[PowerPC] Add support for TAR

[deliverable/binutils-gdb.git] / gdb / nat / linux-btrace.c

diff --git a/gdb/nat/linux-btrace.c b/gdb/nat/linux-btrace.c
index 301649b4983f1982a435aaad6a46b6eb28f1c2d9..83afe881a83835706bad3b34e3e799d52346b9f3 100644 (file)
--- a/gdb/nat/linux-btrace.c
+++ b/gdb/nat/linux-btrace.c
@@ -409,6 +409,34 @@ cpu_supports_bts (void)
     }
 }
 
+/* The perf_event_open syscall failed.  Try to print a helpful error
+   message.  */
+
+static void
+diagnose_perf_event_open_fail ()
+{
+  switch (errno)
+    {
+    case EPERM:
+    case EACCES:
+      {
+       static const char filename[] = "/proc/sys/kernel/perf_event_paranoid";
+       gdb_file_up file = gdb_fopen_cloexec (filename, "r");
+       if (file.get () == nullptr)
+         break;
+
+       int level, found = fscanf (file.get (), "%d", &level);
+       if (found == 1 && level > 2)
+         error (_("You do not have permission to record the process.  "
+                  "Try setting %s to 2 or less."), filename);
+      }
+
+      break;
+    }
+
+  error (_("Failed to start recording: %s"), safe_strerror (errno));
+}
+
 /* Enable branch tracing in BTS format.  */
 
 static struct btrace_target_info *
@@ -441,14 +469,14 @@ linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
   bts->attr.exclude_hv = 1;
   bts->attr.exclude_idle = 1;
 
-  pid = ptid_get_lwp (ptid);
+  pid = ptid.lwp ();
   if (pid == 0)
-    pid = ptid_get_pid (ptid);
+    pid = ptid.pid ();
 
   errno = 0;
   scoped_fd fd (syscall (SYS_perf_event_open, &bts->attr, pid, -1, -1, 0));
   if (fd.get () < 0)
-    error (_("Failed to start recording: %s"), safe_strerror (errno));
+    diagnose_perf_event_open_fail ();
 
   /* Convert the requested size in bytes to pages (rounding up).  */
   pages = ((size_t) conf->size / PAGE_SIZE
@@ -557,9 +585,9 @@ linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
   size_t pages;
   int pid, pg;
 
-  pid = ptid_get_lwp (ptid);
+  pid = ptid.lwp ();
   if (pid == 0)
-    pid = ptid_get_pid (ptid);
+    pid = ptid.pid ();
 
   gdb::unique_xmalloc_ptr<btrace_target_info> tinfo
     (XCNEW (btrace_target_info));
@@ -578,7 +606,7 @@ linux_enable_pt (ptid_t ptid, const struct btrace_config_pt *conf)
   errno = 0;
   scoped_fd fd (syscall (SYS_perf_event_open, &pt->attr, pid, -1, -1, 0));
   if (fd.get () < 0)
-    error (_("Failed to start recording: %s"), safe_strerror (errno));
+    diagnose_perf_event_open_fail ();
 
   /* Allocate the configuration page. */
   scoped_mmap data (nullptr, PAGE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED,