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, 576 insertions, 0 deletions

diff --git a/arch/nds32/mm/alignment.c b/arch/nds32/mm/alignment.c
new file mode 100644
index 000000000000..b96a01b10ca7
--- /dev/null
+++ b/arch/nds32/mm/alignment.c
@@ -0,0 +1,576 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2005-2017 Andes Technology Corporation
+
+#include <linux/proc_fs.h>
+#include <linux/uaccess.h>
+#include <linux/sysctl.h>
+#include <asm/unaligned.h>
+
+#define DEBUG(enable, tagged, ...)				\
+	do{							\
+		if (enable) {					\
+			if (tagged)				\
+			pr_warn("[ %30s() ] ", __func__);	\
+			pr_warn(__VA_ARGS__);			\
+		}						\
+	} while (0)
+
+#define RT(inst)	(((inst) >> 20) & 0x1FUL)
+#define RA(inst)	(((inst) >> 15) & 0x1FUL)
+#define RB(inst)	(((inst) >> 10) & 0x1FUL)
+#define SV(inst)	(((inst) >> 8) & 0x3UL)
+#define IMM(inst)	(((inst) >> 0) & 0x3FFFUL)
+
+#define RA3(inst)	(((inst) >> 3) & 0x7UL)
+#define RT3(inst)	(((inst) >> 6) & 0x7UL)
+#define IMM3U(inst)	(((inst) >> 0) & 0x7UL)
+
+#define RA5(inst)	(((inst) >> 0) & 0x1FUL)
+#define RT4(inst)	(((inst) >> 5) & 0xFUL)
+
+#define __get8_data(val,addr,err)	\
+	__asm__(					\
+	"1:	lbi.bi	%1, [%2], #1\n"			\
+	"2:\n"						\
+	"	.pushsection .text.fixup,\"ax\"\n"	\
+	"	.align	2\n"				\
+	"3:	movi	%0, #1\n"			\
+	"	j	2b\n"				\
+	"	.popsection\n"				\
+	"	.pushsection __ex_table,\"a\"\n"	\
+	"	.align	3\n"				\
+	"	.long	1b, 3b\n"			\
+	"	.popsection\n"				\
+	: "=r" (err), "=&r" (val), "=r" (addr)		\
+	: "0" (err), "2" (addr))
+
+#define get16_data(addr, val_ptr)				\
+	do {							\
+		unsigned int err = 0, v, a = addr;		\
+		__get8_data(v,a,err);				\
+		*val_ptr =  v << 0;				\
+		__get8_data(v,a,err);				\
+		*val_ptr |= v << 8;				\
+		if (err)					\
+			goto fault;				\
+		*val_ptr = le16_to_cpu(*val_ptr);		\
+	} while(0)
+
+#define get32_data(addr, val_ptr)				\
+	do {							\
+		unsigned int err = 0, v, a = addr;		\
+		__get8_data(v,a,err);				\
+		*val_ptr =  v << 0;				\
+		__get8_data(v,a,err);				\
+		*val_ptr |= v << 8;				\
+		__get8_data(v,a,err);				\
+		*val_ptr |= v << 16;				\
+		__get8_data(v,a,err);				\
+		*val_ptr |= v << 24;				\
+		if (err)					\
+			goto fault;				\
+		*val_ptr = le32_to_cpu(*val_ptr);		\
+	} while(0)
+
+#define get_data(addr, val_ptr, len)				\
+	if (len == 2)						\
+		get16_data(addr, val_ptr);			\
+	else							\
+		get32_data(addr, val_ptr);
+
+#define set16_data(addr, val)					\
+	do {							\
+		unsigned int err = 0, *ptr = addr ;		\
+		val = le32_to_cpu(val);				\
+		__asm__(					\
+                "1:	sbi.bi 	%2, [%1], #1\n"			\
+                "	srli 	%2, %2, #8\n"			\
+                "2:	sbi	%2, [%1]\n"			\
+		"3:\n"						\
+		"	.pushsection .text.fixup,\"ax\"\n"	\
+		"	.align	2\n"				\
+		"4:	movi	%0, #1\n"			\
+		"	j	3b\n"				\
+		"	.popsection\n"				\
+		"	.pushsection __ex_table,\"a\"\n"	\
+		"	.align	3\n"				\
+		"	.long	1b, 4b\n"			\
+		"	.long	2b, 4b\n"			\
+		"	.popsection\n"				\
+		: "=r" (err), "+r" (ptr), "+r" (val)		\
+		: "0" (err)					\
+		);						\
+		if (err)					\
+			goto fault;				\
+	} while(0)
+
+#define set32_data(addr, val)					\
+	do {							\
+		unsigned int err = 0, *ptr = addr ;		\
+		val = le32_to_cpu(val);				\
+		__asm__(					\
+                "1:	sbi.bi 	%2, [%1], #1\n"			\
+                "	srli 	%2, %2, #8\n"			\
+                "2:	sbi.bi 	%2, [%1], #1\n"			\
+                "	srli 	%2, %2, #8\n"			\
+                "3:	sbi.bi 	%2, [%1], #1\n"			\
+                "	srli 	%2, %2, #8\n"			\
+                "4:	sbi 	%2, [%1]\n"			\
+		"5:\n"						\
+		"	.pushsection .text.fixup,\"ax\"\n"	\
+		"	.align	2\n"				\
+		"6:	movi	%0, #1\n"			\
+		"	j	5b\n"				\
+		"	.popsection\n"				\
+		"	.pushsection __ex_table,\"a\"\n"	\
+		"	.align	3\n"				\
+		"	.long	1b, 6b\n"			\
+		"	.long	2b, 6b\n"			\
+		"	.long	3b, 6b\n"			\
+		"	.long	4b, 6b\n"			\
+		"	.popsection\n"				\
+		: "=r" (err), "+r" (ptr), "+r" (val)		\
+		: "0" (err)					\
+		);						\
+		if (err)					\
+			goto fault;				\
+	} while(0)
+#define set_data(addr, val, len)				\
+	if (len == 2)						\
+		set16_data(addr, val);				\
+	else							\
+		set32_data(addr, val);
+#define NDS32_16BIT_INSTRUCTION	0x80000000
+
+extern pte_t va_present(struct mm_struct *mm, unsigned long addr);
+extern pte_t va_kernel_present(unsigned long addr);
+extern int va_readable(struct pt_regs *regs, unsigned long addr);
+extern int va_writable(struct pt_regs *regs, unsigned long addr);
+
+int unalign_access_mode = 0, unalign_access_debug = 0;
+
+static inline unsigned long *idx_to_addr(struct pt_regs *regs, int idx)
+{
+	/* this should be consistent with ptrace.h */
+	if (idx >= 0 && idx <= 25)	/* R0-R25 */
+		return &regs->uregs[0] + idx;
+	else if (idx >= 28 && idx <= 30)	/* FP, GP, LP */
+		return &regs->fp + (idx - 28);
+	else if (idx == 31)	/* SP */
+		return &regs->sp;
+	else
+		return NULL;	/* cause a segfault */
+}
+
+static inline unsigned long get_inst(unsigned long addr)
+{
+	return be32_to_cpu(get_unaligned((u32 *) addr));
+}
+
+static inline unsigned long sign_extend(unsigned long val, int len)
+{
+	unsigned long ret = 0;
+	unsigned char *s, *t;
+	int i = 0;
+
+	val = cpu_to_le32(val);
+
+	s = (void *)&val;
+	t = (void *)&ret;
+
+	while (i++ < len)
+		*t++ = *s++;
+
+	if (((*(t - 1)) & 0x80) && (i < 4)) {
+
+		while (i++ <= 4)
+			*t++ = 0xff;
+	}
+
+	return le32_to_cpu(ret);
+}
+
+static inline int do_16(unsigned long inst, struct pt_regs *regs)
+{
+	int imm, regular, load, len, addr_mode, idx_mode;
+	unsigned long unaligned_addr, target_val, source_idx, target_idx,
+	    shift = 0;
+	switch ((inst >> 9) & 0x3F) {
+
+	case 0x12:		/* LHI333    */
+		imm = 1;
+		regular = 1;
+		load = 1;
+		len = 2;
+		addr_mode = 3;
+		idx_mode = 3;
+		break;
+	case 0x10:		/* LWI333    */
+		imm = 1;
+		regular = 1;
+		load = 1;
+		len = 4;
+		addr_mode = 3;
+		idx_mode = 3;
+		break;
+	case 0x11:		/* LWI333.bi */
+		imm = 1;
+		regular = 0;
+		load = 1;
+		len = 4;
+		addr_mode = 3;
+		idx_mode = 3;
+		break;
+	case 0x1A:		/* LWI450    */
+		imm = 0;
+		regular = 1;
+		load = 1;
+		len = 4;
+		addr_mode = 5;
+		idx_mode = 4;
+		break;
+	case 0x16:		/* SHI333    */
+		imm = 1;
+		regular = 1;
+		load = 0;
+		len = 2;
+		addr_mode = 3;
+		idx_mode = 3;
+		break;
+	case 0x14:		/* SWI333    */
+		imm = 1;
+		regular = 1;
+		load = 0;
+		len = 4;
+		addr_mode = 3;
+		idx_mode = 3;
+		break;
+	case 0x15:		/* SWI333.bi */
+		imm = 1;
+		regular = 0;
+		load = 0;
+		len = 4;
+		addr_mode = 3;
+		idx_mode = 3;
+		break;
+	case 0x1B:		/* SWI450    */
+		imm = 0;
+		regular = 1;
+		load = 0;
+		len = 4;
+		addr_mode = 5;
+		idx_mode = 4;
+		break;
+
+	default:
+		return -EFAULT;
+	}
+
+	if (addr_mode == 3) {
+		unaligned_addr = *idx_to_addr(regs, RA3(inst));
+		source_idx = RA3(inst);
+	} else {
+		unaligned_addr = *idx_to_addr(regs, RA5(inst));
+		source_idx = RA5(inst);
+	}
+
+	if (idx_mode == 3)
+		target_idx = RT3(inst);
+	else
+		target_idx = RT4(inst);
+
+	if (imm)
+		shift = IMM3U(inst) * len;
+
+	if (regular)
+		unaligned_addr += shift;
+
+	if (load) {
+		if (!access_ok(VERIFY_READ, (void *)unaligned_addr, len))
+			return -EACCES;
+
+		get_data(unaligned_addr, &target_val, len);
+		*idx_to_addr(regs, target_idx) = target_val;
+	} else {
+		if (!access_ok(VERIFY_WRITE, (void *)unaligned_addr, len))
+			return -EACCES;
+		target_val = *idx_to_addr(regs, target_idx);
+		set_data((void *)unaligned_addr, target_val, len);
+	}
+
+	if (!regular)
+		*idx_to_addr(regs, source_idx) = unaligned_addr + shift;
+	regs->ipc += 2;
+
+	return 0;
+fault:
+	return -EACCES;
+}
+
+static inline int do_32(unsigned long inst, struct pt_regs *regs)
+{
+	int imm, regular, load, len, sign_ext;
+	unsigned long unaligned_addr, target_val, shift;
+
+	unaligned_addr = *idx_to_addr(regs, RA(inst));
+
+	switch ((inst >> 25) << 1) {
+
+	case 0x02:		/* LHI       */
+		imm = 1;
+		regular = 1;
+		load = 1;
+		len = 2;
+		sign_ext = 0;
+		break;
+	case 0x0A:		/* LHI.bi    */
+		imm = 1;
+		regular = 0;
+		load = 1;
+		len = 2;
+		sign_ext = 0;
+		break;
+	case 0x22:		/* LHSI      */
+		imm = 1;
+		regular = 1;
+		load = 1;
+		len = 2;
+		sign_ext = 1;
+		break;
+	case 0x2A:		/* LHSI.bi   */
+		imm = 1;
+		regular = 0;
+		load = 1;
+		len = 2;
+		sign_ext = 1;
+		break;
+	case 0x04:		/* LWI       */
+		imm = 1;
+		regular = 1;
+		load = 1;
+		len = 4;
+		sign_ext = 0;
+		break;
+	case 0x0C:		/* LWI.bi    */
+		imm = 1;
+		regular = 0;
+		load = 1;
+		len = 4;
+		sign_ext = 0;
+		break;
+	case 0x12:		/* SHI       */
+		imm = 1;
+		regular = 1;
+		load = 0;
+		len = 2;
+		sign_ext = 0;
+		break;
+	case 0x1A:		/* SHI.bi    */
+		imm = 1;
+		regular = 0;
+		load = 0;
+		len = 2;
+		sign_ext = 0;
+		break;
+	case 0x14:		/* SWI       */
+		imm = 1;
+		regular = 1;
+		load = 0;
+		len = 4;
+		sign_ext = 0;
+		break;
+	case 0x1C:		/* SWI.bi    */
+		imm = 1;
+		regular = 0;
+		load = 0;
+		len = 4;
+		sign_ext = 0;
+		break;
+
+	default:
+		switch (inst & 0xff) {
+
+		case 0x01:	/* LH        */
+			imm = 0;
+			regular = 1;
+			load = 1;
+			len = 2;
+			sign_ext = 0;
+			break;
+		case 0x05:	/* LH.bi     */
+			imm = 0;
+			regular = 0;
+			load = 1;
+			len = 2;
+			sign_ext = 0;
+			break;
+		case 0x11:	/* LHS       */
+			imm = 0;
+			regular = 1;
+			load = 1;
+			len = 2;
+			sign_ext = 1;
+			break;
+		case 0x15:	/* LHS.bi    */
+			imm = 0;
+			regular = 0;
+			load = 1;
+			len = 2;
+			sign_ext = 1;
+			break;
+		case 0x02:	/* LW        */
+			imm = 0;
+			regular = 1;
+			load = 1;
+			len = 4;
+			sign_ext = 0;
+			break;
+		case 0x06:	/* LW.bi     */
+			imm = 0;
+			regular = 0;
+			load = 1;
+			len = 4;
+			sign_ext = 0;
+			break;
+		case 0x09:	/* SH        */
+			imm = 0;
+			regular = 1;
+			load = 0;
+			len = 2;
+			sign_ext = 0;
+			break;
+		case 0x0D:	/* SH.bi     */
+			imm = 0;
+			regular = 0;
+			load = 0;
+			len = 2;
+			sign_ext = 0;
+			break;
+		case 0x0A:	/* SW        */
+			imm = 0;
+			regular = 1;
+			load = 0;
+			len = 4;
+			sign_ext = 0;
+			break;
+		case 0x0E:	/* SW.bi     */
+			imm = 0;
+			regular = 0;
+			load = 0;
+			len = 4;
+			sign_ext = 0;
+			break;
+
+		default:
+			return -EFAULT;
+		}
+	}
+
+	if (imm)
+		shift = IMM(inst) * len;
+	else
+		shift = *idx_to_addr(regs, RB(inst)) << SV(inst);
+
+	if (regular)
+		unaligned_addr += shift;
+
+	if (load) {
+
+		if (!access_ok(VERIFY_READ, (void *)unaligned_addr, len))
+			return -EACCES;
+
+		get_data(unaligned_addr, &target_val, len);
+
+		if (sign_ext)
+			*idx_to_addr(regs, RT(inst)) =
+			    sign_extend(target_val, len);
+		else
+			*idx_to_addr(regs, RT(inst)) = target_val;
+	} else {
+
+		if (!access_ok(VERIFY_WRITE, (void *)unaligned_addr, len))
+			return -EACCES;
+
+		target_val = *idx_to_addr(regs, RT(inst));
+		set_data((void *)unaligned_addr, target_val, len);
+	}
+
+	if (!regular)
+		*idx_to_addr(regs, RA(inst)) = unaligned_addr + shift;
+
+	regs->ipc += 4;
+
+	return 0;
+fault:
+	return -EACCES;
+}
+
+int do_unaligned_access(unsigned long addr, struct pt_regs *regs)
+{
+	unsigned long inst;
+	int ret = -EFAULT;
+	mm_segment_t seg = get_fs();
+
+	inst = get_inst(regs->ipc);
+
+	DEBUG((unalign_access_debug > 0), 1,
+	      "Faulting addr: 0x%08lx, pc: 0x%08lx [inst: 0x%08lx ]\n", addr,
+	      regs->ipc, inst);
+
+	set_fs(USER_DS);
+
+	if (inst & NDS32_16BIT_INSTRUCTION)
+		ret = do_16((inst >> 16) & 0xffff, regs);
+	else
+		ret = do_32(inst, regs);
+	set_fs(seg);
+
+	return ret;
+}
+
+#ifdef CONFIG_PROC_FS
+
+static struct ctl_table alignment_tbl[3] = {
+	{
+	 .procname = "enable",
+	 .data = &unalign_access_mode,
+	 .maxlen = sizeof(unalign_access_mode),
+	 .mode = 0666,
+	 .proc_handler = &proc_dointvec
+	}
+	,
+	{
+	 .procname = "debug_info",
+	 .data = &unalign_access_debug,
+	 .maxlen = sizeof(unalign_access_debug),
+	 .mode = 0644,
+	 .proc_handler = &proc_dointvec
+	}
+	,
+	{}
+};
+
+static struct ctl_table nds32_sysctl_table[2] = {
+	{
+	 .procname = "unaligned_acess",
+	 .mode = 0555,
+	 .child = alignment_tbl},
+	{}
+};
+
+static struct ctl_path nds32_path[2] = {
+	{.procname = "nds32"},
+	{}
+};
+
+/*
+ * Initialize nds32 alignment-correction interface
+ */
+static int __init nds32_sysctl_init(void)
+{
+	register_sysctl_paths(nds32_path, nds32_sysctl_table);
+	return 0;
+}
+
+__initcall(nds32_sysctl_init);
+#endif /* CONFIG_PROC_FS */