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[Object] Skip section offset checking for /<XFGHASHMAP>/ 

Starting from Windows SDK for Windows 11 (10.0.22000.x), all the system
libraries (.lib files) contain a section with the '/<XFGHASHMAP>/' name.
This looks like the libraries are built with control flow guard enabled:
https://docs.microsoft.com/en-us/cpp/build/reference/guard-enable-control-flow-guard?view=msvc-170

To let the LLVM tools (llvm-ar, llvm-lib) work with these libraries,
this patch just skips the section offset check for sections with the
'/<XFGHASHMAP>/' name.

Closes: llvm/llvm-project#53814

Signed-off-by: Pavel Samolysov <pavel.samolysov@intel.com>

Reviewed By: jhenderson, thieta

Differential Revision: https://reviews.llvm.org/D120645
This commit is contained in:
Pavel Samolysov 2022-03-02 13:05:46 +02:00 committed by Martin Storsjö
parent df0a2b4f30
commit 2397f67166
2 changed files with 37 additions and 0 deletions
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4
llvm/lib/Object/Archive.cpp
View File

@ -256,6 +256,10 @@ Expected<StringRef> ArchiveMemberHeader::getName(uint64_t Size) const {
return Name;
if (Name.size() == 2 && Name[1] == '/') // String table.
return Name;
// System libraries from the Windows SDK for Windows 11 contain this symbol.
// It looks like a CFG guard: we just skip it for now.
if (Name.equals("/<XFGHASHMAP>/"))
return Name;
// It's a long name.
// Get the string table offset.
std::size_t StringOffset;

33
llvm/test/tools/llvm-lib/xfghashmap-list.test Normal file
View File

@ -0,0 +1,33 @@
# RUN: rm -rf %t && mkdir -p %t && cd %t
# RUN: llvm-mc -triple=x86_64-pc-windows-msvc -filetype=obj -o a.obj %S/Inputs/a.s
# RUN: llvm-mc -triple=x86_64-pc-windows-msvc -filetype=obj -o b.obj %S/Inputs/b.s
# RUN: llvm-lib /out:xfghashmap.lib a.obj b.obj
## Replace a section in the library file with /<XFGHASHMAP>/ emulating
## a library from the Windows SDK for Windows 11.
# RUN: %python %s xfghashmap.lib b.obj/
## This should print the /<XFGHASHMAP>/ section as well as an .obj one.
# RUN: llvm-lib /list %t/xfghashmap.lib | FileCheck %s
# CHECK: a.obj
# CHECK: /<XFGHASHMAP>/
# CHECK-NOT: b.obj
import sys
if len(sys.argv) < 3:
print("Use: python3 xfghashmap-list.test <LIBRARY_FILE> <TEMPLATE>")
exit(1)
template = bytes(sys.argv[2], 'utf-8')
xfghashmap = b'/<XFGHASHMAP>/'
data = None
with open(sys.argv[1], "rb") as inp:
data = inp.read()
with open(sys.argv[1], "wb") as outp:
pos = data.find(template)
outp.write(data[:pos])
outp.write(xfghashmap)
outp.write(data[pos + len(xfghashmap):])