s390: move sys_call_table and last_break from thread_info to thread_struct

[mirror_ubuntu-zesty-kernel.git] / arch / s390 / kernel / ptrace.c

/*
 *  Ptrace user space interface.
 *
 *    Copyright IBM Corp. 1999, 2010
 *    Author(s): Denis Joseph Barrow
 *               Martin Schwidefsky (schwidefsky@de.ibm.com)
 */

#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/errno.h>
#include <linux/ptrace.h>
#include <linux/user.h>
#include <linux/security.h>
#include <linux/audit.h>
#include <linux/signal.h>
#include <linux/elf.h>
#include <linux/regset.h>
#include <linux/tracehook.h>
#include <linux/seccomp.h>
#include <linux/compat.h>
#include <trace/syscall.h>
#include <asm/segment.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/pgalloc.h>
#include <asm/uaccess.h>
#include <asm/unistd.h>
#include <asm/switch_to.h>
#include "entry.h"

#ifdef CONFIG_COMPAT
#include "compat_ptrace.h"
#endif

#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>

void update_cr_regs(struct task_struct *task)
{
        struct pt_regs *regs = task_pt_regs(task);
        struct thread_struct *thread = &task->thread;
        struct per_regs old, new;

        /* Take care of the enable/disable of transactional execution. */
        if (MACHINE_HAS_TE) {
                unsigned long cr, cr_new;

                __ctl_store(cr, 0, 0);
                /* Set or clear transaction execution TXC bit 8. */
                cr_new = cr | (1UL << 55);
                if (task->thread.per_flags & PER_FLAG_NO_TE)
                        cr_new &= ~(1UL << 55);
                if (cr_new != cr)
                        __ctl_load(cr_new, 0, 0);
                /* Set or clear transaction execution TDC bits 62 and 63. */
                __ctl_store(cr, 2, 2);
                cr_new = cr & ~3UL;
                if (task->thread.per_flags & PER_FLAG_TE_ABORT_RAND) {
                        if (task->thread.per_flags & PER_FLAG_TE_ABORT_RAND_TEND)
                                cr_new |= 1UL;
                        else
                                cr_new |= 2UL;
                }
                if (cr_new != cr)
                        __ctl_load(cr_new, 2, 2);
        }
        /* Copy user specified PER registers */
        new.control = thread->per_user.control;
        new.start = thread->per_user.start;
        new.end = thread->per_user.end;

        /* merge TIF_SINGLE_STEP into user specified PER registers. */
        if (test_tsk_thread_flag(task, TIF_SINGLE_STEP) ||
            test_tsk_thread_flag(task, TIF_UPROBE_SINGLESTEP)) {
                if (test_tsk_thread_flag(task, TIF_BLOCK_STEP))
                        new.control |= PER_EVENT_BRANCH;
                else
                        new.control |= PER_EVENT_IFETCH;
                new.control |= PER_CONTROL_SUSPENSION;
                new.control |= PER_EVENT_TRANSACTION_END;
                if (test_tsk_thread_flag(task, TIF_UPROBE_SINGLESTEP))
                        new.control |= PER_EVENT_IFETCH;
                new.start = 0;
                new.end = -1UL;
        }

        /* Take care of the PER enablement bit in the PSW. */
        if (!(new.control & PER_EVENT_MASK)) {
                regs->psw.mask &= ~PSW_MASK_PER;
                return;
        }
        regs->psw.mask |= PSW_MASK_PER;
        __ctl_store(old, 9, 11);
        if (memcmp(&new, &old, sizeof(struct per_regs)) != 0)
                __ctl_load(new, 9, 11);
}

void user_enable_single_step(struct task_struct *task)
{
        clear_tsk_thread_flag(task, TIF_BLOCK_STEP);
        set_tsk_thread_flag(task, TIF_SINGLE_STEP);
}

void user_disable_single_step(struct task_struct *task)
{
        clear_tsk_thread_flag(task, TIF_BLOCK_STEP);
        clear_tsk_thread_flag(task, TIF_SINGLE_STEP);
}

void user_enable_block_step(struct task_struct *task)
{
        set_tsk_thread_flag(task, TIF_SINGLE_STEP);
        set_tsk_thread_flag(task, TIF_BLOCK_STEP);
}

/*
 * Called by kernel/ptrace.c when detaching..
 *
 * Clear all debugging related fields.
 */
void ptrace_disable(struct task_struct *task)
{
        memset(&task->thread.per_user, 0, sizeof(task->thread.per_user));
        memset(&task->thread.per_event, 0, sizeof(task->thread.per_event));
        clear_tsk_thread_flag(task, TIF_SINGLE_STEP);
        clear_pt_regs_flag(task_pt_regs(task), PIF_PER_TRAP);
        task->thread.per_flags = 0;
}

#define __ADDR_MASK 7

static inline unsigned long __peek_user_per(struct task_struct *child,
                                            addr_t addr)
{
        struct per_struct_kernel *dummy = NULL;

        if (addr == (addr_t) &dummy->cr9)
                /* Control bits of the active per set. */
                return test_thread_flag(TIF_SINGLE_STEP) ?
                        PER_EVENT_IFETCH : child->thread.per_user.control;
        else if (addr == (addr_t) &dummy->cr10)
                /* Start address of the active per set. */
                return test_thread_flag(TIF_SINGLE_STEP) ?
                        0 : child->thread.per_user.start;
        else if (addr == (addr_t) &dummy->cr11)
                /* End address of the active per set. */
                return test_thread_flag(TIF_SINGLE_STEP) ?
                        -1UL : child->thread.per_user.end;
        else if (addr == (addr_t) &dummy->bits)
                /* Single-step bit. */
                return test_thread_flag(TIF_SINGLE_STEP) ?
                        (1UL << (BITS_PER_LONG - 1)) : 0;
        else if (addr == (addr_t) &dummy->starting_addr)
                /* Start address of the user specified per set. */
                return child->thread.per_user.start;
        else if (addr == (addr_t) &dummy->ending_addr)
                /* End address of the user specified per set. */
                return child->thread.per_user.end;
        else if (addr == (addr_t) &dummy->perc_atmid)
                /* PER code, ATMID and AI of the last PER trap */
                return (unsigned long)
                        child->thread.per_event.cause << (BITS_PER_LONG - 16);
        else if (addr == (addr_t) &dummy->address)
                /* Address of the last PER trap */
                return child->thread.per_event.address;
        else if (addr == (addr_t) &dummy->access_id)
                /* Access id of the last PER trap */
                return (unsigned long)
                        child->thread.per_event.paid << (BITS_PER_LONG - 8);
        return 0;
}

