x86, ptrace: support for branch trace store(BTS)

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Changes to the last version:
- split implementation into two layers: ds/bts and ptrace
- renamed TIF's
- save/restore ds save area msr in __switch_to_xtra()
- make block-stepping only look at BTF bit

Signed-off-by: Markus Metzger <markus.t.metzger@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 212 insertions, 0 deletions

diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
index 3399c1be79b8..8d0dd8b5effe 100644
--- a/arch/x86/kernel/ptrace.c
+++ b/arch/x86/kernel/ptrace.c
@@ -2,6 +2,9 @@
 /*
  * 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>
@@ -26,6 +29,14 @@
 #include <asm/desc.h>
 #include <asm/prctl.h>
 #include <asm/proto.h>
+#include <asm/ds.h>
+
+
+/*
+ * The maximal size of a BTS buffer per traced task in number of BTS
+ * records.
+ */
+#define PTRACE_BTS_BUFFER_MAX 4000
 
 /*
  * does not yet catch signals sent when the child dies.
@@ -455,6 +466,165 @@ static int ptrace_set_debugreg(struct task_struct *child,
         return 0;
 }
 
+static int ptrace_bts_max_buffer_size(void)
+{
+        return PTRACE_BTS_BUFFER_MAX;
+}
+
+static int ptrace_bts_get_buffer_size(struct task_struct *child)
+{
+        if (!child->thread.ds_area_msr)
+                return -ENXIO;
+
+        return ds_get_bts_size((void *)child->thread.ds_area_msr);
+}
+
+static int ptrace_bts_get_index(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;
+
+        if (!child->thread.ds_area_msr)
+                return -ENXIO;
+
+        retval = ds_read_bts((void *)child->thread.ds_area_msr,
+                             index, &ret);
+        if (retval)
+                return retval;
+
+        if (copy_to_user(out, &ret, sizeof(ret)))
+                return -EFAULT;
+
+        return sizeof(ret);
+}
+
+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_config(struct task_struct *child,
+                             unsigned long options)
+{
+        unsigned long debugctl_mask = ds_debugctl_mask();
+        int retval;
+
+        retval = ptrace_bts_get_buffer_size(child);
+        if (retval < 0)
+                return retval;
+        if (retval == 0)
+                return -ENXIO;
+
+        if (options & PTRACE_BTS_O_TRACE_TASK) {
+                child->thread.debugctlmsr |= debugctl_mask;
+                set_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
+        } else {
+                /* there is no way for us to check whether we 'own'
+                 * the respective bits in the DEBUGCTL MSR, we're
+                 * about to clear */
+                child->thread.debugctlmsr &= ~debugctl_mask;
+
+                if (!child->thread.debugctlmsr)
+                        clear_tsk_thread_flag(child, TIF_DEBUGCTLMSR);
+        }
+
+        if (options & PTRACE_BTS_O_TIMESTAMPS)
+                set_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
+        else
+                clear_tsk_thread_flag(child, TIF_BTS_TRACE_TS);
+
+        return 0;
+}
+
+static int ptrace_bts_status(struct task_struct *child)
+{
+        unsigned long debugctl_mask = ds_debugctl_mask();
+        int retval, status = 0;
+
+        retval = ptrace_bts_get_buffer_size(child);
+        if (retval < 0)
+                return retval;
+        if (retval == 0)
+                return -ENXIO;
+
+        if (ptrace_bts_get_buffer_size(child) <= 0)
+                return -ENXIO;
+
+        if (test_tsk_thread_flag(child, TIF_DEBUGCTLMSR) &&
+            child->thread.debugctlmsr & debugctl_mask)
+                status |= PTRACE_BTS_O_TRACE_TASK;
+        if (test_tsk_thread_flag(child, TIF_BTS_TRACE_TS))
+                status |= PTRACE_BTS_O_TIMESTAMPS;
+
+        return status;
+}
+
+static int ptrace_bts_allocate_bts(struct task_struct *child,
+                                   int size_in_records)
+{
+        int retval = 0;
+        void *ds;
+
+        if (size_in_records < 0)
+                return -EINVAL;
+
+        if (size_in_records > ptrace_bts_max_buffer_size())
+                return -EINVAL;
+
+        if (size_in_records == 0) {
+                ptrace_bts_config(child, /* options = */ 0);
+        } else {
+                retval = ds_allocate(&ds, size_in_records);
+                if (retval)
+                        return retval;
+        }
+
+        if (child->thread.ds_area_msr)
+                ds_free((void **)&child->thread.ds_area_msr);
+
+        child->thread.ds_area_msr = (unsigned long)ds;
+        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 retval;
+}
+
+void ptrace_bts_take_timestamp(struct task_struct *tsk,
+                               enum bts_qualifier qualifier)
+{
+        struct bts_struct rec = {
+                .qualifier = qualifier,
+                .variant.timestamp = sched_clock()
+        };
+
+        if (ptrace_bts_get_buffer_size(tsk) <= 0)
+                return;
+
+        ptrace_bts_write_record(tsk, &rec);
+}
+
 /*
  * Called by kernel/ptrace.c when detaching..
  *
@@ -466,6 +636,11 @@ void ptrace_disable(struct task_struct *child)
 #ifdef TIF_SYSCALL_EMU
         clear_tsk_thread_flag(child, TIF_SYSCALL_EMU);
 #endif
+        ptrace_bts_config(child, /* options = */ 0);
+        if (child->thread.ds_area_msr) {
+            ds_free((void **)&child->thread.ds_area_msr);
+            clear_tsk_thread_flag(child, TIF_DS_AREA_MSR);
+        }
 }
 
 long arch_ptrace(struct task_struct *child, long request, long addr, long data)
@@ -626,6 +801,36 @@ long arch_ptrace(struct task_struct *child, long request, long addr, long data)
                 break;
 #endif
 
+        case PTRACE_BTS_MAX_BUFFER_SIZE:
+                ret = ptrace_bts_max_buffer_size();
+                break;
+
+        case PTRACE_BTS_ALLOCATE_BUFFER:
+                ret = ptrace_bts_allocate_bts(child, data);
+                break;
+
+        case PTRACE_BTS_GET_BUFFER_SIZE:
+                ret = ptrace_bts_get_buffer_size(child);
+                break;
+
+        case PTRACE_BTS_GET_INDEX:
+                ret = ptrace_bts_get_index(child);
+                break;
+
+        case PTRACE_BTS_READ_RECORD:
+                ret = ptrace_bts_read_record
+                        (child, data,
+                         (struct bts_struct __user *) addr);
+                break;
+
+        case PTRACE_BTS_CONFIG:
+                ret = ptrace_bts_config(child, data);
+                break;
+
+        case PTRACE_BTS_STATUS:
+                ret = ptrace_bts_status(child);
+                break;
+
         default:
                 ret = ptrace_request(child, request, addr, data);
                 break;
@@ -809,6 +1014,13 @@ asmlinkage long sys32_ptrace(long request, u32 pid, u32 addr, u32 data)
         case PTRACE_SETOPTIONS:
         case PTRACE_SET_THREAD_AREA:
         case PTRACE_GET_THREAD_AREA:
+        case PTRACE_BTS_MAX_BUFFER_SIZE:
+        case PTRACE_BTS_ALLOCATE_BUFFER:
+        case PTRACE_BTS_GET_BUFFER_SIZE:
+        case PTRACE_BTS_GET_INDEX:
+        case PTRACE_BTS_READ_RECORD:
+        case PTRACE_BTS_CONFIG:
+        case PTRACE_BTS_STATUS:
                 return sys_ptrace(request, pid, addr, data);
 
         default: