[src/trunk]: src/tests/lib/libi386 Compile USER_LDT by default, but, put it b...

[maxv <maxv%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9e690b38a8e7
branches:  trunk
changeset: 1012000:9e690b38a8e7
user:      maxv <maxv%NetBSD.org@localhost>
date:      Sun Jul 19 14:31:31 2020 +0000

description:
Compile USER_LDT by default, but, put it behind a privileged sysctl that
defaults to disabled. To enable:

        # sysctl -w machdep.user_ldt=1

diffstat:

 sys/arch/amd64/conf/ALL        |   6 +++---
 sys/arch/amd64/conf/GENERIC    |   6 +++---
 sys/arch/x86/x86/x86_machdep.c |  20 +++++++++++++++++---
 tests/lib/libi386/t_user_ldt.c |   4 ++--
 4 files changed, 25 insertions(+), 11 deletions(-)

diffs (128 lines):

diff -r eed42ba10a65 -r 9e690b38a8e7 sys/arch/amd64/conf/ALL
--- a/sys/arch/amd64/conf/ALL   Sun Jul 19 14:27:07 2020 +0000
+++ b/sys/arch/amd64/conf/ALL   Sun Jul 19 14:31:31 2020 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: ALL,v 1.156 2020/07/14 00:45:52 yamaguchi Exp $
+# $NetBSD: ALL,v 1.157 2020/07/19 14:31:31 maxv Exp $
 # From NetBSD: GENERIC,v 1.787 2006/10/01 18:37:54 bouyer Exp
 #
 # ALL machine description file
@@ -17,14 +17,14 @@
 
 options        INCLUDE_CONFIG_FILE     # embed config file in kernel binary
 
-#ident         "ALL-$Revision: 1.156 $"
+#ident         "ALL-$Revision: 1.157 $"
 
 maxusers       64              # estimated number of users
 
 makeoptions    USE_SSP=yes
 
 # CPU-related options.
-#options       USER_LDT        # user-settable LDT; used by WINE
+options        USER_LDT        # User-settable LDT, used by Wine
 options        X86EMU          # 386 Real Mode emulator
 #options       PAE             # PAE mode (36 bits physical addressing)
 makeoptions    SPECTRE_V2_GCC_MITIGATION=1     # GCC Spectre variant 2
diff -r eed42ba10a65 -r 9e690b38a8e7 sys/arch/amd64/conf/GENERIC
--- a/sys/arch/amd64/conf/GENERIC       Sun Jul 19 14:27:07 2020 +0000
+++ b/sys/arch/amd64/conf/GENERIC       Sun Jul 19 14:31:31 2020 +0000
@@ -1,4 +1,4 @@
-# $NetBSD: GENERIC,v 1.572 2020/07/14 01:05:06 yamaguchi Exp $
+# $NetBSD: GENERIC,v 1.573 2020/07/19 14:31:31 maxv Exp $
 #
 # GENERIC machine description file
 #
@@ -22,7 +22,7 @@
 
 options        INCLUDE_CONFIG_FILE     # embed config file in kernel binary
 
-#ident         "GENERIC-$Revision: 1.572 $"
+#ident         "GENERIC-$Revision: 1.573 $"
 
 maxusers       64              # estimated number of users
 
@@ -74,7 +74,7 @@
 options        SYSCTL_INCLUDE_DESCR    # Include sysctl descriptions in kernel
 
 # CPU-related options
-#options       USER_LDT        # User-settable LDT, used by Wine
+options        USER_LDT        # User-settable LDT, used by Wine
 options        SVS             # Separate Virtual Space
 options        PCPU_IDT        # Per CPU IDTs
 
diff -r eed42ba10a65 -r 9e690b38a8e7 sys/arch/x86/x86/x86_machdep.c
--- a/sys/arch/x86/x86/x86_machdep.c    Sun Jul 19 14:27:07 2020 +0000
+++ b/sys/arch/x86/x86/x86_machdep.c    Sun Jul 19 14:31:31 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: x86_machdep.c,v 1.144 2020/07/04 21:02:16 chs Exp $    */
+/*     $NetBSD: x86_machdep.c,v 1.145 2020/07/19 14:31:31 maxv Exp $   */
 
 /*-
  * Copyright (c) 2002, 2006, 2007 YAMAMOTO Takashi,
@@ -31,7 +31,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: x86_machdep.c,v 1.144 2020/07/04 21:02:16 chs Exp $");
+__KERNEL_RCSID(0, "$NetBSD: x86_machdep.c,v 1.145 2020/07/19 14:31:31 maxv Exp $");
 
 #include "opt_modular.h"
 #include "opt_physmem.h"
@@ -95,6 +95,8 @@
 static bool x86_cpu_idle_ipi;
 static char x86_cpu_idle_text[16];
 
+static bool x86_user_ldt_enabled __read_mostly = false;
+
 #ifdef XEN
 
 #include <xen/xen.h>
@@ -1178,9 +1180,14 @@
 
        switch (action) {
        case KAUTH_MACHDEP_IOPERM_GET:
+               result = KAUTH_RESULT_ALLOW;
+               break;
+
        case KAUTH_MACHDEP_LDT_GET:
        case KAUTH_MACHDEP_LDT_SET:
-               result = KAUTH_RESULT_ALLOW;
+               if (x86_user_ldt_enabled) {
+                       result = KAUTH_RESULT_ALLOW;
+               }
                break;
 
        default:
@@ -1432,6 +1439,13 @@
                       CTL_CREATE, CTL_EOL);
 #endif
 
+       sysctl_createv(clog, 0, NULL, NULL,
+                      CTLFLAG_READWRITE,
+                      CTLTYPE_BOOL, "user_ldt",
+                      SYSCTL_DESCR("Whether USER_LDT is enabled"),
+                      NULL, 0, &x86_user_ldt_enabled, 0,
+                      CTL_MACHDEP, CTL_CREATE, CTL_EOL);
+
 #ifndef XENPV
        void sysctl_speculation_init(struct sysctllog **);
        sysctl_speculation_init(clog);
diff -r eed42ba10a65 -r 9e690b38a8e7 tests/lib/libi386/t_user_ldt.c
--- a/tests/lib/libi386/t_user_ldt.c    Sun Jul 19 14:27:07 2020 +0000
+++ b/tests/lib/libi386/t_user_ldt.c    Sun Jul 19 14:31:31 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: t_user_ldt.c,v 1.4 2020/07/03 16:07:52 maxv Exp $      */
+/*     $NetBSD: t_user_ldt.c,v 1.5 2020/07/19 14:31:31 maxv Exp $      */
 
 /*
  * Copyright (c) 2020 The NetBSD Foundation, Inc.
@@ -58,7 +58,7 @@
        int ret;
 
        ret = i386_get_ldt(0, &desc, 1);
-       user_ldt_supported = (ret != -1) || (errno != ENOSYS);
+       user_ldt_supported = (ret != -1) || (errno != ENOSYS && errno != EPERM);
 }
 
 static void