[Lldb-commits] [lldb] Add support for reading the dynamic symbol table from PT_DYNAMIC (PR #112596)

[Pavel Labath via lldb-commits]

================
@@ -0,0 +1,631 @@
+## This test verifies that loading an ELF file that has no section headers can
+## load the dynamic symbol table using the DT_SYMTAB, DT_SYMENT, DT_HASH or
+## the DT_GNU_HASH .dynamic key/value pairs that are loaded via the PT_DYNAMIC
+## segment.
+##
+## This test will convert a shared library from yaml, strip its section headers,
+## and varify that LLDB can load the dynamic symbol table. We must manually
+## strip the section headers from a full shared library because our ELF YAML
+## support in obj2yaml/yaml2obj doesn't support ELF files with program headers
+## only, they must have sections or the file doesn't get recreated correctlty.
+
+# RUN: yaml2obj %s -o %t
+# RUN: llvm-strip --strip-sections %t -o %t.noshdrs
+
+# RUN: %lldb -b \
+# RUN:   -o "target create -d '%t.noshdrs'" \
+# RUN:   -o "image dump objfile" \
+# RUN:   | FileCheck %s --dump-input=always
+# CHECK: (lldb) image dump objfile
+# CHECK: Dumping headers for 1 module(s).
+# CHECK: ObjectFileELF, file =
+# CHECK: ELF Header
+# Make sure there are no section headers
+# CHECK: e_shnum = 0x00000000
+# Make sure we were able to load the symbols
+# CHECK: elf-dynsym.yaml.tmp.noshdrs, num_symbols = 9:
+# CHECK: [ 0] 1 Undefined 0x0000000000000000 0x0000000000000000 0x00000022 __cxa_finalize
+# CHECK: [ 1] 2 X Undefined 0x0000000000000000 0x0000000000000000 0x00000012 puts
+# CHECK: [ 2] 3 Undefined 0x0000000000000000 0x0000000000000000 0x00000020 _ITM_deregisterTMCloneTable
+# CHECK: [ 3] 4 Undefined 0x0000000000000000 0x0000000000000000 0x00000020 __gmon_start__
+# CHECK: [ 4] 5 Undefined 0x0000000000000000 0x0000000000000000 0x00000020 _ITM_registerTMCloneTable
+# CHECK: [ 5] 6 X Code 0x0000000000001135 0x0000000000000016 0x00000012 baz()
+# CHECK: [ 6] 7 X Code 0x000000000000111f 0x0000000000000016 0x00000012 bar()
+# CHECK: [ 7] 8 X Code 0x000000000000114b 0x0000000000000016 0x00000012 biz()
+# CHECK: [ 8] 9 X Code 0x0000000000001109 0x0000000000000016 0x00000012 foo()
+
+--- !ELF
----------------
labath wrote:

I see the problem. I used the version of lld on my system, and it looks like the behavior has changed slightly for the version at HEAD. Sorry about that. I believe this has everything you need:
```
$ bin/llvm-mc -triple=x86_64-pc-linux -filetype=obj -o - - <<<".globl defined, undefined; defined:" | bin/ld.lld /dev/stdin -o - --hash-style=gnu -export-dynamic -shared -z nosectionheader  | llvm-readelf - -d -l

Elf file type is DYN (Shared object file)
Entry point 0x0
There are 6 program headers, starting at offset 64

Program Headers:
  Type           Offset   VirtAddr           PhysAddr           FileSiz  MemSiz   Flg Align
  PHDR           0x000040 0x0000000000000040 0x0000000000000040 0x000188 0x000188 R   0x8
  LOAD           0x000000 0x0000000000000000 0x0000000000000000 0x000243 0x000243 R   0x1000
  LOAD           0x000248 0x0000000000002248 0x0000000000002248 0x000060 0x000db8 RW  0x1000
  DYNAMIC        0x000248 0x0000000000002248 0x0000000000002248 0x000060 0x000060 RW  0x8
  GNU_RELRO      0x000248 0x0000000000002248 0x0000000000002248 0x000060 0x000db8 R   0x1
  GNU_STACK      0x000000 0x0000000000000000 0x0000000000000000 0x000000 0x000000 RW  0x0

 Section to Segment mapping:
  Segment Sections...
   00     
   01     
   02     
   03     
   04     
   05     
Dynamic section at offset 0x248 contains 6 entries:
  Tag                Type       Name/Value
  0x0000000000000006 (SYMTAB)   0x1c8
  0x000000000000000b (SYMENT)   24 (bytes)
  0x0000000000000005 (STRTAB)   0x230
  0x000000000000000a (STRSZ)    19 (bytes)
  0x000000006ffffef5 (GNU_HASH) 0x210
  0x0000000000000000 (NULL)     0x0
```

https://github.com/llvm/llvm-project/pull/112596