1 /*
2 * pv/mm.c
3 *
4 * Memory managment code for PV guests
5 *
6 * Copyright (c) 2002-2005 K A Fraser
7 * Copyright (c) 2004 Christian Limpach
8 *
9 * This program is free software; you can redistribute it and/or
10 * modify it under the terms and conditions of the GNU General Public
11 * License, version 2, as published by the Free Software Foundation.
12 *
13 * This program is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * General Public License for more details.
17 *
18 * You should have received a copy of the GNU General Public
19 * License along with this program; If not, see <http://www.gnu.org/licenses/>.
20 */
21
22 #include <xen/guest_access.h>
23
24 #include <asm/current.h>
25 #include <asm/p2m.h>
26
27 #include "mm.h"
28
29 /* Override macros from asm/page.h to make them work with mfn_t */
30 #undef mfn_to_page
31 #define mfn_to_page(mfn) __mfn_to_page(mfn_x(mfn))
32 #undef page_to_mfn
33 #define page_to_mfn(pg) _mfn(__page_to_mfn(pg))
34
35 /*
36 * Get a mapping of a PV guest's l1e for this linear address. The return
37 * pointer should be unmapped using unmap_domain_page().
38 */
map_guest_l1e(unsigned long linear,mfn_t * gl1mfn)39 l1_pgentry_t *map_guest_l1e(unsigned long linear, mfn_t *gl1mfn)
40 {
41 l2_pgentry_t l2e;
42
43 ASSERT(!paging_mode_translate(current->domain));
44 ASSERT(!paging_mode_external(current->domain));
45
46 if ( unlikely(!__addr_ok(linear)) )
47 return NULL;
48
49 /* Find this l1e and its enclosing l1mfn in the linear map. */
50 if ( __copy_from_user(&l2e,
51 &__linear_l2_table[l2_linear_offset(linear)],
52 sizeof(l2_pgentry_t)) )
53 return NULL;
54
55 /* Check flags that it will be safe to read the l1e. */
56 if ( (l2e_get_flags(l2e) & (_PAGE_PRESENT | _PAGE_PSE)) != _PAGE_PRESENT )
57 return NULL;
58
59 *gl1mfn = l2e_get_mfn(l2e);
60
61 return (l1_pgentry_t *)map_domain_page(*gl1mfn) + l1_table_offset(linear);
62 }
63
64 /*
65 * Read the guest's l1e that maps this address, from the kernel-mode
66 * page tables.
67 */
guest_get_eff_kern_l1e(unsigned long linear)68 static l1_pgentry_t guest_get_eff_kern_l1e(unsigned long linear)
69 {
70 struct vcpu *curr = current;
71 const bool user_mode = !(curr->arch.flags & TF_kernel_mode);
72 l1_pgentry_t l1e;
73
74 if ( user_mode )
75 toggle_guest_pt(curr);
76
77 l1e = guest_get_eff_l1e(linear);
78
79 if ( user_mode )
80 toggle_guest_pt(curr);
81
82 return l1e;
83 }
84
85 /*
86 * Map a guest's LDT page (covering the byte at @offset from start of the LDT)
87 * into Xen's virtual range. Returns true if the mapping changed, false
88 * otherwise.
89 */
pv_map_ldt_shadow_page(unsigned int offset)90 bool pv_map_ldt_shadow_page(unsigned int offset)
91 {
92 struct vcpu *curr = current;
93 struct domain *currd = curr->domain;
94 struct page_info *page;
95 l1_pgentry_t gl1e, *pl1e;
96 unsigned long linear = curr->arch.pv_vcpu.ldt_base + offset;
97
98 BUG_ON(unlikely(in_irq()));
99
100 /*
101 * Hardware limit checking should guarantee this property. NB. This is
102 * safe as updates to the LDT can only be made by MMUEXT_SET_LDT to the
103 * current vcpu, and vcpu_reset() will block until this vcpu has been
104 * descheduled before continuing.
105 */
106 ASSERT((offset >> 3) <= curr->arch.pv_vcpu.ldt_ents);
107
108 if ( is_pv_32bit_domain(currd) )
109 linear = (uint32_t)linear;
110
111 gl1e = guest_get_eff_kern_l1e(linear);
112 if ( unlikely(!(l1e_get_flags(gl1e) & _PAGE_PRESENT)) )
113 return false;
114
115 page = get_page_from_gfn(currd, l1e_get_pfn(gl1e), NULL, P2M_ALLOC);
116 if ( unlikely(!page) )
117 return false;
118
119 if ( unlikely(!get_page_type(page, PGT_seg_desc_page)) )
120 {
121 put_page(page);
122 return false;
123 }
124
125 pl1e = &pv_ldt_ptes(curr)[offset >> PAGE_SHIFT];
126 l1e_add_flags(gl1e, _PAGE_RW);
127
128 spin_lock(&curr->arch.pv_vcpu.shadow_ldt_lock);
129 l1e_write(pl1e, gl1e);
130 curr->arch.pv_vcpu.shadow_ldt_mapcnt++;
131 spin_unlock(&curr->arch.pv_vcpu.shadow_ldt_lock);
132
133 return true;
134 }
135
136 /*
137 * Local variables:
138 * mode: C
139 * c-file-style: "BSD"
140 * c-basic-offset: 4
141 * tab-width: 4
142 * indent-tabs-mode: nil
143 * End:
144 */
145