/* By Ross Biro 1/23/92 */
/*
 * Pentium III FXSR, SSE support
 *      Gareth Hughes <gareth@valinux.com>, May 2000
 *
 * BTS tracing
 *      Markus Metzger <markus.t.metzger@intel.com>, Dec 2007
 */

#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/regset.h>
#include <linux/user.h>
#include <linux/elf.h>
#include <linux/security.h>
#include <linux/audit.h>
#include <linux/seccomp.h>
#include <linux/signal.h>

#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/system.h>
#include <asm/processor.h>
#include <asm/i387.h>
#include <asm/debugreg.h>
#include <asm/ldt.h>
#include <asm/desc.h>
#include <asm/prctl.h>
#include <asm/proto.h>
#include <asm/ds.h>

#include "tls.h"

enum x86_regset {
        REGSET_GENERAL,
        REGSET_FP,
        REGSET_XFP,
        REGSET_TLS,
};

/*
 * does not yet catch signals sent when the child dies.
 * in exit.c or in signal.c.
 */

/*
 * Determines which flags the user has access to [1 = access, 0 = no access].
 */
#define FLAG_MASK_32            ((unsigned long)                        \
                                 (X86_EFLAGS_CF | X86_EFLAGS_PF |       \
                                  X86_EFLAGS_AF | X86_EFLAGS_ZF |       \
                                  X86_EFLAGS_SF | X86_EFLAGS_TF |       \
                                  X86_EFLAGS_DF | X86_EFLAGS_OF |       \
                                  X86_EFLAGS_RF | X86_EFLAGS_AC))

/*
 * Determines whether a value may be installed in a segment register.
 */
static inline bool invalid_selector(u16 value)
{
        return unlikely(value != 0 && (value & SEGMENT_RPL_MASK) != USER_RPL);
}

#ifdef CONFIG_X86_32

#define FLAG_MASK               FLAG_MASK_32

static long *pt_regs_access(struct pt_regs *regs, unsigned long regno)
{
        BUILD_BUG_ON(offsetof(struct pt_regs, bx) != 0);
        regno >>= 2;
        if (regno > FS)
                --regno;
        return &regs->bx + regno;
}

static u16 get_segment_reg(struct task_struct *task, unsigned long offset)
{
        /*
         * Returning the value truncates it to 16 bits.
         */
        unsigned int retval;
        if (offset != offsetof(struct user_regs_struct, gs))
                retval = *pt_regs_access(task_pt_regs(task), offset);
        else {
                retval = task->thread.gs;
                if (task == current)
                        savesegment(gs, retval);
        }
        return retval;
}

static int set_segment_reg(struct task_struct *task,
                           unsigned long offset, u16 value)
{
        /*
         * The value argument was already truncated to 16 bits.
         */
        if (invalid_selector(value))
                return -EIO;

        /*
         * For %cs and %ss we cannot permit a null selector.
         * We can permit a bogus selector as long as it has USER_RPL.
         * Null selectors are fine for other segment registers, but
         * we will never get back to user mode with invalid %cs or %ss
         * and will take the trap in iret instead.  Much code relies
         * on user_mode() to distinguish a user trap frame (which can
         * safely use invalid selectors) from a kernel trap frame.
         */
        switch (offset) {
        case offsetof(struct user_regs_struct, cs):
        case offsetof(struct user_regs_struct, ss):
                if (unlikely(value == 0))
                        return -EIO;

        default:
                *pt_regs_access(task_pt_regs(task), offset) = value;
                break;

        case offsetof(struct user_regs_struct, gs):
                task->thread.gs = value;
                if (task == current)
                        /*
                         * The user-mode %gs is not affected by
                         * kernel entry, so we must update the CPU.
                         */
                        loadsegment(gs, value);
        }

        return 0;
}

static unsigned long debugreg_addr_limit(struct task_struct *task)
{
        return TASK_SIZE - 3;
}

#else  /* CONFIG_X86_64 */

#define FLAG_MASK               (FLAG_MASK_32 | X86_EFLAGS_NT)

static unsigned long *pt_regs_access(struct pt_regs *regs, unsigned long offset)
{
        BUILD_BUG_ON(offsetof(struct pt_regs, r15) != 0);
        return &regs->r15 + (offset / sizeof(regs->r15));
}

static u16 get_segment_reg(struct task_struct *task, unsigned long offset)
{
        /*
         * Returning the value truncates it to 16 bits.
         */
        unsigned int seg;

        switch (offset) {
        case offsetof(struct user_regs_struct, fs):
                if (task == current) {
                        /* Older gas can't assemble movq %?s,%r?? */
                        asm("movl %%fs,%0" : "=r" (seg));
                        return seg;
                }
                return task->thread.fsindex;
        case offsetof(struct user_regs_struct, gs):
                if (task == current) {
                        asm("movl %%gs,%0" : "=r" (seg));
                        return seg;
                }
                return task->thread.gsindex;
        case offsetof(struct user_regs_struct, ds):
                if (task == current) {
                        asm("movl %%ds,%0" : "=r" (seg));
                        return seg;
                }
                return task->thread.ds;
        case offsetof(struct user_regs_struct, es):
                if (task == current) {
                        asm("movl %%es,%0" : "=r" (seg));
                        return seg;
                }
                return task->thread.es;

        case offsetof(struct user_regs_struct, cs):
        case offsetof(struct user_regs_struct, ss):
                break;
        }
        return *pt_regs_access(task_pt_regs(task), offset);
}

static int set_segment_reg(struct task_struct *task,
                           unsigned long offset, u16 value)
{
        /*
         * The value argument was already truncated to 16 bits.
         */
        if (invalid_selector(value))
                return -EIO;

