[llvm] 5f8e51a - [llvm-readobj] - Add a few warnings for --gnu-hash-table.
Georgii Rymar via llvm-commits
llvm-commits at lists.llvm.org
Thu Jan 30 03:03:11 PST 2020
Author: Georgii Rymar
Date: 2020-01-30T14:02:24+03:00
New Revision: 5f8e51a9d4a36cfd9e8f934a351865680927d10e
URL: https://github.com/llvm/llvm-project/commit/5f8e51a9d4a36cfd9e8f934a351865680927d10e
DIFF: https://github.com/llvm/llvm-project/commit/5f8e51a9d4a36cfd9e8f934a351865680927d10e.diff
LOG: [llvm-readobj] - Add a few warnings for --gnu-hash-table.
The current implementation stops dumping in case of a single error
it handles, though we can continue dumping.
This patch refines it: it adds a few warnings and a few test cases.
Differential revision: https://reviews.llvm.org/D73269
Added:
Modified:
llvm/test/tools/llvm-readobj/ELF/gnuhash.test
llvm/tools/llvm-readobj/ELFDumper.cpp
Removed:
################################################################################
diff --git a/llvm/test/tools/llvm-readobj/ELF/gnuhash.test b/llvm/test/tools/llvm-readobj/ELF/gnuhash.test
index 5981a7db2636..c680e0071f28 100644
--- a/llvm/test/tools/llvm-readobj/ELF/gnuhash.test
+++ b/llvm/test/tools/llvm-readobj/ELF/gnuhash.test
@@ -100,3 +100,217 @@ ProgramHeaders:
Sections:
- Section: .gnu.hash
- Section: .dynamic
+
+## Check we report a warning if there is no dynamic symbol section in the object.
+
+# RUN: yaml2obj --docnum=3 %s -o %t.nodynsym
+# RUN: llvm-readobj --gnu-hash-table %t.nodynsym 2>&1 | FileCheck %s -DFILE=%t.nodynsym --check-prefix=NODYNSYM
+# RUN: llvm-readelf --gnu-hash-table %t.nodynsym 2>&1 | FileCheck %s -DFILE=%t.nodynsym --check-prefix=NODYNSYM
+
+# NODYNSYM: GnuHashTable {
+# NODYNSYM-NEXT: Num Buckets: 1
+# NODYNSYM-NEXT: First Hashed Symbol Index: 0
+# NODYNSYM-NEXT: Num Mask Words: 1
+# NODYNSYM-NEXT: Shift Count: 0
+# NODYNSYM-NEXT: Bloom Filter: [0x0]
+# NODYNSYM-NEXT: Buckets: [0]
+# NODYNSYM-NEXT: warning: '[[FILE]]': unable to dump 'Values' for the SHT_GNU_HASH section: no dynamic symbol table found
+# NODYNSYM-NEXT: }
+
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_DYN
+ Machine: EM_X86_64
+Sections:
+ - Name: .gnu.hash
+ Type: SHT_GNU_HASH
+ Flags: [ SHF_ALLOC ]
+ Header:
+ SymNdx: 0x0
+ Shift2: 0x0
+ BloomFilter: [ 0x0 ]
+ HashBuckets: [ 0x0 ]
+ HashValues: [ 0x0 ]
+ - Name: .dynamic
+ Type: SHT_DYNAMIC
+ Flags: [ SHF_ALLOC ]
+ Entries:
+ - Tag: DT_GNU_HASH
+ Value: 0x0
+ - Tag: DT_NULL
+ Value: 0x0
+ProgramHeaders:
+ - Type: PT_LOAD
+ Flags: [ PF_R, PF_X ]
+ Sections:
+ - Section: .gnu.hash
+ - Section: .dynamic
+
+## Check what we do when the index of the first symbol in the dynamic symbol table
+## included in the hash table is larger than the number of dynamic symbols.
+
+# RUN: yaml2obj --docnum=4 %s -o %t.brokensymndx
+# RUN: llvm-readobj --gnu-hash-table %t.brokensymndx 2>&1 \
+# RUN: | FileCheck %s -DFILE=%t.brokensymndx --check-prefix=SYMNDX
+# RUN: llvm-readelf --gnu-hash-table %t.brokensymndx 2>&1 \
+# RUN: | FileCheck %s -DFILE=%t.brokensymndx --check-prefix=SYMNDX
+
+# SYMNDX: GnuHashTable {
+# SYMNDX-NEXT: Num Buckets: 1
+# SYMNDX-NEXT: First Hashed Symbol Index: 2
+# SYMNDX-NEXT: Num Mask Words: 1
+# SYMNDX-NEXT: Shift Count: 0
+# SYMNDX-NEXT: Bloom Filter: [0x1]
+# SYMNDX-NEXT: Buckets: [2]
+# SYMNDX-NEXT: warning: '[[FILE]]': the first hashed symbol index (2) is larger than the number of dynamic symbols (2)
+# SYMNDX-NEXT: }
+
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_DYN
+ Machine: EM_X86_64
+Sections:
+ - Name: .gnu.hash
+ Type: SHT_GNU_HASH
+ Flags: [ SHF_ALLOC ]
+ Header:
+ SymNdx: 0x2
+ Shift2: 0x0
+ BloomFilter: [ 0x1 ]
+ HashBuckets: [ 0x2 ]
+ HashValues: [ 0x3 ]
+ - Name: .dynamic
+ Type: SHT_DYNAMIC
+ Flags: [ SHF_ALLOC ]
+ Link: 0
+ Entries:
+ - Tag: DT_GNU_HASH
+ Value: 0x0
+ - Tag: DT_NULL
+ Value: 0x0
+DynamicSymbols:
+ - Name: aaa
+ Binding: STB_GLOBAL
+ProgramHeaders:
+ - Type: PT_LOAD
+ Flags: [ PF_R, PF_X ]
+ Sections:
+ - Section: .gnu.hash
+ - Section: .dynamic
+
+## Check we emit a warning when the dynamic symbol table is empty.
+## A valid dynamic symbol table should have at least one symbol: the symbol with index 0.
+
+# RUN: yaml2obj --docnum=5 %s -o %t.emptydynsym
+# RUN: llvm-readobj --gnu-hash-table %t.emptydynsym 2>&1 \
+# RUN: | FileCheck %s -DFILE=%t.emptydynsym --check-prefix=EMPTY-DYNSYM
+# RUN: llvm-readelf --gnu-hash-table %t.emptydynsym 2>&1 \
+# RUN: | FileCheck %s -DFILE=%t.emptydynsym --check-prefix=EMPTY-DYNSYM
+
+# EMPTY-DYNSYM: GnuHashTable {
+# EMPTY-DYNSYM-NEXT: Num Buckets: 1
+# EMPTY-DYNSYM-NEXT: First Hashed Symbol Index: 0
+# EMPTY-DYNSYM-NEXT: Num Mask Words: 1
+# EMPTY-DYNSYM-NEXT: Shift Count: 0
+# EMPTY-DYNSYM-NEXT: Bloom Filter: [0x0]
+# EMPTY-DYNSYM-NEXT: Buckets: [0]
+# EMPTY-DYNSYM-NEXT: warning: '[[FILE]]': unable to dump 'Values' for the SHT_GNU_HASH section: the dynamic symbol table is empty
+# EMPTY-DYNSYM-NEXT: }
+
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_DYN
+ Machine: EM_X86_64
+Sections:
+ - Name: .gnu.hash
+ Type: SHT_GNU_HASH
+ Flags: [ SHF_ALLOC ]
+ Header:
+ SymNdx: 0x0
+ Shift2: 0x0
+ BloomFilter: [ 0x0 ]
+ HashBuckets: [ 0x0 ]
+ HashValues: [ 0x0 ]
+ - Name: .dynamic
+ Type: SHT_DYNAMIC
+ Flags: [ SHF_ALLOC ]
+ Link: 0
+ Entries:
+ - Tag: DT_GNU_HASH
+ Value: 0x0
+ - Tag: DT_NULL
+ Value: 0x0
+ - Name: .dynsym
+ Type: SHT_DYNSYM
+ Size: 0
+ProgramHeaders:
+ - Type: PT_LOAD
+ Flags: [ PF_R, PF_X ]
+ Sections:
+ - Section: .gnu.hash
+ - Section: .dynamic
+
+## Linkers might produce an empty no-op SHT_GNU_HASH section when
+## there are no dynamic symbols or when all dynamic symbols are undefined.
+## Such sections normally have a single zero entry in the bloom
+## filter, a single zero entry in the hash bucket and no values.
+##
+## The index of the first symbol in the dynamic symbol table
+## included in the hash table can be set to the number of dynamic symbols,
+## which is one larger than the index of the last dynamic symbol.
+## For empty tables however, this value is unimportant and can be ignored.