/*
 * Read the word at offset addr from the user area of a process. The
 * trouble here is that the information is littered over different
 * locations. The process registers are found on the kernel stack,
 * the floating point stuff and the trace settings are stored in
 * the task structure. In addition the different structures in
 * struct user contain pad bytes that should be read as zeroes.
 * Lovely...
 */
static unsigned long __peek_user(struct task_struct *child, addr_t addr)
{
        struct user *dummy = NULL;
        addr_t offset, tmp;

        if (addr < (addr_t) &dummy->regs.acrs) {
                /*
                 * psw and gprs are stored on the stack
                 */
                tmp = *(addr_t *)((addr_t) &task_pt_regs(child)->psw + addr);
                if (addr == (addr_t) &dummy->regs.psw.mask) {
                        /* Return a clean psw mask. */
                        tmp &= PSW_MASK_USER | PSW_MASK_RI;
                        tmp |= PSW_USER_BITS;
                }

        } else if (addr < (addr_t) &dummy->regs.orig_gpr2) {
                /*
                 * access registers are stored in the thread structure
                 */
                offset = addr - (addr_t) &dummy->regs.acrs;
                /*
                 * Very special case: old & broken 64 bit gdb reading
                 * from acrs[15]. Result is a 64 bit value. Read the
                 * 32 bit acrs[15] value and shift it by 32. Sick...
                 */
                if (addr == (addr_t) &dummy->regs.acrs[15])
                        tmp = ((unsigned long) child->thread.acrs[15]) << 32;
                else
                        tmp = *(addr_t *)((addr_t) &child->thread.acrs + offset);

        } else if (addr == (addr_t) &dummy->regs.orig_gpr2) {
                /*
                 * orig_gpr2 is stored on the kernel stack
                 */
                tmp = (addr_t) task_pt_regs(child)->orig_gpr2;

        } else if (addr < (addr_t) &dummy->regs.fp_regs) {
                /*
                 * prevent reads of padding hole between
                 * orig_gpr2 and fp_regs on s390.
                 */
                tmp = 0;

        } else if (addr == (addr_t) &dummy->regs.fp_regs.fpc) {
                /*
                 * floating point control reg. is in the thread structure
                 */
                tmp = child->thread.fpu.fpc;
                tmp <<= BITS_PER_LONG - 32;

        } else if (addr < (addr_t) (&dummy->regs.fp_regs + 1)) {
                /*
                 * floating point regs. are either in child->thread.fpu
                 * or the child->thread.fpu.vxrs array
                 */
                offset = addr - (addr_t) &dummy->regs.fp_regs.fprs;
                if (MACHINE_HAS_VX)
                        tmp = *(addr_t *)
                               ((addr_t) child->thread.fpu.vxrs + 2*offset);
                else
                        tmp = *(addr_t *)
                               ((addr_t) child->thread.fpu.fprs + offset);

        } else if (addr < (addr_t) (&dummy->regs.per_info + 1)) {
                /*
                 * Handle access to the per_info structure.
                 */
                addr -= (addr_t) &dummy->regs.per_info;
                tmp = __peek_user_per(child, addr);

        } else
                tmp = 0;

        return tmp;
}

static int
peek_user(struct task_struct *child, addr_t addr, addr_t data)
{
        addr_t tmp, mask;

        /*
         * Stupid gdb peeks/pokes the access registers in 64 bit with
         * an alignment of 4. Programmers from hell...
         */
        mask = __ADDR_MASK;
        if (addr >= (addr_t) &((struct user *) NULL)->regs.acrs &&
            addr < (addr_t) &((struct user *) NULL)->regs.orig_gpr2)
                mask = 3;
        if ((addr & mask) || addr > sizeof(struct user) - __ADDR_MASK)
                return -EIO;

        tmp = __peek_user(child, addr);
        return put_user(tmp, (addr_t __user *) data);
}

static inline void __poke_user_per(struct task_struct *child,
                                   addr_t addr, addr_t data)
{
        struct per_struct_kernel *dummy = NULL;

        /*
         * There are only three fields in the per_info struct that the
         * debugger user can write to.
         * 1) cr9: the debugger wants to set a new PER event mask
         * 2) starting_addr: the debugger wants to set a new starting
         *    address to use with the PER event mask.
         * 3) ending_addr: the debugger wants to set a new ending
         *    address to use with the PER event mask.
         * The user specified PER event mask and the start and end
         * addresses are used only if single stepping is not in effect.
         * Writes to any other field in per_info are ignored.
         */
        if (addr == (addr_t) &dummy->cr9)
                /* PER event mask of the user specified per set. */
                child->thread.per_user.control =
                        data & (PER_EVENT_MASK | PER_CONTROL_MASK);
        else if (addr == (addr_t) &dummy->starting_addr)
                /* Starting address of the user specified per set. */
                child->thread.per_user.start = data;
        else if (addr == (addr_t) &dummy->ending_addr)
                /* Ending address of the user specified per set. */
                child->thread.per_user.end = data;
}

/*
 * Write a word to the user area of a process at location addr. This
 * operation does have an additional problem compared to peek_user.
 * Stores to the program status word and on the floating point
 * control register needs to get checked for validity.
 */
static int __poke_user(struct task_struct *child, addr_t addr, addr_t data)
{
        struct user *dummy = NULL;
        addr_t offset;

        if (addr < (addr_t) &dummy->regs.acrs) {
                /*
                 * psw and gprs are stored on the stack
                 */
                if (addr == (addr_t) &dummy->regs.psw.mask) {
                        unsigned long mask = PSW_MASK_USER;

                        mask |= is_ri_task(child) ? PSW_MASK_RI : 0;
                        if ((data ^ PSW_USER_BITS) & ~mask)
                                /* Invalid psw mask. */
                                return -EINVAL;
                        if ((data & PSW_MASK_ASC) == PSW_ASC_HOME)
                                /* Invalid address-space-control bits */
                                return -EINVAL;
                        if ((data & PSW_MASK_EA) && !(data & PSW_MASK_BA))
                                /* Invalid addressing mode bits */
                                return -EINVAL;
                }
                *(addr_t *)((addr_t) &task_pt_regs(child)->psw + addr) = data;