        switch (offset) {
        case offsetof(struct user_regs_struct,fs):
                /*
                 * If this is setting fs as for normal 64-bit use but
                 * setting fs_base has implicitly changed it, leave it.
                 */
                if ((value == FS_TLS_SEL && task->thread.fsindex == 0 &&
                     task->thread.fs != 0) ||
                    (value == 0 && task->thread.fsindex == FS_TLS_SEL &&
                     task->thread.fs == 0))
                        break;
                task->thread.fsindex = value;
                if (task == current)
                        loadsegment(fs, task->thread.fsindex);
                break;
        case offsetof(struct user_regs_struct,gs):
                /*
                 * If this is setting gs as for normal 64-bit use but
                 * setting gs_base has implicitly changed it, leave it.
                 */
                if ((value == GS_TLS_SEL && task->thread.gsindex == 0 &&
                     task->thread.gs != 0) ||
                    (value == 0 && task->thread.gsindex == GS_TLS_SEL &&
                     task->thread.gs == 0))
                        break;
                task->thread.gsindex = value;
                if (task == current)
                        load_gs_index(task->thread.gsindex);
                break;
        case offsetof(struct user_regs_struct,ds):
                task->thread.ds = value;
                if (task == current)
                        loadsegment(ds, task->thread.ds);
                break;
        case offsetof(struct user_regs_struct,es):
                task->thread.es = value;
                if (task == current)
                        loadsegment(es, task->thread.es);
                break;

                /*
                 * Can't actually change these in 64-bit mode.
                 */
        case offsetof(struct user_regs_struct,cs):
                if (unlikely(value == 0))
                        return -EIO;
#ifdef CONFIG_IA32_EMULATION
                if (test_tsk_thread_flag(task, TIF_IA32))
                        task_pt_regs(task)->cs = value;
#endif
                break;
        case offsetof(struct user_regs_struct,ss):
                if (unlikely(value == 0))
                        return -EIO;
#ifdef CONFIG_IA32_EMULATION
                if (test_tsk_thread_flag(task, TIF_IA32))
                        task_pt_regs(task)->ss = value;
#endif
                break;
        }

        return 0;
}

static unsigned long debugreg_addr_limit(struct task_struct *task)
{
#ifdef CONFIG_IA32_EMULATION
        if (test_tsk_thread_flag(task, TIF_IA32))
                return IA32_PAGE_OFFSET - 3;
#endif
        return TASK_SIZE64 - 7;
}

#endif  /* CONFIG_X86_32 */

static unsigned long get_flags(struct task_struct *task)
{
        unsigned long retval = task_pt_regs(task)->flags;

        /*
         * If the debugger set TF, hide it from the readout.
         */
        if (test_tsk_thread_flag(task, TIF_FORCED_TF))
                retval &= ~X86_EFLAGS_TF;

        return retval;
}

static int set_flags(struct task_struct *task, unsigned long value)
{
        struct pt_regs *regs = task_pt_regs(task);

        /*
         * If the user value contains TF, mark that
         * it was not "us" (the debugger) that set it.
         * If not, make sure it stays set if we had.
         */
        if (value & X86_EFLAGS_TF)
                clear_tsk_thread_flag(task, TIF_FORCED_TF);
        else if (test_tsk_thread_flag(task, TIF_FORCED_TF))
                value |= X86_EFLAGS_TF;

        regs->flags = (regs->flags & ~FLAG_MASK) | (value & FLAG_MASK);

        return 0;
}

static int putreg(struct task_struct *child,
                  unsigned long offset, unsigned long value)
{
        switch (offset) {
        case offsetof(struct user_regs_struct, cs):
        case offsetof(struct user_regs_struct, ds):
        case offsetof(struct user_regs_struct, es):
        case offsetof(struct user_regs_struct, fs):
        case offsetof(struct user_regs_struct, gs):
        case offsetof(struct user_regs_struct, ss):
                return set_segment_reg(child, offset, value);

        case offsetof(struct user_regs_struct, flags):
                return set_flags(child, value);

#ifdef CONFIG_X86_64
        /*
         * Orig_ax is really just a flag with small positive and
         * negative values, so make sure to always sign-extend it
         * from 32 bits so that it works correctly regardless of
         * whether we come from a 32-bit environment or not.
         */
        case offsetof(struct user_regs_struct, orig_ax):
                value = (long) (s32) value;
                break;

        case offsetof(struct user_regs_struct,fs_base):
                if (value >= TASK_SIZE_OF(child))
                        return -EIO;
                /*
                 * When changing the segment base, use do_arch_prctl
                 * to set either thread.fs or thread.fsindex and the
                 * corresponding GDT slot.
                 */
                if (child->thread.fs != value)
                        return do_arch_prctl(child, ARCH_SET_FS, value);
                return 0;
        case offsetof(struct user_regs_struct,gs_base):
                /*
                 * Exactly the same here as the %fs handling above.
                 */
                if (value >= TASK_SIZE_OF(child))
                        return -EIO;
                if (child->thread.gs != value)
                        return do_arch_prctl(child, ARCH_SET_GS, value);
                return 0;
#endif
        }

        *pt_regs_access(task_pt_regs(child), offset) = value;
        return 0;
}

static unsigned long getreg(struct task_struct *task, unsigned long offset)
{
        switch (offset) {
        case offsetof(struct user_regs_struct, cs):
        case offsetof(struct user_regs_struct, ds):
        case offsetof(struct user_regs_struct, es):
        case offsetof(struct user_regs_struct, fs):
        case offsetof(struct user_regs_struct, gs):
        case offsetof(struct user_regs_struct, ss):
                return get_segment_reg(task, offset);

        case offsetof(struct user_regs_struct, flags):
                return get_flags(task);

