#!/usr/bin/stap
#
# Copyright (C) 2022 Red Hat, Inc.
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library.  If not, see
# <http://www.gnu.org/licenses/>.
#
# A script that captures the VMSA blob for the boot vCPU and
# first additional vCPU, when a KVM guest is booted with SEV-ES
#
# NOTE: This directly references specific structures and places in the
#       kernel source code. It is expected that this example will need to be
#       edited to match the kernel you intend to run it against.
#
# The captured VMSA will be printed to the console in hex format,
# and can be converted to the required binary format by feeding
# it through
#
# perl -e 'while (<>) { print pack("C64", map { hex($_) } ( $_ =~ m/../g )); }' > vmsa.bin
#

probe begin {
  printf("Running\n")
}

function dump_vmsa(addr:long) {
  printf("VMSA\n")
  for (i = 0; i < 4096 ; i+= 64) {
    printf("%.64M\n", addr + i);
  }
}

# This line number will need to be updated for the specific kernel
# version that is being probed. The line that needs to be targeted
# is the one between the call to clflush_cache_range(...) and the
# call to sev_issue_cmd(kvm, SEV_CMD_LAUNCH_UPDATE...).
#
# Line 635 is correct for Linux v6.3
probe module("kvm_amd").statement("__sev_launch_update_vmsa@arch/x86/kvm/svm/sev.c:635") {
  dump_vmsa($svm->sev_es->vmsa)
}