1 files changed, 314 insertions, 378 deletions

diff --git a/arch/x86/kernel/ds.c b/arch/x86/kernel/ds.c
index a2d1176c38ee..19a8c2c0389f 100644
--- a/arch/x86/kernel/ds.c
+++ b/arch/x86/kernel/ds.c
@@ -7,13 +7,12 @@
  *
  * It manages:
  * - per-thread and per-cpu allocation of BTS and PEBS
- * - buffer memory allocation (optional)
- * - buffer overflow handling
+ * - buffer overflow handling (to be done)
  * - buffer access
  *
  * It assumes:
- * - get_task_struct on all parameter tasks
- * - current is allowed to trace parameter tasks
+ * - get_task_struct on all traced tasks
+ * - current is allowed to trace tasks
  *
  *
  * Copyright (C) 2007-2008 Intel Corporation.
@@ -28,6 +27,7 @@
 #include <linux/slab.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
+#include <linux/kernel.h>
 
 
 /*
@@ -44,6 +44,33 @@ struct ds_configuration {
 };
 static struct ds_configuration ds_cfg;
 
+/*
+ * A BTS or PEBS tracer.
+ *
+ * This holds the configuration of the tracer and serves as a handle
+ * to identify tracers.
+ */
+struct ds_tracer {
+        /* the DS context (partially) owned by this tracer */
+        struct ds_context *context;
+        /* the buffer provided on ds_request() and its size in bytes */
+        void *buffer;
+        size_t size;
+};
+
+struct bts_tracer {
+        /* the common DS part */
+        struct ds_tracer ds;
+        /* buffer overflow notification function */
+        bts_ovfl_callback_t ovfl;
+};
+
+struct pebs_tracer {
+        /* the common DS part */
+        struct ds_tracer ds;
+        /* buffer overflow notification function */
+        pebs_ovfl_callback_t ovfl;
+};
 
 /*
  * Debug Store (DS) save area configuration (see Intel64 and IA32
@@ -107,34 +134,13 @@ static inline void ds_set(unsigned char *base, enum ds_qualifier qual,
         (*(unsigned long *)base) = value;
 }
 
+#define DS_ALIGNMENT (1 << 3)   /* BTS and PEBS buffer alignment */
 
-/*
- * Locking is done only for allocating BTS or PEBS resources and for
- * guarding context and buffer memory allocation.
- *
- * Most functions require the current task to own the ds context part
- * they are going to access. All the locking is done when validating
- * access to the context.
- */
-static spinlock_t ds_lock = __SPIN_LOCK_UNLOCKED(ds_lock);
 
 /*
- * Validate that the current task is allowed to access the BTS/PEBS
- * buffer of the parameter task.
- *
- * Returns 0, if access is granted; -Eerrno, otherwise.
+ * Locking is done only for allocating BTS or PEBS resources.
  */
-static inline int ds_validate_access(struct ds_context *context,
-                                     enum ds_qualifier qual)
-{
-        if (!context)
-                return -EPERM;
-
-        if (context->owner[qual] == current)
-                return 0;
-
-        return -EPERM;
-}
+static spinlock_t ds_lock = __SPIN_LOCK_UNLOCKED(ds_lock);
 
 
 /*
@@ -183,51 +189,13 @@ static inline int check_tracer(struct task_struct *task)
  *
  * Contexts are use-counted. They are allocated on first access and
  * deallocated when the last user puts the context.
- *
- * We distinguish between an allocating and a non-allocating get of a
- * context:
- * - the allocating get is used for requesting BTS/PEBS resources. It
- *   requires the caller to hold the global ds_lock.
- * - the non-allocating get is used for all other cases. A
- *   non-existing context indicates an error. It acquires and releases
- *   the ds_lock itself for obtaining the context.
- *
- * A context and its DS configuration are allocated and deallocated
- * together. A context always has a DS configuration of the
- * appropriate size.
  */
 static DEFINE_PER_CPU(struct ds_context *, system_context);
 