#ifdef CONFIG_X86_64
        case offsetof(struct user_regs_struct, fs_base): {
                /*
                 * do_arch_prctl may have used a GDT slot instead of
                 * the MSR.  To userland, it appears the same either
                 * way, except the %fs segment selector might not be 0.
                 */
                unsigned int seg = task->thread.fsindex;
                if (task->thread.fs != 0)
                        return task->thread.fs;
                if (task == current)
                        asm("movl %%fs,%0" : "=r" (seg));
                if (seg != FS_TLS_SEL)
                        return 0;
                return get_desc_base(&task->thread.tls_array[FS_TLS]);
        }
        case offsetof(struct user_regs_struct, gs_base): {
                /*
                 * Exactly the same here as the %fs handling above.
                 */
                unsigned int seg = task->thread.gsindex;
                if (task->thread.gs != 0)
                        return task->thread.gs;
                if (task == current)
                        asm("movl %%gs,%0" : "=r" (seg));
                if (seg != GS_TLS_SEL)
                        return 0;
                return get_desc_base(&task->thread.tls_array[GS_TLS]);
        }
#endif
        }

        return *pt_regs_access(task_pt_regs(task), offset);
}

static int genregs_get(struct task_struct *target,
                       const struct user_regset *regset,
                       unsigned int pos, unsigned int count,
                       void *kbuf, void __user *ubuf)
{
        if (kbuf) {
                unsigned long *k = kbuf;
                while (count > 0) {
                        *k++ = getreg(target, pos);
                        count -= sizeof(*k);
                        pos += sizeof(*k);
                }
        } else {
                unsigned long __user *u = ubuf;
                while (count > 0) {
                        if (__put_user(getreg(target, pos), u++))
                                return -EFAULT;
                        count -= sizeof(*u);
                        pos += sizeof(*u);
                }
        }

        return 0;
}

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

/*
 * This function is trivial and will be inlined by the compiler.
 * Having it separates the implementation details of debug
 * registers from the interface details of ptrace.
 */
static unsigned long ptrace_get_debugreg(struct task_struct *child, int n)
{
        switch (n) {
        case 0:         return child->thread.debugreg0;
        case 1:         return child->thread.debugreg1;
        case 2:         return child->thread.debugreg2;
        case 3:         return child->thread.debugreg3;
        case 6:         return child->thread.debugreg6;
        case 7:         return child->thread.debugreg7;
        }
        return 0;
}

static int ptrace_set_debugreg(struct task_struct *child,
                               int n, unsigned long data)
{
        int i;

        if (unlikely(n == 4 || n == 5))
                return -EIO;

        if (n < 4 && unlikely(data >= debugreg_addr_limit(child)))
                return -EIO;

        switch (n) {
        case 0:         child->thread.debugreg0 = data; break;
        case 1:         child->thread.debugreg1 = data; break;
        case 2:         child->thread.debugreg2 = data; break;
        case 3:         child->thread.debugreg3 = data; break;

        case 6:
                if ((data & ~0xffffffffUL) != 0)
                        return -EIO;
                child->thread.debugreg6 = data;
                break;

        case 7:
                /*
                 * Sanity-check data. Take one half-byte at once with
                 * check = (val >> (16 + 4*i)) & 0xf. It contains the
                 * R/Wi and LENi bits; bits 0 and 1 are R/Wi, and bits
                 * 2 and 3 are LENi. Given a list of invalid values,
                 * we do mask |= 1 << invalid_value, so that
                 * (mask >> check) & 1 is a correct test for invalid
                 * values.
                 *
                 * R/Wi contains the type of the breakpoint /
                 * watchpoint, LENi contains the length of the watched
                 * data in the watchpoint case.
                 *
                 * The invalid values are:
                 * - LENi == 0x10 (undefined), so mask |= 0x0f00.       [32-bit]
                 * - R/Wi == 0x10 (break on I/O reads or writes), so
                 *   mask |= 0x4444.
                 * - R/Wi == 0x00 && LENi != 0x00, so we have mask |=
                 *   0x1110.
                 *
                 * Finally, mask = 0x0f00 | 0x4444 | 0x1110 == 0x5f54.
                 *
                 * See the Intel Manual "System Programming Guide",
                 * 15.2.4
                 *
                 * Note that LENi == 0x10 is defined on x86_64 in long
                 * mode (i.e. even for 32-bit userspace software, but
                 * 64-bit kernel), so the x86_64 mask value is 0x5454.
                 * See the AMD manual no. 24593 (AMD64 System Programming)
                 */
#ifdef CONFIG_X86_32
#define DR7_MASK        0x5f54
#else
#define DR7_MASK        0x5554
#endif
                data &= ~DR_CONTROL_RESERVED;
                for (i = 0; i < 4; i++)
                        if ((DR7_MASK >> ((data >> (16 + 4*i)) & 0xf)) & 1)
                                return -EIO;
                child->thread.debugreg7 = data;
                if (data)
                        set_tsk_thread_flag(child, TIF_DEBUG);
                else
                        clear_tsk_thread_flag(child, TIF_DEBUG);
                break;
        }

        return 0;
}

#ifdef X86_BTS

static int ptrace_bts_get_size(struct task_struct *child)
{
        if (!child->thread.ds_area_msr)
                return -ENXIO;

        return ds_get_bts_index((void *)child->thread.ds_area_msr);
}

static int ptrace_bts_read_record(struct task_struct *child,
                                  long index,
                                  struct bts_struct __user *out)
{
        struct bts_struct ret;
        int retval;
        int bts_end;
        int bts_index;

        if (!child->thread.ds_area_msr)
                return -ENXIO;

        if (index < 0)
                return -EINVAL;

        bts_end = ds_get_bts_end((void *)child->thread.ds_area_msr);
        if (bts_end <= index)
                return -EINVAL;

