jory/upx
1
0
Fork 0
Code Issues Pull Requests 1 Actions Packages Projects Releases Wiki Activity

PackDjgpp2::canPack() allows "loose" (non-contiguous) text,data,bss

Browse Source 
Hack: grow text to eliminate gap; don't complain unless bss overlaps data
https://github.com/upx/upx/issues/45
	modified:   p_djgpp2.cpp
This commit is contained in:
John Reiser 2022-08-28 15:39:36 -07:00 committed by Markus F.X.J. Oberhumer
parent ee242ba987
commit eb68ab91cd
1 changed files with 17 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
src/p_djgpp2.cpp
View File

@ -251,14 +251,25 @@ bool PackDjgpp2::canPack()
if (opt->force == 0) if (opt->force == 0)
if (text->size != coff_hdr.a_tsize || data->size != coff_hdr.a_dsize) if (text->size != coff_hdr.a_tsize || data->size != coff_hdr.a_dsize)
throwAlreadyPacked(); throwAlreadyPacked();
// Check for gap in vaddr between text and data, or between data and bss.
if (text->vaddr + text->size != data->vaddr if (text->vaddr + text->size != data->vaddr
|| data->vaddr + data->size != bss->vaddr) || data->vaddr + data->size != bss->vaddr)
{ {
if (text->vaddr + text->size < data->vaddr && // "Non-standard" layout of text,data,bss: not contiguous in vaddr.
data->vaddr - text->vaddr == data->scnptr - text->scnptr) // But should be OK if no overlap.
// Check for no overlap of text and data:
// neither by vaddr, nor by image data
if (text->vaddr + text->size <= data->vaddr &&
data->scnptr - text->scnptr <= data->vaddr - text->vaddr)
{ {
// This hack is needed to compress Quake 1! // Examples: Quake1; FreePascal(DOS) install.exe (github-issue45)
text->size = coff_hdr.a_tsize = data->vaddr - text->vaddr; // Hack: enlarge text image data to eliminate the gap.
text->size = coff_hdr.a_tsize = data->scnptr - text->scnptr;
// But complain if this causes overlap in vaddr
if (text->vaddr + text->size > data->vaddr)
throwAlreadyPacked();
} }
else else
throwAlreadyPacked(); throwAlreadyPacked();
@ -326,7 +337,8 @@ void PackDjgpp2::pack(OutputFile *fo)
linker->defineSymbol("original_entry", coff_hdr.a_entry); linker->defineSymbol("original_entry", coff_hdr.a_entry);
linker->defineSymbol("length_of_bss", ph.overlap_overhead / 4); linker->defineSymbol("length_of_bss", ph.overlap_overhead / 4);
defineDecompressorSymbols(); defineDecompressorSymbols();
assert(bss->vaddr == ((size + 0x1ff) &~ 0x1ff) + (text->vaddr &~ 0x1ff)); // Just need no overlap; non-contiguous (gap length > 0)) is OK
assert(bss->vaddr >= ((size + 0x1ff) &~ 0x1ff) + (text->vaddr &~ 0x1ff));
linker->defineSymbol("stack_for_lzma", bss->vaddr + bss->size); linker->defineSymbol("stack_for_lzma", bss->vaddr + bss->size);
linker->defineSymbol("start_of_uncompressed", text->vaddr - hdrsize); linker->defineSymbol("start_of_uncompressed", text->vaddr - hdrsize);
linker->defineSymbol("start_of_compressed", data->vaddr); linker->defineSymbol("start_of_compressed", data->vaddr);