[JITLink][ELF] Handle BSS sections, improve some error messages.

This patch enables basic BSS section handling, and improves a couple of error
messages in the ELF section parsing code.

Patch by Christian Schafmeister. Thanks Christian!

Differential Revision: https://reviews.llvm.org/D88867

diff --git a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
index 2029543..40c7d04 100644 (file)
--- a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
@@ -357,6 +357,9 @@ private:
         if (SecRef.sh_type == ELF::SHT_SYMTAB)
           // TODO: Dynamic?
           SymTab = SecRef;
+      } else {
+        auto &Section = G->createSection(*Name, Prot);
+        G->createZeroFillBlock(Section, Size, Address, Alignment, 0);
       }
     }
 
@@ -480,7 +483,8 @@ private:
         return Name.takeError();
       auto Section = G->findSectionByName(*Name);
       if (!Section)
-        return make_error<llvm::StringError>("Could not find a section",
+        return make_error<llvm::StringError>("Could not find a section " +
+                                             *Name,
                                              llvm::inconvertibleErrorCode());
       // we only have one for now
       auto blocks = Section->blocks();
@@ -527,7 +531,8 @@ private:
           auto JitSection = G->findSectionByName(*sectName);
           if (!JitSection)
             return make_error<llvm::StringError>(
-                "Could not find a section", llvm::inconvertibleErrorCode());
+                "Could not find the JitSection " + *sectName,
+                llvm::inconvertibleErrorCode());
           auto bs = JitSection->blocks();
           if (bs.empty())
             return make_error<llvm::StringError>(

diff --git a/llvm/test/ExecutionEngine/JITLink/X86/ELF_x86-64_relocations.s b/llvm/test/ExecutionEngine/JITLink/X86/ELF_x86-64_relocations.s
index ca9c926..0eef111 100644 (file)
--- a/llvm/test/ExecutionEngine/JITLink/X86/ELF_x86-64_relocations.s
+++ b/llvm/test/ExecutionEngine/JITLink/X86/ELF_x86-64_relocations.s
@@ -46,6 +46,17 @@ named_data:
         .long   42
         .size   named_data, 4
 
+# Test BSS / zero-fill section handling.
+# llvm-jitlink: *{4}bss_variable = 0
+
+       .type   bss_variable,@object
+       .bss
+       .globl  bss_variable
+       .p2align        2
+bss_variable:
+       .long   0
+       .size   bss_variable, 4
+
         .ident  "clang version 10.0.0-4ubuntu1 "
         .section        ".note.GNU-stack","",@progbits
-        .addrsig
\ No newline at end of file
+        .addrsig