+
+# RUN: yaml2obj --docnum=6 %s -o %t.empty
+# RUN: llvm-readobj --gnu-hash-table %t.empty 2>&1 \
+# RUN: | FileCheck %s -DFILE=%t.empty --check-prefix=EMPTY --implicit-check-not="warning:"
+# RUN: llvm-readelf --gnu-hash-table %t.empty 2>&1 \
+# RUN: | FileCheck %s -DFILE=%t.empty --check-prefix=EMPTY --implicit-check-not="warning:"
+
+# EMPTY: GnuHashTable {
+# EMPTY-NEXT: Num Buckets: 1
+# EMPTY-NEXT: First Hashed Symbol Index: 1
+# EMPTY-NEXT: Num Mask Words: 1
+# EMPTY-NEXT: Shift Count: 0
+# EMPTY-NEXT: Bloom Filter: [0x0]
+# EMPTY-NEXT: Buckets: [0]
+# EMPTY-NEXT: Values: []
+# EMPTY-NEXT: }
+
+--- !ELF
+FileHeader:
+ Class: ELFCLASS64
+ Data: ELFDATA2LSB
+ Type: ET_DYN
+ Machine: EM_X86_64
+Sections:
+ - Name: .gnu.hash
+ Type: SHT_GNU_HASH
+ Flags: [ SHF_ALLOC ]
+ Header:
+ SymNdx: 0x1
+ Shift2: 0x0
+ BloomFilter: [ 0x0 ]
+ HashBuckets: [ 0x0 ]
+ HashValues: [ ]
+ - Name: .dynamic
+ Type: SHT_DYNAMIC
+ Flags: [ SHF_ALLOC ]
+ Link: 0
+ Entries:
+ - Tag: DT_GNU_HASH
+ Value: 0x0
+ - Tag: DT_NULL
+ Value: 0x0
+DynamicSymbols: []
+ProgramHeaders:
+ - Type: PT_LOAD
+ Flags: [ PF_R, PF_X ]
+ Sections:
+ - Section: .gnu.hash
+ - Section: .dynamic
diff --git a/llvm/tools/llvm-readobj/ELFDumper.cpp b/llvm/tools/llvm-readobj/ELFDumper.cpp
index 626ac415ee3a..cd6600bf174f 100644
--- a/llvm/tools/llvm-readobj/ELFDumper.cpp
+++ b/llvm/tools/llvm-readobj/ELFDumper.cpp
@@ -2495,12 +2495,50 @@ template <typename ELFT> void ELFDumper<ELFT>::printGnuHashTable() {
W.printNumber("First Hashed Symbol Index", GnuHashTable->symndx);
W.printNumber("Num Mask Words", GnuHashTable->maskwords);
W.printNumber("Shift Count", GnuHashTable->shift2);
- W.printHexList("Bloom Filter", GnuHashTable->filter());
- W.printList("Buckets", GnuHashTable->buckets());
- Elf_Sym_Range Syms = dynamic_symbols();
- unsigned NumSyms = std::distance(Syms.begin(), Syms.end());
- if (!NumSyms)
- reportError(createError("No dynamic symbol section"), ObjF->getFileName());
+
+ ArrayRef<typename ELFT::Off> BloomFilter = GnuHashTable->filter();
+ W.printHexList("Bloom Filter", BloomFilter);
+
+ ArrayRef<Elf_Word> Buckets = GnuHashTable->buckets();
+ W.printList("Buckets", Buckets);
+
+ if (!DynSymRegion.Addr) {
+ reportWarning(createError("unable to dump 'Values' for the SHT_GNU_HASH "
+ "section: no dynamic symbol table found"),
+ ObjF->getFileName());
+ return;
+ }
+
+ size_t NumSyms = dynamic_symbols().size();
+ if (!NumSyms) {
+ reportWarning(createError("unable to dump 'Values' for the SHT_GNU_HASH "
+ "section: the dynamic symbol table is empty"),
+ ObjF->getFileName());
+ return;
+ }
+
+ if (GnuHashTable->symndx >= NumSyms) {
+ // A normal empty GNU hash table section produced by linker might have
+ // symndx set to the number of dynamic symbols + 1 (for the zero symbol)
+ // and have dummy null values in the Bloom filter and in the buckets
+ // vector. It happens because the value of symndx is not important for
+ // dynamic loaders when the GNU hash table is empty. They just skip the
+ // whole object during symbol lookup. In such cases, the symndx value is
+ // irrelevant and we should not report a warning.
+ bool IsEmptyHashTable =
+ llvm::all_of(Buckets, [](Elf_Word V) { return V == 0; });
+
+ if (!IsEmptyHashTable) {
+ reportWarning(
+ createError("the first hashed symbol index (" +
+ Twine(GnuHashTable->symndx) +
+ ") is larger than the number of dynamic symbols (" +
+ Twine(NumSyms) + ")"),
+ ObjF->getFileName());
+ return;
+ }
+ }
+
W.printHexList("Values", GnuHashTable->values(NumSyms));
}
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