 #define this_system_context per_cpu(system_context, smp_processor_id())
 
-/*
- * Returns the pointer to the parameter task's context or to the
- * system-wide context, if task is NULL.
- *
- * Increases the use count of the returned context, if not NULL.
- */
 static inline struct ds_context *ds_get_context(struct task_struct *task)
 {
-        struct ds_context *context;
-        unsigned long irq;
-
-        spin_lock_irqsave(&ds_lock, irq);
-
-        context = (task ? task->thread.ds_ctx : this_system_context);
-        if (context)
-                context->count++;
-
-        spin_unlock_irqrestore(&ds_lock, irq);
-
-        return context;
-}
-
-/*
- * Same as ds_get_context, but allocates the context and it's DS
- * structure, if necessary; returns NULL; if out of memory.
- */
-static inline struct ds_context *ds_alloc_context(struct task_struct *task)
-{
         struct ds_context **p_context =
                 (task ? &task->thread.ds_ctx : &this_system_context);
         struct ds_context *context = *p_context;
@@ -238,16 +206,9 @@ static inline struct ds_context *ds_alloc_context(struct task_struct *task)
                 if (!context)
                         return NULL;
 
-                context->ds = kzalloc(ds_cfg.sizeof_ds, GFP_KERNEL);
-                if (!context->ds) {
-                        kfree(context);
-                        return NULL;
-                }
-
                 spin_lock_irqsave(&ds_lock, irq);
 
                 if (*p_context) {
-                        kfree(context->ds);
                         kfree(context);
 
                         context = *p_context;
@@ -272,10 +233,6 @@ static inline struct ds_context *ds_alloc_context(struct task_struct *task)
         return context;
 }
 
-/*
- * Decreases the use count of the parameter context, if not NULL.
- * Deallocates the context, if the use count reaches zero.
- */
 static inline void ds_put_context(struct ds_context *context)
 {
         unsigned long irq;
@@ -296,13 +253,6 @@ static inline void ds_put_context(struct ds_context *context)
         if (!context->task || (context->task == current))
                 wrmsrl(MSR_IA32_DS_AREA, 0);
 
-        put_tracer(context->task);
-
-        /* free any leftover buffers from tracers that did not
-         * deallocate them properly. */
-        kfree(context->buffer[ds_bts]);
-        kfree(context->buffer[ds_pebs]);
-        kfree(context->ds);
         kfree(context);
  out:
         spin_unlock_irqrestore(&ds_lock, irq);
@@ -312,345 +262,342 @@ static inline void ds_put_context(struct ds_context *context)
 /*
  * Handle a buffer overflow
  *
- * task: the task whose buffers are overflowing;
- *       NULL for a buffer overflow on the current cpu
  * context: the ds context
  * qual: the buffer type
  */
-static void ds_overflow(struct task_struct *task, struct ds_context *context,
-                        enum ds_qualifier qual)
-{
-        if (!context)
-                return;
-
-        if (context->callback[qual])
-                (*context->callback[qual])(task);
-
-        /* todo: do some more overflow handling */
+static void ds_overflow(struct ds_context *context, enum ds_qualifier qual)
+{
+        switch (qual) {
+        case ds_bts: {
+                struct bts_tracer *tracer =
+                        container_of(context->owner[qual],
+                                     struct bts_tracer, ds);
+                if (tracer->ovfl)
+                        tracer->ovfl(tracer);
+        }
+                break;
+        case ds_pebs: {
+                struct pebs_tracer *tracer =
+                        container_of(context->owner[qual],
+                                     struct pebs_tracer, ds);
+                if (tracer->ovfl)
+                        tracer->ovfl(tracer);
+        }
+                break;
+        }
 }
 
