[src/trunk]: src/sys/arch Add most of my USER_LDT code for amd64, but disable...

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

details:   https://anonhg.NetBSD.org/src/rev/2b97ce39fac6
branches:  trunk
changeset: 821717:2b97ce39fac6
user:      maxv <maxv%NetBSD.org@localhost>
date:      Tue Feb 14 09:11:05 2017 +0000

description:
Add most of my USER_LDT code for amd64, but disable it and put a comment
about why Wine still does not work.

Nothing changes, but at least it is a step forward.

diffstat:

 sys/arch/amd64/amd64/trap.c    |   8 ++++-
 sys/arch/x86/x86/sys_machdep.c |  59 +++++++++++++++++++++++++++++++++++++----
 2 files changed, 59 insertions(+), 8 deletions(-)

diffs (180 lines):

diff -r 1be88361c275 -r 2b97ce39fac6 sys/arch/amd64/amd64/trap.c
--- a/sys/arch/amd64/amd64/trap.c       Tue Feb 14 09:07:35 2017 +0000
+++ b/sys/arch/amd64/amd64/trap.c       Tue Feb 14 09:11:05 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: trap.c,v 1.89 2017/01/18 05:11:59 kamil Exp $  */
+/*     $NetBSD: trap.c,v 1.90 2017/02/14 09:11:05 maxv Exp $   */
 
 /*-
  * Copyright (c) 1998, 2000 The NetBSD Foundation, Inc.
@@ -68,7 +68,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: trap.c,v 1.89 2017/01/18 05:11:59 kamil Exp $");
+__KERNEL_RCSID(0, "$NetBSD: trap.c,v 1.90 2017/02/14 09:11:05 maxv Exp $");
 
 #include "opt_ddb.h"
 #include "opt_kgdb.h"
@@ -373,6 +373,10 @@
                        break;
                case 0x848e:    /* mov 0xa8(%rsp),%es (8e 84 24 a8 00 00 00) */
                case 0x9c8e:    /* mov 0xb0(%rsp),%ds (8e 9c 24 b0 00 00 00) */
+#ifdef USER_LDT
+               case 0xa48e:    /* mov 0xa0(%rsp),%fs (8e a4 24 a0 00 00 00) */
+               case 0xac8e:    /* mov 0x98(%rsp),%gs (8e ac 24 98 00 00 00) */
+#endif
                        /*
                         * We faulted loading one of the user segment registers.
                         * The stack frame containing the user registers is
diff -r 1be88361c275 -r 2b97ce39fac6 sys/arch/x86/x86/sys_machdep.c
--- a/sys/arch/x86/x86/sys_machdep.c    Tue Feb 14 09:07:35 2017 +0000
+++ b/sys/arch/x86/x86/sys_machdep.c    Tue Feb 14 09:11:05 2017 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: sys_machdep.c,v 1.31 2017/02/05 10:42:21 maxv Exp $    */
+/*     $NetBSD: sys_machdep.c,v 1.32 2017/02/14 09:11:05 maxv Exp $    */
 
 /*-
  * Copyright (c) 1998, 2007, 2009 The NetBSD Foundation, Inc.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: sys_machdep.c,v 1.31 2017/02/05 10:42:21 maxv Exp $");
+__KERNEL_RCSID(0, "$NetBSD: sys_machdep.c,v 1.32 2017/02/14 09:11:05 maxv Exp $");
 
 #include "opt_mtrr.h"
 #include "opt_perfctrs.h"
@@ -68,8 +68,23 @@
 #include <machine/mtrr.h>
 
 #ifdef __x86_64__
+/*
+ * The code for USER_LDT on amd64 is mostly functional, but it is still not
+ * enabled.
+ *
+ * On amd64 we are allowing only 8-byte-sized entries in the LDT, and we are
+ * not allowing the user to overwrite the existing entries (below LDT_SIZE).
+ * Note that USER_LDT is used only by 32bit applications, under compat_netbsd32.
+ * This is theoretically enough for Wine to work.
+ *
+ * However, letting segment registers have different location breaks amd64's
+ * Thread Local Storage: %fs and %gs must be reloaded when returning to
+ * userland. See the tech-kern@ archive from February 2017. A patch has been
+ * proposed to fix that, but Wine still randomly crashes; it is not clear
+ * whether the issues come from Wine, from netbsd32 or from the patch itself.
+ */
+#undef USER_LDT
 /* Need to be checked. */
-#undef USER_LDT
 #undef PERFCTRS
 #undef IOPERM
 #else
@@ -168,14 +183,23 @@
            ua->start + ua->num > 8192)
                return (EINVAL);
 
