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

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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>
This commit is contained in:
Pekka Enberg
2015-06-01 16:39:39 +01:00
committed by Will Deacon
parent 342d95c20a
commit 48cf387734
1 changed files with 24 additions and 1 deletions
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kvm.c
+24 -1
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@@ -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]);
}
}