        /* translate the ptrace bts index into the ds bts index */
        bts_index = ds_get_bts_index((void *)child->thread.ds_area_msr);
        bts_index -= (index + 1);
        if (bts_index < 0)
                bts_index += bts_end;

        retval = ds_read_bts((void *)child->thread.ds_area_msr,
                             bts_index, &ret);
        if (retval < 0)
                return retval;

        if (copy_to_user(out, &ret, sizeof(ret)))
                return -EFAULT;

        return sizeof(ret);
}

static int ptrace_bts_clear(struct task_struct *child)
{
        if (!child->thread.ds_area_msr)
                return -ENXIO;

        return ds_clear((void *)child->thread.ds_area_msr);
}

static int ptrace_bts_drain(struct task_struct *child,
                            long size,
                            struct bts_struct __user *out)
{
        int end, i;
        void *ds = (void *)child->thread.ds_area_msr;

        if (!ds)
                return -ENXIO;

        end = ds_get_bts_index(ds);
        if (end <= 0)
                return end;

        if (size < (end * sizeof(struct bts_struct)))
                return -EIO;

        for (i = 0; i < end; i++, out++) {
                struct bts_struct ret;
                int retval;

                retval = ds_read_bts(ds, i, &ret);
                if (retval < 0)
                        return retval;

                if (copy_to_user(out, &ret, sizeof(ret)))
                        return -EFAULT;
        }

        ds_clear(ds);

        return end;
}

static int ptrace_bts_config(struct task_struct *child,
                             long cfg_size,
                             const struct ptrace_bts_config __user *ucfg)
{
        struct ptrace_bts_config cfg;
        int bts_size, ret = 0;
        void *ds;

        if (cfg_size < sizeof(cfg))
                return -EIO;

        if (copy_from_user(&cfg, ucfg, sizeof(cfg)))
                return -EFAULT;

        if ((int)cfg.size < 0)
                return -EINVAL;

        bts_size = 0;
        ds = (void *)child->thread.ds_area_msr;
        if (ds) {
                bts_size = ds_get_bts_size(ds);
                if (bts_size < 0)
                        return bts_size;
        }
        cfg.size = PAGE_ALIGN(cfg.size);

        if (bts_size != cfg.size) {
                ret = ptrace_bts_realloc(child, cfg.size,
                                         cfg.flags & PTRACE_BTS_O_CUT_SIZE);
                if (ret < 0)
                        goto errout;

                ds = (void *)child->thread.ds_area_msr;
        }

        if (cfg.flags & PTRACE_BTS_O_SIGNAL)
                ret = ds_set_overflow(ds, DS_O_SIGNAL);
        else
                ret = ds_set_overflow(ds, DS_O_WRAP);
        if (ret < 0)
                goto errout;

        if (cfg.flags & PTRACE_BTS_O_TRACE)
                child->thread.debugctlmsr |= ds_debugctl_mask();
        else
                child->thread.debugctlmsr &= ~ds_debugctl_mask();

        if (cfg.flags & PTRACE_BTS_O_SCHED)
                set_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
        else
                clear_tsk_thread_flag(child, TIF_BTS_TRACE_TS);

        ret = sizeof(cfg);

out:
        if (child->thread.debugctlmsr)
                set_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
        else
                clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);

        return ret;

errout:
        child->thread.debugctlmsr &= ~ds_debugctl_mask();
        clear_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
        goto out;
}

static int ptrace_bts_status(struct task_struct *child,
                             long cfg_size,
                             struct ptrace_bts_config __user *ucfg)
{
        void *ds = (void *)child->thread.ds_area_msr;
        struct ptrace_bts_config cfg;

        if (cfg_size < sizeof(cfg))
                return -EIO;

        memset(&cfg, 0, sizeof(cfg));

        if (ds) {
                cfg.size = ds_get_bts_size(ds);

                if (ds_get_overflow(ds) == DS_O_SIGNAL)
                        cfg.flags |= PTRACE_BTS_O_SIGNAL;

                if (test_tsk_thread_flag(child, TIF_DEBUGCTLMSR) &&
                    child->thread.debugctlmsr & ds_debugctl_mask())
                        cfg.flags |= PTRACE_BTS_O_TRACE;

                if (test_tsk_thread_flag(child, TIF_BTS_TRACE_TS))
                        cfg.flags |= PTRACE_BTS_O_SCHED;
        }

        cfg.bts_size = sizeof(struct bts_struct);

        if (copy_to_user(ucfg, &cfg, sizeof(cfg)))
                return -EFAULT;

        return sizeof(cfg);
}


static int ptrace_bts_write_record(struct task_struct *child,
                                   const struct bts_struct *in)
{
        int retval;

        if (!child->thread.ds_area_msr)
                return -ENXIO;

        retval = ds_write_bts((void *)child->thread.ds_area_msr, in);
        if (retval)
                return retval;

        return sizeof(*in);
}

static int ptrace_bts_realloc(struct task_struct *child,
                              int size, int reduce_size)
{
        unsigned long rlim, vm;
        int ret, old_size;

        if (size < 0)
                return -EINVAL;

        old_size = ds_get_bts_size((void *)child->thread.ds_area_msr);
        if (old_size < 0)
                return old_size;

        ret = ds_free((void **)&child->thread.ds_area_msr);
        if (ret < 0)
                goto out;

        size >>= PAGE_SHIFT;
        old_size >>= PAGE_SHIFT;

        current->mm->total_vm  -= old_size;
        current->mm->locked_vm -= old_size;

        if (size == 0)
                goto out;

        rlim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
        vm = current->mm->total_vm  + size;
        if (rlim < vm) {
                ret = -ENOMEM;

                if (!reduce_size)
                        goto out;

                size = rlim - current->mm->total_vm;
                if (size <= 0)
                        goto out;
        }

        rlim = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
        vm = current->mm->locked_vm  + size;
        if (rlim < vm) {
                ret = -ENOMEM;

                if (!reduce_size)
                        goto out;

                size = rlim - current->mm->locked_vm;
                if (size <= 0)
                        goto out;
        }

        ret = ds_allocate((void **)&child->thread.ds_area_msr,
                          size << PAGE_SHIFT);
        if (ret < 0)
                goto out;

        current->mm->total_vm  += size;
        current->mm->locked_vm += size;

out:
        if (child->thread.ds_area_msr)
                set_tsk_thread_flag(child, TIF_DS_AREA_MSR);
        else
                clear_tsk_thread_flag(child, TIF_DS_AREA_MSR);

        return ret;
}

void ptrace_bts_take_timestamp(struct task_struct *tsk,
                               enum bts_qualifier qualifier)
{
        struct bts_struct rec = {
                .qualifier = qualifier,
                .variant.jiffies = jiffies_64
        };

        ptrace_bts_write_record(tsk, &rec);
}
#endif /* X86_BTS */

/*
 * Called by kernel/ptrace.c when detaching..
 *
 * Make sure the single step bit is not set.
 */
void ptrace_disable(struct task_struct *child)
{
        user_disable_single_step(child);
#ifdef TIF_SYSCALL_EMU
        clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
#endif
        if (child->thread.ds_area_msr) {
#ifdef X86_BTS
                ptrace_bts_realloc(child, 0, 0);
#endif
                child->thread.debugctlmsr &= ~ds_debugctl_mask();
                if (!child->thread.debugctlmsr)
                        clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
                clear_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
        }
}

#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
static const struct user_regset_view user_x86_32_view; /* Initialized below. */
#endif

long arch_ptrace(struct task_struct *child, long request, long addr, long data)
{
        int ret;
        unsigned long __user *datap = (unsigned long __user *)data;

        switch (request) {
        /* read the word at location addr in the USER area. */
        case PTRACE_PEEKUSR: {
                unsigned long tmp;

                ret = -EIO;
                if ((addr & (sizeof(data) - 1)) || addr < 0 ||
                    addr >= sizeof(struct user))
                        break;

                tmp = 0;  /* Default return condition */
                if (addr < sizeof(struct user_regs_struct))
                        tmp = getreg(child, addr);
                else if (addr >= offsetof(struct user, u_debugreg[0]) &&
                         addr <= offsetof(struct user, u_debugreg[7])) {
                        addr -= offsetof(struct user, u_debugreg[0]);
                        tmp = ptrace_get_debugreg(child, addr / sizeof(data));
                }
                ret = put_user(tmp, datap);
                break;
        }

        case PTRACE_POKEUSR: /* write the word at location addr in the USER area */
                ret = -EIO;
                if ((addr & (sizeof(data) - 1)) || addr < 0 ||
                    addr >= sizeof(struct user))
                        break;

                if (addr < sizeof(struct user_regs_struct))
                        ret = putreg(child, addr, data);
                else if (addr >= offsetof(struct user, u_debugreg[0]) &&
                         addr <= offsetof(struct user, u_debugreg[7])) {
                        addr -= offsetof(struct user, u_debugreg[0]);
                        ret = ptrace_set_debugreg(child,
                                                  addr / sizeof(data), data);
                }
                break;

        case PTRACE_GETREGS:    /* Get all gp regs from the child. */
                return copy_regset_to_user(child,
                                           task_user_regset_view(current),
                                           REGSET_GENERAL,
                                           0, sizeof(struct user_regs_struct),
                                           datap);

        case PTRACE_SETREGS:    /* Set all gp regs in the child. */
                return copy_regset_from_user(child,
                                             task_user_regset_view(current),
                                             REGSET_GENERAL,
                                             0, sizeof(struct user_regs_struct),
                                             datap);

        case PTRACE_GETFPREGS:  /* Get the child FPU state. */
                return copy_regset_to_user(child,
                                           task_user_regset_view(current),
                                           REGSET_FP,
                                           0, sizeof(struct user_i387_struct),
                                           datap);

        case PTRACE_SETFPREGS:  /* Set the child FPU state. */
                return copy_regset_from_user(child,
                                             task_user_regset_view(current),
                                             REGSET_FP,
                                             0, sizeof(struct user_i387_struct),
                                             datap);

#ifdef CONFIG_X86_32
        case PTRACE_GETFPXREGS: /* Get the child extended FPU state. */
                return copy_regset_to_user(child, &user_x86_32_view,
                                           REGSET_XFP,
                                           0, sizeof(struct user_fxsr_struct),
                                           datap) ? -EIO : 0;

        case PTRACE_SETFPXREGS: /* Set the child extended FPU state. */
                return copy_regset_from_user(child, &user_x86_32_view,
                                             REGSET_XFP,
                                             0, sizeof(struct user_fxsr_struct),
                                             datap) ? -EIO : 0;
#endif

#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
        case PTRACE_GET_THREAD_AREA:
                if (addr < 0)
                        return -EIO;
                ret = do_get_thread_area(child, addr,
                                         (struct user_desc __user *) data);
                break;

        case PTRACE_SET_THREAD_AREA:
                if (addr < 0)
                        return -EIO;
                ret = do_set_thread_area(child, addr,
                                         (struct user_desc __user *) data, 0);
                break;
#endif

