1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
|
From 4517e2046610722879761bcdb60edbb2b929c848 Mon Sep 17 00:00:00 2001
From: Richard Henderson <richard.henderson@linaro.org>
Date: Wed, 28 Feb 2024 10:25:14 -1000
Subject: [PATCH 1/5] linux-user/x86_64: Handle the vsyscall page in
open_self_maps_{2,4}
This is the only case in which we expect to have no host memory backing
for a guest memory page, because in general linux user processes cannot
map any pages in the top half of the 64-bit address space.
Upstream-Status: Submitted [https://www.mail-archive.com/qemu-devel@nongnu.org/msg1026793.html]
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2170
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
linux-user/syscall.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index a114f29a8..8307a8a61 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -7922,6 +7922,10 @@ static void open_self_maps_4(const struct open_self_maps_data *d,
path = "[heap]";
} else if (start == info->vdso) {
path = "[vdso]";
+#ifdef TARGET_X86_64
+ } else if (start == TARGET_VSYSCALL_PAGE) {
+ path = "[vsyscall]";
+#endif
}
/* Except null device (MAP_ANON), adjust offset for this fragment. */
@@ -8010,6 +8014,18 @@ static int open_self_maps_2(void *opaque, target_ulong guest_start,
uintptr_t host_start = (uintptr_t)g2h_untagged(guest_start);
uintptr_t host_last = (uintptr_t)g2h_untagged(guest_end - 1);
+#ifdef TARGET_X86_64
+ /*
+ * Because of the extremely high position of the page within the guest
+ * virtual address space, this is not backed by host memory at all.
+ * Therefore the loop below would fail. This is the only instance
+ * of not having host backing memory.
+ */
+ if (guest_start == TARGET_VSYSCALL_PAGE) {
+ return open_self_maps_3(opaque, guest_start, guest_end, flags);
+ }
+#endif
+
while (1) {
IntervalTreeNode *n =
interval_tree_iter_first(d->host_maps, host_start, host_start);
--
2.34.1
|
