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[LLD][COFF] Follow up comments on pr146610 #147152

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2 changes: 1 addition & 1 deletion lld/COFF/Config.h
Original file line number Diff line number Diff line change
Expand Up @@ -307,7 +307,7 @@ struct Configuration {
bool warnDebugInfoUnusable = true;
bool warnLongSectionNames = true;
bool warnStdcallFixup = true;
bool warnExportedDllMain = true;
bool warnImportedDllMain = true;
bool incremental = true;
bool integrityCheck = false;
bool killAt = false;
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4 changes: 2 additions & 2 deletions lld/COFF/Driver.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1643,8 +1643,8 @@ void LinkerDriver::linkerMain(ArrayRef<const char *> argsArr) {
config->warnLocallyDefinedImported = false;
else if (s == "longsections")
config->warnLongSectionNames = false;
else if (s == "exporteddllmain")
config->warnExportedDllMain = false;
else if (s == "importeddllmain")
config->warnImportedDllMain = false;
// Other warning numbers are ignored.
}
}
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14 changes: 7 additions & 7 deletions lld/COFF/InputFiles.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -128,13 +128,13 @@ static bool fixupDllMain(COFFLinkerContext &ctx, llvm::object::Archive *file,
file->getFileName() +
": could not get the buffer for a child buffer of the archive");
if (identify_magic(mb.getBuffer()) == file_magic::coff_import_library) {
if (ctx.config.warnExportedDllMain) {
if (ctx.config.warnImportedDllMain) {
// We won't place DllMain symbols in the symbol table if they are
// coming from a import library. This message can be ignored with the flag
// '/ignore:exporteddllmain'
// '/ignore:importeddllmain'
Warn(ctx)
<< file->getFileName()
<< ": skipping exported DllMain symbol [exporteddllmain]\nNOTE: this "
<< ": skipping imported DllMain symbol [importeddllmain]\nNOTE: this "
"might be a mistake when the DLL/library was produced.";
}
skipDllMain = true;
Expand Down Expand Up @@ -207,10 +207,10 @@ void ArchiveFile::parse() {
// Read the symbol table to construct Lazy objects.
bool skipDllMain = false;
for (const Archive::Symbol &sym : file->symbols()) {
// If the DllMain symbol was exported by mistake, skip importing it
// otherwise we might end up with a import thunk in the final binary which
// is wrong.
if (sym.getName() == "__imp_DllMain" || sym.getName() == "DllMain") {
// If an import library provides the DllMain symbol, skip importing it, as
// we should be using our own DllMain, not another DLL's DllMain.
if (sym.getName() == "__imp_DllMain" || sym.getName() == "DllMain" ||
sym.getName() == "_DllMain") {
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We shouldn't be testing two different syntaxes, we should only be testing the right one for each architecture. (Otherwise we'd be matching an unrelated symbol on x86_64 too, even if using a symbol named _DllMain there also would be kinda odd.) IIRC you can do e.g. mangle("DllMain") to get the right symbol name. And the same goes for the __imp_ form too, on i386 it would be __imp__DllMain, so Twine("__imp_") + mangle("DllMain") or something along those lines.

if (fixupDllMain(ctx, file.get(), sym, skipDllMain))
continue;
}
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59 changes: 59 additions & 0 deletions lld/test/COFF/imported-dllmain-i386.test
Original file line number Diff line number Diff line change
@@ -0,0 +1,59 @@
REQUIRES: x86
RUN: split-file %s %t.dir && cd %t.dir

RUN: llvm-mc -filetype=obj -triple=i386-windows a.s -o a.obj

RUN: llvm-mc -filetype=obj -triple=i386-windows b1.s -o b1.obj
RUN: llvm-mc -filetype=obj -triple=i386-windows b2.s -o b2.obj

### This is the line where our problem occurs. Here, we export the DllMain symbol which shouldn't happen normally.
RUN: lld-link b1.obj b2.obj -out:b.dll -dll -implib:b.lib -entry:DllMain -export:bar -export:DllMain -safeseh:no

RUN: llvm-mc -filetype=obj -triple=i386-windows c.s -o c.obj
RUN: lld-link -lib c.obj -out:c.lib

### Later, if b.lib is provided before other libs/objs that export DllMain statically, we previously were using the dllimported DllMain from b.lib, which is wrong.
RUN: lld-link a.obj b.lib c.lib -dll -out:out.dll -entry:DllMain -safeseh:no 2>&1 | FileCheck -check-prefix=WARN %s
RUN: lld-link a.obj b.lib c.lib -dll -out:out.dll -entry:DllMain -ignore:importeddllmain -safeseh:no 2>&1 | FileCheck -check-prefix=IGNORED --allow-empty %s
RUN: llvm-objdump --private-headers -d out.dll | FileCheck -check-prefix=DISASM %s

WARN: lld-link: warning: b.lib: skipping imported DllMain symbol [importeddllmain]
IGNORED-NOT: lld-link: warning: b.lib: skipping imported DllMain symbol [importeddllmain]

DISASM: The Import Tables:
DISASM: DLL Name: b.dll
DISASM-NOT: DllMain
DISASM: bar
DISASM: Disassembly of section .text:
DISASM-EMPTY:
DISASM-NEXT: b0 01 movb $0x1, %al
DISASM-NEXT: c3 retl

#--- a.s
.text
.globl _foo
_foo:
call *__imp__bar
ret

#--- b1.s
.text
.globl _bar
_bar:
ret

#--- b2.s
.intel_syntax noprefix
.text
.globl _DllMain
_DllMain:
xor al, al
ret

#--- c.s
.intel_syntax noprefix
.text
.globl _DllMain
_DllMain:
mov al, 1
ret
Original file line number Diff line number Diff line change
Expand Up @@ -14,11 +14,11 @@ RUN: lld-link -lib c.obj -out:c.lib

### Later, if b.lib is provided before other libs/objs that export DllMain statically, we previously were using the dllimported DllMain from b.lib, which is wrong.
RUN: lld-link a.obj b.lib c.lib -dll -out:out.dll -entry:DllMain 2>&1 | FileCheck -check-prefix=WARN %s
RUN: lld-link a.obj b.lib c.lib -dll -out:out.dll -entry:DllMain -ignore:exporteddllmain 2>&1 | FileCheck -check-prefix=IGNORED --allow-empty %s
RUN: lld-link a.obj b.lib c.lib -dll -out:out.dll -entry:DllMain -ignore:importeddllmain 2>&1 | FileCheck -check-prefix=IGNORED --allow-empty %s
RUN: llvm-objdump --private-headers -d out.dll | FileCheck -check-prefix=DISASM %s

WARN: lld-link: warning: b.lib: skipping exported DllMain symbol [exporteddllmain]
IGNORED-NOT: lld-link: warning: b.lib: skipping exported DllMain symbol [exporteddllmain]
WARN: lld-link: warning: b.lib: skipping imported DllMain symbol [importeddllmain]
IGNORED-NOT: lld-link: warning: b.lib: skipping imported DllMain symbol [importeddllmain]

DISASM: The Import Tables:
DISASM: DLL Name: b.dll
Expand Down
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