[PATCH V4 1/5] KVM: X86: Memory ROE documentation

From: Ahmed Abd El Mawgood
Date: Sat Oct 20 2018 - 18:23:55 EST

Following up with my previous threads on KVM assisted Anti rootkit
The current version doesn't address the attacks involving pages
remapping. It is still design in progress, nevertheless, it will be in
my later patch sets.

Signed-off-by: Ahmed Abd El Mawgood <ahmedsoliman0x666@xxxxxxxxx>
Documentation/virtual/kvm/hypercalls.txt | 31 ++++++++++++++++++++++++
1 file changed, 31 insertions(+)

diff --git a/Documentation/virtual/kvm/hypercalls.txt b/Documentation/virtual/kvm/hypercalls.txt
index da24c138c8d1..8af64d826f03 100644
--- a/Documentation/virtual/kvm/hypercalls.txt
+++ b/Documentation/virtual/kvm/hypercalls.txt
@@ -141,3 +141,34 @@ a0 corresponds to the APIC ID in the third argument (a2), bit 1
corresponds to the APIC ID a2+1, and so on.

Returns the number of CPUs to which the IPIs were delivered successfully.
+Architecture: x86
+Status: active
+Purpose: Hypercall used to apply Read-Only Enforcement to guest memory and
+Usage 1:
+Returns non-signed number that represents the current version of ROE
+implementation current version.
+Usage 2:
+ a0: ROE_MPROTECT (requires version >= 1)
+ a1: Start address aligned to page boundary.
+ a2: Number of pages to be protected.
+This configuration lets a guest kernel have part of its read/write memory
+converted into read-only. This action is irreversible.
+Upon successful run, the number of pages protected is returned.
+Error codes:
+ -KVM_ENOSYS: system call being triggered from ring 3 or it is not
+ implemented.
+ -EINVAL: error based on given parameters.
+Notes: KVM_HC_ROE can not be triggered from guest Ring 3 (user mode). The
+reason is that user mode malicious software can make use of it to enforce read
+only protection on an arbitrary memory page thus crashing the kernel.