        } else if (addr < (addr_t) (&dummy->regs.orig_gpr2)) {
                /*
                 * access registers are stored in the thread structure
                 */
                offset = addr - (addr_t) &dummy->regs.acrs;
                /*
                 * Very special case: old & broken 64 bit gdb writing
                 * to acrs[15] with a 64 bit value. Ignore the lower
                 * half of the value and write the upper 32 bit to
                 * acrs[15]. Sick...
                 */
                if (addr == (addr_t) &dummy->regs.acrs[15])
                        child->thread.acrs[15] = (unsigned int) (data >> 32);
                else
                        *(addr_t *)((addr_t) &child->thread.acrs + offset) = data;

        } else if (addr == (addr_t) &dummy->regs.orig_gpr2) {
                /*
                 * orig_gpr2 is stored on the kernel stack
                 */
                task_pt_regs(child)->orig_gpr2 = data;

        } else if (addr < (addr_t) &dummy->regs.fp_regs) {
                /*
                 * prevent writes of padding hole between
                 * orig_gpr2 and fp_regs on s390.
                 */
                return 0;

        } else if (addr == (addr_t) &dummy->regs.fp_regs.fpc) {
                /*
                 * floating point control reg. is in the thread structure
                 */
                if ((unsigned int) data != 0 ||
                    test_fp_ctl(data >> (BITS_PER_LONG - 32)))
                        return -EINVAL;
                child->thread.fpu.fpc = data >> (BITS_PER_LONG - 32);

        } else if (addr < (addr_t) (&dummy->regs.fp_regs + 1)) {
                /*
                 * floating point regs. are either in child->thread.fpu
                 * or the child->thread.fpu.vxrs array
                 */
                offset = addr - (addr_t) &dummy->regs.fp_regs.fprs;
                if (MACHINE_HAS_VX)
                        *(addr_t *)((addr_t)
                                child->thread.fpu.vxrs + 2*offset) = data;
                else
                        *(addr_t *)((addr_t)
                                child->thread.fpu.fprs + offset) = data;

        } else if (addr < (addr_t) (&dummy->regs.per_info + 1)) {
                /*
                 * Handle access to the per_info structure.
                 */
                addr -= (addr_t) &dummy->regs.per_info;
                __poke_user_per(child, addr, data);

        }

        return 0;
}

static int poke_user(struct task_struct *child, addr_t addr, addr_t data)
{
        addr_t mask;

        /*
         * Stupid gdb peeks/pokes the access registers in 64 bit with
         * an alignment of 4. Programmers from hell indeed...
         */
        mask = __ADDR_MASK;
        if (addr >= (addr_t) &((struct user *) NULL)->regs.acrs &&
            addr < (addr_t) &((struct user *) NULL)->regs.orig_gpr2)
                mask = 3;
        if ((addr & mask) || addr > sizeof(struct user) - __ADDR_MASK)
                return -EIO;

        return __poke_user(child, addr, data);
}

long arch_ptrace(struct task_struct *child, long request,
                 unsigned long addr, unsigned long data)
{
        ptrace_area parea; 
        int copied, ret;

        switch (request) {
        case PTRACE_PEEKUSR:
                /* read the word at location addr in the USER area. */
                return peek_user(child, addr, data);

        case PTRACE_POKEUSR:
                /* write the word at location addr in the USER area */
                return poke_user(child, addr, data);

        case PTRACE_PEEKUSR_AREA:
        case PTRACE_POKEUSR_AREA:
                if (copy_from_user(&parea, (void __force __user *) addr,
                                                        sizeof(parea)))
                        return -EFAULT;
                addr = parea.kernel_addr;
                data = parea.process_addr;
                copied = 0;
                while (copied < parea.len) {
                        if (request == PTRACE_PEEKUSR_AREA)
                                ret = peek_user(child, addr, data);
                        else {
                                addr_t utmp;
                                if (get_user(utmp,
                                             (addr_t __force __user *) data))
                                        return -EFAULT;
                                ret = poke_user(child, addr, utmp);
                        }
                        if (ret)
                                return ret;
                        addr += sizeof(unsigned long);
                        data += sizeof(unsigned long);
                        copied += sizeof(unsigned long);
                }
                return 0;
        case PTRACE_GET_LAST_BREAK:
                put_user(child->thread.last_break,
                         (unsigned long __user *) data);
                return 0;
        case PTRACE_ENABLE_TE:
                if (!MACHINE_HAS_TE)
                        return -EIO;
                child->thread.per_flags &= ~PER_FLAG_NO_TE;
                return 0;
        case PTRACE_DISABLE_TE:
                if (!MACHINE_HAS_TE)
                        return -EIO;
                child->thread.per_flags |= PER_FLAG_NO_TE;
                child->thread.per_flags &= ~PER_FLAG_TE_ABORT_RAND;
                return 0;
        case PTRACE_TE_ABORT_RAND:
                if (!MACHINE_HAS_TE || (child->thread.per_flags & PER_FLAG_NO_TE))
                        return -EIO;
                switch (data) {
                case 0UL:
                        child->thread.per_flags &= ~PER_FLAG_TE_ABORT_RAND;
                        break;
                case 1UL:
                        child->thread.per_flags |= PER_FLAG_TE_ABORT_RAND;
                        child->thread.per_flags |= PER_FLAG_TE_ABORT_RAND_TEND;
                        break;
                case 2UL:
                        child->thread.per_flags |= PER_FLAG_TE_ABORT_RAND;
                        child->thread.per_flags &= ~PER_FLAG_TE_ABORT_RAND_TEND;
                        break;
                default:
                        return -EINVAL;
                }
                return 0;
        default:
                return ptrace_request(child, request, addr, data);
        }
}

#ifdef CONFIG_COMPAT
/*
 * Now the fun part starts... a 31 bit program running in the
 * 31 bit emulation tracing another program. PTRACE_PEEKTEXT,
 * PTRACE_PEEKDATA, PTRACE_POKETEXT and PTRACE_POKEDATA are easy
 * to handle, the difference to the 64 bit versions of the requests
 * is that the access is done in multiples of 4 byte instead of
 * 8 bytes (sizeof(unsigned long) on 31/64 bit).
 * The ugly part are PTRACE_PEEKUSR, PTRACE_PEEKUSR_AREA,
 * PTRACE_POKEUSR and PTRACE_POKEUSR_AREA. If the traced program
 * is a 31 bit program too, the content of struct user can be
 * emulated. A 31 bit program peeking into the struct user of
 * a 64 bit program is a no-no.
 */

