[llvm-branch-commits] [llvm] a817f46 - [JITLink][ELF] Skip DWARF sections in ELF objects.

Lang Hames via llvm-branch-commits llvm-branch-commits at lists.llvm.org
Sun Jan 17 17:54:07 PST 2021


Author: Lang Hames
Date: 2021-01-18T12:42:48+11:00
New Revision: a817f46d50c34ea6b798d28bd5fa6a3ee7435497

URL: https://github.com/llvm/llvm-project/commit/a817f46d50c34ea6b798d28bd5fa6a3ee7435497
DIFF: https://github.com/llvm/llvm-project/commit/a817f46d50c34ea6b798d28bd5fa6a3ee7435497.diff

LOG: [JITLink][ELF] Skip DWARF sections in ELF objects.

This matches current JITLink/MachO behavior and avoids processing currently
unsupported relocations.

Added: 
    llvm/test/ExecutionEngine/JITLink/X86/ELF_skip_debug_sections.s

Modified: 
    llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
index f3a150d23737..30366a82a043 100644
--- a/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
+++ b/llvm/lib/ExecutionEngine/JITLink/ELF_x86_64.cpp
@@ -24,6 +24,7 @@ using namespace llvm::jitlink;
 using namespace llvm::jitlink::ELF_x86_64_Edges;
 
 namespace {
+
 class ELF_x86_64_GOTAndStubsBuilder
     : public BasicGOTAndStubsBuilder<ELF_x86_64_GOTAndStubsBuilder> {
 public:
@@ -110,6 +111,14 @@ class ELF_x86_64_GOTAndStubsBuilder
   Section *GOTSection = nullptr;
   Section *StubsSection = nullptr;
 };
+
+const char *const DwarfSectionNames[] = {
+#define HANDLE_DWARF_SECTION(ENUM_NAME, ELF_NAME, CMDLINE_NAME, OPTION)        \
+  ELF_NAME,
+#include "llvm/BinaryFormat/Dwarf.def"
+#undef HANDLE_DWARF_SECTION
+};
+
 } // namespace
 
 const uint8_t ELF_x86_64_GOTAndStubsBuilder::NullGOTEntryContent[8] = {
@@ -191,6 +200,14 @@ static Error optimizeELF_x86_64_GOTAndStubs(LinkGraph &G) {
 
   return Error::success();
 }
+
+static bool isDwarfSection(StringRef SectionName) {
+  for (auto &DwarfSectionName : DwarfSectionNames)
+    if (SectionName == DwarfSectionName)
+      return true;
+  return false;
+}
+
 namespace llvm {
 namespace jitlink {
 
@@ -305,6 +322,16 @@ class ELFLinkGraphBuilder_x86_64 {
       auto Name = Obj.getSectionName(SecRef);
       if (!Name)
         return Name.takeError();
+
+      // Skip Dwarf sections.
+      if (isDwarfSection(*Name)) {
+        LLVM_DEBUG({
+          dbgs() << *Name
+                 << " is a debug section: No graph section will be created.\n";
+        });
+        continue;
+      }
+
       sys::Memory::ProtectionFlags Prot;
       if (SecRef.sh_flags & ELF::SHF_EXECINSTR) {
         Prot = static_cast<sys::Memory::ProtectionFlags>(sys::Memory::MF_READ |
@@ -373,6 +400,10 @@ class ELFLinkGraphBuilder_x86_64 {
       auto RelSectName = Obj.getSectionName(SecRef);
       if (!RelSectName)
         return RelSectName.takeError();
+
+      LLVM_DEBUG({
+        dbgs() << "Adding relocations from section " << *RelSectName << "\n";
+      });
       // Deal with .eh_frame later
       if (*RelSectName == StringRef(".rela.eh_frame"))
         continue;
@@ -385,6 +416,18 @@ class ELFLinkGraphBuilder_x86_64 {
       if (!UpdateSectionName)
         return UpdateSectionName.takeError();
 
