Windows gdb+gdbserver: Share $_siginfo reading code

Both GDB and GDBserver have similar code to read the $_siginfo data.
This patch moves the bulk of it to gdb/nat/windows-nat.c so it can be
shared.

Change-Id: I47fc0d3323be5b6f6fcfe912b768051a41910666

4 files changed, 65 insertions, 75 deletions

diff --git a/gdb/nat/windows-nat.c b/gdb/nat/windows-nat.c
index d43d549..4fd717e 100644
--- a/gdb/nat/windows-nat.c
+++ b/gdb/nat/windows-nat.c
@@ -153,6 +153,55 @@ windows_thread_info::thread_name ()
   return name.get ();
 }
 
+/* Read Windows signal info.  See nat/windows-nat.h.  */
+
+bool
+windows_thread_info::xfer_siginfo (gdb_byte *readbuf,
+				   ULONGEST offset, ULONGEST len,
+				   ULONGEST *xfered_len)
+{
+  if (last_event.dwDebugEventCode != EXCEPTION_DEBUG_EVENT)
+    return false;
+
+  if (readbuf == nullptr)
+    return false;
+
+  EXCEPTION_RECORD &er = last_event.u.Exception.ExceptionRecord;
+
+  char *buf = (char *) &er;
+  size_t bufsize = sizeof (er);
+
+#ifdef __x86_64__
+  EXCEPTION_RECORD32 er32;
+  if (proc->wow64_process)
+    {
+      buf = (char *) &er32;
+      bufsize = sizeof (er32);
+
+      er32.ExceptionCode = er.ExceptionCode;
+      er32.ExceptionFlags = er.ExceptionFlags;
+      er32.ExceptionRecord
+	= (uintptr_t) er.ExceptionRecord;
+      er32.ExceptionAddress
+	= (uintptr_t) er.ExceptionAddress;
+      er32.NumberParameters = er.NumberParameters;
+      for (int i = 0; i < EXCEPTION_MAXIMUM_PARAMETERS; i++)
+	er32.ExceptionInformation[i] = er.ExceptionInformation[i];
+    }
+#endif
+
+  if (offset > bufsize)
+    return false;
+
+  if (offset + len > bufsize)
+    len = bufsize - offset;
+
+  memcpy (readbuf, buf + offset, len);
+  *xfered_len = len;
+
+  return true;
+}
+
 /* Try to determine the executable filename.
 
    EXE_NAME_RET is a pointer to a buffer whose size is EXE_NAME_MAX_LEN.
diff --git a/gdb/nat/windows-nat.h b/gdb/nat/windows-nat.h
index 26b1eae..af96811 100644
--- a/gdb/nat/windows-nat.h
+++ b/gdb/nat/windows-nat.h
@@ -70,6 +70,15 @@ struct windows_thread_info
      the next call.  */
   const char *thread_name ();
 
+  /* Read LEN bytes of the thread's $_siginfo into READBUF, starting
+     at OFFSET.  Store the number of actually-read bytes in
+     XFERED_LEN.  Returns true on success, false on failure.  Passing
+     READBUF as NULL indicates that the caller is trying to write to
+     $_siginfo, which is a failure case.  */
+  bool xfer_siginfo (gdb_byte *readbuf,
+		     ULONGEST offset, ULONGEST len,
+		     ULONGEST *xfered_len);
+
   /* The process this thread belongs to.  */
   windows_process_info *proc;
 
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index 1608c47..4871d18 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -3111,44 +3111,10 @@ windows_xfer_siginfo (gdb_byte *readbuf, ULONGEST offset, ULONGEST len,
 {
   windows_thread_info *th = windows_process.find_thread (inferior_ptid);
 
-  if (th->last_event.dwDebugEventCode != EXCEPTION_DEBUG_EVENT)
-    return TARGET_XFER_E_IO;
-
-  EXCEPTION_RECORD &er = th->last_event.u.Exception.ExceptionRecord;
-
-  char *buf = (char *) &er;
-  size_t bufsize = sizeof (er);
-
-#ifdef __x86_64__
-  EXCEPTION_RECORD32 er32;
-  if (windows_process.wow64_process)
-    {
-      buf = (char *) &er32;
-      bufsize = sizeof (er32);
-
-      er32.ExceptionCode = er.ExceptionCode;
-      er32.ExceptionFlags = er.ExceptionFlags;
-      er32.ExceptionRecord = (uintptr_t) er.ExceptionRecord;
-      er32.ExceptionAddress = (uintptr_t) er.ExceptionAddress;
-      er32.NumberParameters = er.NumberParameters;
-      for (int i = 0; i < EXCEPTION_MAXIMUM_PARAMETERS; i++)
-	er32.ExceptionInformation[i] = er.ExceptionInformation[i];
-    }
-#endif
-
-  if (readbuf == nullptr)
-    return TARGET_XFER_E_IO;
-
-  if (offset > bufsize)
+  if (th->xfer_siginfo (readbuf, offset, len, xfered_len))
+    return TARGET_XFER_OK;
+  else
     return TARGET_XFER_E_IO;
-
-  if (offset + len > bufsize)
-    len = bufsize - offset;
-
-  memcpy (readbuf, buf + offset, len);
-  *xfered_len = len;
-
-  return TARGET_XFER_OK;
 }
 
 enum target_xfer_status
diff --git a/gdbserver/win32-low.cc b/gdbserver/win32-low.cc
index 985c6a0..4707acc 100644
--- a/gdbserver/win32-low.cc
+++ b/gdbserver/win32-low.cc
@@ -1308,45 +1308,11 @@ win32_process_target::qxfer_siginfo (const char *annex,
   windows_thread_info *th
     = windows_process.find_thread (current_thread_ptid ());
 
-  if (th->last_event.dwDebugEventCode != EXCEPTION_DEBUG_EVENT)
-    return -1;
-
-  if (readbuf == nullptr)
-    return -1;
-
-  EXCEPTION_RECORD &er = th->last_event.u.Exception.ExceptionRecord;
-
-  char *buf = (char *) &er;
-  size_t bufsize = sizeof (er);
-
-#ifdef __x86_64__
-  EXCEPTION_RECORD32 er32;
-  if (windows_process.wow64_process)
-    {
-      buf = (char *) &er32;
-      bufsize = sizeof (er32);
-
-      er32.ExceptionCode = er.ExceptionCode;
-      er32.ExceptionFlags = er.ExceptionFlags;
-      er32.ExceptionRecord
-	= (uintptr_t) er.ExceptionRecord;
-      er32.ExceptionAddress
-	= (uintptr_t) er.ExceptionAddress;
-      er32.NumberParameters = er.NumberParameters;
-      for (int i = 0; i < EXCEPTION_MAXIMUM_PARAMETERS; i++)
-	er32.ExceptionInformation[i] = er.ExceptionInformation[i];
-    }
-#endif
-
-  if (offset > bufsize)
+  ULONGEST xfered_len;
+  if (th->xfer_siginfo (readbuf, offset, len, &xfered_len))
+    return xfered_len;
+  else
     return -1;
-
-  if (offset + len > bufsize)
-    len = bufsize - offset;
-
-  memcpy (readbuf, buf + offset, len);
-
-  return len;
 }
 
 bool