[llvm] [ELF] Add support for CREL to getSectionAndRelocations (PR #126445)

[Aiden Grossman via llvm-commits]

https://github.com/boomanaiden154 updated https://github.com/llvm/llvm-project/pull/126445

>From 694df281c6fb70a25a78ecc73bf751075840144a Mon Sep 17 00:00:00 2001
From: Aiden Grossman <aidengrossman at google.com>
Date: Mon, 10 Feb 2025 00:10:20 +0000
Subject: [PATCH 1/2] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20in?=
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Created using spr 1.3.4
---
 llvm/lib/Object/ELF.cpp                     | 10 +++++++++-
 llvm/tools/llvm-readobj/ELFDumper.cpp       | 10 ++++++++++
 llvm/unittests/Object/ELFObjectFileTest.cpp | 17 ++++++++++++++++-
 3 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/llvm/lib/Object/ELF.cpp b/llvm/lib/Object/ELF.cpp
index b6d0699ee4fe080..8cb3d7eb141766d 100644
--- a/llvm/lib/Object/ELF.cpp
+++ b/llvm/lib/Object/ELF.cpp
@@ -747,6 +747,13 @@ decodeBBAddrMapImpl(const ELFFile<ELFT> &EF,
     assert(RelaSec &&
            "Can't read a SHT_LLVM_BB_ADDR_MAP section in a relocatable "
            "object file without providing a relocation section.");
+    // We might end up with relocations in CREL here. If we do, return an
+    // error since we do not currently support them.
+    if (RelaSec->sh_type == ELF::SHT_CREL)
+      return createError("unable to read relocations for section " +
+                         describe(EF, Sec) +
+                         " as the corresponding relocation section format is "
+                         "CREL, which is not currently supported.");
     Expected<typename ELFFile<ELFT>::Elf_Rela_Range> Relas = EF.relas(*RelaSec);
     if (!Relas)
       return createError("unable to read relocations for section " +
@@ -958,7 +965,8 @@ ELFFile<ELFT>::getSectionAndRelocations(
         continue;
     }
 
-    if (Sec.sh_type != ELF::SHT_RELA && Sec.sh_type != ELF::SHT_REL)
+    if (Sec.sh_type != ELF::SHT_RELA && Sec.sh_type != ELF::SHT_REL &&
+        Sec.sh_type != ELF::SHT_CREL)
       continue;
 
     Expected<const Elf_Shdr *> RelSecOrErr = this->getSection(Sec.sh_info);
diff --git a/llvm/tools/llvm-readobj/ELFDumper.cpp b/llvm/tools/llvm-readobj/ELFDumper.cpp
index 7806eea6a0c52df..faad89710daa978 100644
--- a/llvm/tools/llvm-readobj/ELFDumper.cpp
+++ b/llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -6833,6 +6833,16 @@ void ELFDumper<ELFT>::printRelocatableStackSizes(
       continue;
     }
 
+    // We might end up with relocations in CREL here. If we do, report a
+    // warning since we do not currently support them.
+    if (RelocSec->sh_type == ELF::SHT_CREL) {
+      reportWarning(createError(".stack_sizes (" + describe(*StackSizesELFSec) +
+                                ") has a corresponding CREL relocation "
+                                "section, which is not currently supported."),
+                    FileName);
+      continue;
+    }
+
     // A .stack_sizes section header's sh_link field is supposed to point
     // to the section that contains the functions whose stack sizes are
     // described in it.
diff --git a/llvm/unittests/Object/ELFObjectFileTest.cpp b/llvm/unittests/Object/ELFObjectFileTest.cpp
index 2a0921690914b4a..493e673d6a07db7 100644
--- a/llvm/unittests/Object/ELFObjectFileTest.cpp
+++ b/llvm/unittests/Object/ELFObjectFileTest.cpp
@@ -8,6 +8,7 @@
 
 #include "llvm/Object/ELFObjectFile.h"
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/BinaryFormat/ELF.h"
 #include "llvm/ObjectYAML/yaml2obj.h"
 #include "llvm/Support/BlockFrequency.h"
 #include "llvm/Support/MemoryBuffer.h"
@@ -1433,7 +1434,8 @@ TEST(ELFObjectFileTest, GetSectionAndRelocations) {
     // Basic verification to make sure we have the correct section types.
     for (auto const &[Sec, RelaSec] : *SecToRelocMapOrErr) {
       ASSERT_EQ(Sec->sh_type, ELF::SHT_PROGBITS);
-      ASSERT_EQ(RelaSec->sh_type, ELF::SHT_RELA);
+      ASSERT_TRUE(RelaSec->sh_type == ELF::SHT_RELA ||
+                  RelaSec->sh_type == ELF::SHT_CREL);
     }
   };
 
@@ -1503,6 +1505,19 @@ TEST(ELFObjectFileTest, GetSectionAndRelocations) {
   DoCheckFails(MissingRelocatableContent, DefaultMatcher,
                "SHT_RELA section with index 1: failed to get a "
                "relocated section: invalid section index: 255");
+
+  StringRef OneTextSectionCREL = R"(
+Sections:
+  - Name: .text
+    Type: SHT_PROGBITS
+    Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
+  - Name: .crel.tex
+    Type: SHT_CREL
+    Flags: [ SHF_INFO_LINK ]
+    Info: .text
+)";
+
+  DoCheckSucceeds(OneTextSectionCREL, DefaultMatcher);
 }
 
 TEST(ELFObjectFileTest, ELFSymbolRefLess) {

>From 9b7c6ec239db332f197b90a770decb697b71148a Mon Sep 17 00:00:00 2001
From: Aiden Grossman <aidengrossman at google.com>
Date: Mon, 10 Feb 2025 18:17:42 +0000
Subject: [PATCH 2/2] address feedback

Created using spr 1.3.4
---
 llvm/tools/llvm-readobj/ELFDumper.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/tools/llvm-readobj/ELFDumper.cpp b/llvm/tools/llvm-readobj/ELFDumper.cpp
index faad89710daa978..2128a95510f2269 100644
--- a/llvm/tools/llvm-readobj/ELFDumper.cpp
+++ b/llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -6838,7 +6838,7 @@ void ELFDumper<ELFT>::printRelocatableStackSizes(
     if (RelocSec->sh_type == ELF::SHT_CREL) {
       reportWarning(createError(".stack_sizes (" + describe(*StackSizesELFSec) +
                                 ") has a corresponding CREL relocation "
-                                "section, which is not currently supported."),
+                                "section, which is not currently supported"),
                     FileName);
       continue;
     }