From 7988fcad5b9ff891b48b2aed099c1e70920c192f Mon Sep 17 00:00:00 2001
From: Owen Anderson <resistor@mac.com>
Date: Wed, 30 Apr 2025 23:01:06 +1200
Subject: [PATCH] [CHERIoT] Add an ELF flag for RISCV_CHERIOT.

---
 lld/ELF/Arch/RISCV.cpp                        |  4 +++
 llvm/include/llvm/BinaryFormat/ELF.h          |  1 +
 llvm/lib/ObjectYAML/ELFYAML.cpp               |  1 +
 .../RISCV/MCTargetDesc/RISCVELFStreamer.cpp   |  8 +++--
 .../CodeGen/RISCV/cheri/cheriot-elf-flags.ll  | 32 +++++++++++++++++++
 llvm/tools/llvm-readobj/ELFDumper.cpp         | 18 ++++++-----
 6 files changed, 54 insertions(+), 10 deletions(-)
 create mode 100644 llvm/test/CodeGen/RISCV/cheri/cheriot-elf-flags.ll

diff --git a/lld/ELF/Arch/RISCV.cpp b/lld/ELF/Arch/RISCV.cpp
index b20c04b7c24c6..9e2786cc1221f 100644
--- a/lld/ELF/Arch/RISCV.cpp
+++ b/lld/ELF/Arch/RISCV.cpp
@@ -192,6 +192,10 @@ uint32_t RISCV::calcEFlags() const {
     if ((eflags & EF_RISCV_CAP_MODE) != (target & EF_RISCV_CAP_MODE))
       Err(ctx) << f
                << ": cannot link object files with different EF_RISCV_CAP_MODE";
+
+    if ((eflags & EF_RISCV_CHERIOT) != (target & EF_RISCV_CHERIOT))
+      Err(ctx) << f
+               << ": cannot link object files with different EF_RISCV_CHERIOT";
   }
 
   return target;
diff --git a/llvm/include/llvm/BinaryFormat/ELF.h b/llvm/include/llvm/BinaryFormat/ELF.h
index 99797794f659d..14847538ab502 100644
--- a/llvm/include/llvm/BinaryFormat/ELF.h
+++ b/llvm/include/llvm/BinaryFormat/ELF.h
@@ -702,6 +702,7 @@ enum : unsigned {
   // CHERI-specific flags
   EF_RISCV_CHERIABI = 0x00010000,
   EF_RISCV_CAP_MODE = 0x00020000,
+  EF_RISCV_CHERIOT = 0x00040000,
 };
 