 
-/*
- * Allocate a non-pageable buffer of the parameter size.
- * Checks the memory and the locked memory rlimit.
- *
- * Returns the buffer, if successful;
- *         NULL, if out of memory or rlimit exceeded.
- *
- * size: the requested buffer size in bytes
- * pages (out): if not NULL, contains the number of pages reserved
- */
-static inline void *ds_allocate_buffer(size_t size, unsigned int *pages)
+static void ds_install_ds_config(struct ds_context *context,
+                                 enum ds_qualifier qual,
+                                 void *base, size_t size, size_t ith)
 {
-        unsigned long rlim, vm, pgsz;
-        void *buffer;
-
-        pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
-
-        rlim = current->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
-        vm   = current->mm->total_vm  + pgsz;
-        if (rlim < vm)
-                return NULL;
+        unsigned long buffer, adj;
 
-        rlim = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
-        vm   = current->mm->locked_vm  + pgsz;
-        if (rlim < vm)
-                return NULL;
+        /* adjust the buffer address and size to meet alignment
+         * constraints:
+         * - buffer is double-word aligned
+         * - size is multiple of record size
+         *
+         * We checked the size at the very beginning; we have enough
+         * space to do the adjustment.
+         */
+        buffer = (unsigned long)base;
 
-        buffer = kzalloc(size, GFP_KERNEL);
-        if (!buffer)
-                return NULL;
+        adj = ALIGN(buffer, DS_ALIGNMENT) - buffer;
+        buffer += adj;
+        size   -= adj;
 
-        current->mm->total_vm  += pgsz;
-        current->mm->locked_vm += pgsz;
+        size /= ds_cfg.sizeof_rec[qual];
+        size *= ds_cfg.sizeof_rec[qual];
 
-        if (pages)
-                *pages = pgsz;
+        ds_set(context->ds, qual, ds_buffer_base, buffer);
+        ds_set(context->ds, qual, ds_index, buffer);
+        ds_set(context->ds, qual, ds_absolute_maximum, buffer + size);
 
-        return buffer;
+        /* The value for 'no threshold' is -1, which will set the
+         * threshold outside of the buffer, just like we want it.
+         */
+        ds_set(context->ds, qual,
+               ds_interrupt_threshold, buffer + size - ith);
 }
 
-static int ds_request(struct task_struct *task, void *base, size_t size,
-                      ds_ovfl_callback_t ovfl, enum ds_qualifier qual)
+static int ds_request(struct ds_tracer *tracer, enum ds_qualifier qual,
+                      struct task_struct *task,
+                      void *base, size_t size, size_t th)
 {
         struct ds_context *context;
-        unsigned long buffer, adj;
-        const unsigned long alignment = (1 << 3);
         unsigned long irq;
-        int error = 0;
+        int error;
 
+        error = -EOPNOTSUPP;
         if (!ds_cfg.sizeof_ds)
-                return -EOPNOTSUPP;
+                goto out;
+
+        error = -EINVAL;
+        if (!base)
+                goto out;
 
         /* we require some space to do alignment adjustments below */
-        if (size < (alignment + ds_cfg.sizeof_rec[qual]))
-                return -EINVAL;
+        error = -EINVAL;
+        if (size < (DS_ALIGNMENT + ds_cfg.sizeof_rec[qual]))
+                goto out;
 
-        /* buffer overflow notification is not yet implemented */
-        if (ovfl)
-                return -EOPNOTSUPP;
+        if (th != (size_t)-1) {
+                th *= ds_cfg.sizeof_rec[qual];
+
+                error = -EINVAL;
+                if (size <= th)
+                        goto out;
+        }
 
+        tracer->buffer = base;
+        tracer->size = size;
 
-        context = ds_alloc_context(task);
+        error = -ENOMEM;
+        context = ds_get_context(task);
         if (!context)
-                return -ENOMEM;
+                goto out;
+        tracer->context = context;
+
 
         spin_lock_irqsave(&ds_lock, irq);
 
         error = -EPERM;
         if (!check_tracer(task))
                 goto out_unlock;
-
         get_tracer(task);
 
