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Date:      Tue, 16 Jun 2020 20:25:46 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 247327] i386 linuxulator doesn't support more than one LDT
Message-ID:  <bug-247327-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D247327

            Bug ID: 247327
           Summary: i386 linuxulator doesn't support more than one LDT
           Product: Base System
           Version: CURRENT
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: trasz@FreeBSD.org

Alex S reported that Proton (which is Wine distribution integrated with Ste=
am)
depends on functionality mentioned at
https://github.com/freebsd/freebsd/blob/8989bc4581101acb0dda31d9c4f9b6ec473=
2c5cf/sys/i386/linux/linux_machdep.c#L582:

/*
 * Semantics of Linux version: every thread in the system has array of
 * 3 tls descriptors. 1st is GLIBC TLS, 2nd is WINE, 3rd unknown. This
 * syscall loads one of the selected tls decriptors with a value and
 * also loads GDT descriptors 6, 7 and 8 with the content of the
 * per-thread descriptors.
 *
 * Semantics of FreeBSD version: I think we can ignore that Linux has 3
 * per-thread descriptors and use just the 1st one. The tls_array[]
 * is used only in set/get-thread_area() syscalls and for loading the
 * GDT descriptors. In FreeBSD we use just one GDT descriptor for TLS
 * so we will load just one.
 *
 * XXX: this doesn't work when a user space process tries to use more
 * than 1 TLS segment. Comment in the Linux sources says wine might do
 * this.
 */

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