arm64: Debugging support

This patch adds ptrace, debug monitors and hardware breakpoints support.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

1 files changed, 1126 insertions, 0 deletions

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
new file mode 100644
index 000000000000..490f7537a270
--- /dev/null
+++ b/arch/arm64/kernel/ptrace.c
@@ -0,0 +1,1126 @@
+/*
+ * Based on arch/arm/kernel/ptrace.c
+ *
+ * By Ross Biro 1/23/92
+ * edited by Linus Torvalds
+ * ARM modifications Copyright (C) 2000 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License 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, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/ptrace.h>
+#include <linux/user.h>
+#include <linux/security.h>
+#include <linux/init.h>
+#include <linux/signal.h>
+#include <linux/uaccess.h>
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
+#include <linux/regset.h>
+#include <linux/tracehook.h>
+#include <linux/elf.h>
+
+#include <asm/compat.h>
+#include <asm/debug-monitors.h>
+#include <asm/pgtable.h>
+#include <asm/traps.h>
+#include <asm/system_misc.h>
+
+/*
+ * TODO: does not yet catch signals sent when the child dies.
+ * in exit.c or in signal.c.
+ */
+
+/*
+ * Called by kernel/ptrace.c when detaching..
+ */
+void ptrace_disable(struct task_struct *child)
+{
+}
+
+/*
+ * Handle hitting a breakpoint.
+ */
+static int ptrace_break(struct pt_regs *regs)
+{
+	siginfo_t info = {
+		.si_signo = SIGTRAP,
+		.si_errno = 0,
+		.si_code  = TRAP_BRKPT,
+		.si_addr  = (void __user *)instruction_pointer(regs),
+	};
+
+	force_sig_info(SIGTRAP, &info, current);
+	return 0;
+}
+
+static int arm64_break_trap(unsigned long addr, unsigned int esr,
+			    struct pt_regs *regs)
+{
+	return ptrace_break(regs);
+}
+
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+/*
+ * Handle hitting a HW-breakpoint.
+ */
+static void ptrace_hbptriggered(struct perf_event *bp,
+				struct perf_sample_data *data,
+				struct pt_regs *regs)
+{
+	struct arch_hw_breakpoint *bkpt = counter_arch_bp(bp);
+	siginfo_t info = {
+		.si_signo	= SIGTRAP,
+		.si_errno	= 0,
+		.si_code	= TRAP_HWBKPT,
+		.si_addr	= (void __user *)(bkpt->trigger),
+	};
+
+#ifdef CONFIG_COMPAT
+	int i;
+
+	if (!is_compat_task())
+		goto send_sig;
+
+	for (i = 0; i < ARM_MAX_BRP; ++i) {
+		if (current->thread.debug.hbp_break[i] == bp) {
+			info.si_errno = (i << 1) + 1;
+			break;
+		}
+	}
+	for (i = ARM_MAX_BRP; i < ARM_MAX_HBP_SLOTS && !bp; ++i) {
+		if (current->thread.debug.hbp_watch[i] == bp) {
+			info.si_errno = -((i << 1) + 1);
+			break;
+		}
+	}
+
+send_sig:
+#endif
+	force_sig_info(SIGTRAP, &info, current);
+}
+
+/*
+ * Unregister breakpoints from this task and reset the pointers in
+ * the thread_struct.
+ */
+void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
+{
+	int i;
+	struct thread_struct *t = &tsk->thread;
+
+	for (i = 0; i < ARM_MAX_BRP; i++) {
+		if (t->debug.hbp_break[i]) {
+			unregister_hw_breakpoint(t->debug.hbp_break[i]);
+			t->debug.hbp_break[i] = NULL;
+		}
+	}
+
+	for (i = 0; i < ARM_MAX_WRP; i++) {
+		if (t->debug.hbp_watch[i]) {
+			unregister_hw_breakpoint(t->debug.hbp_watch[i]);
+			t->debug.hbp_watch[i] = NULL;
+		}
+	}
+}
+
+void ptrace_hw_copy_thread(struct task_struct *tsk)
+{
+	memset(&tsk->thread.debug, 0, sizeof(struct debug_info));
+}
+
+static struct perf_event *ptrace_hbp_get_event(unsigned int note_type,
+					       struct task_struct *tsk,
+					       unsigned long idx)
+{
+	struct perf_event *bp = ERR_PTR(-EINVAL);
+
+	switch (note_type) {
+	case NT_ARM_HW_BREAK:
+		if (idx < ARM_MAX_BRP)
+			bp = tsk->thread.debug.hbp_break[idx];
+		break;
+	case NT_ARM_HW_WATCH:
+		if (idx < ARM_MAX_WRP)
+			bp = tsk->thread.debug.hbp_watch[idx];
+		break;
+	}
+
+	return bp;
+}
+
+static int ptrace_hbp_set_event(unsigned int note_type,
+				struct task_struct *tsk,
+				unsigned long idx,
+				struct perf_event *bp)
+{
+	int err = -EINVAL;
+
+	switch (note_type) {
+	case NT_ARM_HW_BREAK:
+		if (idx < ARM_MAX_BRP) {
+			tsk->thread.debug.hbp_break[idx] = bp;
+			err = 0;
+		}
+		break;
+	case NT_ARM_HW_WATCH:
+		if (idx < ARM_MAX_WRP) {
+			tsk->thread.debug.hbp_watch[idx] = bp;
+			err = 0;
+		}
+		break;
+	}
+
+	return err;
+}
+
+static struct perf_event *ptrace_hbp_create(unsigned int note_type,
+					    struct task_struct *tsk,
+					    unsigned long idx)
+{
+	struct perf_event *bp;
+	struct perf_event_attr attr;
+	int err, type;
+
+	switch (note_type) {
+	case NT_ARM_HW_BREAK:
+		type = HW_BREAKPOINT_X;
+		break;
+	case NT_ARM_HW_WATCH:
+		type = HW_BREAKPOINT_RW;
+		break;
+	default:
+		return ERR_PTR(-EINVAL);
+	}
+
+	ptrace_breakpoint_init(&attr);
+
+	/*
+	 * Initialise fields to sane defaults
+	 * (i.e. values that will pass validation).
+	 */
+	attr.bp_addr	= 0;
+	attr.bp_len	= HW_BREAKPOINT_LEN_4;
+	attr.bp_type	= type;
+	attr.disabled	= 1;
+
+	bp = register_user_hw_breakpoint(&attr, ptrace_hbptriggered, NULL, tsk);
+	if (IS_ERR(bp))
+		return bp;
+
+	err = ptrace_hbp_set_event(note_type, tsk, idx, bp);
+	if (err)
+		return ERR_PTR(err);
+
+	return bp;
+}
+
+static int ptrace_hbp_fill_attr_ctrl(unsigned int note_type,
+				     struct arch_hw_breakpoint_ctrl ctrl,
+				     struct perf_event_attr *attr)
+{
+	int err, len, type;
+
+	err = arch_bp_generic_fields(ctrl, &len, &type);
+	if (err)
+		return err;
+
+	switch (note_type) {
+	case NT_ARM_HW_BREAK:
+		if ((type & HW_BREAKPOINT_X) != type)
+			return -EINVAL;
+		break;
+	case NT_ARM_HW_WATCH:
+		if ((type & HW_BREAKPOINT_RW) != type)
+			return -EINVAL;
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	attr->bp_len	= len;
+	attr->bp_type	= type;
+	attr->disabled	= !ctrl.enabled;
+
+	return 0;
+}
+
+static int ptrace_hbp_get_resource_info(unsigned int note_type, u32 *info)
+{
+	u8 num;
+	u32 reg = 0;
+
+	switch (note_type) {
+	case NT_ARM_HW_BREAK:
+		num = hw_breakpoint_slots(TYPE_INST);
+		break;
+	case NT_ARM_HW_WATCH:
+		num = hw_breakpoint_slots(TYPE_DATA);
+		break;
+	default:
+		return -EINVAL;
+	}
+
+	reg |= debug_monitors_arch();
+	reg <<= 8;
+	reg |= num;
+
+	*info = reg;
+	return 0;
+}
+
+static int ptrace_hbp_get_ctrl(unsigned int note_type,
+			       struct task_struct *tsk,
+			       unsigned long idx,
+			       u32 *ctrl)
+{
+	struct perf_event *bp = ptrace_hbp_get_event(note_type, tsk, idx);
+
+	if (IS_ERR(bp))
+		return PTR_ERR(bp);
+
+	*ctrl = bp ? encode_ctrl_reg(counter_arch_bp(bp)->ctrl) : 0;
+	return 0;
+}
+
+static int ptrace_hbp_get_addr(unsigned int note_type,
+			       struct task_struct *tsk,
+			       unsigned long idx,
+			       u64 *addr)
+{
+	struct perf_event *bp = ptrace_hbp_get_event(note_type, tsk, idx);
+
+	if (IS_ERR(bp))
+		return PTR_ERR(bp);
+
+	*addr = bp ? bp->attr.bp_addr : 0;
+	return 0;
+}
+
+static struct perf_event *ptrace_hbp_get_initialised_bp(unsigned int note_type,
+							struct task_struct *tsk,
+							unsigned long idx)
+{
+	struct perf_event *bp = ptrace_hbp_get_event(note_type, tsk, idx);
+
+	if (!bp)
+		bp = ptrace_hbp_create(note_type, tsk, idx);
+
+	return bp;
+}
+
+static int ptrace_hbp_set_ctrl(unsigned int note_type,
+			       struct task_struct *tsk,
+			       unsigned long idx,
+			       u32 uctrl)
+{
+	int err;
+	struct perf_event *bp;
+	struct perf_event_attr attr;
+	struct arch_hw_breakpoint_ctrl ctrl;
+
+	bp = ptrace_hbp_get_initialised_bp(note_type, tsk, idx);
+	if (IS_ERR(bp)) {
+		err = PTR_ERR(bp);
+		return err;
+	}
+
+	attr = bp->attr;
+	decode_ctrl_reg(uctrl, &ctrl);
+	err = ptrace_hbp_fill_attr_ctrl(note_type, ctrl, &attr);
+	if (err)
+		return err;
+
+	return modify_user_hw_breakpoint(bp, &attr);
+}
+
+static int ptrace_hbp_set_addr(unsigned int note_type,
+			       struct task_struct *tsk,
+			       unsigned long idx,
+			       u64 addr)
+{
+	int err;
+	struct perf_event *bp;
+	struct perf_event_attr attr;
+
+	bp = ptrace_hbp_get_initialised_bp(note_type, tsk, idx);
+	if (IS_ERR(bp)) {
+		err = PTR_ERR(bp);
+		return err;
+	}
+
+	attr = bp->attr;
+	attr.bp_addr = addr;
+	err = modify_user_hw_breakpoint(bp, &attr);
+	return err;
+}
+
+#define PTRACE_HBP_ADDR_SZ	sizeof(u64)
+#define PTRACE_HBP_CTRL_SZ	sizeof(u32)
+#define PTRACE_HBP_REG_OFF	sizeof(u32)
+
+static int hw_break_get(struct task_struct *target,
+			const struct user_regset *regset,
+			unsigned int pos, unsigned int count,
+			void *kbuf, void __user *ubuf)
+{
+	unsigned int note_type = regset->core_note_type;
+	int ret, idx = 0, offset = PTRACE_HBP_REG_OFF, limit;
+	u32 info, ctrl;
+	u64 addr;
+
+	/* Resource info */
+	ret = ptrace_hbp_get_resource_info(note_type, &info);
+	if (ret)
+		return ret;
+
+	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &info, 0, 4);
+	if (ret)
+		return ret;
+
+	/* (address, ctrl) registers */
+	limit = regset->n * regset->size;
+	while (count && offset < limit) {
+		ret = ptrace_hbp_get_addr(note_type, target, idx, &addr);
+		if (ret)
+			return ret;
+		ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &addr,
+					  offset, offset + PTRACE_HBP_ADDR_SZ);
+		if (ret)
+			return ret;
+		offset += PTRACE_HBP_ADDR_SZ;
+
+		ret = ptrace_hbp_get_ctrl(note_type, target, idx, &ctrl);
+		if (ret)
+			return ret;
+		ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, &ctrl,
+					  offset, offset + PTRACE_HBP_CTRL_SZ);
+		if (ret)
+			return ret;
+		offset += PTRACE_HBP_CTRL_SZ;
+		idx++;
+	}
+
+	return 0;
+}
+
+static int hw_break_set(struct task_struct *target,
+			const struct user_regset *regset,
+			unsigned int pos, unsigned int count,
+			const void *kbuf, const void __user *ubuf)
+{
+	unsigned int note_type = regset->core_note_type;
+	int ret, idx = 0, offset = PTRACE_HBP_REG_OFF, limit;
+	u32 ctrl;
+	u64 addr;
+
+	/* Resource info */
+	ret = user_regset_copyin_ignore(&pos, &count, &kbuf, &ubuf, 0, 4);
+	if (ret)
+		return ret;
+
