[PATCH] D59496: [llvm-objcopy] - Fix a st_name of the first symbol table entry.
George Rimar via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Wed Mar 20 07:55:51 PDT 2019
grimar updated this revision to Diff 191496.
grimar marked an inline comment as done.
grimar added a comment.
- Updated implementation.
So `StringTableBuilder` reserves a null byte at start for ELF tables:
https://github.com/llvm-mirror/llvm/blob/master/lib/MC/StringTableBuilder.cpp#L38
Seems what we want is just to use it explicitly. For that, I reassign the index of an empty string after finalization.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D59496/new/
https://reviews.llvm.org/D59496
Files:
lib/MC/StringTableBuilder.cpp
test/tools/llvm-objcopy/ELF/symbol-empty-name.test
Index: test/tools/llvm-objcopy/ELF/symbol-empty-name.test
===================================================================
--- /dev/null
+++ test/tools/llvm-objcopy/ELF/symbol-empty-name.test
@@ -0,0 +1,47 @@
+# RUN: yaml2obj %s > %t
+# RUN: llvm-objcopy %t %t2
+# RUN: llvm-readobj -t %t2 | FileCheck %s
+
+## Check that all values of the null symbol are zeroes.
+
+# CHECK: Symbols [
+# CHECK-NEXT: Symbol {
+# CHECK-NEXT: Name: (0)
+# CHECK-NEXT: Value: 0x0
+# CHECK-NEXT: Size: 0
+# CHECK-NEXT: Binding: Local (0x0)
+# CHECK-NEXT: Type: None (0x0)
+# CHECK-NEXT: Other: 0
+# CHECK-NEXT: Section: Undefined (0x0)
+# CHECK-NEXT: }
+
+## Check we emit a zero in st_name field when a symbol has no name.
+
+# CHECK: Name: .text (0)
+# CHECK-NEXT: Value: 0x0
+# CHECK-NEXT: Size: 0
+# CHECK-NEXT: Binding: Local (0x0)
+# CHECK-NEXT: Type: Section (0x3)
+# CHECK-NEXT: Other: 0
+# CHECK-NEXT: Section: .text (0x1)
+# CHECK-NEXT: }
+
+!ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_EXEC
+ Machine: EM_X86_64
+Sections:
+ - Name: .text
+ Type: SHT_PROGBITS
+ Flags: [ SHF_ALLOC, SHF_EXECINSTR ]
+Symbols:
+ Local:
+ - Name: ""
+ Type: STT_SECTION
+ Section: .text
+ Global:
+ # We need to have a named symbol, otherwise the original
+ # issue that was fixed is not reproduced by this test.
+ - Name: foo
Index: lib/MC/StringTableBuilder.cpp
===================================================================
--- lib/MC/StringTableBuilder.cpp
+++ lib/MC/StringTableBuilder.cpp
@@ -159,6 +159,11 @@
if (K == MachO)
Size = alignTo(Size, 4); // Pad to multiple of 4.
+
+ // Empty strings in according to ELF specification should have zero indexes.
+ // In initSize() we explicitly reserved a null byte at the start for that.
+ if (K == ELF)
+ StringIndexMap[CachedHashStringRef("")] = 0;
}
void StringTableBuilder::clear() {
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