[llvm] [readobj][AArch64] Parse AArch64 build attributes (PR #124276)

[Oliver Stannard via llvm-commits]

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@@ -0,0 +1,152 @@
+//===-AArch64AttributeParser.cpp-AArch64 Attribute Information Printer-===//
+//
+// 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/Support/AArch64AttributeParser.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/AArch64BuildAttributes.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/ScopedPrinter.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cstdint>
+
+using namespace llvm;
+
+Error AArch64AttributeParser::parse(ArrayRef<uint8_t> Section,
+                                    llvm::endianness Endian) {
+
+  unsigned SectionNumber = 0;
+  de = DataExtractor(Section, Endian == llvm::endianness::little, 0);
+
+  // Early returns have specific errors. Consume the Error in cursor.
+  struct ClearCursorError {
+    DataExtractor::Cursor &Cursor;
+    ~ClearCursorError() { consumeError(Cursor.takeError()); }
+  } Clear{cursor};
+
+  /*
+    AArch64 build attributes layout:
+    <format-version: ‘A’> --> There is only one version, 'A' (0x41)
+    [ <uint32: subsection-length> <NTBS: vendor-name> <bytes: vendor-data> ]
+      --> subsection-length: the offset from the start of this subsection to the
+    start of the next one.
+      --> vendor-name: NUL-terminated byte string.
+      --> vendor-data expands to:
+        [ <uint8: optional> <uint8: parameter type> <attribute>*]
+          --> optional: 0- required, 1- optional
+          --> type: 0- ULEB128, 1- NTBS
+          --> attribute: <tag, value>* pair. Tag is ULEB128, value is <parameter
+    type> type.
+  */
+
+  // Get format-version
+  uint8_t FormatVersion = de.getU8(cursor);
+  if (ELFAttrs::Format_Version != FormatVersion)
+    return createStringError(errc::invalid_argument,
+                             "unrecognized format-version: 0x" +
+                                 utohexstr(FormatVersion));
+
+  while (!de.eof(cursor)) {
+    uint32_t BASubsectionLength = de.getU32(cursor);
+    // Minimal valid BA subsection header size is at least 8: length(4) name(at
+    // least a single char + null) optionality(1) and type(1)
+    if (BASubsectionLength < 8)
+      return createStringError(
+          errc::invalid_argument,
+          "invalid AArch64 build attribute subsection size at offset: " +
+              utohexstr(cursor.tell() - 4));
+
+    StringRef VendorName = de.getCStrRef(cursor);
+    // The layout of a private subsection (--> vendor name does not starts with
+    // 'aeabi') is unknown, skip)
+    if (!VendorName.starts_with("aeabi")) {
+      sw->startLine()
+          << "** Skipping private AArch64 build attributes subsection: "
+          << VendorName << "\n";
+      // Offset in Section
+      uint64_t OffsetInSection = cursor.tell();
+      // Size: 4 bytes, Vendor Name: VendorName.size() + 1 (null termination)
+      uint32_t BytesForLengthName = 4 + (VendorName.size() + 1);
+      cursor.seek(OffsetInSection + BASubsectionLength - BytesForLengthName);
+      continue;
+    }
+    // All public subsections names must be known
+    if (VendorName.starts_with("aeabi")) {
+      if (!("aeabi_feature_and_bits" == VendorName ||
----------------
ostannard wrote:

We should be able to print any "aeabi*" subsection, because the format is known, even if the tag names aren't.

https://github.com/llvm/llvm-project/pull/124276