+	/* (address, ctrl) registers */
+	limit = regset->n * regset->size;
+	while (count && offset < limit) {
+		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &addr,
+					 offset, offset + PTRACE_HBP_ADDR_SZ);
+		if (ret)
+			return ret;
+		ret = ptrace_hbp_set_addr(note_type, target, idx, addr);
+		if (ret)
+			return ret;
+		offset += PTRACE_HBP_ADDR_SZ;
+
+		ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &ctrl,
+					 offset, offset + PTRACE_HBP_CTRL_SZ);
+		if (ret)
+			return ret;
+		ret = ptrace_hbp_set_ctrl(note_type, target, idx, ctrl);
+		if (ret)
+			return ret;
+		offset += PTRACE_HBP_CTRL_SZ;
+		idx++;
+	}
+
+	return 0;
+}
+#endif	/* CONFIG_HAVE_HW_BREAKPOINT */
+
+static int gpr_get(struct task_struct *target,
+		   const struct user_regset *regset,
+		   unsigned int pos, unsigned int count,
+		   void *kbuf, void __user *ubuf)
+{
+	struct user_pt_regs *uregs = &task_pt_regs(target)->user_regs;
+	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, uregs, 0, -1);
+}
+
+static int gpr_set(struct task_struct *target, const struct user_regset *regset,
+		   unsigned int pos, unsigned int count,
+		   const void *kbuf, const void __user *ubuf)
+{
+	int ret;
+	struct user_pt_regs newregs;
+
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &newregs, 0, -1);
+	if (ret)
+		return ret;
+
+	if (!valid_user_regs(&newregs))
+		return -EINVAL;
+
+	task_pt_regs(target)->user_regs = newregs;
+	return 0;
+}
+
+/*
+ * TODO: update fp accessors for lazy context switching (sync/flush hwstate)
+ */
+static int fpr_get(struct task_struct *target, const struct user_regset *regset,
+		   unsigned int pos, unsigned int count,
+		   void *kbuf, void __user *ubuf)
+{
+	struct user_fpsimd_state *uregs;
+	uregs = &target->thread.fpsimd_state.user_fpsimd;
+	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, uregs, 0, -1);
+}
+
+static int fpr_set(struct task_struct *target, const struct user_regset *regset,
+		   unsigned int pos, unsigned int count,
+		   const void *kbuf, const void __user *ubuf)
+{
+	int ret;
+	struct user_fpsimd_state newstate;
+
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &newstate, 0, -1);
+	if (ret)
+		return ret;
+
+	target->thread.fpsimd_state.user_fpsimd = newstate;
+	return ret;
+}
+
+static int tls_get(struct task_struct *target, const struct user_regset *regset,
+		   unsigned int pos, unsigned int count,
+		   void *kbuf, void __user *ubuf)
+{
+	unsigned long *tls = &target->thread.tp_value;
+	return user_regset_copyout(&pos, &count, &kbuf, &ubuf, tls, 0, -1);
+}
+
+static int tls_set(struct task_struct *target, const struct user_regset *regset,
+		   unsigned int pos, unsigned int count,
+		   const void *kbuf, const void __user *ubuf)
+{
+	int ret;
+	unsigned long tls;
+
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &tls, 0, -1);
+	if (ret)
+		return ret;
+
+	target->thread.tp_value = tls;
+	return ret;
+}
+
+enum aarch64_regset {
+	REGSET_GPR,
+	REGSET_FPR,
+	REGSET_TLS,
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+	REGSET_HW_BREAK,
+	REGSET_HW_WATCH,
+#endif
+};
+
+static const struct user_regset aarch64_regsets[] = {
+	[REGSET_GPR] = {
+		.core_note_type = NT_PRSTATUS,
+		.n = sizeof(struct user_pt_regs) / sizeof(u64),
+		.size = sizeof(u64),
+		.align = sizeof(u64),
+		.get = gpr_get,
+		.set = gpr_set
+	},
+	[REGSET_FPR] = {
+		.core_note_type = NT_PRFPREG,
+		.n = sizeof(struct user_fpsimd_state) / sizeof(u32),
+		/*
+		 * We pretend we have 32-bit registers because the fpsr and
+		 * fpcr are 32-bits wide.