-        error = -EALREADY;
-        if (context->owner[qual] == current)
-                goto out_put_tracer;
         error = -EPERM;
-        if (context->owner[qual] != NULL)
+        if (context->owner[qual])
                 goto out_put_tracer;
-        context->owner[qual] = current;
+        context->owner[qual] = tracer;
 
         spin_unlock_irqrestore(&ds_lock, irq);
 
 
-        error = -ENOMEM;
-        if (!base) {
-                base = ds_allocate_buffer(size, &context->pages[qual]);
-                if (!base)
-                        goto out_release;
-
-                context->buffer[qual]   = base;
-        }
-        error = 0;
+        ds_install_ds_config(context, qual, base, size, th);
 
-        context->callback[qual] = ovfl;
-
-        /* adjust the buffer address and size to meet alignment
-         * constraints:
-         * - buffer is double-word aligned
-         * - size is multiple of record size
-         *
-         * We checked the size at the very beginning; we have enough
-         * space to do the adjustment.
-         */
-        buffer = (unsigned long)base;
-
-        adj = ALIGN(buffer, alignment) - buffer;
-        buffer += adj;
-        size   -= adj;
-
-        size /= ds_cfg.sizeof_rec[qual];
-        size *= ds_cfg.sizeof_rec[qual];
-
-        ds_set(context->ds, qual, ds_buffer_base, buffer);
-        ds_set(context->ds, qual, ds_index, buffer);
-        ds_set(context->ds, qual, ds_absolute_maximum, buffer + size);
-
-        if (ovfl) {
-                /* todo: select a suitable interrupt threshold */
-        } else
-                ds_set(context->ds, qual,
-                       ds_interrupt_threshold, buffer + size + 1);
-
-        /* we keep the context until ds_release */
-        return error;
-
- out_release:
-        context->owner[qual] = NULL;
-        ds_put_context(context);
-        put_tracer(task);
-        return error;
+        return 0;
 
  out_put_tracer:
-        spin_unlock_irqrestore(&ds_lock, irq);
-        ds_put_context(context);
         put_tracer(task);
-        return error;
-
  out_unlock:
         spin_unlock_irqrestore(&ds_lock, irq);
         ds_put_context(context);
+        tracer->context = NULL;
+ out:
         return error;
 }
 
-int ds_request_bts(struct task_struct *task, void *base, size_t size,
-                   ds_ovfl_callback_t ovfl)
+struct bts_tracer *ds_request_bts(struct task_struct *task,
+                                  void *base, size_t size,
+                                  bts_ovfl_callback_t ovfl, size_t th)
 {
-        return ds_request(task, base, size, ovfl, ds_bts);
-}
+        struct bts_tracer *tracer;
+        int error;
 
-int ds_request_pebs(struct task_struct *task, void *base, size_t size,
-                    ds_ovfl_callback_t ovfl)
-{
-        return ds_request(task, base, size, ovfl, ds_pebs);
+        /* buffer overflow notification is not yet implemented */
+        error = -EOPNOTSUPP;
+        if (ovfl)
+                goto out;
+
+        error = -ENOMEM;
+        tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
+        if (!tracer)
+                goto out;
+        tracer->ovfl = ovfl;
+
+        error = ds_request(&tracer->ds, ds_bts, task, base, size, th);
+        if (error < 0)
+                goto out_tracer;
+
+        return tracer;
+
+ out_tracer:
+        kfree(tracer);
+ out:
+        return ERR_PTR(error);
 }
 
-static int ds_release(struct task_struct *task, enum ds_qualifier qual)
+struct pebs_tracer *ds_request_pebs(struct task_struct *task,
+                                    void *base, size_t size,
+                                    pebs_ovfl_callback_t ovfl, size_t th)
 {
-        struct ds_context *context;
+        struct pebs_tracer *tracer;
         int error;
 
-        context = ds_get_context(task);
-        error = ds_validate_access(context, qual);
-        if (error < 0)
+        /* buffer overflow notification is not yet implemented */
+        error = -EOPNOTSUPP;
+        if (ovfl)
                 goto out;
 
