diff mbox series

[v8,08/10] btrace, linux: Enable ptwrite packets.

Message ID 20230321154626.448816-9-felix.willgerodt@intel.com
State New
Headers
Series Extensions for PTWRITE |

Commit Message

Felix Willgerodt March 21, 2023, 3:46 p.m. UTC 
  Enable ptwrite in the PT config, if it is supported by the kernel.
---
 gdb/nat/linux-btrace.c | 29 +++++++++++++++++++++++++++++
 gdb/record-btrace.c    |  5 +++++
 2 files changed, 34 insertions(+)
diff mbox series

Patch

diff --git a/gdb/nat/linux-btrace.c b/gdb/nat/linux-btrace.c
index c5b3f1c93cf..e320eaa12ce 100644
--- a/gdb/nat/linux-btrace.c
+++ b/gdb/nat/linux-btrace.c
@@ -417,6 +417,29 @@  cpu_supports_bts (void)
     }
 }
 
+/* Check whether the linux target supports Intel Processor Trace PTWRITE.  */
+
+static bool
+linux_supports_ptwrite ()
+{
+  static const char filename[]
+      = "/sys/bus/event_source/devices/intel_pt/caps/ptwrite";
+  gdb_file_up file = gdb_fopen_cloexec (filename, "r");
+
+  if (file.get () == nullptr)
+    return false;
+
+  int status, found = fscanf (file.get (), "%d", &status);
+
+  if (found != 1)
+    {
+      warning (_("Failed to determine ptwrite support from %s."), filename);
+      return false;
+    }
+
+  return status == 1;
+}
+
 /* The perf_event_open syscall failed.  Try to print a helpful error
    message.  */
 
@@ -626,6 +649,12 @@  linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
   pt->attr.exclude_hv = 1;
   pt->attr.exclude_idle = 1;
 
+  if (conf->ptwrite && linux_supports_ptwrite ())
+    {
+      pt->attr.config |= 0x1000;
+      tinfo->conf.pt.ptwrite = conf->ptwrite;
+    }
+
   errno = 0;
   scoped_fd fd (syscall (SYS_perf_event_open, &pt->attr, pid, -1, -1, 0));
   if (fd.get () < 0)
diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
index 22687e889ec..0b36ce5fdf6 100644
--- a/gdb/record-btrace.c
+++ b/gdb/record-btrace.c
@@ -3291,4 +3291,9 @@  to see the actual buffer size."), NULL, show_record_pt_buffer_size_value,
 
   record_btrace_conf.bts.size = 64 * 1024;
   record_btrace_conf.pt.size = 16 * 1024;
+#if (LIBIPT_VERSION >= 0x200)
+  record_btrace_conf.pt.ptwrite = true;
+#else
+  record_btrace_conf.pt.ptwrite = false;
+#endif
 }