1 files changed, 102 insertions, 0 deletions
diff --git a/grub-core/commands/i386/rdmsr.c b/grub-core/commands/i386/rdmsr.c
new file mode 100644
index 0000000..46c4346
--- /dev/null
+++ b/grub-core/commands/i386/rdmsr.c
@@ -0,0 +1,102 @@
+/* rdmsr.c - Read CPU model-specific registers. */
+/*
+ *  GRUB  --  GRand Unified Bootloader
+ *  Copyright (C) 2019  Free Software Foundation, Inc.
+ *  Based on gcc/gcc/config/i386/driver-i386.c
+ *
+ *  GRUB is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  GRUB 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 General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with GRUB.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <grub/dl.h>
+#include <grub/misc.h>
+#include <grub/mm.h>
+#include <grub/env.h>
+#include <grub/command.h>
+#include <grub/extcmd.h>
+#include <grub/i18n.h>
+#include <grub/i386/cpuid.h>
+#include <grub/i386/rdmsr.h>
+
+GRUB_MOD_LICENSE("GPLv3+");
+
+static grub_extcmd_t cmd_read;
+
+static const struct grub_arg_option options[] =
+{
+  {0, 'v', 0, N_("Save read value into variable VARNAME."),
+  N_("VARNAME"), ARG_TYPE_STRING},
+  {0, 0, 0, 0, 0, 0}
+};
+
+static grub_err_t
+grub_cmd_msr_read (grub_extcmd_context_t ctxt, int argc, char **argv)
+{
+  grub_uint32_t manufacturer[3], max_cpuid, a, b, c, features, addr;
+  grub_uint64_t value;
+  const char *ptr;
+  char buf[sizeof("1122334455667788")];
+
+  /*
+   * The CPUID instruction should be used to determine whether MSRs
+   * are supported. (CPUID.01H:EDX[5] = 1)
+   */
+  if (! grub_cpu_is_cpuid_supported ())
+    return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
+
+  grub_cpuid (0, max_cpuid, manufacturer[0], manufacturer[2], manufacturer[1]);
+
+  if (max_cpuid < 1)
+    return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
+
+  grub_cpuid (1, a, b, c, features);
+
+  if (!(features & (1 << 5)))
+    return grub_error (GRUB_ERR_BUG, N_("unsupported instruction"));
+
+  if (argc != 1)
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument expected"));
+
+  grub_errno = GRUB_ERR_NONE;
+  ptr = argv[0];
+  addr = grub_strtoul (ptr, &ptr, 0);
+
+  if (grub_errno != GRUB_ERR_NONE)
+    return grub_errno;
+  if (*ptr != '\0')
+    return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("invalid argument"));
+
+  value = grub_msr_read (addr);
+
+  if (ctxt->state[0].set)
+    {
+      grub_snprintf (buf, sizeof(buf), "%llx", (unsigned long long) value);
+      grub_env_set (ctxt->state[0].arg, buf);
+    }
+  else
+    grub_printf ("0x%llx\n", (unsigned long long) value);
+
+  return GRUB_ERR_NONE;
+}
+
+GRUB_MOD_INIT(rdmsr)
+{
+  cmd_read = grub_register_extcmd ("rdmsr", grub_cmd_msr_read, 0, N_("ADDR"),
+				   N_("Read a CPU model specific register."),
+				   options);
+}
+
+GRUB_MOD_FINI(rdmsr)
+{
+  grub_unregister_extcmd (cmd_read);
+}