+		 */
+		.size = sizeof(u32),
+		.align = sizeof(u32),
+		.get = fpr_get,
+		.set = fpr_set
+	},
+	[REGSET_TLS] = {
+		.core_note_type = NT_ARM_TLS,
+		.n = 1,
+		.size = sizeof(void *),
+		.align = sizeof(void *),
+		.get = tls_get,
+		.set = tls_set,
+	},
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+	[REGSET_HW_BREAK] = {
+		.core_note_type = NT_ARM_HW_BREAK,
+		.n = sizeof(struct user_hwdebug_state) / sizeof(u32),
+		.size = sizeof(u32),
+		.align = sizeof(u32),
+		.get = hw_break_get,
+		.set = hw_break_set,
+	},
+	[REGSET_HW_WATCH] = {
+		.core_note_type = NT_ARM_HW_WATCH,
+		.n = sizeof(struct user_hwdebug_state) / sizeof(u32),
+		.size = sizeof(u32),
+		.align = sizeof(u32),
+		.get = hw_break_get,
+		.set = hw_break_set,
+	},
+#endif
+};
+
+static const struct user_regset_view user_aarch64_view = {
+	.name = "aarch64", .e_machine = EM_AARCH64,
+	.regsets = aarch64_regsets, .n = ARRAY_SIZE(aarch64_regsets)
+};
+
+#ifdef CONFIG_COMPAT
+#include <linux/compat.h>
+
+enum compat_regset {
+	REGSET_COMPAT_GPR,
+	REGSET_COMPAT_VFP,
+};
+
+static int compat_gpr_get(struct task_struct *target,
+			  const struct user_regset *regset,
+			  unsigned int pos, unsigned int count,
+			  void *kbuf, void __user *ubuf)
+{
+	int ret = 0;
+	unsigned int i, start, num_regs;
+
+	/* Calculate the number of AArch32 registers contained in count */
+	num_regs = count / regset->size;
+
+	/* Convert pos into an register number */
+	start = pos / regset->size;
+
+	if (start + num_regs > regset->n)
+		return -EIO;
+
+	for (i = 0; i < num_regs; ++i) {
+		unsigned int idx = start + i;
+		void *reg;
+
+		switch (idx) {
+		case 15:
+			reg = (void *)&task_pt_regs(target)->pc;
+			break;
+		case 16:
+			reg = (void *)&task_pt_regs(target)->pstate;
+			break;
+		case 17:
+			reg = (void *)&task_pt_regs(target)->orig_x0;
+			break;
+		default:
+			reg = (void *)&task_pt_regs(target)->regs[idx];
+		}
+
+		ret = copy_to_user(ubuf, reg, sizeof(compat_ulong_t));
+
+		if (ret)
+			break;
+		else
+			ubuf += sizeof(compat_ulong_t);
+	}
+
+	return ret;
+}
+
+static int compat_gpr_set(struct task_struct *target,
+			  const struct user_regset *regset,
+			  unsigned int pos, unsigned int count,
+			  const void *kbuf, const void __user *ubuf)
+{
+	struct pt_regs newregs;
+	int ret = 0;
+	unsigned int i, start, num_regs;
+
+	/* Calculate the number of AArch32 registers contained in count */
+	num_regs = count / regset->size;
+
+	/* Convert pos into an register number */
+	start = pos / regset->size;
+
+	if (start + num_regs > regset->n)
+		return -EIO;
+
+	newregs = *task_pt_regs(target);
+
+	for (i = 0; i < num_regs; ++i) {
+		unsigned int idx = start + i;
+		void *reg;
+
+		switch (idx) {
+		case 15:
+			reg = (void *)&newregs.pc;
+			break;
+		case 16:
+			reg = (void *)&newregs.pstate;
+			break;
+		case 17:
+			reg = (void *)&newregs.orig_x0;
+			break;
+		default:
+			reg = (void *)&newregs.regs[idx];
+		}
+
+		ret = copy_from_user(reg, ubuf, sizeof(compat_ulong_t));
+
+		if (ret)
+			goto out;
+		else
+			ubuf += sizeof(compat_ulong_t);
+	}
+
+	if (valid_user_regs(&newregs.user_regs))
+		*task_pt_regs(target) = newregs;
+	else
+		ret = -EINVAL;
+
+out:
+	return ret;
+}
+
+static int compat_vfp_get(struct task_struct *target,
+			  const struct user_regset *regset,
+			  unsigned int pos, unsigned int count,
+			  void *kbuf, void __user *ubuf)
+{
+	struct user_fpsimd_state *uregs;
+	compat_ulong_t fpscr;
+	int ret;
+
+	uregs = &target->thread.fpsimd_state.user_fpsimd;
+
+	/*
+	 * The VFP registers are packed into the fpsimd_state, so they all sit
+	 * nicely together for us. We just need to create the fpscr separately.
