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[COFF] Write the debug directory and build id to a separate section for MinGW 

For dwarf debug info, an executable normally either contains the debug
info, or it is stripped out. To reduce the storage needed (slightly)
for the debug info kept separately from the released, stripped binaries,
one can choose to only copy the debug data from the original executable
(essentially the reverse of the strip operation), producing a file with
only debug info.

When copying the debug data from an executable with GNU objcopy,
the build id and debug directory need to reside in a separate section,
as this will be kept while the rest of the .rdata section is removed.

Differential Revision: https://reviews.llvm.org/D49352

llvm-svn: 337526
This commit is contained in:
Martin Storsjo 2018-07-20 05:44:34 +00:00
parent ea9c580994
commit a55fc71614
2 changed files with 22 additions and 2 deletions
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8
lld/COFF/Writer.cpp
View File

@ -201,6 +201,7 @@ private:
OutputSection *TextSec;
OutputSection *RdataSec;
OutputSection *BuildidSec;
OutputSection *DataSec;
OutputSection *PdataSec;
OutputSection *IdataSec;
@ -420,6 +421,7 @@ void Writer::createSections() {
TextSec = CreateSection(".text", CODE | R | X);
CreateSection(".bss", BSS | R | W);
RdataSec = CreateSection(".rdata", DATA | R);
BuildidSec = CreateSection(".buildid", DATA | R);
DataSec = CreateSection(".data", DATA | R | W);
PdataSec = CreateSection(".pdata", DATA | R);
IdataSec = CreateSection(".idata", DATA | R);
@ -503,6 +505,8 @@ void Writer::createMiscChunks() {
if (Config->Debug) {
DebugDirectory = make<DebugDirectoryChunk>(DebugRecords);
OutputSection *DebugInfoSec = Config->MinGW ? BuildidSec : RdataSec;
// Make a CVDebugRecordChunk even when /DEBUG:CV is not specified. We
// output a PDB no matter what, and this chunk provides the only means of
// allowing a debugger to match a PDB and an executable. So we need it even
@ -511,9 +515,9 @@ void Writer::createMiscChunks() {
BuildId = CVChunk;
DebugRecords.push_back(CVChunk);
RdataSec->addChunk(DebugDirectory);
DebugInfoSec->addChunk(DebugDirectory);
for (Chunk *C : DebugRecords)
RdataSec->addChunk(C);
DebugInfoSec->addChunk(C);
}
// Create SEH table. x86-only.

16
lld/test/COFF/debug-reloc.s
View File

@ -5,7 +5,13 @@
# RUN: lld-link -lldmingw -debug:dwarf -out:%t.exe -entry:mainfunc -subsystem:console %t.obj
# RUN: llvm-readobj -sections %t.exe | FileCheck %s -check-prefix SECTIONS
# RUN: llvm-readobj -coff-basereloc %t.exe | FileCheck %s -check-prefix RELOCS
# RUN: llvm-readobj -file-headers %t.exe | FileCheck %s -check-prefix HEADERS
# RUN: llvm-readobj -coff-debug-directory %t.exe | FileCheck %s -check-prefix DEBUG
# SECTIONS: Number: 2
# SECTIONS-NEXT: Name: .buildid (2E 62 75 69 6C 64 69 64)
# SECTIONS-NEXT: VirtualSize: 0x35
# SECTIONS-NEXT: VirtualAddress: 0x2000
# SECTIONS: Number: 3
# SECTIONS-NEXT: Name: .data (2E 64 61 74 61 00 00 00)
# SECTIONS-NEXT: VirtualSize: 0x8
@ -22,6 +28,16 @@
# RELOCS-NEXT: }
# RELOCS-NEXT: ]
# HEADERS: DebugRVA: 0x2000
# HEADERS: DebugSize: 0x1C
# DEBUG: DebugDirectory [
# DEBUG: DebugEntry {
# DEBUG: Type: CodeView (0x2)
# DEBUG: SizeOfData: 0x19
# DEBUG: AddressOfRawData: 0x201C
# DEBUG: PointerToRawData: 0x61C
.text
.def mainfunc;
.scl 2;