labath created this revision.
labath added reviewers: JDevlieghere, MaskRay, clayborg.
Herald added a subscriber: aprantl.
Herald added a project: LLDB.
The intention here is to prune out line sequences addresses referring
outside any known sections. Such line sequences are typically produced
by dead-stripped code, which leaves behind some debug info.
These line sequences were pretty much ignored already -- they would fail
at the LineTable::ConvertEntryAtIndexToLineEntry stage. However, they
still made it into the line table and into the "image dump line-table"
output, which was printing random nonsense as a result.
This avoids putting these sequences into the line table in the first
place, which makes them smaller (some files have a lot of dead line
sequences) and hopefully slightly speeds up code which iterates through
the line table linearly.
It also makes the "image dump line-table" output sane, which means I can
write my test for handling of different linker tombstoning behaviors.
Depends on D84401 <https://reviews.llvm.org/D84401>.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D84402
Files:
lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
lldb/test/Shell/SymbolFile/DWARF/debug_line-tombstone.s
Index: lldb/test/Shell/SymbolFile/DWARF/debug_line-tombstone.s
===================================================================
--- lldb/test/Shell/SymbolFile/DWARF/debug_line-tombstone.s
+++ lldb/test/Shell/SymbolFile/DWARF/debug_line-tombstone.s
@@ -1,27 +1,48 @@
-# This test that we don't get confused by line tables containing a tombstone
-# (-1) value, as produced by recent lld's. Line sequences with the tombstone
-# value should be completely ignored. The tombstone sequence is deliberately
-# longer so that any attempt at an address binary search will likely land inside
-# the sequence.
+# Test handling of line table tombstone strategies by various linkers. When a
+# section not added to the final binary (either due to --gc-sections or comdats)
+# (elf) linkers still need to resolve debug info relocations to it. This test
+# simulates tombstoning behavior of bfd gold and lld linkers.
+# - ld.bfd will resolve all relocations to zero
+# - ld.gold (and lld before D81784) could also resolve the relocations to a
+# small value (zero+relocation addend), although this is not likely to happen
+# in line tables.
+# - ld.lld since D81784, resolves the relocations to -1
+# These line tables should be ignored. bfd and gold tombstones can be ambiguous
+# if the binary has sections in the low addresses, but we should definitely
+# ignore them if they fall outside of any section.
-# RUN: llvm-mc --filetype=obj --triple=x86_64-pc-linux %s -o %t
-# RUN: %lldb -o "image lookup -n main -v" -o "image dump line-table main.cpp" \
-# RUN: -o exit %t | FileCheck %s
+# REQUIRES: x86, lld
-# CHECK-LABEL: image lookup -n main -v
-# CHECK: LineEntry: [0x0000000000001000-0x0000000000001001): main.cpp:1
+# RUN: llvm-mc --filetype=obj --triple=x86_64-pc-linux %s -o %t.lld.o --defsym TOMBSTONE=-1
+# RUN: ld.lld -o %t.lld %t.lld.o --image-base=0x10000
+# RUN: %lldb -o "image lookup -n _start -v" -o "image dump line-table main.cpp" \
+# RUN: -o exit %t.lld | FileCheck %s
+
+# RUN: llvm-mc --filetype=obj --triple=x86_64-pc-linux %s -o %t.bfd.o --defsym TOMBSTONE=0
+# RUN: ld.lld -o %t.bfd %t.bfd.o --image-base=0x10000
+# RUN: %lldb -o "image lookup -n _start -v" -o "image dump line-table main.cpp" \
+# RUN: -o exit %t.bfd | FileCheck %s
+
+# RUN: llvm-mc --filetype=obj --triple=x86_64-pc-linux %s -o %t.gold.o --defsym TOMBSTONE=47
+# RUN: ld.lld -o %t.gold %t.gold.o --image-base=0x10000
+# RUN: %lldb -o "image lookup -n _start -v" -o "image dump line-table main.cpp" \
+# RUN: -o exit %t.gold | FileCheck %s
+
+# CHECK-LABEL: image lookup -n _start -v
+# CHECK: LineEntry: [0x0000000000020000-0x0000000000020001): main.cpp:1
# CHECK-LABEL: image dump line-table main.cpp
# CHECK-NEXT: Line table for main.cpp
-# CHECK-NEXT: 0x0000000000001000: main.cpp:1
-# CHECK-NEXT: 0x0000000000001001: main.cpp:1
+# CHECK-NEXT: 0x0000000000020000: main.cpp:1
+# CHECK-NEXT: 0x0000000000020001: main.cpp:1
# CHECK-EMPTY:
# CHECK-NEXT: exit
+ .globl _start
.text
-.space 0x1000
-main:
+ .p2align 16
+_start:
nop
-.Lmain_end:
+.L_start_end:
.section .debug_abbrev,"",@progbits
.byte 1 # Abbreviation Code
@@ -52,8 +73,8 @@
.asciz "Hand-written DWARF" # DW_AT_producer
.asciz "main.cpp" # DW_AT_name
.long 0 # DW_AT_stmt_list
- .quad main-.text # DW_AT_low_pc
- .long .Lmain_end-main # DW_AT_high_pc
+ .quad _start # DW_AT_low_pc
+ .long .L_start_end-_start # DW_AT_high_pc
.Ldebug_info_end0:
.section .debug_line,"",@progbits
@@ -75,7 +96,7 @@
.byte 0
.Lprologue1_end:
.byte 0, 9, 2 # DW_LNE_set_address
- .quad -1
+ .quad TOMBSTONE
.byte 1 # DW_LNS_copy
.byte 33 # address += 1, line += 1
.byte 33 # address += 1, line += 1
@@ -97,7 +118,7 @@
.byte 0, 1, 1 # DW_LNE_end_sequence
.byte 0, 9, 2 # DW_LNE_set_address
- .quad main-.text
+ .quad _start
.byte 18 # address += 0, line += 0
.byte 2 # DW_LNS_advance_pc
.uleb128 1
Index: lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
===================================================================
--- lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -1039,7 +1039,10 @@
std::vector<std::unique_ptr<LineSequence>> sequences;
// The Sequences view contains only valid line sequences. Don't iterate over
// the Rows directly.
+ SectionList &list = *GetObjectFile()->GetModule()->GetSectionList();
for (const llvm::DWARFDebugLine::Sequence &seq : line_table->Sequences) {
+ if (!list.ContainsFileAddressRange(seq.LowPC, seq.HighPC - seq.LowPC))
+ continue;
std::unique_ptr<LineSequence> sequence =
LineTable::CreateLineSequenceContainer();
for (unsigned idx = seq.FirstRowIndex; idx < seq.LastRowIndex; ++idx) {
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