/*
 * Same as peek_user_per but for a 31 bit program.
 */
static inline __u32 __peek_user_per_compat(struct task_struct *child,
                                           addr_t addr)
{
        struct compat_per_struct_kernel *dummy32 = NULL;

        if (addr == (addr_t) &dummy32->cr9)
                /* Control bits of the active per set. */
                return (__u32) test_thread_flag(TIF_SINGLE_STEP) ?
                        PER_EVENT_IFETCH : child->thread.per_user.control;
        else if (addr == (addr_t) &dummy32->cr10)
                /* Start address of the active per set. */
                return (__u32) test_thread_flag(TIF_SINGLE_STEP) ?
                        0 : child->thread.per_user.start;
        else if (addr == (addr_t) &dummy32->cr11)
                /* End address of the active per set. */
                return test_thread_flag(TIF_SINGLE_STEP) ?
                        PSW32_ADDR_INSN : child->thread.per_user.end;
        else if (addr == (addr_t) &dummy32->bits)
                /* Single-step bit. */
                return (__u32) test_thread_flag(TIF_SINGLE_STEP) ?
                        0x80000000 : 0;
        else if (addr == (addr_t) &dummy32->starting_addr)
                /* Start address of the user specified per set. */
                return (__u32) child->thread.per_user.start;
        else if (addr == (addr_t) &dummy32->ending_addr)
                /* End address of the user specified per set. */
                return (__u32) child->thread.per_user.end;
        else if (addr == (addr_t) &dummy32->perc_atmid)
                /* PER code, ATMID and AI of the last PER trap */
                return (__u32) child->thread.per_event.cause << 16;
        else if (addr == (addr_t) &dummy32->address)
                /* Address of the last PER trap */
                return (__u32) child->thread.per_event.address;
        else if (addr == (addr_t) &dummy32->access_id)
                /* Access id of the last PER trap */
                return (__u32) child->thread.per_event.paid << 24;
        return 0;
}

/*
 * Same as peek_user but for a 31 bit program.
 */
static u32 __peek_user_compat(struct task_struct *child, addr_t addr)
{
        struct compat_user *dummy32 = NULL;
        addr_t offset;
        __u32 tmp;

        if (addr < (addr_t) &dummy32->regs.acrs) {
                struct pt_regs *regs = task_pt_regs(child);
                /*
                 * psw and gprs are stored on the stack
                 */
                if (addr == (addr_t) &dummy32->regs.psw.mask) {
                        /* Fake a 31 bit psw mask. */
                        tmp = (__u32)(regs->psw.mask >> 32);
                        tmp &= PSW32_MASK_USER | PSW32_MASK_RI;
                        tmp |= PSW32_USER_BITS;
                } else if (addr == (addr_t) &dummy32->regs.psw.addr) {
                        /* Fake a 31 bit psw address. */
                        tmp = (__u32) regs->psw.addr |
                                (__u32)(regs->psw.mask & PSW_MASK_BA);
                } else {
                        /* gpr 0-15 */
                        tmp = *(__u32 *)((addr_t) &regs->psw + addr*2 + 4);
                }
        } else if (addr < (addr_t) (&dummy32->regs.orig_gpr2)) {
                /*
                 * access registers are stored in the thread structure
                 */
                offset = addr - (addr_t) &dummy32->regs.acrs;
                tmp = *(__u32*)((addr_t) &child->thread.acrs + offset);

        } else if (addr == (addr_t) (&dummy32->regs.orig_gpr2)) {
                /*
                 * orig_gpr2 is stored on the kernel stack
                 */
                tmp = *(__u32*)((addr_t) &task_pt_regs(child)->orig_gpr2 + 4);

        } else if (addr < (addr_t) &dummy32->regs.fp_regs) {
                /*
                 * prevent reads of padding hole between
                 * orig_gpr2 and fp_regs on s390.
                 */
                tmp = 0;

        } else if (addr == (addr_t) &dummy32->regs.fp_regs.fpc) {
                /*
                 * floating point control reg. is in the thread structure
                 */
                tmp = child->thread.fpu.fpc;

        } else if (addr < (addr_t) (&dummy32->regs.fp_regs + 1)) {
                /*
                 * floating point regs. are either in child->thread.fpu
                 * or the child->thread.fpu.vxrs array
                 */
                offset = addr - (addr_t) &dummy32->regs.fp_regs.fprs;
                if (MACHINE_HAS_VX)
                        tmp = *(__u32 *)
                               ((addr_t) child->thread.fpu.vxrs + 2*offset);
                else
                        tmp = *(__u32 *)
                               ((addr_t) child->thread.fpu.fprs + offset);

        } else if (addr < (addr_t) (&dummy32->regs.per_info + 1)) {
                /*
                 * Handle access to the per_info structure.
                 */
                addr -= (addr_t) &dummy32->regs.per_info;
                tmp = __peek_user_per_compat(child, addr);

        } else
                tmp = 0;

        return tmp;
}

static int peek_user_compat(struct task_struct *child,
                            addr_t addr, addr_t data)
{
        __u32 tmp;

        if (!is_compat_task() || (addr & 3) || addr > sizeof(struct user) - 3)
                return -EIO;

        tmp = __peek_user_compat(child, addr);
        return put_user(tmp, (__u32 __user *) data);
}

/*
 * Same as poke_user_per but for a 31 bit program.
 */
static inline void __poke_user_per_compat(struct task_struct *child,
                                          addr_t addr, __u32 data)
{
        struct compat_per_struct_kernel *dummy32 = NULL;

        if (addr == (addr_t) &dummy32->cr9)
                /* PER event mask of the user specified per set. */
                child->thread.per_user.control =
                        data & (PER_EVENT_MASK | PER_CONTROL_MASK);
        else if (addr == (addr_t) &dummy32->starting_addr)
                /* Starting address of the user specified per set. */
                child->thread.per_user.start = data;
        else if (addr == (addr_t) &dummy32->ending_addr)
                /* Ending address of the user specified per set. */
                child->thread.per_user.end = data;
}

