[llvm] 784c7de - [elfabi] Fix a bug when .dynsym contains no non-local symbol

[Haowei Wu via llvm-commits]

Author: Haowei Wu
Date: 2021-02-19T11:36:53-08:00
New Revision: 784c7debb21795a0c0a4188590a7eac14f170744

URL: https://github.com/llvm/llvm-project/commit/784c7debb21795a0c0a4188590a7eac14f170744
DIFF: https://github.com/llvm/llvm-project/commit/784c7debb21795a0c0a4188590a7eac14f170744.diff

LOG: [elfabi] Fix a bug when .dynsym contains no non-local symbol

This patch fixed a bug when elbabi was supplied with a tbe file
contains no non-local symbol. Before this patch, it wrote 0 to
sh_info of the .dynsym section, making the ELF stub file invalid.
This patch fixed this issue.

Differential Revision: https://reviews.llvm.org/D96930

Added: 
    llvm/test/tools/llvm-elfabi/write-stub-no-nonlocal-symbol.test

Modified: 
    llvm/lib/InterfaceStub/ELFObjHandler.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/InterfaceStub/ELFObjHandler.cpp b/llvm/lib/InterfaceStub/ELFObjHandler.cpp
index 255d301362eb..9deb5ba0ae45 100644
--- a/llvm/lib/InterfaceStub/ELFObjHandler.cpp
+++ b/llvm/lib/InterfaceStub/ELFObjHandler.cpp
@@ -303,7 +303,10 @@ template <class ELFT> class ELFStubBuilder {
     SymTab.Shdr.sh_flags = SHF_ALLOC;
     SymTab.Shdr.sh_addr = SymTab.Addr;
     SymTab.Shdr.sh_offset = SymTab.Offset;
-    SymTab.Shdr.sh_info = SymTab.Size / sizeof(Elf_Sym) > 1 ? 1 : 0;
+    // Only non-local symbols are included in the tbe file, so .dynsym only
+    // contains 1 local symbol (the undefined symbol at index 0). The sh_info
+    // should always be 1.
+    SymTab.Shdr.sh_info = 1;
     SymTab.Shdr.sh_size = SymTab.Size;
     SymTab.Shdr.sh_name = this->ShStrTab.Content.getOffset(SymTab.Name);
     SymTab.Shdr.sh_addralign = SymTab.Align;

diff  --git a/llvm/test/tools/llvm-elfabi/write-stub-no-nonlocal-symbol.test b/llvm/test/tools/llvm-elfabi/write-stub-no-nonlocal-symbol.test
new file mode 100644
index 000000000000..98dece0e37d6
--- /dev/null
+++ b/llvm/test/tools/llvm-elfabi/write-stub-no-nonlocal-symbol.test
@@ -0,0 +1,86 @@
+## Test writing stub elf when symbol table contains no non-local symbol.
+
+# RUN: llvm-elfabi %s --output-target=elf64-little %t
+# RUN: llvm-readobj -S %t | FileCheck %s -DCLASS="64-bit (0x2)" -DDE="LittleEndian (0x1)" -DHS=64 -DPHES=56 -DSHES=64 -DDYNSYMAL=8 -DDYNSYMES=24 -DDYNAMICAL=8 -DDYNAMICES=16 -DDYNTABZ=000000000
+
+--- !tapi-tbe
+TbeVersion: 1.0
+Arch: x86_64
+NeededLibs:
+  - libc.so.6
+Symbols: {}
+...
+
+# CHECK:      Section {
+# CHECK-NEXT:   Index: 0
+# CHECK-NEXT:   Name:  (0)
+# CHECK-NEXT:   Type: SHT_NULL
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Address: 0x0
+# CHECK-NEXT:   Offset: 0x0
+# CHECK-NEXT:   Size: 0
+# CHECK-NEXT:   Link: 0
+# CHECK-NEXT:   Info: 0
+# CHECK-NEXT:   AddressAlignment: 0
+# CHECK-NEXT:   EntrySize: 0
+# CHECK-NEXT: }
+# CHECK-NEXT: Section {
+# CHECK-NEXT:   Index: 1
+# CHECK-NEXT:   Name: .dynsym
+# CHECK-NEXT:   Type: SHT_DYNSYM
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_ALLOC
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Address:
+# CHECK-NEXT:   Offset:
+# CHECK-NEXT:   Size:
+# CHECK-NEXT:   Link: 2
+# CHECK-NEXT:   Info: 1
+# CHECK-NEXT:   AddressAlignment: [[DYNSYMAL]]
+# CHECK-NEXT:   EntrySize: [[DYNSYMES]]
+# CHECK-NEXT: }
+# CHECK-NEXT: Section {
+# CHECK-NEXT:   Index: 2
+# CHECK-NEXT:   Name: .dynstr
+# CHECK-NEXT:   Type: SHT_STRTAB
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_ALLOC
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Address:
+# CHECK-NEXT:   Offset:
+# CHECK-NEXT:   Size:
+# CHECK-NEXT:   Link: 0
+# CHECK-NEXT:   Info: 0
+# CHECK-NEXT:   AddressAlignment: 1
+# CHECK-NEXT:   EntrySize: 0
+# CHECK-NEXT: }
+# CHECK-NEXT: Section {
+# CHECK-NEXT:   Index: 3
+# CHECK-NEXT:   Name: .dynamic
+# CHECK-NEXT:   Type: SHT_DYNAMIC
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:     SHF_ALLOC
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Address:
+# CHECK-NEXT:   Offset:
+# CHECK-NEXT:   Size:
+# CHECK-NEXT:   Link: 2
+# CHECK-NEXT:   Info: 0
+# CHECK-NEXT:   AddressAlignment: [[DYNAMICAL]]
+# CHECK-NEXT:   EntrySize: [[DYNAMICES]]
+# CHECK-NEXT: }
+# CHECK-NEXT: Section {
+# CHECK-NEXT:   Index: 4
+# CHECK-NEXT:   Name: .shstrtab
+# CHECK-NEXT:   Type: SHT_STRTAB
+# CHECK-NEXT:   Flags [
+# CHECK-NEXT:   ]
+# CHECK-NEXT:   Address:
+# CHECK-NEXT:   Offset:
+# CHECK-NEXT:   Size:
+# CHECK-NEXT:   Link: 0
+# CHECK-NEXT:   Info: 0
+# CHECK-NEXT:   AddressAlignment: 1
+# CHECK-NEXT:   EntrySize: 0
+# CHECK-NEXT: }