[Lldb-commits] [PATCH] D63540: Fix lookup of symbols at the same address with no size vs. size

Jan Kratochvil via Phabricator via lldb-commits lldb-commits at lists.llvm.org
Wed Jun 19 03:54:41 PDT 2019


jankratochvil created this revision.
jankratochvil added reviewers: clayborg, labath.
jankratochvil added a project: LLDB.
Herald added subscribers: teemperor, aprantl.

This fixes a failing testcase on Fedora 30 x86_64 (regression Fedora 29->30):

  PASS:
  ./bin/lldb ./lldb-test-build.noindex/functionalities/unwind/noreturn/TestNoreturnUnwind.test_dwarf/a.out -o 'settings set symbols.enable-external-lookup false' -o r -o bt -o quit
    * frame #0: 0x00007ffff7aa6e75 libc.so.6`__GI_raise + 325
      frame #1: 0x00007ffff7a91895 libc.so.6`__GI_abort + 295
      frame #2: 0x0000000000401140 a.out`func_c at main.c:12:2
      frame #3: 0x000000000040113a a.out`func_b at main.c:18:2
      frame #4: 0x0000000000401134 a.out`func_a at main.c:26:2
      frame #5: 0x000000000040112e a.out`main(argc=<unavailable>, argv=<unavailable>) at main.c:32:2
      frame #6: 0x00007ffff7a92f33 libc.so.6`__libc_start_main + 243
      frame #7: 0x000000000040106e a.out`_start + 46

vs.

  FAIL - unrecognized abort() function:
  ./bin/lldb ./lldb-test-build.noindex/functionalities/unwind/noreturn/TestNoreturnUnwind.test_dwarf/a.out -o 'settings set symbols.enable-external-lookup false' -o r -o bt -o quit
    * frame #0: 0x00007ffff7aa6e75 libc.so.6`.annobin_raise.c + 325
      frame #1: 0x00007ffff7a91895 libc.so.6`.annobin_loadmsgcat.c_end.unlikely + 295
      frame #2: 0x0000000000401140 a.out`func_c at main.c:12:2
      frame #3: 0x000000000040113a a.out`func_b at main.c:18:2
      frame #4: 0x0000000000401134 a.out`func_a at main.c:26:2
      frame #5: 0x000000000040112e a.out`main(argc=<unavailable>, argv=<unavailable>) at main.c:32:2
      frame #6: 0x00007ffff7a92f33 libc.so.6`.annobin_libc_start.c + 243
      frame #7: 0x000000000040106e a.out`.annobin_init.c.hot + 46

The extra ELF symbols are there due to Annobin <https://fedoraproject.org/wiki/Changes/Annobin> (I did not investigate why this problem happened specifically since F-30 and not since F-28).
It is due to:

  Symbol table '.dynsym' contains 2361 entries:
  Valu e          Size Type   Bind   Vis     Name
  0000000000022769   5 FUNC   LOCAL  DEFAULT _nl_load_domain.cold
  000000000002276e   0 NOTYPE LOCAL  HIDDEN  .annobin_abort.c.unlikely
  ...
  000000000002276e   0 NOTYPE LOCAL  HIDDEN  .annobin_loadmsgcat.c_end.unlikely
  ...
  000000000002276e   0 NOTYPE LOCAL  HIDDEN  .annobin_textdomain.c_end.unlikely
  000000000002276e 548 FUNC   GLOBAL DEFAULT abort
  000000000002276e 548 FUNC   GLOBAL DEFAULT abort@@GLIBC_2.2.5
  000000000002276e 548 FUNC   LOCAL  DEFAULT __GI_abort
  0000000000022992   0 NOTYPE LOCAL  HIDDEN  .annobin_abort.c_end.unlikely

GDB has some more complicated preferences between overlapping and/or sharing address symbols, I have made here so far the most simple fix for this case.


Repository:
  rLLDB LLDB

https://reviews.llvm.org/D63540

Files:
  lldb/lit/SymbolFile/Inputs/sizeless-symbol.s
  lldb/lit/SymbolFile/sizeless-symbol.test
  lldb/source/Symbol/Symtab.cpp


Index: lldb/source/Symbol/Symtab.cpp
===================================================================
--- lldb/source/Symbol/Symtab.cpp
+++ lldb/source/Symbol/Symtab.cpp
@@ -873,7 +873,7 @@
         m_file_addr_to_index.Append(entry);
       }
     }
-    const size_t num_entries = m_file_addr_to_index.GetSize();
+    const ssize_t num_entries = m_file_addr_to_index.GetSize();
     if (num_entries > 0) {
       m_file_addr_to_index.Sort();
 
@@ -893,11 +893,15 @@
       // entries that didn't already have a size from the Symbol (e.g. if we
       // have a plain linker symbol with an address only, instead of debug info
       // where we get an address and a size and a type, etc.)
-      for (size_t i = 0; i < num_entries; i++) {
+      // Check symbols downwards as symbols at the same address with size will
+      // be ordered after zero-sized symbols.
+      for (ssize_t i = num_entries - 1 ; i >= 0; --i) {
         FileRangeToIndexMap::Entry *entry =
             m_file_addr_to_index.GetMutableEntryAtIndex(i);
-        if (entry->GetByteSize() == 0) {
-          addr_t curr_base_addr = entry->GetRangeBase();
+        if (entry->GetByteSize() > 0)
+          continue;
+        addr_t curr_base_addr = entry->GetRangeBase();
+        if (i == num_entries - 1 || m_file_addr_to_index.GetMutableEntryAtIndex(i + 1)->GetRangeBase() != curr_base_addr) {
           const RangeVector<addr_t, addr_t>::Entry *containing_section =
               section_ranges.FindEntryThatContains(curr_base_addr);
 
@@ -909,7 +913,7 @@
                 (entry->GetRangeBase() - containing_section->GetRangeBase());
           }
 
-          for (size_t j = i; j < num_entries; j++) {
+          for (ssize_t j = i; j < num_entries; j++) {
             FileRangeToIndexMap::Entry *next_entry =
                 m_file_addr_to_index.GetMutableEntryAtIndex(j);
             addr_t next_base_addr = next_entry->GetRangeBase();
Index: lldb/lit/SymbolFile/sizeless-symbol.test
===================================================================
--- /dev/null
+++ lldb/lit/SymbolFile/sizeless-symbol.test
@@ -0,0 +1,7 @@
+# RUN: %clang %S/Inputs/sizeless-symbol.s -c -o %t.o
+# RUN: %lldb %t.o -s %s -o quit | FileCheck %s
+
+image lookup --address 1
+# CHECK: Summary: sizeless-symbol.test.tmp.o`sizeful
+image lookup --address 2
+# CHECK: Summary: sizeless-symbol.test.tmp.o`sizeful + 1
Index: lldb/lit/SymbolFile/Inputs/sizeless-symbol.s
===================================================================
--- /dev/null
+++ lldb/lit/SymbolFile/Inputs/sizeless-symbol.s
@@ -0,0 +1,12 @@
+        .text
+        .byte   0
+sizeless:
+        .globl  sizeless 
+        .type   sizeless, @object
+sizeful:
+        .globl  sizeful
+        .type   sizeful, @object
+        .byte   0
+        .byte   0
+sizeend:
+        .size   sizeful, sizeend - sizeful


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