+	 */
+	ret = user_regset_copyout(&pos, &count, &kbuf, &ubuf, uregs, 0,
+				  VFP_STATE_SIZE - sizeof(compat_ulong_t));
+
+	if (count && !ret) {
+		fpscr = (uregs->fpsr & VFP_FPSCR_STAT_MASK) |
+			(uregs->fpcr & VFP_FPSCR_CTRL_MASK);
+		ret = put_user(fpscr, (compat_ulong_t *)ubuf);
+	}
+
+	return ret;
+}
+
+static int compat_vfp_set(struct task_struct *target,
+			  const struct user_regset *regset,
+			  unsigned int pos, unsigned int count,
+			  const void *kbuf, const void __user *ubuf)
+{
+	struct user_fpsimd_state *uregs;
+	compat_ulong_t fpscr;
+	int ret;
+
+	if (pos + count > VFP_STATE_SIZE)
+		return -EIO;
+
+	uregs = &target->thread.fpsimd_state.user_fpsimd;
+
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, uregs, 0,
+				 VFP_STATE_SIZE - sizeof(compat_ulong_t));
+
+	if (count && !ret) {
+		ret = get_user(fpscr, (compat_ulong_t *)ubuf);
+		uregs->fpsr = fpscr & VFP_FPSCR_STAT_MASK;
+		uregs->fpcr = fpscr & VFP_FPSCR_CTRL_MASK;
+	}
+
+	return ret;
+}
+
+static const struct user_regset aarch32_regsets[] = {
+	[REGSET_COMPAT_GPR] = {
+		.core_note_type = NT_PRSTATUS,
+		.n = COMPAT_ELF_NGREG,
+		.size = sizeof(compat_elf_greg_t),
+		.align = sizeof(compat_elf_greg_t),
+		.get = compat_gpr_get,
+		.set = compat_gpr_set
+	},
+	[REGSET_COMPAT_VFP] = {
+		.core_note_type = NT_ARM_VFP,
+		.n = VFP_STATE_SIZE / sizeof(compat_ulong_t),
+		.size = sizeof(compat_ulong_t),
+		.align = sizeof(compat_ulong_t),
+		.get = compat_vfp_get,
+		.set = compat_vfp_set
+	},
+};
+
+static const struct user_regset_view user_aarch32_view = {
+	.name = "aarch32", .e_machine = EM_ARM,
+	.regsets = aarch32_regsets, .n = ARRAY_SIZE(aarch32_regsets)
+};
+
+int aarch32_break_trap(struct pt_regs *regs)
+{
+	unsigned int instr;
+	bool bp = false;
+	void __user *pc = (void __user *)instruction_pointer(regs);
+
+	if (compat_thumb_mode(regs)) {
+		/* get 16-bit Thumb instruction */
+		get_user(instr, (u16 __user *)pc);
+		if (instr == AARCH32_BREAK_THUMB2_LO) {
+			/* get second half of 32-bit Thumb-2 instruction */
+			get_user(instr, (u16 __user *)(pc + 2));
+			bp = instr == AARCH32_BREAK_THUMB2_HI;
+		} else {
+			bp = instr == AARCH32_BREAK_THUMB;
+		}
+	} else {
+		/* 32-bit ARM instruction */
+		get_user(instr, (u32 __user *)pc);
+		bp = (instr & ~0xf0000000) == AARCH32_BREAK_ARM;
+	}
+
+	if (bp)
+		return ptrace_break(regs);
+	return 1;
+}
+
+static int compat_ptrace_read_user(struct task_struct *tsk, compat_ulong_t off,
+				   compat_ulong_t __user *ret)
+{
+	compat_ulong_t tmp;
+
+	if (off & 3)
+		return -EIO;
+
+	if (off == PT_TEXT_ADDR)
+		tmp = tsk->mm->start_code;
+	else if (off == PT_DATA_ADDR)
+		tmp = tsk->mm->start_data;
+	else if (off == PT_TEXT_END_ADDR)
+		tmp = tsk->mm->end_code;
+	else if (off < sizeof(compat_elf_gregset_t))
+		return copy_regset_to_user(tsk, &user_aarch32_view,
+					   REGSET_COMPAT_GPR, off,
+					   sizeof(compat_ulong_t), ret);
+	else if (off >= COMPAT_USER_SZ)
+		return -EIO;
+	else
+		tmp = 0;
+
+	return put_user(tmp, ret);
+}
+
+static int compat_ptrace_write_user(struct task_struct *tsk, compat_ulong_t off,
+				    compat_ulong_t val)
+{
+	int ret;
+
+	if (off & 3 || off >= COMPAT_USER_SZ)
+		return -EIO;
+
+	if (off >= sizeof(compat_elf_gregset_t))
+		return 0;
+
+	ret = copy_regset_from_user(tsk, &user_aarch32_view,
+				    REGSET_COMPAT_GPR, off,
+				    sizeof(compat_ulong_t),
+				    &val);
+	return ret;
+}
+
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+
+/*
+ * Convert a virtual register number into an index for a thread_info
+ * breakpoint array. Breakpoints are identified using positive numbers
+ * whilst watchpoints are negative. The registers are laid out as pairs
+ * of (address, control), each pair mapping to a unique hw_breakpoint struct.
