From aa7ada1dfbe21a0c83474eb3de54e08eb607f8b8 Mon Sep 17 00:00:00 2001
From: Pavel Labath <pavel@labath.sk>
Date: Mon, 21 Jul 2025 08:46:21 +0200
Subject: [Object] Beginnings of SFrame parser and dumper (#147294)

This PR adds the SFrameParser class and uses it from llvm-readobj to
dump the section contents. Currently, it only supports parsing the
SFrame section header. Other parts of the section will be added in
follow-up patches.

llvm-readobj uses the same sframe flag syntax as GNU readelf, but I have
not attempted match the output format of the tool. I'm starting with the
"llvm" output format because it's easier to generate and lets us
tweak the format to make it useful for testing the generation code. If
needed, support for the GNU format could be added by overriding this
functionality in the GNU ELF Dumper.

For more information, see the [sframe
specification](https://sourceware.org/binutils/wiki/sframe) and the
related
[RFC](https://discourse.llvm.org/t/rfc-adding-sframe-support-to-llvm/86900).
---
 llvm/lib/Object/SFrameParser.cpp | 55 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 55 insertions(+)
 create mode 100644 llvm/lib/Object/SFrameParser.cpp

(limited to 'llvm/lib/Object/SFrameParser.cpp')

diff --git a/llvm/lib/Object/SFrameParser.cpp b/llvm/lib/Object/SFrameParser.cpp
new file mode 100644
index 000000000000..2d74d1d6b382
--- /dev/null
+++ b/llvm/lib/Object/SFrameParser.cpp
@@ -0,0 +1,55 @@
+//===- SFrameParser.cpp ---------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Object/SFrameParser.h"
+#include "llvm/BinaryFormat/SFrame.h"
+#include "llvm/Object/Error.h"
+#include "llvm/Support/FormatVariadic.h"
+
+using namespace llvm;
+using namespace llvm::object;
+
+template <typename T>
+static Expected<const T &> getDataSliceAs(ArrayRef<uint8_t> Data,
+                                          uint64_t Offset) {
+  static_assert(std::is_trivial_v<T>);
+  if (Data.size() < Offset + sizeof(T)) {
+    return createStringError(
+        formatv("unexpected end of data at offset {0:x} while reading [{1:x}, "
+                "{2:x})",
+                Data.size(), Offset, Offset + sizeof(T))
+            .str(),
+        object_error::unexpected_eof);
+  }
+  return *reinterpret_cast<const T *>(Data.data() + Offset);
+}
+
+template <endianness E>
+Expected<SFrameParser<E>> SFrameParser<E>::create(ArrayRef<uint8_t> Contents) {
+  Expected<const sframe::Preamble<E> &> Preamble =
+      getDataSliceAs<sframe::Preamble<E>>(Contents, 0);
+  if (!Preamble)
+    return Preamble.takeError();
+
+  if (Preamble->Magic != sframe::Magic)
+    return createError(
+        formatv("invalid magic number ({0:x+4})", Preamble->Magic.value()));
+  if (Preamble->Version != sframe::Version::V2)
+    return createError(
+        formatv("invalid/unsupported version number ({0})",
+                static_cast<unsigned>(Preamble->Version.value())));
+
+  Expected<const sframe::Header<E> &> Header =
+      getDataSliceAs<sframe::Header<E>>(Contents, 0);
+  if (!Header)
+    return Header.takeError();
+  return SFrameParser(Contents, *Header);
+}
+
+template class llvm::object::SFrameParser<endianness::big>;
+template class llvm::object::SFrameParser<endianness::little>;
-- 
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