#ifdef CONFIG_X86_64
                /* normal 64bit interface to access TLS data.
                   Works just like arch_prctl, except that the arguments
                   are reversed. */
        case PTRACE_ARCH_PRCTL:
                ret = do_arch_prctl(child, data, addr);
                break;
#endif

        /*
         * These bits need more cooking - not enabled yet:
         */
#ifdef X86_BTS
        case PTRACE_BTS_CONFIG:
                ret = ptrace_bts_config
                        (child, data, (struct ptrace_bts_config __user *)addr);
                break;

        case PTRACE_BTS_STATUS:
                ret = ptrace_bts_status
                        (child, data, (struct ptrace_bts_config __user *)addr);
                break;

        case PTRACE_BTS_SIZE:
                ret = ptrace_bts_get_size(child);
                break;

        case PTRACE_BTS_GET:
                ret = ptrace_bts_read_record
                        (child, data, (struct bts_struct __user *) addr);

                break;

        case PTRACE_BTS_CLEAR:
                ret = ptrace_bts_clear(child);
                break;

        case PTRACE_BTS_DRAIN:
                ret = ptrace_bts_drain
                        (child, data, (struct bts_struct __user *) addr);
                break;
#endif

        default:
                ret = ptrace_request(child, request, addr, data);
                break;
        }

        return ret;
}

#ifdef CONFIG_IA32_EMULATION

#include <linux/compat.h>
#include <linux/syscalls.h>
#include <asm/ia32.h>
#include <asm/user32.h>

#define R32(l,q)                                                        \
        case offsetof(struct user32, regs.l):                           \
                regs->q = value; break

#define SEG32(rs)                                                       \
        case offsetof(struct user32, regs.rs):                          \
                return set_segment_reg(child,                           \
                                       offsetof(struct user_regs_struct, rs), \
                                       value);                          \
                break

static int putreg32(struct task_struct *child, unsigned regno, u32 value)
{
        struct pt_regs *regs = task_pt_regs(child);

        switch (regno) {

        SEG32(cs);
        SEG32(ds);
        SEG32(es);
        SEG32(fs);
        SEG32(gs);
        SEG32(ss);

        R32(ebx, bx);
        R32(ecx, cx);
        R32(edx, dx);
        R32(edi, di);
        R32(esi, si);
        R32(ebp, bp);
        R32(eax, ax);
        R32(eip, ip);
        R32(esp, sp);

        case offsetof(struct user32, regs.orig_eax):
                /*
                 * Sign-extend the value so that orig_eax = -1
                 * causes (long)orig_ax < 0 tests to fire correctly.
                 */
                regs->orig_ax = (long) (s32) value;
                break;

        case offsetof(struct user32, regs.eflags):
                return set_flags(child, value);

        case offsetof(struct user32, u_debugreg[0]) ...
                offsetof(struct user32, u_debugreg[7]):
                regno -= offsetof(struct user32, u_debugreg[0]);
                return ptrace_set_debugreg(child, regno / 4, value);

        default:
                if (regno > sizeof(struct user32) || (regno & 3))
                        return -EIO;

                /*
                 * Other dummy fields in the virtual user structure
                 * are ignored
                 */
                break;
        }
        return 0;
}

#undef R32
#undef SEG32

#define R32(l,q)                                                        \
        case offsetof(struct user32, regs.l):                           \
                *val = regs->q; break

#define SEG32(rs)                                                       \
        case offsetof(struct user32, regs.rs):                          \
                *val = get_segment_reg(child,                           \
                                       offsetof(struct user_regs_struct, rs)); \
                break

static int getreg32(struct task_struct *child, unsigned regno, u32 *val)
{
        struct pt_regs *regs = task_pt_regs(child);

        switch (regno) {

        SEG32(ds);
        SEG32(es);
        SEG32(fs);
        SEG32(gs);

        R32(cs, cs);
        R32(ss, ss);
        R32(ebx, bx);
        R32(ecx, cx);
        R32(edx, dx);
        R32(edi, di);
        R32(esi, si);
        R32(ebp, bp);
        R32(eax, ax);
        R32(orig_eax, orig_ax);
        R32(eip, ip);
        R32(esp, sp);

        case offsetof(struct user32, regs.eflags):
                *val = get_flags(child);
                break;

        case offsetof(struct user32, u_debugreg[0]) ...
                offsetof(struct user32, u_debugreg[7]):
                regno -= offsetof(struct user32, u_debugreg[0]);
                *val = ptrace_get_debugreg(child, regno / 4);
                break;

        default:
                if (regno > sizeof(struct user32) || (regno & 3))
                        return -EIO;

                /*
                 * Other dummy fields in the virtual user structure
                 * are ignored
                 */
                *val = 0;
                break;
        }
        return 0;
}

#undef R32
#undef SEG32

static int genregs32_get(struct task_struct *target,
                         const struct user_regset *regset,
                         unsigned int pos, unsigned int count,
                         void *kbuf, void __user *ubuf)
{
        if (kbuf) {
                compat_ulong_t *k = kbuf;
                while (count > 0) {
                        getreg32(target, pos, k++);
                        count -= sizeof(*k);
                        pos += sizeof(*k);
                }
        } else {
                compat_ulong_t __user *u = ubuf;
                while (count > 0) {
                        compat_ulong_t word;
                        getreg32(target, pos, &word);
                        if (__put_user(word, u++))
                                return -EFAULT;
                        count -= sizeof(*u);
                        pos += sizeof(*u);
                }
        }

        return 0;
}

static int genregs32_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 = 0;
        if (kbuf) {
                const compat_ulong_t *k = kbuf;
                while (count > 0 && !ret) {
                        ret = putreg32(target, pos, *k++);
                        count -= sizeof(*k);
                        pos += sizeof(*k);
                }
        } else {
                const compat_ulong_t __user *u = ubuf;
                while (count > 0 && !ret) {
                        compat_ulong_t word;
                        ret = __get_user(word, u++);
                        if (ret)
                                break;
                        ret = putreg32(target, pos, word);
                        count -= sizeof(*u);
                        pos += sizeof(*u);
                }
        }
        return ret;
}