+ * Register 0 is reserved for describing resource information.
+ */
+static int compat_ptrace_hbp_num_to_idx(compat_long_t num)
+{
+	return (abs(num) - 1) >> 1;
+}
+
+static int compat_ptrace_hbp_get_resource_info(u32 *kdata)
+{
+	u8 num_brps, num_wrps, debug_arch, wp_len;
+	u32 reg = 0;
+
+	num_brps	= hw_breakpoint_slots(TYPE_INST);
+	num_wrps	= hw_breakpoint_slots(TYPE_DATA);
+
+	debug_arch	= debug_monitors_arch();
+	wp_len		= 8;
+	reg		|= debug_arch;
+	reg		<<= 8;
+	reg		|= wp_len;
+	reg		<<= 8;
+	reg		|= num_wrps;
+	reg		<<= 8;
+	reg		|= num_brps;
+
+	*kdata = reg;
+	return 0;
+}
+
+static int compat_ptrace_hbp_get(unsigned int note_type,
+				 struct task_struct *tsk,
+				 compat_long_t num,
+				 u32 *kdata)
+{
+	u64 addr = 0;
+	u32 ctrl = 0;
+
+	int err, idx = compat_ptrace_hbp_num_to_idx(num);;
+
+	if (num & 1) {
+		err = ptrace_hbp_get_addr(note_type, tsk, idx, &addr);
+		*kdata = (u32)addr;
+	} else {
+		err = ptrace_hbp_get_ctrl(note_type, tsk, idx, &ctrl);
+		*kdata = ctrl;
+	}
+
+	return err;
+}
+
+static int compat_ptrace_hbp_set(unsigned int note_type,
+				 struct task_struct *tsk,
+				 compat_long_t num,
+				 u32 *kdata)
+{
+	u64 addr;
+	u32 ctrl;
+
+	int err, idx = compat_ptrace_hbp_num_to_idx(num);
+
+	if (num & 1) {
+		addr = *kdata;
+		err = ptrace_hbp_set_addr(note_type, tsk, idx, addr);
+	} else {
+		ctrl = *kdata;
+		err = ptrace_hbp_set_ctrl(note_type, tsk, idx, ctrl);
+	}
+
+	return err;
+}
+
+static int compat_ptrace_gethbpregs(struct task_struct *tsk, compat_long_t num,
+				    compat_ulong_t __user *data)
+{
+	int ret;
+	u32 kdata;
+	mm_segment_t old_fs = get_fs();
+
+	set_fs(KERNEL_DS);
+	/* Watchpoint */
+	if (num < 0) {
+		ret = compat_ptrace_hbp_get(NT_ARM_HW_WATCH, tsk, num, &kdata);
+	/* Resource info */
+	} else if (num == 0) {
+		ret = compat_ptrace_hbp_get_resource_info(&kdata);
+	/* Breakpoint */
+	} else {
+		ret = compat_ptrace_hbp_get(NT_ARM_HW_BREAK, tsk, num, &kdata);
+	}
+	set_fs(old_fs);
+
+	if (!ret)
+		ret = put_user(kdata, data);
+
+	return ret;
+}
+
+static int compat_ptrace_sethbpregs(struct task_struct *tsk, compat_long_t num,
+				    compat_ulong_t __user *data)
+{
+	int ret;
+	u32 kdata = 0;
+	mm_segment_t old_fs = get_fs();
+
+	if (num == 0)
+		return 0;
+
+	ret = get_user(kdata, data);
+	if (ret)
+		return ret;
+
+	set_fs(KERNEL_DS);
+	if (num < 0)
+		ret = compat_ptrace_hbp_set(NT_ARM_HW_WATCH, tsk, num, &kdata);
+	else
+		ret = compat_ptrace_hbp_set(NT_ARM_HW_BREAK, tsk, num, &kdata);
+	set_fs(old_fs);
+
+	return ret;
+}
+#endif	/* CONFIG_HAVE_HW_BREAKPOINT */
+
+long compat_arch_ptrace(struct task_struct *child, compat_long_t request,
+			compat_ulong_t caddr, compat_ulong_t cdata)
+{
+	unsigned long addr = caddr;
+	unsigned long data = cdata;
+	void __user *datap = compat_ptr(data);
+	int ret;
+
+	switch (request) {
+		case PTRACE_PEEKUSR:
+			ret = compat_ptrace_read_user(child, addr, datap);
+			break;
+
+		case PTRACE_POKEUSR:
+			ret = compat_ptrace_write_user(child, addr, data);
+			break;
+
+		case PTRACE_GETREGS:
+			ret = copy_regset_to_user(child,
+						  &user_aarch32_view,
+						  REGSET_COMPAT_GPR,
+						  0, sizeof(compat_elf_gregset_t),
+						  datap);
+			break;
+
+		case PTRACE_SETREGS:
+			ret = copy_regset_from_user(child,
+						    &user_aarch32_view,
+						    REGSET_COMPAT_GPR,
+						    0, sizeof(compat_elf_gregset_t),
+						    datap);
+			break;
+
+		case PTRACE_GET_THREAD_AREA:
+			ret = put_user((compat_ulong_t)child->thread.tp_value,
+				       (compat_ulong_t __user *)datap);
+			break;
+
+		case PTRACE_SET_SYSCALL:
+			task_pt_regs(child)->syscallno = data;
+			ret = 0;
+			break;
+
+		case COMPAT_PTRACE_GETVFPREGS:
+			ret = copy_regset_to_user(child,
+						  &user_aarch32_view,
+						  REGSET_COMPAT_VFP,
+						  0, VFP_STATE_SIZE,
+						  datap);
+			break;
+
+		case COMPAT_PTRACE_SETVFPREGS:
+			ret = copy_regset_from_user(child,
+						    &user_aarch32_view,
+						    REGSET_COMPAT_VFP,
+						    0, VFP_STATE_SIZE,
+						    datap);
+			break;
+
+#ifdef CONFIG_HAVE_HW_BREAKPOINT
+		case PTRACE_GETHBPREGS:
+			ret = compat_ptrace_gethbpregs(child, addr, datap);
+			break;
+
+		case PTRACE_SETHBPREGS:
+			ret = compat_ptrace_sethbpregs(child, addr, datap);
+			break;
+#endif
+
+		default:
+			ret = compat_ptrace_request(child, request, addr,
+						    data);
+			break;
+	}
+
+	return ret;
+}
+#endif /* CONFIG_COMPAT */
+
+const struct user_regset_view *task_user_regset_view(struct task_struct *task)
+{
+#ifdef CONFIG_COMPAT
+	if (is_compat_thread(task_thread_info(task)))
+		return &user_aarch32_view;
+#endif
+	return &user_aarch64_view;
+}
+
+long arch_ptrace(struct task_struct *child, long request,
+		 unsigned long addr, unsigned long data)
+{
+	return ptrace_request(child, request, addr, data);
+}
+
+
+static int __init ptrace_break_init(void)
+{
+	hook_debug_fault_code(DBG_ESR_EVT_BRK, arm64_break_trap, SIGTRAP,
+			      TRAP_BRKPT, "ptrace BRK handler");
+	return 0;
+}
+core_initcall(ptrace_break_init);
+
+
+asmlinkage int syscall_trace(int dir, struct pt_regs *regs)
+{
+	unsigned long saved_reg;
+
+	if (!test_thread_flag(TIF_SYSCALL_TRACE))
+		return regs->syscallno;
+
+	if (is_compat_task()) {
+		/* AArch32 uses ip (r12) for scratch */
+		saved_reg = regs->regs[12];
+		regs->regs[12] = dir;
+	} else {
+		/*
+		 * Save X7. X7 is used to denote syscall entry/exit:
+		 *   X7 = 0 -> entry, = 1 -> exit
+		 */
+		saved_reg = regs->regs[7];
+		regs->regs[7] = dir;
+	}
+
+	if (dir)
+		tracehook_report_syscall_exit(regs, 0);
+	else if (tracehook_report_syscall_entry(regs))
+		regs->syscallno = ~0UL;
+
+	if (is_compat_task())
+		regs->regs[12] = saved_reg;
+	else
+		regs->regs[7] = saved_reg;
+
+	return regs->syscallno;
+}