+#ifdef __x86_64__
+       if (ua->start * sizeof(union descriptor) < LDT_SIZE)
+               return EINVAL;
+#endif
+
        mutex_enter(&cpu_lock);
 
        if (pmap->pm_ldt != NULL) {
                nldt = pmap->pm_ldt_len / sizeof(*lp);
                lp = pmap->pm_ldt;
        } else {
+#ifdef __x86_64__
+               nldt = LDT_SIZE / sizeof(*lp);
+#else
                nldt = NLDT;
-               lp = ldtstore;
+#endif
+               lp = (union descriptor *)ldtstore;
        }
 
        if (ua->start > nldt) {
@@ -244,6 +268,12 @@
        size_t old_len, new_len;
        union descriptor *old_ldt, *new_ldt;
 
+#ifdef __x86_64__
+       const size_t min_ldt_size = LDT_SIZE;
+#else
+       const size_t min_ldt_size = NLDT * sizeof(union descriptor);
+#endif
+
        error = kauth_authorize_machdep(l->l_cred, KAUTH_MACHDEP_LDT_SET,
            NULL, NULL, NULL, NULL);
        if (error)
@@ -253,6 +283,11 @@
            ua->start + ua->num > 8192)
                return (EINVAL);
 
+#ifdef __x86_64__
+       if (ua->start * sizeof(union descriptor) < LDT_SIZE)
+               return EINVAL;
+#endif
+
        /* Check descriptors for access violations. */
        for (i = 0; i < ua->num; i++) {
                union descriptor *desc = &descv[i];
@@ -261,6 +296,12 @@
                case SDT_SYSNULL:
                        desc->sd.sd_p = 0;
                        break;
+#ifdef __x86_64__
+               case SDT_SYS286CGT:
+               case SDT_SYS386CGT:
+                       /* We don't allow these on amd64. */
+                       return EACCES;
+#else
                case SDT_SYS286CGT:
                case SDT_SYS386CGT:
                        /*
@@ -277,6 +318,7 @@
                                return EACCES;
                        }
                        break;
+#endif
                case SDT_MEMEC:
                case SDT_MEMEAC:
                case SDT_MEMERC:
@@ -324,7 +366,7 @@
        for (;;) {
                new_len = (ua->start + ua->num) * sizeof(union descriptor);
                new_len = max(new_len, pmap->pm_ldt_len);
-               new_len = max(new_len, NLDT * sizeof(union descriptor));
+               new_len = max(new_len, min_ldt_size);
                new_len = round_page(new_len);
                new_ldt = (union descriptor *)uvm_km_alloc(kernel_map,
                    new_len, 0, UVM_KMF_WIRED | UVM_KMF_ZERO | UVM_KMF_WAITVA);
@@ -347,7 +389,7 @@
                old_ldt = NULL;
                old_len = 0;
                old_sel = -1;
-               memcpy(new_ldt, ldtstore, NLDT * sizeof(union descriptor));
+               memcpy(new_ldt, ldtstore, min_ldt_size);
        }
 
        /* Apply requested changes. */
@@ -768,6 +810,10 @@
                error = x86_iopl(l, SCARG(uap, parms), retval);
                break;
 
+#ifdef i386
+       /*
+        * On amd64, this is done via netbsd32_sysarch.
+        */
        case X86_GET_LDT: 
                error = x86_get_ldt(l, SCARG(uap, parms), retval);
                break;
@@ -775,6 +821,7 @@
        case X86_SET_LDT: 
                error = x86_set_ldt(l, SCARG(uap, parms), retval);
                break;
+#endif
 
        case X86_GET_IOPERM: 
                error = x86_get_ioperm(l, SCARG(uap, parms), retval);