release/21.x: [LLD][COFF] Follow up comments on pr146610 (#147152) #149906
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This is a follow-up PR for post-commit comments in llvm#146610 - Changed "exporteddllmain" references to "importeddllmain". - Add support for x86 target and test coverage. - Changed a comment to better express why we're skipping importing `DllMain`. (cherry picked from commit fcacd4e)
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@aganea What do you think about merging this PR to the release branch? |
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@llvm/pr-subscribers-lld-coff @llvm/pr-subscribers-platform-windows Author: None (llvmbot) ChangesBackport fcacd4e Requested by: @mstorsjo Full diff: https://github.com/llvm/llvm-project/pull/149906.diff 5 Files Affected:
diff --git a/lld/COFF/Config.h b/lld/COFF/Config.h
index 79b63e5b7236f..9220c847f356d 100644
--- a/lld/COFF/Config.h
+++ b/lld/COFF/Config.h
@@ -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;
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index 283aeed1a19cd..0f649ff1cf4f8 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -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.
}
}
diff --git a/lld/COFF/InputFiles.cpp b/lld/COFF/InputFiles.cpp
index 0b7dbea8cdd99..2a6b63cbacca1 100644
--- a/lld/COFF/InputFiles.cpp
+++ b/lld/COFF/InputFiles.cpp
@@ -117,8 +117,6 @@ static coff_symbol_generic *cloneSymbol(COFFSymbolRef sym) {
// Skip importing DllMain thunks from import libraries.
static bool fixupDllMain(COFFLinkerContext &ctx, llvm::object::Archive *file,
const Archive::Symbol &sym, bool &skipDllMain) {
- if (skipDllMain)
- return true;
const Archive::Child &c =
CHECK(sym.getMember(), file->getFileName() +
": could not get the member for symbol " +
@@ -128,13 +126,13 @@ 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;
@@ -204,14 +202,24 @@ void ArchiveFile::parse() {
}
}
- // Read the symbol table to construct Lazy objects.
bool skipDllMain = false;
+ StringRef mangledDllMain, impMangledDllMain;
+
+ // The calls below will fail if we haven't set the machine type yet. Instead
+ // of failing, it is preferable to skip this "imported DllMain" check if we
+ // don't know the machine type at this point.
+ if (!file->isEmpty() && ctx.config.machine != IMAGE_FILE_MACHINE_UNKNOWN) {
+ mangledDllMain = archiveSymtab->mangle("DllMain");
+ impMangledDllMain = uniqueSaver().save("__imp_" + mangledDllMain);
+ }
+
+ // Read the symbol table to construct Lazy objects.
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 (fixupDllMain(ctx, file.get(), sym, skipDllMain))
+ // 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 (!mangledDllMain.empty() && (sym.getName() == mangledDllMain ||
+ sym.getName() == impMangledDllMain)) {
+ if (skipDllMain || fixupDllMain(ctx, file.get(), sym, skipDllMain))
continue;
}
archiveSymtab->addLazyArchive(this, sym);
diff --git a/lld/test/COFF/imported-dllmain-i386.test b/lld/test/COFF/imported-dllmain-i386.test
new file mode 100644
index 0000000000000..f8aa09006999c
--- /dev/null
+++ b/lld/test/COFF/imported-dllmain-i386.test
@@ -0,0 +1,58 @@
+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: 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
diff --git a/lld/test/COFF/exported-dllmain.test b/lld/test/COFF/imported-dllmain.test
similarity index 86%
rename from lld/test/COFF/exported-dllmain.test
rename to lld/test/COFF/imported-dllmain.test
index fcf6ed1005379..fa8579b1b41c5 100644
--- a/lld/test/COFF/exported-dllmain.test
+++ b/lld/test/COFF/imported-dllmain.test
@@ -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
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|
@llvm/pr-subscribers-lld Author: None (llvmbot) ChangesBackport fcacd4e Requested by: @mstorsjo Full diff: https://github.com/llvm/llvm-project/pull/149906.diff 5 Files Affected:
diff --git a/lld/COFF/Config.h b/lld/COFF/Config.h
index 79b63e5b7236f..9220c847f356d 100644
--- a/lld/COFF/Config.h
+++ b/lld/COFF/Config.h
@@ -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;
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
index 283aeed1a19cd..0f649ff1cf4f8 100644
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -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.
}
}
diff --git a/lld/COFF/InputFiles.cpp b/lld/COFF/InputFiles.cpp
index 0b7dbea8cdd99..2a6b63cbacca1 100644
--- a/lld/COFF/InputFiles.cpp
+++ b/lld/COFF/InputFiles.cpp
@@ -117,8 +117,6 @@ static coff_symbol_generic *cloneSymbol(COFFSymbolRef sym) {
// Skip importing DllMain thunks from import libraries.
static bool fixupDllMain(COFFLinkerContext &ctx, llvm::object::Archive *file,
const Archive::Symbol &sym, bool &skipDllMain) {
- if (skipDllMain)
- return true;
const Archive::Child &c =
CHECK(sym.getMember(), file->getFileName() +
": could not get the member for symbol " +
@@ -128,13 +126,13 @@ 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;
@@ -204,14 +202,24 @@ void ArchiveFile::parse() {
}
}
- // Read the symbol table to construct Lazy objects.
bool skipDllMain = false;
+ StringRef mangledDllMain, impMangledDllMain;
+
+ // The calls below will fail if we haven't set the machine type yet. Instead
+ // of failing, it is preferable to skip this "imported DllMain" check if we
+ // don't know the machine type at this point.
+ if (!file->isEmpty() && ctx.config.machine != IMAGE_FILE_MACHINE_UNKNOWN) {
+ mangledDllMain = archiveSymtab->mangle("DllMain");
+ impMangledDllMain = uniqueSaver().save("__imp_" + mangledDllMain);
+ }
+
+ // Read the symbol table to construct Lazy objects.
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 (fixupDllMain(ctx, file.get(), sym, skipDllMain))
+ // 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 (!mangledDllMain.empty() && (sym.getName() == mangledDllMain ||
+ sym.getName() == impMangledDllMain)) {
+ if (skipDllMain || fixupDllMain(ctx, file.get(), sym, skipDllMain))
continue;
}
archiveSymtab->addLazyArchive(this, sym);
diff --git a/lld/test/COFF/imported-dllmain-i386.test b/lld/test/COFF/imported-dllmain-i386.test
new file mode 100644
index 0000000000000..f8aa09006999c
--- /dev/null
+++ b/lld/test/COFF/imported-dllmain-i386.test
@@ -0,0 +1,58 @@
+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: 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
diff --git a/lld/test/COFF/exported-dllmain.test b/lld/test/COFF/imported-dllmain.test
similarity index 86%
rename from lld/test/COFF/exported-dllmain.test
rename to lld/test/COFF/imported-dllmain.test
index fcf6ed1005379..fa8579b1b41c5 100644
--- a/lld/test/COFF/exported-dllmain.test
+++ b/lld/test/COFF/imported-dllmain.test
@@ -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
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aganea
approved these changes
Jul 21, 2025
github-project-automation
bot
moved this from Needs Triage
to Needs Merge
in LLVM Release Status
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Backport fcacd4e
Requested by: @mstorsjo