[Xen-changelog] Set guest selectors to be null if it's not valid when switch to

[Xen patchbot -unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User kaf24@xxxxxxxxxxxxxxxxxxxx
# Node ID e04b0805febb44a922fcdd4744b9e71a65064417
# Parent  f069a06e650f773a7eba6ecf19fe30c241db5dc2
Set guest selectors to be null if it's not valid when switch to
protected-mode in the guest firmware.

Signed-off-by: Chengyuan Li <chengyuan.li@xxxxxxxxx>
Signed-off-by: Asit Mallick <asit.k.mallick@xxxxxxxxx>

diff -r f069a06e650f -r e04b0805febb tools/firmware/vmxassist/vm86.c
--- a/tools/firmware/vmxassist/vm86.c   Wed Sep 28 21:18:30 2005
+++ b/tools/firmware/vmxassist/vm86.c   Thu Sep 29 08:59:46 2005
@@ -470,10 +470,21 @@
        unsigned long long entry;
 
        /* protected mode: use seg as index into gdt */
-       if (sel == 0 || sel > oldctx.gdtr_limit)
+       if (sel > oldctx.gdtr_limit)
                return 0;
 
+    if (sel == 0) {
+        arbytes->fields.null_bit = 1;
+        return 1;
+    }
+
        entry =  ((unsigned long long *) oldctx.gdtr_base)[sel >> 3];
+
+    /* Check the P bit fisrt*/
+    if (!((entry >> (15+32)) & 0x1) && sel != 0) {
+        return 0;
+    }
+
        *base =  (((entry >> (56-24)) & 0xFF000000) |
                  ((entry >> (32-16)) & 0x00FF0000) |
                  ((entry >> (   16)) & 0x0000FFFF));
@@ -519,22 +530,42 @@
        if (load_seg(regs->ves, &oldctx.es_base,
                                &oldctx.es_limit, &oldctx.es_arbytes))
                oldctx.es_sel = regs->ves;
+    else {
+        load_seg(0, &oldctx.es_base,&oldctx.es_limit, &oldctx.es_arbytes);
+        oldctx.es_sel = 0;
+    }
 
        if (load_seg(regs->uss, &oldctx.ss_base,
                                &oldctx.ss_limit, &oldctx.ss_arbytes))
                oldctx.ss_sel = regs->uss;
+    else {
+        load_seg(0, &oldctx.ss_base, &oldctx.ss_limit, &oldctx.ss_arbytes);
+        oldctx.ss_sel = 0;
+    }
 
        if (load_seg(regs->vds, &oldctx.ds_base,
                                &oldctx.ds_limit, &oldctx.ds_arbytes))
                oldctx.ds_sel = regs->vds;
+    else {
+        load_seg(0, &oldctx.ds_base, &oldctx.ds_limit, &oldctx.ds_arbytes);
+        oldctx.ds_sel = 0;
+    }
 
        if (load_seg(regs->vfs, &oldctx.fs_base,
                                &oldctx.fs_limit, &oldctx.fs_arbytes))
                oldctx.fs_sel = regs->vfs;
+    else {
+        load_seg(0, &oldctx.fs_base, &oldctx.fs_limit, &oldctx.fs_arbytes);
+        oldctx.fs_sel = 0;
+    }
 
        if (load_seg(regs->vgs, &oldctx.gs_base,
                                &oldctx.gs_limit, &oldctx.gs_arbytes))
                oldctx.gs_sel = regs->vgs;
+    else {
+        load_seg(0, &oldctx.gs_base, &oldctx.gs_limit, &oldctx.gs_arbytes);
+        oldctx.gs_sel = 0;
+    }
 
        /* initialize jump environment to warp back to protected mode */
        regs->cs = CODE_SELECTOR;

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