 // ELF Relocation types for RISC-V
diff --git a/llvm/lib/ObjectYAML/ELFYAML.cpp b/llvm/lib/ObjectYAML/ELFYAML.cpp
index e75ffa60876de..526c76c411b5e 100644
--- a/llvm/lib/ObjectYAML/ELFYAML.cpp
+++ b/llvm/lib/ObjectYAML/ELFYAML.cpp
@@ -555,6 +555,7 @@ void ScalarBitSetTraits<ELFYAML::ELF_EF>::bitset(IO &IO,
     BCase(EF_RISCV_TSO);
     BCase(EF_RISCV_CHERIABI);
     BCase(EF_RISCV_CAP_MODE);
+    BCase(EF_RISCV_CHERIOT);
     break;
   case ELF::EM_SPARC32PLUS:
     BCase(EF_SPARC_32PLUS);
diff --git a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp
index b2a079cb288b9..3b8ebaa281a34 100644
--- a/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp
+++ b/llvm/lib/Target/RISCV/MCTargetDesc/RISCVELFStreamer.cpp
@@ -103,10 +103,14 @@ void RISCVTargetELFStreamer::finish() {
   case RISCVABI::ABI_ILP32:
   case RISCVABI::ABI_LP64:
     break;
-  case RISCVABI::ABI_IL32PC64:
-  case RISCVABI::ABI_L64PC128:
   case RISCVABI::ABI_CHERIOT:
   case RISCVABI::ABI_CHERIOT_BAREMETAL:
+    EFlags |= ELF::EF_RISCV_RVE;
+    EFlags |= ELF::EF_RISCV_CHERIABI;
+    EFlags |= ELF::EF_RISCV_CHERIOT;
+    break;
+  case RISCVABI::ABI_IL32PC64:
+  case RISCVABI::ABI_L64PC128:
     EFlags |= ELF::EF_RISCV_CHERIABI;
     break;
   case RISCVABI::ABI_ILP32F:
diff --git a/llvm/test/CodeGen/RISCV/cheri/cheriot-elf-flags.ll b/llvm/test/CodeGen/RISCV/cheri/cheriot-elf-flags.ll
new file mode 100644
index 0000000000000..c0cc45836a063
--- /dev/null
+++ b/llvm/test/CodeGen/RISCV/cheri/cheriot-elf-flags.ll
@@ -0,0 +1,32 @@
+; RUN: llc --filetype=obj --mcpu=cheriot --mtriple=riscv32-unknown-unknown -target-abi cheriot  %s -mattr=+xcheri,+cap-mode -o - | llvm-readelf -a - | FileCheck %s
+
+; CHECK-LABEL: ELF Header:
+; CHECK:          Flags: 0x70009, RVC, RVE, cheriabi, capability mode, cheriot
+
+target datalayout = "e-m:e-pf200:64:64:64:32-p:32:32-i64:64-n32-S128-A200-P200-G200"
+target triple = "riscv32cheriot-unknown-cheriotrtos"
+
+
+define void @foo()  addrspace(200) #0 {
+entry:
+  ret void
+}
+
+attributes #0 = { minsize mustprogress nounwind optsize "frame-pointer"="none" "min-legal-vector-width"="0" "no-builtins" "no-trapping-math"="true" "stack-protector-buffer-size"="8" "target-cpu"="cheriot" "target-features"="+relax,+xcheri,-64bit,-save-restore" }
+
+!llvm.linker.options = !{}
+!llvm.module.flags = !{!0, !1, !2}
+!llvm.ident = !{!3}
+
+!0 = !{i32 1, !"wchar_size", i32 2}
+!1 = !{i32 1, !"target-abi", !"cheriot"}
+!2 = !{i32 1, !"SmallDataLimit", i32 8}
+!3 = !{!"clang version 13.0.0 (ssh://git@github.com/CHERIoT-Platform/llvm-project 42ccdb1bcc7eb0bf8cc8e493850359f828515495)"}
+!4 = !{i64 0, i64 4, !5, i64 4, i64 4, !5, i64 8, i64 4, !5}
+!5 = !{!6, !6, i64 0}
+!6 = !{!"int", !7, i64 0}
+!7 = !{!"omnipotent char", !8, i64 0}
+!8 = !{!"Simple C++ TBAA"}
+!9 = !{i64 0, i64 128, !10}
+!10 = !{!7, !7, i64 0}
+
diff --git a/llvm/tools/llvm-readobj/ELFDumper.cpp b/llvm/tools/llvm-readobj/ELFDumper.cpp
index dab84fed9c661..91b3acd4905be 100644
--- a/llvm/tools/llvm-readobj/ELFDumper.cpp
+++ b/llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -1688,14 +1688,16 @@ const EnumEntry<unsigned> ElfHeaderNVPTXFlags[] = {
 };
 
 const EnumEntry<unsigned> ElfHeaderRISCVFlags[] = {
-  ENUM_ENT(EF_RISCV_RVC, "RVC"),
-  ENUM_ENT(EF_RISCV_FLOAT_ABI_SINGLE, "single-float ABI"),
-  ENUM_ENT(EF_RISCV_FLOAT_ABI_DOUBLE, "double-float ABI"),
-  ENUM_ENT(EF_RISCV_FLOAT_ABI_QUAD, "quad-float ABI"),
-  ENUM_ENT(EF_RISCV_RVE, "RVE"),
-  ENUM_ENT(EF_RISCV_TSO, "TSO"),
-  ENUM_ENT(EF_RISCV_CHERIABI, "cheriabi"),
-  ENUM_ENT(EF_RISCV_CAP_MODE, "capability mode"),
+    ENUM_ENT(EF_RISCV_RVC, "RVC"),
+    ENUM_ENT(EF_RISCV_FLOAT_ABI_SINGLE, "single-float ABI"),
+    ENUM_ENT(EF_RISCV_FLOAT_ABI_DOUBLE, "double-float ABI"),
+    ENUM_ENT(EF_RISCV_FLOAT_ABI_QUAD, "quad-float ABI"),
+    ENUM_ENT(EF_RISCV_RVE, "RVE"),
+    ENUM_ENT(EF_RISCV_TSO, "TSO"),
+    ENUM_ENT(EF_RISCV_CHERIABI, "cheriabi"),
+    ENUM_ENT(EF_RISCV_CAP_MODE, "capability mode"),
+    ENUM_ENT(EF_RISCV_CHERIOT, "cheriot"),
+
 };
 
 const EnumEntry<unsigned> ElfHeaderSPARCFlags[] = {