x86, ptrace: PEBS support

Polish the ds.h interface and add support for PEBS.

Ds.c is meant to be the resource allocator for per-thread and per-cpu
BTS and PEBS recording.
It is used by ptrace/utrace to provide execution tracing of debugged tasks.
It will be used by profilers (e.g. perfmon2).
It may be used by kernel debuggers to provide a kernel execution trace.

Changes in detail:
- guard DS and ptrace by CONFIG macros
- separate DS and BTS more clearly
- simplify field accesses
- add functions to manage PEBS buffers
- add simple protection/allocation mechanism
- added support for Atom

Opens:
- buffer overflow handling
  Currently, only circular buffers are supported. This is all we need
  for debugging. Profilers would want an overflow notification.
  This is planned to be added when perfmon2 is made to use the ds.h
  interface.
- utrace intermediate layer

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

1 files changed, 8 insertions, 6 deletions

diff --git a/include/asm-x86/ptrace-abi.h b/include/asm-x86/ptrace-abi.h
index f224eb3c3157..9bcaa75cbcaf 100644
--- a/include/asm-x86/ptrace-abi.h
+++ b/include/asm-x86/ptrace-abi.h
@@ -80,8 +80,9 @@
 
 #define PTRACE_SINGLEBLOCK      33      /* resume execution until next branch */
 
-#ifndef __ASSEMBLY__
+#ifdef CONFIG_X86_PTRACE_BTS
 
+#ifndef __ASSEMBLY__
 #include <asm/types.h>
 
 /* configuration/status structure used in PTRACE_BTS_CONFIG and
@@ -97,20 +98,20 @@ struct ptrace_bts_config {
         /* actual size of bts_struct in bytes */
         __u32 bts_size;
 };
-#endif
+#endif /* __ASSEMBLY__ */
 
 #define PTRACE_BTS_O_TRACE      0x1 /* branch trace */
 #define PTRACE_BTS_O_SCHED      0x2 /* scheduling events w/ jiffies */
 #define PTRACE_BTS_O_SIGNAL     0x4 /* send SIG<signal> on buffer overflow
                                        instead of wrapping around */
-#define PTRACE_BTS_O_CUT_SIZE   0x8 /* cut requested size to max available
-                                       instead of failing */
+#define PTRACE_BTS_O_ALLOC      0x8 /* (re)allocate buffer */
 
 #define PTRACE_BTS_CONFIG       40
 /* Configure branch trace recording.
    ADDR points to a struct ptrace_bts_config.
    DATA gives the size of that buffer.
-   A new buffer is allocated, iff the size changes.
+   A new buffer is allocated, if requested in the flags.
+   An overflow signal may only be requested for new buffers.
    Returns the number of bytes read.
 */
 #define PTRACE_BTS_STATUS       41
@@ -119,7 +120,7 @@ struct ptrace_bts_config {
    Returns the number of bytes written.
 */
 #define PTRACE_BTS_SIZE         42
-/* Return the number of available BTS records.
+/* Return the number of available BTS records for draining.
    DATA and ADDR are ignored.
 */
 #define PTRACE_BTS_GET          43
@@ -139,5 +140,6 @@ struct ptrace_bts_config {
    BTS records are read from oldest to newest.
    Returns number of BTS records drained.
 */
+#endif /* CONFIG_X86_PTRACE_BTS */
 
 #endif