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>

7 files changed, 152 insertions, 3 deletions

diff --git a/include/asm-x86/ds.h b/include/asm-x86/ds.h
new file mode 100644
index 000000000000..edd8467740a6
--- /dev/null
+++ b/include/asm-x86/ds.h
@@ -0,0 +1,65 @@
+/*
+ * Debug Store (DS) support
+ *
+ * This provides a low-level interface to the hardware's Debug Store
+ * feature that is used for last branch recording (LBR) and
+ * precise-event based sampling (PEBS).
+ *
+ * Different architectures use a different DS layout/pointer size.
+ * The below functions therefore work on a void*.
+ *
+ *
+ * Since there is no user for PEBS, yet, only LBR (or branch
+ * trace store, BTS) is supported.
+ *
+ *
+ * Copyright (C) 2007 Intel Corporation.
+ * Markus Metzger <markus.t.metzger@intel.com>, Dec 2007
+ */
+
+#ifndef _ASM_X86_DS_H
+#define _ASM_X86_DS_H
+
+#include <linux/types.h>
+#include <linux/init.h>
+
+struct cpuinfo_x86;
+
+
+/* a branch trace record entry
+ *
+ * In order to unify the interface between various processor versions,
+ * we use the below data structure for all processors.
+ */
+enum bts_qualifier {
+        BTS_INVALID = 0,
+        BTS_BRANCH,
+        BTS_TASK_ARRIVES,
+        BTS_TASK_DEPARTS
+};
+
+struct bts_struct {
+        enum bts_qualifier qualifier;
+        union {
+                /* BTS_BRANCH */
+                struct {
+                        long from_ip;
+                        long to_ip;
+                } lbr;
+                /* BTS_TASK_ARRIVES or
+                   BTS_TASK_DEPARTS */
+                unsigned long long timestamp;
+        } variant;
+};
+
+
+extern int ds_allocate(void **, size_t);
+extern int ds_free(void **);
+extern int ds_get_bts_size(void *);
+extern int ds_get_bts_index(void *);
+extern int ds_read_bts(void *, size_t, struct bts_struct *);
+extern int ds_write_bts(void *, const struct bts_struct *);
+extern unsigned long ds_debugctl_mask(void);
+extern void __cpuinit ds_init_intel(struct cpuinfo_x86 *c);
+
+#endif /* _ASM_X86_DS_H */
diff --git a/include/asm-x86/processor_32.h b/include/asm-x86/processor_32.h
index 0d83da198127..9c0ab7f26bd9 100644
--- a/include/asm-x86/processor_32.h
+++ b/include/asm-x86/processor_32.h
@@ -360,6 +360,9 @@ struct thread_struct {
         unsigned long   io_bitmap_max;
 /* MSR_IA32_DEBUGCTLMSR value to switch in if TIF_DEBUGCTLMSR is set.  */
         unsigned long   debugctlmsr;
+/* Debug Store - if not 0 points to a DS Save Area configuration;
+ *               goes into MSR_IA32_DS_AREA */
+        unsigned long   ds_area_msr;
 };
 
 #define INIT_THREAD  {                                                  \
diff --git a/include/asm-x86/processor_64.h b/include/asm-x86/processor_64.h
index 0780f3e3fdfe..7b7f8a142e20 100644
--- a/include/asm-x86/processor_64.h
+++ b/include/asm-x86/processor_64.h
@@ -240,6 +240,9 @@ struct thread_struct {
         unsigned io_bitmap_max;
 /* MSR_IA32_DEBUGCTLMSR value to switch in if TIF_DEBUGCTLMSR is set.  */
         unsigned long   debugctlmsr;
+/* Debug Store - if not 0 points to a DS Save Area configuration;
+ *               goes into MSR_IA32_DS_AREA */
+        unsigned long   ds_area_msr;
 /* cached TLS descriptors. */
         u64 tls_array[GDT_ENTRY_TLS_ENTRIES];
 } __attribute__((aligned(16)));
diff --git a/include/asm-x86/ptrace-abi.h b/include/asm-x86/ptrace-abi.h
index adce6b51df2e..6fadc5214e14 100644
--- a/include/asm-x86/ptrace-abi.h
+++ b/include/asm-x86/ptrace-abi.h
@@ -80,4 +80,56 @@
 
