From: Pekka Enberg <penberg@cs.helsinki.fi>
Date: Sun, 11 Apr 2010 09:45:15 +0000 (+0300)
Subject: kvm: Don't crash debug dump if address isn't in guest memory
X-Git-Tag: next-20110824~3^2~528^2~175
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=ea77d0e1088ddfcb44e0038293e92bf47f9c32fe;p=karo-tx-linux.git

kvm: Don't crash debug dump if address isn't in guest memory

We don't do MMU translation in the hypevisor for guest memory addresses which
causes us to try to dereference invalid pointers.  Work around the problem by
checking that a pointer is in guest memory before dumping the contents.

Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
---

diff --git a/tools/kvm/kvm.c b/tools/kvm/kvm.c
index 64316875db87..11dec87ef0e5 100644
--- a/tools/kvm/kvm.c
+++ b/tools/kvm/kvm.c
@@ -50,6 +50,11 @@ const char *kvm_exit_reasons[] = {
 	DEFINE_KVM_EXIT_REASON(KVM_EXIT_INTERNAL_ERROR),
 };
 
+static inline bool host_ptr_in_ram(struct kvm *self, void *p)
+{
+	return self->ram_start <= p && p < (self->ram_start + self->ram_size);
+}
+
 static inline uint32_t segment_to_flat(uint16_t selector, uint16_t offset)
 {
 	return ((uint32_t)selector << 4) + (uint32_t) offset;
@@ -650,6 +655,9 @@ void kvm__show_code(struct kvm *self)
 	printf("Code: ");
 
 	for (i = 0; i < code_len; i++, ip++) {
+		if (!host_ptr_in_ram(self, ip))
+			break;
+
 		c = *ip;
 
 		if (ip == guest_flat_to_host(self, ip_to_flat(self, self->regs.rip)))
@@ -678,9 +686,20 @@ void kvm__show_page_tables(struct kvm *self)
 		die("KVM_GET_SREGS failed");
 
 	pte4	= guest_flat_to_host(self, self->sregs.cr3);
+	if (!host_ptr_in_ram(self, pte4))
+		return;
+
 	pte3	= guest_flat_to_host(self, (*pte4 & ~0xfff));
+	if (!host_ptr_in_ram(self, pte3))
+		return;
+
 	pte2	= guest_flat_to_host(self, (*pte3 & ~0xfff));
+	if (!host_ptr_in_ram(self, pte2))
+		return;
+
 	pte1	= guest_flat_to_host(self, (*pte2 & ~0xfff));
+	if (!host_ptr_in_ram(self, pte1))
+		return;
 
 	printf("Page Tables:\n");
 	if (*pte2 & (1 << 7))
@@ -700,8 +719,12 @@ void kvm__dump_mem(struct kvm *self, unsigned long addr, unsigned long size)
 
 	p = guest_flat_to_host(self, addr);
 
-	for (n = 0; n < size; n+=8)
+	for (n = 0; n < size; n+=8) {
+		if (!host_ptr_in_ram(self, p + n))
+			break;
+
 		printf("  0x%08lx: %02x %02x %02x %02x  %02x %02x %02x %02x\n",
 			addr + n, p[n + 0], p[n + 1], p[n + 2], p[n + 3],
 				  p[n + 4], p[n + 5], p[n + 6], p[n + 7]);
+	}
 }