-        kfree(context->buffer[qual]);
-        context->buffer[qual] = NULL;
+        error = -ENOMEM;
+        tracer = kzalloc(sizeof(*tracer), GFP_KERNEL);
+        if (!tracer)
+                goto out;
+        tracer->ovfl = ovfl;
 
-        current->mm->total_vm  -= context->pages[qual];
-        current->mm->locked_vm -= context->pages[qual];
-        context->pages[qual] = 0;
-        context->owner[qual] = NULL;
+        error = ds_request(&tracer->ds, ds_pebs, task, base, size, th);
+        if (error < 0)
+                goto out_tracer;
 
-        /*
-         * we put the context twice:
-         *   once for the ds_get_context
-         *   once for the corresponding ds_request
-         */
-        ds_put_context(context);
+        return tracer;
+
+ out_tracer:
+        kfree(tracer);
  out:
-        ds_put_context(context);
-        return error;
+        return ERR_PTR(error);
 }
 
-int ds_release_bts(struct task_struct *task)
+static void ds_release(struct ds_tracer *tracer, enum ds_qualifier qual)
 {
-        return ds_release(task, ds_bts);
+        BUG_ON(tracer->context->owner[qual] != tracer);
+        tracer->context->owner[qual] = NULL;
+
+        put_tracer(tracer->context->task);
+        ds_put_context(tracer->context);
 }
 
-int ds_release_pebs(struct task_struct *task)
+int ds_release_bts(struct bts_tracer *tracer)
 {
-        return ds_release(task, ds_pebs);
+        if (!tracer)
+                return -EINVAL;
+
+        ds_release(&tracer->ds, ds_bts);
+        kfree(tracer);
+
+        return 0;
 }
 
-static int ds_get_index(struct task_struct *task, size_t *pos,
-                        enum ds_qualifier qual)
+int ds_release_pebs(struct pebs_tracer *tracer)
 {
-        struct ds_context *context;
-        unsigned long base, index;
-        int error;
+        if (!tracer)
+                return -EINVAL;
 
-        context = ds_get_context(task);
-        error = ds_validate_access(context, qual);
-        if (error < 0)
-                goto out;
+        ds_release(&tracer->ds, ds_pebs);
+        kfree(tracer);
+
+        return 0;
+}
+
+static size_t ds_get_index(struct ds_context *context, enum ds_qualifier qual)
+{
+        unsigned long base, index;
 
         base  = ds_get(context->ds, qual, ds_buffer_base);
         index = ds_get(context->ds, qual, ds_index);
 
-        error = ((index - base) / ds_cfg.sizeof_rec[qual]);
-        if (pos)
-                *pos = error;
- out:
-        ds_put_context(context);
-        return error;
+        return (index - base) / ds_cfg.sizeof_rec[qual];
 }
 
-int ds_get_bts_index(struct task_struct *task, size_t *pos)
+int ds_get_bts_index(struct bts_tracer *tracer, size_t *pos)
 {
-        return ds_get_index(task, pos, ds_bts);
+        if (!tracer)
+                return -EINVAL;
+
+        if (!pos)
+                return -EINVAL;
+
+        *pos = ds_get_index(tracer->ds.context, ds_bts);
+
+        return 0;
 }
 
-int ds_get_pebs_index(struct task_struct *task, size_t *pos)
+int ds_get_pebs_index(struct pebs_tracer *tracer, size_t *pos)
 {
-        return ds_get_index(task, pos, ds_pebs);
+        if (!tracer)
+                return -EINVAL;
+
+        if (!pos)
+                return -EINVAL;
+
+        *pos = ds_get_index(tracer->ds.context, ds_pebs);
+
+        return 0;
 }
 