+      // Don't process relocations for debug sections.
+      if (isDwarfSection(*UpdateSectionName)) {
+        LLVM_DEBUG({
+          dbgs() << "  Target is dwarf section " << *UpdateSectionName
+                 << ". Skipping.\n";
+        });
+        continue;
+      } else
+        LLVM_DEBUG({
+          dbgs() << "  For target section " << *UpdateSectionName << "\n";
+        });
+
       auto JITSection = G->findSectionByName(*UpdateSectionName);
       if (!JITSection)
         return make_error<llvm::StringError>(
@@ -473,6 +516,9 @@ class ELFLinkGraphBuilder_x86_64 {
       auto Name = Obj.getSectionName(SecRef);
       if (!Name)
         return Name.takeError();
+
+      LLVM_DEBUG(dbgs() << "Processing symbol section " << *Name << ":\n");
+
       auto Section = G->findSectionByName(*Name);
       if (!Section)
         return make_error<llvm::StringError>("Could not find a section " +
@@ -531,6 +577,10 @@ class ELFLinkGraphBuilder_x86_64 {
           if (!sectName)
             return Name.takeError();
 
+          // Skip debug section symbols.
+          if (isDwarfSection(*sectName))
+            continue;
+
           auto JitSection = G->findSectionByName(*sectName);
           if (!JitSection)
             return make_error<llvm::StringError>(

