[COFF] Add exported functions to gfids table for /guard:cf
Summary:
MSVC does this, and we should to.
The .gfids table is a table of RVAs, so it's impossible for a DLL to
indicate that an imported symbol is address taken. Therefore, exports
appear to be listed as address taken by the DLL that exports them.
This fixes an issue that Firefox ran into here:
https://bugzilla.mozilla.org/show_bug.cgi?id=1485016#c12
In Firefox, the export directive came from a .def file, but we need to
do this for any kind of export.
Reviewers: dmajor, hans, amccarth, alex
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D54723
git-svn-id: https://llvm.org/svn/llvm-project/lld/trunk@347623 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/COFF/Writer.cpp b/COFF/Writer.cpp
index deb4376..e5796d9 100644
--- a/COFF/Writer.cpp
+++ b/COFF/Writer.cpp
@@ -1304,6 +1304,25 @@
RVASet.insert({C, Off});
}
+// Given a symbol, add it to the GFIDs table if it is a live, defined, function
+// symbol in an executable section.
+static void maybeAddAddressTakenFunction(SymbolRVASet &AddressTakenSyms,
+ Symbol *S) {
+ auto *D = dyn_cast_or_null<DefinedCOFF>(S);
+
+ // Ignore undefined symbols and references to non-functions (e.g. globals and
+ // labels).
+ if (!D ||
+ D->getCOFFSymbol().getComplexType() != COFF::IMAGE_SYM_DTYPE_FUNCTION)
+ return;
+
+ // Mark the symbol as address taken if it's in an executable section.
+ Chunk *RefChunk = D->getChunk();
+ OutputSection *OS = RefChunk ? RefChunk->getOutputSection() : nullptr;
+ if (OS && OS->Header.Characteristics & IMAGE_SCN_MEM_EXECUTE)
+ addSymbolToRVASet(AddressTakenSyms, D);
+}
+
// Visit all relocations from all section contributions of this object file and
// mark the relocation target as address-taken.
static void markSymbolsWithRelocations(ObjFile *File,
@@ -1322,17 +1341,7 @@
continue;
Symbol *Ref = SC->File->getSymbol(Reloc.SymbolTableIndex);
- if (auto *D = dyn_cast_or_null<DefinedCOFF>(Ref)) {
- if (D->getCOFFSymbol().getComplexType() != COFF::IMAGE_SYM_DTYPE_FUNCTION)
- // Ignore relocations against non-functions (e.g. labels).
- continue;
-
- // Mark the symbol if it's in an executable section.
- Chunk *RefChunk = D->getChunk();
- OutputSection *OS = RefChunk ? RefChunk->getOutputSection() : nullptr;
- if (OS && OS->Header.Characteristics & IMAGE_SCN_MEM_EXECUTE)
- addSymbolToRVASet(UsedSymbols, D);
- }
+ maybeAddAddressTakenFunction(UsedSymbols, Ref);
}
}
}
@@ -1359,7 +1368,11 @@
// Mark the image entry as address-taken.
if (Config->Entry)
- addSymbolToRVASet(AddressTakenSyms, cast<Defined>(Config->Entry));
+ maybeAddAddressTakenFunction(AddressTakenSyms, Config->Entry);
+
+ // Mark exported symbols in executable sections as address-taken.
+ for (Export &E : Config->Exports)
+ maybeAddAddressTakenFunction(AddressTakenSyms, E.Sym);
// Ensure sections referenced in the gfid table are 16-byte aligned.
for (const ChunkAndOffset &C : AddressTakenSyms)
diff --git a/test/COFF/gfids-export.s b/test/COFF/gfids-export.s
new file mode 100644
index 0000000..87a4f4b
--- /dev/null
+++ b/test/COFF/gfids-export.s
@@ -0,0 +1,44 @@
+# REQUIRES: x86
+# RUN: llvm-mc -triple x86_64-pc-win32 %s -filetype=obj -o %t.obj
+# RUN: lld-link %t.obj -guard:cf -dll -out:%t.dll -noentry
+# RUN: llvm-readobj -coff-load-config %t.dll | FileCheck %s --check-prefix=CHECK
+
+# There should be a single entry in the table for the exported symbol.
+#
+# CHECK: GuardFidTable [
+# CHECK-NEXT: 0x180001000
+# CHECK-NEXT: ]
+
+ .def func_export; .scl 2; .type 32; .endef
+ .globl func_export
+ .section .text,"xr",one_only,func_export
+ .p2align 4
+func_export:
+ movl $1, %eax
+ .globl label_export
+label_export:
+ movl $2, %eax
+ ret
+
+ .data
+ .globl data_export
+data_export:
+ .long 42
+
+ .section .drectve,"dr"
+ .ascii " /EXPORT:func_export"
+ .ascii " /EXPORT:label_export"
+ .ascii " /EXPORT:data_export"
+
+
+# Load configuration directory entry (winnt.h _IMAGE_LOAD_CONFIG_DIRECTORY64).
+# The linker will define the __guard_* symbols.
+ .section .rdata,"dr"
+.globl _load_config_used
+_load_config_used:
+ .long 256
+ .fill 124, 1, 0
+ .quad __guard_fids_table
+ .quad __guard_fids_count
+ .long __guard_flags
+ .fill 128, 1, 0