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;
        __u32 val;

        switch (request) {
        case PTRACE_PEEKUSR:
                ret = getreg32(child, addr, &val);
                if (ret == 0)
                        ret = put_user(val, (__u32 __user *)datap);
                break;

        case PTRACE_POKEUSR:
                ret = putreg32(child, addr, data);
                break;

        case PTRACE_GETREGS:    /* Get all gp regs from the child. */
                return copy_regset_to_user(child, &user_x86_32_view,
                                           REGSET_GENERAL,
                                           0, sizeof(struct user_regs_struct32),
                                           datap);

        case PTRACE_SETREGS:    /* Set all gp regs in the child. */
                return copy_regset_from_user(child, &user_x86_32_view,
                                             REGSET_GENERAL, 0,
                                             sizeof(struct user_regs_struct32),
                                             datap);

        case PTRACE_GETFPREGS:  /* Get the child FPU state. */
                return copy_regset_to_user(child, &user_x86_32_view,
                                           REGSET_FP, 0,
                                           sizeof(struct user_i387_ia32_struct),
                                           datap);

        case PTRACE_SETFPREGS:  /* Set the child FPU state. */
                return copy_regset_from_user(
                        child, &user_x86_32_view, REGSET_FP,
                        0, sizeof(struct user_i387_ia32_struct), datap);

        case PTRACE_GETFPXREGS: /* Get the child extended FPU state. */
                return copy_regset_to_user(child, &user_x86_32_view,
                                           REGSET_XFP, 0,
                                           sizeof(struct user32_fxsr_struct),
                                           datap);

        case PTRACE_SETFPXREGS: /* Set the child extended FPU state. */
                return copy_regset_from_user(child, &user_x86_32_view,
                                             REGSET_XFP, 0,
                                             sizeof(struct user32_fxsr_struct),
                                             datap);

        case PTRACE_GET_THREAD_AREA:
        case PTRACE_SET_THREAD_AREA:
                return arch_ptrace(child, request, addr, data);

        default:
                return compat_ptrace_request(child, request, addr, data);
        }

        return ret;
}

#endif  /* CONFIG_IA32_EMULATION */

#ifdef CONFIG_X86_64

static const struct user_regset x86_64_regsets[] = {
        [REGSET_GENERAL] = {
                .core_note_type = NT_PRSTATUS,
                .n = sizeof(struct user_regs_struct) / sizeof(long),
                .size = sizeof(long), .align = sizeof(long),
                .get = genregs_get, .set = genregs_set
        },
        [REGSET_FP] = {
                .core_note_type = NT_PRFPREG,
                .n = sizeof(struct user_i387_struct) / sizeof(long),
                .size = sizeof(long), .align = sizeof(long),
                .active = xfpregs_active, .get = xfpregs_get, .set = xfpregs_set
        },
};

static const struct user_regset_view user_x86_64_view = {
        .name = "x86_64", .e_machine = EM_X86_64,
        .regsets = x86_64_regsets, .n = ARRAY_SIZE(x86_64_regsets)
};

#else  /* CONFIG_X86_32 */

#define user_regs_struct32      user_regs_struct
#define genregs32_get           genregs_get
#define genregs32_set           genregs_set

#define user_i387_ia32_struct   user_i387_struct
#define user32_fxsr_struct      user_fxsr_struct

#endif  /* CONFIG_X86_64 */

#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
static const struct user_regset x86_32_regsets[] = {
        [REGSET_GENERAL] = {
                .core_note_type = NT_PRSTATUS,
                .n = sizeof(struct user_regs_struct32) / sizeof(u32),
                .size = sizeof(u32), .align = sizeof(u32),
                .get = genregs32_get, .set = genregs32_set
        },
        [REGSET_FP] = {
                .core_note_type = NT_PRFPREG,
                .n = sizeof(struct user_i387_ia32_struct) / sizeof(u32),
                .size = sizeof(u32), .align = sizeof(u32),
                .active = fpregs_active, .get = fpregs_get, .set = fpregs_set
        },
        [REGSET_XFP] = {
                .core_note_type = NT_PRXFPREG,
                .n = sizeof(struct user32_fxsr_struct) / sizeof(u32),
                .size = sizeof(u32), .align = sizeof(u32),
                .active = xfpregs_active, .get = xfpregs_get, .set = xfpregs_set
        },
        [REGSET_TLS] = {
                .core_note_type = NT_386_TLS,
                .n = GDT_ENTRY_TLS_ENTRIES, .bias = GDT_ENTRY_TLS_MIN,
                .size = sizeof(struct user_desc),
                .align = sizeof(struct user_desc),
                .active = regset_tls_active,
                .get = regset_tls_get, .set = regset_tls_set
        },
};

static const struct user_regset_view user_x86_32_view = {
        .name = "i386", .e_machine = EM_386,
        .regsets = x86_32_regsets, .n = ARRAY_SIZE(x86_32_regsets)
};
#endif

const struct user_regset_view *task_user_regset_view(struct task_struct *task)
{
#ifdef CONFIG_IA32_EMULATION
        if (test_tsk_thread_flag(task, TIF_IA32))
#endif
#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION
                return &user_x86_32_view;
#endif
#ifdef CONFIG_X86_64
        return &user_x86_64_view;
#endif
}