/*
 * Same as poke_user but for a 31 bit program.
 */
static int __poke_user_compat(struct task_struct *child,
                              addr_t addr, addr_t data)
{
        struct compat_user *dummy32 = NULL;
        __u32 tmp = (__u32) data;
        addr_t offset;

        if (addr < (addr_t) &dummy32->regs.acrs) {
                struct pt_regs *regs = task_pt_regs(child);
                /*
                 * psw, gprs, acrs and orig_gpr2 are stored on the stack
                 */
                if (addr == (addr_t) &dummy32->regs.psw.mask) {
                        __u32 mask = PSW32_MASK_USER;

                        mask |= is_ri_task(child) ? PSW32_MASK_RI : 0;
                        /* Build a 64 bit psw mask from 31 bit mask. */
                        if ((tmp ^ PSW32_USER_BITS) & ~mask)
                                /* Invalid psw mask. */
                                return -EINVAL;
                        if ((data & PSW32_MASK_ASC) == PSW32_ASC_HOME)
                                /* Invalid address-space-control bits */
                                return -EINVAL;
                        regs->psw.mask = (regs->psw.mask & ~PSW_MASK_USER) |
                                (regs->psw.mask & PSW_MASK_BA) |
                                (__u64)(tmp & mask) << 32;
                } else if (addr == (addr_t) &dummy32->regs.psw.addr) {
                        /* Build a 64 bit psw address from 31 bit address. */
                        regs->psw.addr = (__u64) tmp & PSW32_ADDR_INSN;
                        /* Transfer 31 bit amode bit to psw mask. */
                        regs->psw.mask = (regs->psw.mask & ~PSW_MASK_BA) |
                                (__u64)(tmp & PSW32_ADDR_AMODE);
                } else {
                        /* gpr 0-15 */
                        *(__u32*)((addr_t) &regs->psw + addr*2 + 4) = tmp;
                }
        } else if (addr < (addr_t) (&dummy32->regs.orig_gpr2)) {
                /*
                 * access registers are stored in the thread structure
                 */
                offset = addr - (addr_t) &dummy32->regs.acrs;
                *(__u32*)((addr_t) &child->thread.acrs + offset) = tmp;

        } else if (addr == (addr_t) (&dummy32->regs.orig_gpr2)) {
                /*
                 * orig_gpr2 is stored on the kernel stack
                 */
                *(__u32*)((addr_t) &task_pt_regs(child)->orig_gpr2 + 4) = tmp;

        } else if (addr < (addr_t) &dummy32->regs.fp_regs) {
                /*
                 * prevent writess of padding hole between
                 * orig_gpr2 and fp_regs on s390.
                 */
                return 0;

        } else if (addr == (addr_t) &dummy32->regs.fp_regs.fpc) {
                /*
                 * floating point control reg. is in the thread structure
                 */
                if (test_fp_ctl(tmp))
                        return -EINVAL;
                child->thread.fpu.fpc = data;

        } else if (addr < (addr_t) (&dummy32->regs.fp_regs + 1)) {
                /*
                 * floating point regs. are either in child->thread.fpu
                 * or the child->thread.fpu.vxrs array
                 */
                offset = addr - (addr_t) &dummy32->regs.fp_regs.fprs;
                if (MACHINE_HAS_VX)
                        *(__u32 *)((addr_t)
                                child->thread.fpu.vxrs + 2*offset) = tmp;
                else
                        *(__u32 *)((addr_t)
                                child->thread.fpu.fprs + offset) = tmp;

        } else if (addr < (addr_t) (&dummy32->regs.per_info + 1)) {
                /*
                 * Handle access to the per_info structure.
                 */
                addr -= (addr_t) &dummy32->regs.per_info;
                __poke_user_per_compat(child, addr, data);
        }

        return 0;
}

static int poke_user_compat(struct task_struct *child,
                            addr_t addr, addr_t data)
{
        if (!is_compat_task() || (addr & 3) ||
            addr > sizeof(struct compat_user) - 3)
                return -EIO;

        return __poke_user_compat(child, addr, data);
}

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;
        compat_ptrace_area parea;
        int copied, ret;

        switch (request) {
        case PTRACE_PEEKUSR:
                /* read the word at location addr in the USER area. */
                return peek_user_compat(child, addr, data);

        case PTRACE_POKEUSR:
                /* write the word at location addr in the USER area */
                return poke_user_compat(child, addr, data);

        case PTRACE_PEEKUSR_AREA:
        case PTRACE_POKEUSR_AREA:
                if (copy_from_user(&parea, (void __force __user *) addr,
                                                        sizeof(parea)))
                        return -EFAULT;
                addr = parea.kernel_addr;
                data = parea.process_addr;
                copied = 0;
                while (copied < parea.len) {
                        if (request == PTRACE_PEEKUSR_AREA)
                                ret = peek_user_compat(child, addr, data);
                        else {
                                __u32 utmp;
                                if (get_user(utmp,
                                             (__u32 __force __user *) data))
                                        return -EFAULT;
                                ret = poke_user_compat(child, addr, utmp);
                        }
                        if (ret)
                                return ret;
                        addr += sizeof(unsigned int);
                        data += sizeof(unsigned int);
                        copied += sizeof(unsigned int);
                }
                return 0;
        case PTRACE_GET_LAST_BREAK:
                put_user(child->thread.last_break,
                         (unsigned int __user *) data);
                return 0;
        }
        return compat_ptrace_request(child, request, addr, data);
}
#endif

asmlinkage long do_syscall_trace_enter(struct pt_regs *regs)
{
        unsigned long mask = -1UL;

        /*
         * The sysc_tracesys code in entry.S stored the system
         * call number to gprs[2].
         */
        if (test_thread_flag(TIF_SYSCALL_TRACE) &&
            (tracehook_report_syscall_entry(regs) ||
             regs->gprs[2] >= NR_syscalls)) {
                /*
                 * Tracing decided this syscall should not happen or the
                 * debugger stored an invalid system call number. Skip
                 * the system call and the system call restart handling.
                 */
                clear_pt_regs_flag(regs, PIF_SYSCALL);
                return -1;
        }

        /* Do the secure computing check after ptrace. */
        if (secure_computing(NULL)) {
                /* seccomp failures shouldn't expose any additional code. */
                return -1;
        }

        if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
                trace_sys_enter(regs, regs->gprs[2]);

        if (is_compat_task())
                mask = 0xffffffff;

        audit_syscall_entry(regs->gprs[2], regs->orig_gpr2 & mask,
                            regs->gprs[3] &mask, regs->gprs[4] &mask,
                            regs->gprs[5] &mask);

        return regs->gprs[2];
}

asmlinkage void do_syscall_trace_exit(struct pt_regs *regs)
{
        audit_syscall_exit(regs);

        if (unlikely(test_thread_flag(TIF_SYSCALL_TRACEPOINT)))
                trace_sys_exit(regs, regs->gprs[2]);

        if (test_thread_flag(TIF_SYSCALL_TRACE))
                tracehook_report_syscall_exit(regs, 0);
}

