[Object][Archive] Support a new archive member /<ECSYMBOLS>/

[pzheng]

Summary

Some libraries (e.g., arm64rt.lib) from the Windows WDK (version 10.0.22000.0)
contain an undocumented special member '/<ECSYMBOLS>/'. This causes llvm-lib to
fail with the following error:

"truncated or malformed archive (long name offset characters after the '/' are
not all decimal numbers: '<ECSYMBOLS>/' for archive member header at offset 162)"

The '/<ECSYMBOLS>/' member does not seem to be documented anywhere, but might be
related to the ARM64EC ABI Microsoft announced last year.

https://blogs.windows.com/windowsdeveloper/2021/06/28/announcing-arm64ec-building-native-and-interoperable-apps-for-windows-11-on-arm/

[thakis]

Thanks!

[thieta]

I think you can drop the content lines from the test cases. But other that that it looks fine.

[pzheng]

In D127135#3561269, @thieta wrote:

I think you can drop the content lines from the test cases. But other that that it looks fine.

I tried removing the content lines from the test case, but got the following error somehow. Any idea?

"truncated or malformed archive (offset to next archive member past the end of the archive after member foo-arm64ec.obj)"

[mstorsjo]

CC:ing @efriedma here, who's working on the arm64ec support.

[efriedma]

I suspect we'll need to do something with the ECSYMBOLS section at some point, but given the lack of documentation, this is probably good enough for now.

[jhenderson]

In D127135#3561301, @pzheng wrote:

In D127135#3561269, @thieta wrote:

I think you can drop the content lines from the test cases. But other that that it looks fine.

I tried removing the content lines from the test case, but got the following error somehow. Any idea?

"truncated or malformed archive (offset to next archive member past the end of the archive after member foo-arm64ec.obj)"

Did you update the Size fields too? I suspect those might be the problem. I also think you should inline the test input into the test file, since it's presumably only going to be used in the one test - having the test input close to the test commands themselves makes it easier to see what the test is doing. Finally, if you don't need all the library members for the test (it doesn't look to me like you do), you should remove them, leavnig only the ECSYMBOLS one.

[pzheng]

In D127135#3563314, @jhenderson wrote:

In D127135#3561301, @pzheng wrote:

In D127135#3561269, @thieta wrote:

I think you can drop the content lines from the test cases. But other that that it looks fine.

I tried removing the content lines from the test case, but got the following error somehow. Any idea?

"truncated or malformed archive (offset to next archive member past the end of the archive after member foo-arm64ec.obj)"

Did you update the Size fields too? I suspect those might be the problem. I also think you should inline the test input into the test file, since it's presumably only going to be used in the one test - having the test input close to the test commands themselves makes it easier to see what the test is doing. Finally, if you don't need all the library members for the test (it doesn't look to me like you do), you should remove them, leavnig only the ECSYMBOLS one.

Thanks for the tips, @jhenderson. The error is gone after updating the size field. I just pushed the changes to the test here: https://reviews.llvm.org/D127235.

llvm/lib/Object/Archive.cpp

if (Name[0] == '/') {
     if (Name.size() == 1) // Linker member.
       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;
+    // Some libraries (e.g., arm64rt.lib) from the Windows WDK
+    // (version 10.0.22000.0) contain this undocumented special member.
+    if (Name.equals("/<ECSYMBOLS>/"))
+      return Name;
     // It's a long name.
     // Get the string table offset.
     std::size_t StringOffset;
     if (Name.substr(1).rtrim(' ').getAsInteger(10, StringOffset)) {
       std::string Buf;
       raw_string_ostream OS(Buf);
       OS.write_escaped(Name.substr(1).rtrim(' '));
       OS.flush();

llvm/test/tools/llvm-lib/Inputs/ecsymbols.yaml

+--- !Arch
+Members:
+  - Name:            '/'
+    LastModified:    '1654282752'
+    UID:             ''
+    GID:             ''
+    Size:            '12'
+    Content:         0000000100000666666F6F00
+  - Name:            '/'
+    LastModified:    '1654282752'
+    UID:             ''
+    GID:             ''
+    Size:            '22'
+    Content:         02000000FC00000066060000010000000200666F6F00
+  - Name:            '/<ECSYMBOLS>/'
+    LastModified:    '1654282752'
+    UID:             ''
+    GID:             ''
+    Size:            '30'
+    Content:         020000000100010023666F6F0023666F6F24656E7472795F7468756E6B00
+  - Name:            'foo-arm64ec.obj/'
+    LastModified:    '1654282644'
+    UID:             ''
+    GID:             ''
+    AccessMode:      '100666'
+    Size:            '1326'
+    Content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
+  - Name:            'foo-arm64.obj/'
+    LastModified:    '1654282562'
+    UID:             ''
+    GID:             ''
+    AccessMode:      '100666'
+    Size:            '573'
+    Content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
+    PaddingByte:     0xA
+...

llvm/test/tools/llvm-lib/ecsymbols.test

+# Check that llvm-lib can list the members of an archive which contains the
+# special member /<ECSYMBOLS>/.
+
+# RUN: yaml2obj %S/Inputs/ecsymbols.yaml -o %t.lib
+# RUN: llvm-lib /list %t.lib | FileCheck %s
+
+# CHECK: /<ECSYMBOLS>/