-static int ds_get_end(struct task_struct *task, size_t *pos,
-                      enum ds_qualifier qual)
+static size_t ds_get_end(struct ds_context *context, enum ds_qualifier qual)
 {
-        struct ds_context *context;
-        unsigned long base, end;
-        int error;
-
-        context = ds_get_context(task);
-        error = ds_validate_access(context, qual);
-        if (error < 0)
-                goto out;
+        unsigned long base, max;
 
         base = ds_get(context->ds, qual, ds_buffer_base);
-        end  = ds_get(context->ds, qual, ds_absolute_maximum);
+        max  = ds_get(context->ds, qual, ds_absolute_maximum);
 
-        error = ((end - base) / ds_cfg.sizeof_rec[qual]);
-        if (pos)
-                *pos = error;
- out:
-        ds_put_context(context);
-        return error;
+        return (max - base) / ds_cfg.sizeof_rec[qual];
 }
 
-int ds_get_bts_end(struct task_struct *task, size_t *pos)
+int ds_get_bts_end(struct bts_tracer *tracer, size_t *pos)
 {
-        return ds_get_end(task, pos, ds_bts);
+        if (!tracer)
+                return -EINVAL;
+
+        if (!pos)
+                return -EINVAL;
+
+        *pos = ds_get_end(tracer->ds.context, ds_bts);
+
+        return 0;
 }
 
-int ds_get_pebs_end(struct task_struct *task, size_t *pos)
+int ds_get_pebs_end(struct pebs_tracer *tracer, size_t *pos)
 {
-        return ds_get_end(task, pos, ds_pebs);
+        if (!tracer)
+                return -EINVAL;
+
+        if (!pos)
+                return -EINVAL;
+
+        *pos = ds_get_end(tracer->ds.context, ds_pebs);
+
+        return 0;
 }
 
-static int ds_access(struct task_struct *task, size_t index,
-                     const void **record, enum ds_qualifier qual)
+static int ds_access(struct ds_context *context, enum ds_qualifier qual,
+                     size_t index, const void **record)
 {
-        struct ds_context *context;
         unsigned long base, idx;
-        int error;
 
         if (!record)
                 return -EINVAL;
 
-        context = ds_get_context(task);
-        error = ds_validate_access(context, qual);
-        if (error < 0)
-                goto out;
-
         base = ds_get(context->ds, qual, ds_buffer_base);
         idx = base + (index * ds_cfg.sizeof_rec[qual]);
 
-        error = -EINVAL;
         if (idx > ds_get(context->ds, qual, ds_absolute_maximum))
-                goto out;
+                return -EINVAL;
 
         *record = (const void *)idx;
-        error = ds_cfg.sizeof_rec[qual];
- out:
-        ds_put_context(context);
-        return error;
+
+        return ds_cfg.sizeof_rec[qual];
 }
 
-int ds_access_bts(struct task_struct *task, size_t index, const void **record)
+int ds_access_bts(struct bts_tracer *tracer, size_t index,
+                  const void **record)
 {
-        return ds_access(task, index, record, ds_bts);
+        if (!tracer)
+                return -EINVAL;
+
+        return ds_access(tracer->ds.context, ds_bts, index, record);
 }
 
-int ds_access_pebs(struct task_struct *task, size_t index, const void **record)
+int ds_access_pebs(struct pebs_tracer *tracer, size_t index,
+                   const void **record)
 {
-        return ds_access(task, index, record, ds_pebs);
+        if (!tracer)
+                return -EINVAL;
+
+        return ds_access(tracer->ds.context, ds_pebs, index, record);
 }
 
-static int ds_write(struct task_struct *task, const void *record, size_t size,
-                    enum ds_qualifier qual, int force)
+static int ds_write(struct ds_context *context, enum ds_qualifier qual,
+                    const void *record, size_t size)
 {
-        struct ds_context *context;
-        int error;
+        int bytes_written = 0;
 
         if (!record)
                 return -EINVAL;
 