/*
 * user_regset definitions.
 */

static int s390_regs_get(struct task_struct *target,
                         const struct user_regset *regset,
                         unsigned int pos, unsigned int count,
                         void *kbuf, void __user *ubuf)
{
        if (target == current)
                save_access_regs(target->thread.acrs);

        if (kbuf) {
                unsigned long *k = kbuf;
                while (count > 0) {
                        *k++ = __peek_user(target, pos);
                        count -= sizeof(*k);
                        pos += sizeof(*k);
                }
        } else {
                unsigned long __user *u = ubuf;
                while (count > 0) {
                        if (__put_user(__peek_user(target, pos), u++))
                                return -EFAULT;
                        count -= sizeof(*u);
                        pos += sizeof(*u);
                }
        }
        return 0;
}

static int s390_regs_set(struct task_struct *target,
                         const struct user_regset *regset,
                         unsigned int pos, unsigned int count,
                         const void *kbuf, const void __user *ubuf)
{
        int rc = 0;

        if (target == current)
                save_access_regs(target->thread.acrs);

        if (kbuf) {
                const unsigned long *k = kbuf;
                while (count > 0 && !rc) {
                        rc = __poke_user(target, pos, *k++);
                        count -= sizeof(*k);
                        pos += sizeof(*k);
                }
        } else {
                const unsigned long  __user *u = ubuf;
                while (count > 0 && !rc) {
                        unsigned long word;
                        rc = __get_user(word, u++);
                        if (rc)
                                break;
                        rc = __poke_user(target, pos, word);
                        count -= sizeof(*u);
                        pos += sizeof(*u);
                }
        }

        if (rc == 0 && target == current)
                restore_access_regs(target->thread.acrs);

        return rc;
}

static int s390_fpregs_get(struct task_struct *target,
                           const struct user_regset *regset, unsigned int pos,
                           unsigned int count, void *kbuf, void __user *ubuf)
{
        _s390_fp_regs fp_regs;

        if (target == current)
                save_fpu_regs();

        fp_regs.fpc = target->thread.fpu.fpc;
        fpregs_store(&fp_regs, &target->thread.fpu);

        return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
                                   &fp_regs, 0, -1);
}

static int s390_fpregs_set(struct task_struct *target,
                           const struct user_regset *regset, unsigned int pos,
                           unsigned int count, const void *kbuf,
                           const void __user *ubuf)
{
        int rc = 0;
        freg_t fprs[__NUM_FPRS];

        if (target == current)
                save_fpu_regs();

        /* If setting FPC, must validate it first. */
        if (count > 0 && pos < offsetof(s390_fp_regs, fprs)) {
                u32 ufpc[2] = { target->thread.fpu.fpc, 0 };
                rc = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &ufpc,
                                        0, offsetof(s390_fp_regs, fprs));
                if (rc)
                        return rc;
                if (ufpc[1] != 0 || test_fp_ctl(ufpc[0]))
                        return -EINVAL;
                target->thread.fpu.fpc = ufpc[0];
        }

        if (rc == 0 && count > 0)
                rc = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
                                        fprs, offsetof(s390_fp_regs, fprs), -1);
        if (rc)
                return rc;

        if (MACHINE_HAS_VX)
                convert_fp_to_vx(target->thread.fpu.vxrs, fprs);
        else
                memcpy(target->thread.fpu.fprs, &fprs, sizeof(fprs));

        return rc;
}

static int s390_last_break_get(struct task_struct *target,
                               const struct user_regset *regset,
                               unsigned int pos, unsigned int count,
                               void *kbuf, void __user *ubuf)
{
        if (count > 0) {
                if (kbuf) {
                        unsigned long *k = kbuf;
                        *k = target->thread.last_break;
                } else {
                        unsigned long  __user *u = ubuf;
                        if (__put_user(target->thread.last_break, u))
                                return -EFAULT;
                }
        }
        return 0;
}

static int s390_last_break_set(struct task_struct *target,
                               const struct user_regset *regset,
                               unsigned int pos, unsigned int count,
                               const void *kbuf, const void __user *ubuf)
{
        return 0;
}

static int s390_tdb_get(struct task_struct *target,
                        const struct user_regset *regset,
                        unsigned int pos, unsigned int count,
                        void *kbuf, void __user *ubuf)
{
        struct pt_regs *regs = task_pt_regs(target);
        unsigned char *data;

        if (!(regs->int_code & 0x200))
                return -ENODATA;
        data = target->thread.trap_tdb;
        return user_regset_copyout(&pos, &count, &kbuf, &ubuf, data, 0, 256);
}

static int s390_tdb_set(struct task_struct *target,
                        const struct user_regset *regset,
                        unsigned int pos, unsigned int count,
                        const void *kbuf, const void __user *ubuf)
{
        return 0;
}

static int s390_vxrs_low_get(struct task_struct *target,
                             const struct user_regset *regset,
                             unsigned int pos, unsigned int count,
                             void *kbuf, void __user *ubuf)
{
        __u64 vxrs[__NUM_VXRS_LOW];
        int i;

        if (!MACHINE_HAS_VX)
                return -ENODEV;
        if (target == current)
                save_fpu_regs();
        for (i = 0; i < __NUM_VXRS_LOW; i++)
                vxrs[i] = *((__u64 *)(target->thread.fpu.vxrs + i) + 1);
        return user_regset_copyout(&pos, &count, &kbuf, &ubuf, vxrs, 0, -1);
}

static int s390_vxrs_low_set(struct task_struct *target,
                             const struct user_regset *regset,
                             unsigned int pos, unsigned int count,
                             const void *kbuf, const void __user *ubuf)
{
        __u64 vxrs[__NUM_VXRS_LOW];
        int i, rc;

        if (!MACHINE_HAS_VX)
                return -ENODEV;
        if (target == current)
                save_fpu_regs();

