nds32: Exception handling

This patch includes the exception/interrupt entries, pt_reg structure and
related accessors.

/* Unaligned accessing handling*/
Andes processors cannot load/store information which is not naturally
aligned on the bus, i.e., loading a 4 byte data whose start address must
be divisible by 4. If unaligned data accessing is happened, data
unaligned exception will be triggered and user will get SIGSEGV or
kernel oops according to the unaligned address. In order to make user be
able to load/store data from an unaligned address, software load/store
emulation is implemented in arch/nds32/mm/alignment.c to address data
unaligned exception.

Unaligned accessing handling is disabled by default because it is not a
normal case. User can enable this feature by following steps.

A. Compile time:
    1. Enable kernel config CONFIG_ALIGNMENT_TRAP
B. Run time:
    1. Enter /proc/sys/nds32/unaligned_acess folder
    2. Write 1 to file enable_mode to enable unaligned accessing
       handling. User can disable it by writing 0 to this file.
    3. Write 1 to file debug to show which unaligned address is under
       processing. User can disable it by writing 0 to this file.

However, unaligned accessing handler cannot work if this unaligned
address is not accessible such as protection violation. On this
condition, the default behaviors for addressing data unaligned exception
still happen

Signed-off-by: Vincent Chen <vincentc@andestech.com>
Signed-off-by: Greentime Hu <greentime@andestech.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 442 insertions, 0 deletions