-        error = -EPERM;
-        context = ds_get_context(task);
-        if (!context)
-                goto out;
-
-        if (!force) {
-                error = ds_validate_access(context, qual);
-                if (error < 0)
-                        goto out;
-        }
-
-        error = 0;
         while (size) {
                 unsigned long base, index, end, write_end, int_th;
                 unsigned long write_size, adj_write_size;
@@ -678,14 +625,14 @@ static int ds_write(struct task_struct *task, const void *record, size_t size,
                         write_end = end;
 
                 if (write_end <= index)
-                        goto out;
+                        break;
 
                 write_size = min((unsigned long) size, write_end - index);
                 memcpy((void *)index, record, write_size);
 
                 record = (const char *)record + write_size;
-                size  -= write_size;
-                error += write_size;
+                size -= write_size;
+                bytes_written += write_size;
 
                 adj_write_size = write_size / ds_cfg.sizeof_rec[qual];
                 adj_write_size *= ds_cfg.sizeof_rec[qual];
@@ -700,47 +647,32 @@ static int ds_write(struct task_struct *task, const void *record, size_t size,
                 ds_set(context->ds, qual, ds_index, index);
 
                 if (index >= int_th)
-                        ds_overflow(task, context, qual);
+                        ds_overflow(context, qual);
         }
 
- out:
-        ds_put_context(context);
-        return error;
+        return bytes_written;
 }
 
-int ds_write_bts(struct task_struct *task, const void *record, size_t size)
+int ds_write_bts(struct bts_tracer *tracer, const void *record, size_t size)
 {
-        return ds_write(task, record, size, ds_bts, /* force = */ 0);
-}
+        if (!tracer)
+                return -EINVAL;
 
-int ds_write_pebs(struct task_struct *task, const void *record, size_t size)
-{
-        return ds_write(task, record, size, ds_pebs, /* force = */ 0);
+        return ds_write(tracer->ds.context, ds_bts, record, size);
 }
 
-int ds_unchecked_write_bts(struct task_struct *task,
-                           const void *record, size_t size)
+int ds_write_pebs(struct pebs_tracer *tracer, const void *record, size_t size)
 {
-        return ds_write(task, record, size, ds_bts, /* force = */ 1);
-}
+        if (!tracer)
+                return -EINVAL;
 
-int ds_unchecked_write_pebs(struct task_struct *task,
-                            const void *record, size_t size)
-{
-        return ds_write(task, record, size, ds_pebs, /* force = */ 1);
+        return ds_write(tracer->ds.context, ds_pebs, record, size);
 }
 
-static int ds_reset_or_clear(struct task_struct *task,
-                             enum ds_qualifier qual, int clear)
+static void ds_reset_or_clear(struct ds_context *context,
+                              enum ds_qualifier qual, int clear)
 {
-        struct ds_context *context;
         unsigned long base, end;
-        int error;
-
-        context = ds_get_context(task);
-        error = ds_validate_access(context, qual);
-        if (error < 0)
-                goto out;
 
         base = ds_get(context->ds, qual, ds_buffer_base);
         end  = ds_get(context->ds, qual, ds_absolute_maximum);
@@ -749,70 +681,69 @@ static int ds_reset_or_clear(struct task_struct *task,
                 memset((void *)base, 0, end - base);
 
         ds_set(context->ds, qual, ds_index, base);
-
-        error = 0;
- out:
-        ds_put_context(context);
-        return error;
 }
 
-int ds_reset_bts(struct task_struct *task)
+int ds_reset_bts(struct bts_tracer *tracer)
 {
-        return ds_reset_or_clear(task, ds_bts, /* clear = */ 0);
+        if (!tracer)
+                return -EINVAL;
+
+        ds_reset_or_clear(tracer->ds.context, ds_bts, /* clear = */ 0);
+
+        return 0;
 }
 
-int ds_reset_pebs(struct task_struct *task)
+int ds_reset_pebs(struct pebs_tracer *tracer)
 {
-        return ds_reset_or_clear(task, ds_pebs, /* clear = */ 0);
+        if (!tracer)
+                return -EINVAL;
+
+        ds_reset_or_clear(tracer->ds.context, ds_pebs, /* clear = */ 0);
+
+        return 0;
 }
 