diff  --git a/llvm/test/ExecutionEngine/JITLink/X86/ELF_skip_debug_sections.s b/llvm/test/ExecutionEngine/JITLink/X86/ELF_skip_debug_sections.s
new file mode 100644
index 000000000000..506bbdfd8844
--- /dev/null
+++ b/llvm/test/ExecutionEngine/JITLink/X86/ELF_skip_debug_sections.s
@@ -0,0 +1,240 @@
+# RUN: llvm-mc -triple=x86_64-pc-linux-gnu -filetype=obj -o %t %s
+# RUN: llvm-jitlink -debug-only=jitlink -noexec %t 2>&1 | FileCheck %s
+#
+# Check that debug sections are not emitted.
+#
+# CHECK: .debug_info is a debug section: No graph section will be created.
+
+	.text
+	.file	"ELF_skip_debug_sections.c"
+	.globl	foo
+	.p2align	4, 0x90
+	.type	foo, at function
+foo:
+.Lfunc_begin0:
+	.file	1 "/tmp" "ELF_skip_debug_sections.c"
+	.loc	1 1 0
+	.cfi_startproc
+
+	.loc	1 2 3 prologue_end
+	movl	$42, %eax
+	retq
+.Ltmp0:
+.Lfunc_end0:
+	.size	foo, .Lfunc_end0-foo
+	.cfi_endproc
+
+	.globl	main
+	.p2align	4, 0x90
+	.type	main, at function
+main:
+.Lfunc_begin1:
+	.loc	1 5 0
+	.cfi_startproc
+
+
+
+	.loc	1 6 3 prologue_end
+	movl	$42, %eax
+	retq
+.Ltmp1:
+.Lfunc_end1:
+	.size	main, .Lfunc_end1-main
+	.cfi_endproc
+
+	.section	.debug_str,"MS", at progbits,1
+.Linfo_string0:
+	.asciz	"clang version 10.0.0-4ubuntu1 "
+.Linfo_string1:
+	.asciz	"ELF_skip_debug_sections.c"
+.Linfo_string2:
+	.asciz	"/tmp"
+.Linfo_string3:
+	.asciz	"foo"
+.Linfo_string4:
+	.asciz	"int"
+.Linfo_string5:
+	.asciz	"main"
+.Linfo_string6:
+	.asciz	"argc"
+.Linfo_string7:
+	.asciz	"argv"
+.Linfo_string8:
+	.asciz	"char"
+	.section	.debug_abbrev,"", at progbits
+	.byte	1
+	.byte	17
+	.byte	1
+	.byte	37
+	.byte	14
+	.byte	19
+	.byte	5
+	.byte	3
+	.byte	14
+	.byte	16
+	.byte	23
+	.byte	27
+	.byte	14
+	.byte	17
+	.byte	1
+	.byte	18
+	.byte	6
+	.byte	0
+	.byte	0
+	.byte	2
+	.byte	46
+	.byte	0
+	.byte	17
+	.byte	1
+	.byte	18
+	.byte	6
+	.byte	64
+	.byte	24
+	.ascii	"\227B"
+	.byte	25
+	.byte	3
+	.byte	14
+	.byte	58
+	.byte	11
+	.byte	59
+	.byte	11
+	.byte	39
+	.byte	25
+	.byte	73
+	.byte	19
+	.byte	63
+	.byte	25
+	.byte	0
+	.byte	0
+	.byte	3
+	.byte	46
+	.byte	1
+	.byte	17
+	.byte	1
+	.byte	18
+	.byte	6
+	.byte	64
+	.byte	24
+	.ascii	"\227B"
+	.byte	25
+	.byte	3
+	.byte	14
+	.byte	58
+	.byte	11
+	.byte	59
+	.byte	11
+	.byte	39
+	.byte	25
+	.byte	73
+	.byte	19
+	.byte	63
+	.byte	25
+	.byte	0
+	.byte	0
+	.byte	4
+	.byte	5
+	.byte	0
+	.byte	2
+	.byte	24
+	.byte	3
+	.byte	14
+	.byte	58
+	.byte	11
+	.byte	59
+	.byte	11
+	.byte	73
+	.byte	19
+	.byte	0
+	.byte	0
+	.byte	5
+	.byte	36
+	.byte	0
+	.byte	3
+	.byte	14
+	.byte	62
+	.byte	11
+	.byte	11
+	.byte	11
+	.byte	0
+	.byte	0
+	.byte	6
+	.byte	15
+	.byte	0
+	.byte	73
+	.byte	19
+	.byte	0
+	.byte	0
+	.byte	0
+	.section	.debug_info,"", at progbits
+.Lcu_begin0:
+	.long	.Ldebug_info_end0-.Ldebug_info_start0
+.Ldebug_info_start0:
+	.short	4
+	.long	.debug_abbrev
+	.byte	8
+	.byte	1
+	.long	.Linfo_string0
+	.short	12
+	.long	.Linfo_string1
+	.long	.Lline_table_start0
+	.long	.Linfo_string2
+	.quad	.Lfunc_begin0
+	.long	.Lfunc_end1-.Lfunc_begin0
+	.byte	2
+	.quad	.Lfunc_begin0
+	.long	.Lfunc_end0-.Lfunc_begin0
+	.byte	1
+	.byte	87
+
+	.long	.Linfo_string3
+	.byte	1
+	.byte	1
+
+	.long	119
+
+	.byte	3
+	.quad	.Lfunc_begin1
+	.long	.Lfunc_end1-.Lfunc_begin1
+	.byte	1
+	.byte	87
+
+	.long	.Linfo_string5
+	.byte	1
+	.byte	5
+
+	.long	119
+
+	.byte	4
+	.byte	1
+	.byte	85
+	.long	.Linfo_string6
+	.byte	1
+	.byte	5
+	.long	119
+	.byte	4
+	.byte	1
+	.byte	84
+	.long	.Linfo_string7
+	.byte	1
+	.byte	5
+	.long	126
+	.byte	0
+	.byte	5
+	.long	.Linfo_string4
+	.byte	5
+	.byte	4
+	.byte	6
+	.long	131
+	.byte	6
+	.long	136
+	.byte	5
+	.long	.Linfo_string8
+	.byte	6
+	.byte	1
+	.byte	0
+.Ldebug_info_end0:
+	.ident	"clang version 10.0.0-4ubuntu1 "
+	.section	".note.GNU-stack","", at progbits
+	.addrsig
+	.section	.debug_line,"", at progbits
+.Lline_table_start0:


        


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