diff --git a/arch/nds32/kernel/traps.c b/arch/nds32/kernel/traps.c
new file mode 100644
index 000000000000..8828b4aeb72b
--- /dev/null
+++ b/arch/nds32/kernel/traps.c
@@ -0,0 +1,442 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/module.h>
+#include <linux/personality.h>
+#include <linux/kallsyms.h>
+#include <linux/hardirq.h>
+#include <linux/kdebug.h>
+#include <linux/sched/task_stack.h>
+#include <linux/uaccess.h>
+
+#include <asm/proc-fns.h>
+#include <asm/unistd.h>
+
+#include <linux/ptrace.h>
+#include <nds32_intrinsic.h>
+
+extern void show_pte(struct mm_struct *mm, unsigned long addr);
+
+/*
+ * Dump out the contents of some memory nicely...
+ */
+void dump_mem(const char *lvl, unsigned long bottom, unsigned long top)
+{
+	unsigned long first;
+	mm_segment_t fs;
+	int i;
+
+	/*
+	 * We need to switch to kernel mode so that we can use __get_user
+	 * to safely read from kernel space.  Note that we now dump the
+	 * code first, just in case the backtrace kills us.
+	 */
+	fs = get_fs();
+	set_fs(KERNEL_DS);
+
+	pr_emerg("%s(0x%08lx to 0x%08lx)\n", lvl, bottom, top);
+
+	for (first = bottom & ~31; first < top; first += 32) {
+		unsigned long p;
+		char str[sizeof(" 12345678") * 8 + 1];
+
+		memset(str, ' ', sizeof(str));
+		str[sizeof(str) - 1] = '\0';
+
+		for (p = first, i = 0; i < 8 && p < top; i++, p += 4) {
+			if (p >= bottom && p < top) {
+				unsigned long val;
+				if (__get_user(val, (unsigned long *)p) == 0)
+					sprintf(str + i * 9, " %08lx", val);
+				else
+					sprintf(str + i * 9, " ????????");
+			}
+		}
+		pr_emerg("%s%04lx:%s\n", lvl, first & 0xffff, str);
+	}
+
+	set_fs(fs);
+}
+
+EXPORT_SYMBOL(dump_mem);
+
+static void dump_instr(struct pt_regs *regs)
+{
+	unsigned long addr = instruction_pointer(regs);
+	mm_segment_t fs;
+	char str[sizeof("00000000 ") * 5 + 2 + 1], *p = str;
+	int i;
+
+	return;
+	/*
+	 * We need to switch to kernel mode so that we can use __get_user
+	 * to safely read from kernel space.  Note that we now dump the
+	 * code first, just in case the backtrace kills us.
+	 */
+	fs = get_fs();
+	set_fs(KERNEL_DS);
+
+	pr_emerg("Code: ");
+	for (i = -4; i < 1; i++) {
+		unsigned int val, bad;
+
+		bad = __get_user(val, &((u32 *) addr)[i]);
+
+		if (!bad) {
+			p += sprintf(p, i == 0 ? "(%08x) " : "%08x ", val);
+		} else {
+			p += sprintf(p, "bad PC value");
+			break;
+		}
+	}
+	pr_emerg("Code: %s\n", str);
+
+	set_fs(fs);
+}
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+#include <linux/ftrace.h>
+static void
+get_real_ret_addr(unsigned long *addr, struct task_struct *tsk, int *graph)
+{
+	if (*addr == (unsigned long)return_to_handler) {
+		int index = tsk->curr_ret_stack;
+
+		if (tsk->ret_stack && index >= *graph) {
+			index -= *graph;
+			*addr = tsk->ret_stack[index].ret;
+			(*graph)++;
+		}
+	}
+}
+#else
+static inline void
+get_real_ret_addr(unsigned long *addr, struct task_struct *tsk, int *graph)
+{
+}
+#endif
+
+#define LOOP_TIMES (100)
+static void __dump(struct task_struct *tsk, unsigned long *base_reg)
+{
+	unsigned long ret_addr;
+	int cnt = LOOP_TIMES, graph = 0;
+	pr_emerg("Call Trace:\n");
+	if (!IS_ENABLED(CONFIG_FRAME_POINTER)) {
+		while (!kstack_end(base_reg)) {
+			ret_addr = *base_reg++;
+			if (__kernel_text_address(ret_addr)) {
+				get_real_ret_addr(&ret_addr, tsk, &graph);
+				print_ip_sym(ret_addr);
+			}
+			if (--cnt < 0)
+				break;
+		}
+	} else {
+		while (!kstack_end((void *)base_reg) &&
+		       !((unsigned long)base_reg & 0x3) &&
+		       ((unsigned long)base_reg >= TASK_SIZE)) {
+			unsigned long next_fp;
+#if !defined(NDS32_ABI_2)
+			ret_addr = base_reg[0];
+			next_fp = base_reg[1];
+#else
+			ret_addr = base_reg[-1];
+			next_fp = base_reg[FP_OFFSET];
+#endif
+			if (__kernel_text_address(ret_addr)) {
+				get_real_ret_addr(&ret_addr, tsk, &graph);