        rc = user_regset_copyin(&pos, &count, &kbuf, &ubuf, vxrs, 0, -1);
        if (rc == 0)
                for (i = 0; i < __NUM_VXRS_LOW; i++)
                        *((__u64 *)(target->thread.fpu.vxrs + i) + 1) = vxrs[i];

        return rc;
}

static int s390_vxrs_high_get(struct task_struct *target,
                              const struct user_regset *regset,
                              unsigned int pos, unsigned int count,
                              void *kbuf, void __user *ubuf)
{
        __vector128 vxrs[__NUM_VXRS_HIGH];

        if (!MACHINE_HAS_VX)
                return -ENODEV;
        if (target == current)
                save_fpu_regs();
        memcpy(vxrs, target->thread.fpu.vxrs + __NUM_VXRS_LOW, sizeof(vxrs));

        return user_regset_copyout(&pos, &count, &kbuf, &ubuf, vxrs, 0, -1);
}

static int s390_vxrs_high_set(struct task_struct *target,
                              const struct user_regset *regset,
                              unsigned int pos, unsigned int count,
                              const void *kbuf, const void __user *ubuf)
{
        int rc;

        if (!MACHINE_HAS_VX)
                return -ENODEV;
        if (target == current)
                save_fpu_regs();

        rc = user_regset_copyin(&pos, &count, &kbuf, &ubuf,
                                target->thread.fpu.vxrs + __NUM_VXRS_LOW, 0, -1);
        return rc;
}

static int s390_system_call_get(struct task_struct *target,
                                const struct user_regset *regset,
                                unsigned int pos, unsigned int count,
                                void *kbuf, void __user *ubuf)
{
        unsigned int *data = &target->thread.system_call;
        return user_regset_copyout(&pos, &count, &kbuf, &ubuf,
                                   data, 0, sizeof(unsigned int));
}

static int s390_system_call_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 *data = &target->thread.system_call;
        return user_regset_copyin(&pos, &count, &kbuf, &ubuf,
                                  data, 0, sizeof(unsigned int));
}

static const struct user_regset s390_regsets[] = {
        {
                .core_note_type = NT_PRSTATUS,
                .n = sizeof(s390_regs) / sizeof(long),
                .size = sizeof(long),
                .align = sizeof(long),
                .get = s390_regs_get,
                .set = s390_regs_set,
        },
        {
                .core_note_type = NT_PRFPREG,
                .n = sizeof(s390_fp_regs) / sizeof(long),
                .size = sizeof(long),
                .align = sizeof(long),
                .get = s390_fpregs_get,
                .set = s390_fpregs_set,
        },
        {
                .core_note_type = NT_S390_SYSTEM_CALL,
                .n = 1,
                .size = sizeof(unsigned int),
                .align = sizeof(unsigned int),
                .get = s390_system_call_get,
                .set = s390_system_call_set,
        },
        {
                .core_note_type = NT_S390_LAST_BREAK,
                .n = 1,
                .size = sizeof(long),
                .align = sizeof(long),
                .get = s390_last_break_get,
                .set = s390_last_break_set,
        },
        {
                .core_note_type = NT_S390_TDB,
                .n = 1,
                .size = 256,
                .align = 1,
                .get = s390_tdb_get,
                .set = s390_tdb_set,
        },
        {
                .core_note_type = NT_S390_VXRS_LOW,
                .n = __NUM_VXRS_LOW,
                .size = sizeof(__u64),
                .align = sizeof(__u64),
                .get = s390_vxrs_low_get,
                .set = s390_vxrs_low_set,
        },
        {
                .core_note_type = NT_S390_VXRS_HIGH,
                .n = __NUM_VXRS_HIGH,
                .size = sizeof(__vector128),
                .align = sizeof(__vector128),
                .get = s390_vxrs_high_get,
                .set = s390_vxrs_high_set,
        },
};

static const struct user_regset_view user_s390_view = {
        .name = UTS_MACHINE,
        .e_machine = EM_S390,
        .regsets = s390_regsets,
        .n = ARRAY_SIZE(s390_regsets)
};

#ifdef CONFIG_COMPAT
static int s390_compat_regs_get(struct task_struct *target,
                                const struct user_regset *regset,
                                unsigned int pos, unsigned int count,
                                void *kbuf, void __user *ubuf)
{
        if (target == current)
                save_access_regs(target->thread.acrs);

        if (kbuf) {
                compat_ulong_t *k = kbuf;
                while (count > 0) {
                        *k++ = __peek_user_compat(target, pos);
                        count -= sizeof(*k);
                        pos += sizeof(*k);
                }
        } else {
                compat_ulong_t __user *u = ubuf;
                while (count > 0) {
                        if (__put_user(__peek_user_compat(target, pos), u++))
                                return -EFAULT;
                        count -= sizeof(*u);
                        pos += sizeof(*u);
                }
        }
        return 0;
}

static int s390_compat_regs_set(struct task_struct *target,
                                const struct user_regset *regset,
                                unsigned int pos, unsigned int count,
                                const void *kbuf, const void __user *ubuf)
{
        int rc = 0;

        if (target == current)
                save_access_regs(target->thread.acrs);

        if (kbuf) {
                const compat_ulong_t *k = kbuf;
                while (count > 0 && !rc) {
                        rc = __poke_user_compat(target, pos, *k++);
                        count -= sizeof(*k);
                        pos += sizeof(*k);
                }
        } else {
                const compat_ulong_t  __user *u = ubuf;
                while (count > 0 && !rc) {
                        compat_ulong_t word;
                        rc = __get_user(word, u++);
                        if (rc)
                                break;
                        rc = __poke_user_compat(target, pos, word);
                        count -= sizeof(*u);
                        pos += sizeof(*u);
                }
        }

        if (rc == 0 && target == current)
                restore_access_regs(target->thread.acrs);

        return rc;
}

static int s390_compat_regs_high_get(struct task_struct *target,
                                     const struct user_regset *regset,
                                     unsigned int pos, unsigned int count,
                                     void *kbuf, void __user *ubuf)
{
        compat_ulong_t *gprs_high;

        gprs_high = (compat_ulong_t *)
                &task_pt_regs(target)->gprs[pos / sizeof(compat_ulong_t)];
        if (kbuf) {
                compat_ulong_t *k = kbuf;
                while (count > 0) {
                        *k++ = *gprs_high;
                        gprs_high += 2;
                        count -= sizeof(*k);
                }
        } else {
                compat_ulong_t __user *u = ubuf;
                while (count > 0) {
                        if (__put_user(*gprs_high, u++))
                                return -EFAULT;
                        gprs_high += 2;
                        count -= sizeof(*u);
                }
        }
        return 0;
}