 #define PTRACE_SINGLEBLOCK      33      /* resume execution until next branch */
 
+/* Return maximal BTS buffer size in number of records,
+   if successuf; -1, otherwise.
+   EOPNOTSUPP...processor does not support bts tracing */
+#define PTRACE_BTS_MAX_BUFFER_SIZE 40
+
+/* Allocate new bts buffer (free old one, if exists) of size DATA bts records;
+   parameter ADDR is ignored.
+   Return 0, if successful; -1, otherwise.
+   EOPNOTSUPP...processor does not support bts tracing
+   EINVAL.......invalid size in records
+   ENOMEM.......out of memory */
+#define PTRACE_BTS_ALLOCATE_BUFFER 41
+
+/* Return the size of the bts buffer in number of bts records,
+   if successful; -1, otherwise.
+   EOPNOTSUPP...processor does not support bts tracing
+   ENXIO........no buffer allocated */
+#define PTRACE_BTS_GET_BUFFER_SIZE 42
+
+/* Return the index of the next bts record to be written,
+   if successful; -1, otherwise.
+   EOPNOTSUPP...processor does not support bts tracing
+   ENXIO........no buffer allocated
+   After the first warp-around, this is the start of the circular bts buffer. */
+#define PTRACE_BTS_GET_INDEX 43
+
+/* Read the DATA'th bts record into a ptrace_bts_record buffer provided in ADDR.
+   Return 0, if successful; -1, otherwise
+   EOPNOTSUPP...processor does not support bts tracing
+   ENXIO........no buffer allocated
+   EINVAL.......invalid index */
+#define PTRACE_BTS_READ_RECORD 44
+
+/* Configure last branch trace; the configuration is given as a bit-mask of
+   PTRACE_BTS_O_* options in DATA; parameter ADDR is ignored.
+   Return 0, if successful; -1, otherwise
+   EOPNOTSUPP...processor does not support bts tracing
+   ENXIO........no buffer allocated */
+#define PTRACE_BTS_CONFIG 45
+
+/* Return the configuration as bit-mask of PTRACE_BTS_O_* options
+   if successful; -1, otherwise.
+   EOPNOTSUPP...processor does not support bts tracing
+   ENXIO........no buffer allocated */
+#define PTRACE_BTS_STATUS 46
+
+/* Trace configuration options */
+/* Collect last branch trace */
+#define PTRACE_BTS_O_TRACE_TASK 0x1
+/* Take timestamps when the task arrives and departs */
+#define PTRACE_BTS_O_TIMESTAMPS 0x2
+
 #endif
diff --git a/include/asm-x86/ptrace.h b/include/asm-x86/ptrace.h
index 9228870f6157..a9a1bab1451a 100644
--- a/include/asm-x86/ptrace.h
+++ b/include/asm-x86/ptrace.h
@@ -4,8 +4,19 @@
 #include <linux/compiler.h>     /* For __user */
 #include <asm/ptrace-abi.h>
 
+
 #ifndef __ASSEMBLY__
 
+#ifdef __KERNEL__
+
+#include <asm/ds.h>
+
+struct task_struct;
+extern void ptrace_bts_take_timestamp(struct task_struct *, enum bts_qualifier);
+
+#endif /* __KERNEL__ */
+
+
 #ifdef __i386__
 /* this struct defines the way the registers are stored on the
    stack during a system call. */
diff --git a/include/asm-x86/thread_info_32.h b/include/asm-x86/thread_info_32.h
index 306fc80800e1..5bd508260ffb 100644
--- a/include/asm-x86/thread_info_32.h
+++ b/include/asm-x86/thread_info_32.h
@@ -140,6 +140,8 @@ static inline struct thread_info *current_thread_info(void)
 #define TIF_NOTSC               20      /* TSC is not accessible in userland */
 #define TIF_FORCED_TF           21      /* true if TF in eflags artificially */
 #define TIF_DEBUGCTLMSR         22      /* uses thread_struct.debugctlmsr */
+#define TIF_DS_AREA_MSR         23      /* uses thread_struct.ds_area_msr */
+#define TIF_BTS_TRACE_TS        24      /* record scheduling event timestamps */
 