+				print_ip_sym(ret_addr);
+			}
+			if (--cnt < 0)
+				break;
+			base_reg = (unsigned long *)next_fp;
+		}
+	}
+	pr_emerg("\n");
+}
+
+void dump_stack(void)
+{
+	unsigned long *base_reg;
+	if (!IS_ENABLED(CONFIG_FRAME_POINTER))
+		__asm__ __volatile__("\tori\t%0, $sp, #0\n":"=r"(base_reg));
+	else
+		__asm__ __volatile__("\tori\t%0, $fp, #0\n":"=r"(base_reg));
+	__dump(NULL, base_reg);
+}
+
+EXPORT_SYMBOL(dump_stack);
+
+void show_stack(struct task_struct *tsk, unsigned long *sp)
+{
+	unsigned long *base_reg;
+
+	if (!tsk)
+		tsk = current;
+	if (!IS_ENABLED(CONFIG_FRAME_POINTER)) {
+		if (tsk != current)
+			base_reg = (unsigned long *)(tsk->thread.cpu_context.sp);
+		else
+			__asm__ __volatile__("\tori\t%0, $sp, #0\n":"=r"(base_reg));
+	} else {
+		if (tsk != current)
+			base_reg = (unsigned long *)(tsk->thread.cpu_context.fp);
+		else
+			__asm__ __volatile__("\tori\t%0, $fp, #0\n":"=r"(base_reg));
+	}
+	__dump(tsk, base_reg);
+	barrier();
+}
+
+DEFINE_SPINLOCK(die_lock);
+
+/*
+ * This function is protected against re-entrancy.
+ */
+void die(const char *str, struct pt_regs *regs, int err)
+{
+	struct task_struct *tsk = current;
+	static int die_counter;
+
+	console_verbose();
+	spin_lock_irq(&die_lock);
+	bust_spinlocks(1);
+
+	pr_emerg("Internal error: %s: %x [#%d]\n", str, err, ++die_counter);
+	print_modules();
+	pr_emerg("CPU: %i\n", smp_processor_id());
+	show_regs(regs);
+	pr_emerg("Process %s (pid: %d, stack limit = 0x%p)\n",
+		 tsk->comm, tsk->pid, task_thread_info(tsk) + 1);
+
+	if (!user_mode(regs) || in_interrupt()) {
+		dump_mem("Stack: ", regs->sp,
+			 THREAD_SIZE + (unsigned long)task_thread_info(tsk));
+		dump_instr(regs);
+		dump_stack();
+	}
+
+	bust_spinlocks(0);
+	spin_unlock_irq(&die_lock);
+	do_exit(SIGSEGV);
+}
+
+EXPORT_SYMBOL(die);
+
+void die_if_kernel(const char *str, struct pt_regs *regs, int err)
+{
+	if (user_mode(regs))
+		return;
+
+	die(str, regs, err);
+}
+
+int bad_syscall(int n, struct pt_regs *regs)
+{
+	siginfo_t info;
+
+	if (current->personality != PER_LINUX) {
+		send_sig(SIGSEGV, current, 1);
+		return regs->uregs[0];
+	}
+
+	info.si_signo = SIGILL;
+	info.si_errno = 0;
+	info.si_code = ILL_ILLTRP;
+	info.si_addr = (void __user *)instruction_pointer(regs) - 4;
+
+	force_sig_info(SIGILL, &info, current);
+	die_if_kernel("Oops - bad syscall", regs, n);
+	return regs->uregs[0];
+}
+
+void __pte_error(const char *file, int line, unsigned long val)
+{
+	pr_emerg("%s:%d: bad pte %08lx.\n", file, line, val);
+}
+
+void __pmd_error(const char *file, int line, unsigned long val)
+{
+	pr_emerg("%s:%d: bad pmd %08lx.\n", file, line, val);
+}
+
+void __pgd_error(const char *file, int line, unsigned long val)
+{
+	pr_emerg("%s:%d: bad pgd %08lx.\n", file, line, val);
+}
+
+extern char *exception_vector, *exception_vector_end;
+void __init trap_init(void)
+{
+	return;
+}
+
+void __init early_trap_init(void)
+{
+	unsigned long ivb = 0;
+	unsigned long base = PAGE_OFFSET;
+
+	memcpy((unsigned long *)base, (unsigned long *)&exception_vector,
+	       ((unsigned long)&exception_vector_end -
+		(unsigned long)&exception_vector));
+	ivb = __nds32__mfsr(NDS32_SR_IVB);
+	/* Check platform support. */
+	if (((ivb & IVB_mskNIVIC) >> IVB_offNIVIC) < 2)
+		panic
+		    ("IVIC mode is not allowed on the platform with interrupt controller\n");
+	__nds32__mtsr((ivb & ~IVB_mskESZ) | (IVB_valESZ16 << IVB_offESZ) |
+		      IVB_BASE, NDS32_SR_IVB);
+	__nds32__mtsr(INT_MASK_INITAIAL_VAL, NDS32_SR_INT_MASK);
+
+	/*
+	 * 0x800 = 128 vectors * 16byte.
+	 * It should be enough to flush a page.
+	 */
+	cpu_cache_wbinval_page(base, true);
+}
+
+void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs,
+		  int error_code, int si_code)
+{
+	struct siginfo info;
+
+	tsk->thread.trap_no = ENTRY_DEBUG_RELATED;
+	tsk->thread.error_code = error_code;
+
+	memset(&info, 0, sizeof(info));
+	info.si_signo = SIGTRAP;
+	info.si_code = si_code;
+	info.si_addr = (void __user *)instruction_pointer(regs);
+	force_sig_info(SIGTRAP, &info, tsk);
+}
+
+void do_debug_trap(unsigned long entry, unsigned long addr,
+		   unsigned long type, struct pt_regs *regs)
+{
+	if (notify_die(DIE_OOPS, "Oops", regs, addr, type, SIGTRAP)
+	    == NOTIFY_STOP)
+		return;
+
+	if (user_mode(regs)) {
+		/* trap_signal */
+		send_sigtrap(current, regs, 0, TRAP_BRKPT);
+	} else {
+		/* kernel_trap */
+		if (!fixup_exception(regs))
+			die("unexpected kernel_trap", regs, 0);
+	}
+}
+
+void unhandled_interruption(struct pt_regs *regs)
+{
+	siginfo_t si;
+	pr_emerg("unhandled_interruption\n");
+	show_regs(regs);
+	if (!user_mode(regs))
+		do_exit(SIGKILL);
+	si.si_signo = SIGKILL;
+	si.si_errno = 0;
+	force_sig_info(SIGKILL, &si, current);
+}
+
+void unhandled_exceptions(unsigned long entry, unsigned long addr,
+			  unsigned long type, struct pt_regs *regs)
+{
+	siginfo_t si;
+	pr_emerg("Unhandled Exception: entry: %lx addr:%lx itype:%lx\n", entry,
+		 addr, type);
+	show_regs(regs);
+	if (!user_mode(regs))
+		do_exit(SIGKILL);
+	si.si_signo = SIGKILL;
+	si.si_errno = 0;
+	si.si_addr = (void *)addr;
+	force_sig_info(SIGKILL, &si, current);
+}
+
+extern int do_page_fault(unsigned long entry, unsigned long addr,
+			 unsigned int error_code, struct pt_regs *regs);
+
+/*
+ * 2:DEF dispatch for TLB MISC exception handler
+*/
+
+void do_dispatch_tlb_misc(unsigned long entry, unsigned long addr,
+			  unsigned long type, struct pt_regs *regs)
+{
+	type = type & (ITYPE_mskINST | ITYPE_mskETYPE);
+	if ((type & ITYPE_mskETYPE) < 5) {
+		/* Permission exceptions */
+		do_page_fault(entry, addr, type, regs);
+	} else
+		unhandled_exceptions(entry, addr, type, regs);
+}
+
+void do_revinsn(struct pt_regs *regs)
+{
+	siginfo_t si;
+	pr_emerg("Reserved Instruction\n");
+	show_regs(regs);
+	if (!user_mode(regs))
+		do_exit(SIGILL);
+	si.si_signo = SIGILL;
+	si.si_errno = 0;
+	force_sig_info(SIGILL, &si, current);
+}
+
+#ifdef CONFIG_ALIGNMENT_TRAP
+extern int unalign_access_mode;
+extern int do_unaligned_access(unsigned long addr, struct pt_regs *regs);
+#endif
+void do_dispatch_general(unsigned long entry, unsigned long addr,
+			 unsigned long itype, struct pt_regs *regs,
+			 unsigned long oipc)
+{
+	unsigned int swid = itype >> ITYPE_offSWID;
+	unsigned long type = itype & (ITYPE_mskINST | ITYPE_mskETYPE);
+	if (type == ETYPE_ALIGNMENT_CHECK) {
+#ifdef CONFIG_ALIGNMENT_TRAP
+		/* Alignment check */
+		if (user_mode(regs) && unalign_access_mode) {
+			int ret;
+			ret = do_unaligned_access(addr, regs);
+
+			if (ret == 0)
+				return;
+
+			if (ret == -EFAULT)
+				pr_emerg
+				    ("Unhandled unaligned access exception\n");
+		}
+#endif
+		do_page_fault(entry, addr, type, regs);
+	} else if (type == ETYPE_RESERVED_INSTRUCTION) {
+		/* Reserved instruction */
+		do_revinsn(regs);
+	} else if (type == ETYPE_TRAP && swid == SWID_RAISE_INTERRUPT_LEVEL) {
+		/* trap, used on v3 EDM target debugging workaround */
+		/*
+		 * DIPC(OIPC) is passed as parameter before
+		 * interrupt is enabled, so the DIPC will not be corrupted
+		 * even though interrupts are coming in
+		 */
+		/*
+		 * 1. update ipc
+		 * 2. update pt_regs ipc with oipc
+		 * 3. update pt_regs ipsw (clear DEX)
+		 */
+		__asm__ volatile ("mtsr %0, $IPC\n\t"::"r" (oipc));
+		regs->ipc = oipc;
+		if (regs->pipsw & PSW_mskDEX) {
+			pr_emerg
+			    ("Nested Debug exception is possibly happened\n");
+			pr_emerg("ipc:%08x pipc:%08x\n",
+				 (unsigned int)regs->ipc,
+				 (unsigned int)regs->pipc);
+		}
+		do_debug_trap(entry, addr, itype, regs);
+		regs->ipsw &= ~PSW_mskDEX;
+	} else
+		unhandled_exceptions(entry, addr, type, regs);
+}