static int s390_compat_regs_high_set(struct task_struct *target,
                                     const struct user_regset *regset,
                                     unsigned int pos, unsigned int count,
                                     const void *kbuf, const void __user *ubuf)
{
        compat_ulong_t *gprs_high;
        int rc = 0;

        gprs_high = (compat_ulong_t *)
                &task_pt_regs(target)->gprs[pos / sizeof(compat_ulong_t)];
        if (kbuf) {
                const compat_ulong_t *k = kbuf;
                while (count > 0) {
                        *gprs_high = *k++;
                        *gprs_high += 2;
                        count -= sizeof(*k);
                }
        } else {
                const compat_ulong_t  __user *u = ubuf;
                while (count > 0 && !rc) {
                        unsigned long word;
                        rc = __get_user(word, u++);
                        if (rc)
                                break;
                        *gprs_high = word;
                        *gprs_high += 2;
                        count -= sizeof(*u);
                }
        }

        return rc;
}

static int s390_compat_last_break_get(struct task_struct *target,
                                      const struct user_regset *regset,
                                      unsigned int pos, unsigned int count,
                                      void *kbuf, void __user *ubuf)
{
        compat_ulong_t last_break;

        if (count > 0) {
                last_break = target->thread.last_break;
                if (kbuf) {
                        unsigned long *k = kbuf;
                        *k = last_break;
                } else {
                        unsigned long  __user *u = ubuf;
                        if (__put_user(last_break, u))
                                return -EFAULT;
                }
        }
        return 0;
}

static int s390_compat_last_break_set(struct task_struct *target,
                                      const struct user_regset *regset,
                                      unsigned int pos, unsigned int count,
                                      const void *kbuf, const void __user *ubuf)
{
        return 0;
}

static const struct user_regset s390_compat_regsets[] = {
        {
                .core_note_type = NT_PRSTATUS,
                .n = sizeof(s390_compat_regs) / sizeof(compat_long_t),
                .size = sizeof(compat_long_t),
                .align = sizeof(compat_long_t),
                .get = s390_compat_regs_get,
                .set = s390_compat_regs_set,
        },
        {
                .core_note_type = NT_PRFPREG,
                .n = sizeof(s390_fp_regs) / sizeof(compat_long_t),
                .size = sizeof(compat_long_t),
                .align = sizeof(compat_long_t),
                .get = s390_fpregs_get,
                .set = s390_fpregs_set,
        },
        {
                .core_note_type = NT_S390_SYSTEM_CALL,
                .n = 1,
                .size = sizeof(compat_uint_t),
                .align = sizeof(compat_uint_t),
                .get = s390_system_call_get,
                .set = s390_system_call_set,
        },
        {
                .core_note_type = NT_S390_LAST_BREAK,
                .n = 1,
                .size = sizeof(long),
                .align = sizeof(long),
                .get = s390_compat_last_break_get,
                .set = s390_compat_last_break_set,
        },
        {
                .core_note_type = NT_S390_TDB,
                .n = 1,
                .size = 256,
                .align = 1,
                .get = s390_tdb_get,
                .set = s390_tdb_set,
        },
        {
                .core_note_type = NT_S390_VXRS_LOW,
                .n = __NUM_VXRS_LOW,
                .size = sizeof(__u64),
                .align = sizeof(__u64),
                .get = s390_vxrs_low_get,
                .set = s390_vxrs_low_set,
        },
        {
                .core_note_type = NT_S390_VXRS_HIGH,
                .n = __NUM_VXRS_HIGH,
                .size = sizeof(__vector128),
                .align = sizeof(__vector128),
                .get = s390_vxrs_high_get,
                .set = s390_vxrs_high_set,
        },
        {
                .core_note_type = NT_S390_HIGH_GPRS,
                .n = sizeof(s390_compat_regs_high) / sizeof(compat_long_t),
                .size = sizeof(compat_long_t),
                .align = sizeof(compat_long_t),
                .get = s390_compat_regs_high_get,
                .set = s390_compat_regs_high_set,
        },
};

static const struct user_regset_view user_s390_compat_view = {
        .name = "s390",
        .e_machine = EM_S390,
        .regsets = s390_compat_regsets,
        .n = ARRAY_SIZE(s390_compat_regsets)
};
#endif

const struct user_regset_view *task_user_regset_view(struct task_struct *task)
{
#ifdef CONFIG_COMPAT
        if (test_tsk_thread_flag(task, TIF_31BIT))
                return &user_s390_compat_view;
#endif
        return &user_s390_view;
}

static const char *gpr_names[NUM_GPRS] = {
        "r0", "r1",  "r2",  "r3",  "r4",  "r5",  "r6",  "r7",
        "r8", "r9", "r10", "r11", "r12", "r13", "r14", "r15",
};

unsigned long regs_get_register(struct pt_regs *regs, unsigned int offset)
{
        if (offset >= NUM_GPRS)
                return 0;
        return regs->gprs[offset];
}

int regs_query_register_offset(const char *name)
{
        unsigned long offset;

        if (!name || *name != 'r')
                return -EINVAL;
        if (kstrtoul(name + 1, 10, &offset))
                return -EINVAL;
        if (offset >= NUM_GPRS)
                return -EINVAL;
        return offset;
}

const char *regs_query_register_name(unsigned int offset)
{
        if (offset >= NUM_GPRS)
                return NULL;
        return gpr_names[offset];
}

static int regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr)
{
        unsigned long ksp = kernel_stack_pointer(regs);

        return (addr & ~(THREAD_SIZE - 1)) == (ksp & ~(THREAD_SIZE - 1));
}

/**
 * regs_get_kernel_stack_nth() - get Nth entry of the stack
 * @regs:pt_regs which contains kernel stack pointer.
 * @n:stack entry number.
 *
 * regs_get_kernel_stack_nth() returns @n th entry of the kernel stack which
 * is specifined by @regs. If the @n th entry is NOT in the kernel stack,
 * this returns 0.
 */
unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs, unsigned int n)
{
        unsigned long addr;

        addr = kernel_stack_pointer(regs) + n * sizeof(long);
        if (!regs_within_kernel_stack(regs, addr))
                return 0;
        return *(unsigned long *)addr;
}