (user_mode(regs)) {
+			struct siginfo info;
+
+			info.si_signo = SIGTRAP;
+			info.si_errno = 0;
+			/*
+			 * Some architecures add some per-thread state
+			 * to distinguish between breakpoint traps and
+			 * trace traps.  We may want to do that, and
+			 * set the si_code value appropriately, or we
+			 * may want to use a different trap0 flavor.
+			 */
+			info.si_code = TRAP_BRKPT;
+			info.si_addr = (void __user *) pt_elr(regs);
+			send_sig_info(SIGTRAP, &info, current);
+		} else {
+#ifdef CONFIG_KGDB
+			kgdb_handle_exception(pt_cause(regs), SIGTRAP,
+					      TRAP_BRKPT, regs);
+#endif
+		}
+		break;
+	}
+	/* Ignore other trap0 codes for now, especially 0 (Angel calls) */
+}
+
+/*
+ * Machine check exception handler
+ */
+void do_machcheck(struct pt_regs *regs)
+{
+	/* Halt and catch fire */
+	__vmstop();
+}
-- 
1.7.1


--

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