-int ds_clear_bts(struct task_struct *task)
+int ds_clear_bts(struct bts_tracer *tracer)
 {
-        return ds_reset_or_clear(task, ds_bts, /* clear = */ 1);
+        if (!tracer)
+                return -EINVAL;
+
+        ds_reset_or_clear(tracer->ds.context, ds_bts, /* clear = */ 1);
+
+        return 0;
 }
 
-int ds_clear_pebs(struct task_struct *task)
+int ds_clear_pebs(struct pebs_tracer *tracer)
 {
-        return ds_reset_or_clear(task, ds_pebs, /* clear = */ 1);
+        if (!tracer)
+                return -EINVAL;
+
+        ds_reset_or_clear(tracer->ds.context, ds_pebs, /* clear = */ 1);
+
+        return 0;
 }
 
-int ds_get_pebs_reset(struct task_struct *task, u64 *value)
+int ds_get_pebs_reset(struct pebs_tracer *tracer, u64 *value)
 {
-        struct ds_context *context;
-        int error;
+        if (!tracer)
+                return -EINVAL;
 
         if (!value)
                 return -EINVAL;
 
-        context = ds_get_context(task);
-        error = ds_validate_access(context, ds_pebs);
-        if (error < 0)
-                goto out;
+        *value = *(u64 *)(tracer->ds.context->ds + (ds_cfg.sizeof_field * 8));
 
-        *value = *(u64 *)(context->ds + (ds_cfg.sizeof_field * 8));
-
-        error = 0;
- out:
-        ds_put_context(context);
-        return error;
+        return 0;
 }
 
-int ds_set_pebs_reset(struct task_struct *task, u64 value)
+int ds_set_pebs_reset(struct pebs_tracer *tracer, u64 value)
 {
-        struct ds_context *context;
-        int error;
-
-        context = ds_get_context(task);
-        error = ds_validate_access(context, ds_pebs);
-        if (error < 0)
-                goto out;
+        if (!tracer)
+                return -EINVAL;
 
-        *(u64 *)(context->ds + (ds_cfg.sizeof_field * 8)) = value;
+        *(u64 *)(tracer->ds.context->ds + (ds_cfg.sizeof_field * 8)) = value;
 
-        error = 0;
- out:
-        ds_put_context(context);
-        return error;
+        return 0;
 }
 
 static const struct ds_configuration ds_cfg_var = {
@@ -840,6 +771,10 @@ static inline void
 ds_configure(const struct ds_configuration *cfg)
 {
         ds_cfg = *cfg;
+
+        printk(KERN_INFO "DS available\n");
+
+        BUG_ON(MAX_SIZEOF_DS < ds_cfg.sizeof_ds);
 }
 
 void __cpuinit ds_init_intel(struct cpuinfo_x86 *c)
@@ -847,17 +782,16 @@ void __cpuinit ds_init_intel(struct cpuinfo_x86 *c)
         switch (c->x86) {
         case 0x6:
                 switch (c->x86_model) {
+                case 0 ... 0xC:
+                        /* sorry, don't know about them */
+                        break;
                 case 0xD:
                 case 0xE: /* Pentium M */
                         ds_configure(&ds_cfg_var);
                         break;
-                case 0xF: /* Core2 */
-                case 0x1C: /* Atom */
+                default: /* Core2, Atom, ... */
                         ds_configure(&ds_cfg_64);
                         break;
-                default:
-                        /* sorry, don't know about them */
-                        break;
                 }
                 break;
         case 0xF:
@@ -884,6 +818,8 @@ void ds_free(struct ds_context *context)
          * is dying. There should not be any user of that context left
          * to disturb us, anymore. */
         unsigned long leftovers = context->count;
-        while (leftovers--)
+        while (leftovers--) {
+                put_tracer(context->task);
                 ds_put_context(context);
+        }
 }