arch,base: Restructure the object file loaders.

This change creates a distinction between object files which hold
executable code, and flat files which don't. The first type of files
have entry points, symbols, etc., while the others are just blobs which
can be shoved into memory. Rather than have those aspects but stub
them out, this change creates a new base class which simply doesn't
have them.

This change also restructures the ELF loader since it's main function
was quite long and doing multiple jobs.

It stops passing the architecture and operating system to the
ObjectFile constructor, since those might not be known at the very top
of the constructor. Instead, those default to Uknown*, and then are
filled in in the constructor body if appropriate. This removes a lot
of plumbing that was hard to actually use in practice.

It also introduces a mechanism to collect generic object file formats
so that they can be tried one by one by the general createObjectFile
function, rather than listing them all there one by one. It's unlikely
that new types of object files will need to be added in a modular way
without being able to modify the core loader code, but it's cleaner to
have that abstraction and modularization like is already there for
process loaders.

Finally, to make it possible to share the code which handles zipped
files for both true object files and also files which will be loaded
into memory but are just blobs, that mechanism is pulled out into a
new class called ImageFileData. It holds a collection of segments
which are set up by the object file and may refer to regions of the
original file, buffers maintained elsewhere, or even nothing to support
bss-es. shared_ptr is used to make it easier to keep track of that
information without having to do so explicitly or worry about deleting
a buffer before everyone was done using it.

Change-Id: I92890266f2ba0a703803cccad675a3ab41f2c4af
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/21467
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Brandon Potter <Brandon.Potter@amd.com>
Maintainer: Gabe Black <gabeblack@google.com>

1 files changed, 52 insertions, 0 deletions

diff --git a/src/base/loader/image_file.hh b/src/base/loader/image_file.hh
new file mode 100644
index 000000000..79d31a433
--- /dev/null
+++ b/src/base/loader/image_file.hh
@@ -0,0 +1,52 @@
+/*
+ * Copyright (c) 2002-2004 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Nathan Binkert
+ *          Steve Reinhardt
+ */
+
+#ifndef __BASE_LOADER_IMAGE_FILE_HH__
+#define __BASE_LOADER_IMAGE_FILE_HH__
+
+#include <cstdint>
+#include <string>
+
+#include "base/loader/image_file_data.hh"
+#include "base/loader/memory_image.hh"
+
+class ImageFile
+{
+  protected:
+    ImageFileDataPtr imageData;
+    ImageFile(ImageFileDataPtr data) : imageData(data) {}
+    virtual ~ImageFile() {}
+
+  public:
+    virtual MemoryImage buildImage() const = 0;
+};
+
+#endif // __BASE_LOADER_IMAGE_FILE_HH__