Skip to content

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

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: main
Choose a base branch
from
Open

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

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
2 changes: 1 addition & 1 deletion lld/COFF/Config.h
View file
Open in desktop
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;
Expand Down
4 changes: 2 additions & 2 deletions lld/COFF/Driver.cpp
View file
Open in desktop
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.
}
}
Expand Down
14 changes: 7 additions & 7 deletions lld/COFF/InputFiles.cpp
View file
Open in desktop
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") {
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

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;
}
Expand Down
59 changes: 59 additions & 0 deletions lld/test/COFF/imported-dllmain-i386.test
View file
Open in desktop
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
6 changes: 3 additions & 3 deletions lld/test/COFF/exported-dllmain.test → lld/test/COFF/imported-dllmain.test
View file
Open in desktop
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
Loading