[COFF] Check for sections larger than 4 GiB

[smeenai]

Summary

Sections are limited to 4 GiB. Error out early if a section exceeds this
size, rather than overflowing the section size and getting confusing
assertion failures/segfaults later.

[smeenai]

I'm not sure how to write a test case for this without creating an object file with a section > 4 GiB (as in that object file will take upwards of 4 GiB on disk). Any ideas?

[ruiu]

How about creating huge .bss sections and link them?

[smeenai]

In D38005#874414, @ruiu wrote:

How about creating huge .bss sections and link them?

Do you mean using yaml2obj? I don't know of a way to do that via assembler directives (and I'd love to learn if there is one).

[davide]

yaml2obj should allow you to create a broken object like that. IIRC there's an example in test/ELF.

[ruiu]

I believe there's a way to create a huge .bss section using assembler, but yaml2obj is fine. We are using it for COFF tests (but not for ELF tests.)

[ruiu]

COFF/Writer.cpp

191

Can you use errro() instead? We use fatal() only for reporting corrupted input files. Files with too large sections are not technically corrupted.

[smeenai]

Change to error and add test.

[smeenai]

Exit with correct error code.

[ruiu]

LGTM

test/COFF/section-size.s

3–5 ↗

(On Diff #115777)

It seems just %t1.obj and %t3.obj suffice.

9 ↗

(On Diff #115777)

Instead of creating a temporary file by cp, you can just pass the same object file twice.

[smeenai]

test/COFF/section-size.s

3–5 ↗

(On Diff #115777)

Sure, will rename.

9 ↗

(On Diff #115777)

lld-link deduplicates input object files: https://reviews.llvm.org/diffusion/L/browse/lld/trunk/COFF/Driver.cpp;313693$295-303. Is there some other way to get around that?

[ruiu]

test/COFF/section-size.s

9 ↗

(On Diff #115777)

Oh, I didn't know that. cp is of course fine if that's the case.

COFF/Writer.cpp

 void OutputSection::addChunk(Chunk *C) {
   Chunks.push_back(C);
   C->setOutputSection(this);
   uint64_t Off = Header.VirtualSize;
   Off = alignTo(Off, C->Alignment);
   C->setRVA(Off);
   C->OutputSectionOff = Off;
   Off += C->getSize();
+  if (Off > UINT32_MAX)
+    fatal("section larger than 4 GiB: " + Name);
   Header.VirtualSize = Off;
   if (C->hasData())
     Header.SizeOfRawData = alignTo(Off, SectorSize);
 }
 
 void OutputSection::addPermissions(uint32_t C) {
   Header.Characteristics |= C & PermMask;
 }