#ifdef CONFIG_X86_32

void send_sigtrap(struct task_struct *tsk, struct pt_regs *regs, int error_code)
{
        struct siginfo info;

        tsk->thread.trap_no = 1;
        tsk->thread.error_code = error_code;

        memset(&info, 0, sizeof(info));
        info.si_signo = SIGTRAP;
        info.si_code = TRAP_BRKPT;

        /* User-mode ip? */
        info.si_addr = user_mode_vm(regs) ? (void __user *) regs->ip : NULL;

        /* Send us the fake SIGTRAP */
        force_sig_info(SIGTRAP, &info, tsk);
}

/* notification of system call entry/exit
 * - triggered by current->work.syscall_trace
 */
int do_syscall_trace(struct pt_regs *regs, int entryexit)
{
        int is_sysemu = test_thread_flag(TIF_SYSCALL_EMU);
        /*
         * With TIF_SYSCALL_EMU set we want to ignore TIF_SINGLESTEP for syscall
         * interception
         */
        int is_singlestep = !is_sysemu && test_thread_flag(TIF_SINGLESTEP);
        int ret = 0;

        /* do the secure computing check first */
        if (!entryexit)
                secure_computing(regs->orig_ax);

        if (unlikely(current->audit_context)) {
                if (entryexit)
                        audit_syscall_exit(AUDITSC_RESULT(regs->ax),
                                                regs->ax);
                /* Debug traps, when using PTRACE_SINGLESTEP, must be sent only
                 * on the syscall exit path. Normally, when TIF_SYSCALL_AUDIT is
                 * not used, entry.S will call us only on syscall exit, not
                 * entry; so when TIF_SYSCALL_AUDIT is used we must avoid
                 * calling send_sigtrap() on syscall entry.
                 *
                 * Note that when PTRACE_SYSEMU_SINGLESTEP is used,
                 * is_singlestep is false, despite his name, so we will still do
                 * the correct thing.
                 */
                else if (is_singlestep)
                        goto out;
        }

        if (!(current->ptrace & PT_PTRACED))
                goto out;

        /* If a process stops on the 1st tracepoint with SYSCALL_TRACE
         * and then is resumed with SYSEMU_SINGLESTEP, it will come in
         * here. We have to check this and return */
        if (is_sysemu && entryexit)
                return 0;

        /* Fake a debug trap */
        if (is_singlestep)
                send_sigtrap(current, regs, 0);

        if (!test_thread_flag(TIF_SYSCALL_TRACE) && !is_sysemu)
                goto out;

        /* the 0x80 provides a way for the tracing parent to distinguish
           between a syscall stop and SIGTRAP delivery */
        /* Note that the debugger could change the result of test_thread_flag!*/
        ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD) ? 0x80:0));

        /*
         * this isn't the same as continuing with a signal, but it will do
         * for normal use.  strace only continues with a signal if the
         * stopping signal is not SIGTRAP.  -brl
         */
        if (current->exit_code) {
                send_sig(current->exit_code, current, 1);
                current->exit_code = 0;
        }
        ret = is_sysemu;
out:
        if (unlikely(current->audit_context) && !entryexit)
                audit_syscall_entry(AUDIT_ARCH_I386, regs->orig_ax,
                                    regs->bx, regs->cx, regs->dx, regs->si);
        if (ret == 0)
                return 0;

        regs->orig_ax = -1; /* force skip of syscall restarting */
        if (unlikely(current->audit_context))
                audit_syscall_exit(AUDITSC_RESULT(regs->ax), regs->ax);
        return 1;
}

#else  /* CONFIG_X86_64 */

static void syscall_trace(struct pt_regs *regs)
{

#if 0
        printk("trace %s ip %lx sp %lx ax %d origrax %d caller %lx tiflags %x ptrace %x\n",
               current->comm,
               regs->ip, regs->sp, regs->ax, regs->orig_ax, __builtin_return_address(0),
               current_thread_info()->flags, current->ptrace);
#endif

        ptrace_notify(SIGTRAP | ((current->ptrace & PT_TRACESYSGOOD)
                                ? 0x80 : 0));
        /*
         * this isn't the same as continuing with a signal, but it will do
         * for normal use.  strace only continues with a signal if the
         * stopping signal is not SIGTRAP.  -brl
         */
        if (current->exit_code) {
                send_sig(current->exit_code, current, 1);
                current->exit_code = 0;
        }
}

asmlinkage void syscall_trace_enter(struct pt_regs *regs)
{
        /* do the secure computing check first */
        secure_computing(regs->orig_ax);

        if (test_thread_flag(TIF_SYSCALL_TRACE)
            && (current->ptrace & PT_PTRACED))
                syscall_trace(regs);

        if (unlikely(current->audit_context)) {
                if (test_thread_flag(TIF_IA32)) {
                        audit_syscall_entry(AUDIT_ARCH_I386,
                                            regs->orig_ax,
                                            regs->bx, regs->cx,
                                            regs->dx, regs->si);
                } else {
                        audit_syscall_entry(AUDIT_ARCH_X86_64,
                                            regs->orig_ax,
                                            regs->di, regs->si,
                                            regs->dx, regs->r10);
                }
        }
}

asmlinkage void syscall_trace_leave(struct pt_regs *regs)
{
        if (unlikely(current->audit_context))
                audit_syscall_exit(AUDITSC_RESULT(regs->ax), regs->ax);

        if ((test_thread_flag(TIF_SYSCALL_TRACE)
             || test_thread_flag(TIF_SINGLESTEP))
            && (current->ptrace & PT_PTRACED))
                syscall_trace(regs);
}

#endif  /* CONFIG_X86_32 */