 #define _TIF_SYSCALL_TRACE      (1<<TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING         (1<<TIF_SIGPENDING)
@@ -157,6 +159,8 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_NOTSC              (1<<TIF_NOTSC)
 #define _TIF_FORCED_TF          (1<<TIF_FORCED_TF)
 #define _TIF_DEBUGCTLMSR        (1<<TIF_DEBUGCTLMSR)
+#define _TIF_DS_AREA_MSR        (1<<TIF_DS_AREA_MSR)
+#define _TIF_BTS_TRACE_TS       (1<<TIF_BTS_TRACE_TS)
 
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK \
@@ -166,8 +170,12 @@ static inline struct thread_info *current_thread_info(void)
 #define _TIF_ALLWORK_MASK       (0x0000FFFF & ~_TIF_SECCOMP)
 
 /* flags to check in __switch_to() */
-#define _TIF_WORK_CTXSW_NEXT (_TIF_IO_BITMAP | _TIF_NOTSC | _TIF_DEBUG | _TIF_DEBUGCTLMSR)
-#define _TIF_WORK_CTXSW_PREV (_TIF_IO_BITMAP | _TIF_NOTSC | _TIF_DEBUGCTLMSR)
+#define _TIF_WORK_CTXSW \
+    (_TIF_IO_BITMAP | _TIF_NOTSC | _TIF_DEBUGCTLMSR | \
+     _TIF_DS_AREA_MSR | _TIF_BTS_TRACE_TS)
+#define _TIF_WORK_CTXSW_PREV _TIF_WORK_CTXSW
+#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW | _TIF_DEBUG)
+
 
 /*
  * Thread-synchronous status.
diff --git a/include/asm-x86/thread_info_64.h b/include/asm-x86/thread_info_64.h
index ee35fd12b541..c2911a99cc32 100644
--- a/include/asm-x86/thread_info_64.h
+++ b/include/asm-x86/thread_info_64.h
@@ -123,6 +123,8 @@ static inline struct thread_info *stack_thread_info(void)
 #define TIF_FREEZE              23      /* is freezing for suspend */
 #define TIF_FORCED_TF           24      /* true if TF in eflags artificially */
 #define TIF_DEBUGCTLMSR         25      /* uses thread_struct.debugctlmsr */
+#define TIF_DS_AREA_MSR 25      /* uses thread_struct.ds_area_msr */
+#define TIF_BTS_TRACE_TS        26      /* record scheduling event timestamps */
 
 #define _TIF_SYSCALL_TRACE      (1<<TIF_SYSCALL_TRACE)
 #define _TIF_SIGPENDING         (1<<TIF_SIGPENDING)
@@ -142,6 +144,8 @@ static inline struct thread_info *stack_thread_info(void)
 #define _TIF_FREEZE             (1<<TIF_FREEZE)
 #define _TIF_FORCED_TF          (1<<TIF_FORCED_TF)
 #define _TIF_DEBUGCTLMSR        (1<<TIF_DEBUGCTLMSR)
+#define _TIF_DS_AREA_MSR        (1<<TIF_DS_AREA_MSR)
+#define _TIF_BTS_TRACE_TS       (1<<TIF_BTS_TRACE_TS)
 
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK \
@@ -153,7 +157,10 @@ static inline struct thread_info *stack_thread_info(void)
         (_TIF_SIGPENDING|_TIF_SINGLESTEP|_TIF_MCE_NOTIFY|_TIF_HRTICK_RESCHED)
 
 /* flags to check in __switch_to() */
-#define _TIF_WORK_CTXSW (_TIF_DEBUG|_TIF_IO_BITMAP|_TIF_DEBUGCTLMSR)
+#define _TIF_WORK_CTXSW \
+    (_TIF_IO_BITMAP|_TIF_DEBUGCTLMSR|_TIF_DS_AREA_MSR|_TIF_BTS_TRACE_TS)
+#define _TIF_WORK_CTXSW_PREV _TIF_WORK_CTXSW
+#define _TIF_WORK_CTXSW_NEXT (_TIF_WORK_CTXSW|_TIF_DEBUG)
 
 #define PREEMPT_ACTIVE     0x10000000