i386/msr: Extract and improve MSR support detection code

Currently rdmsr and wrmsr commands have own MSR support detection code.
This code is the same. So, it is duplicated. Additionally, this code
cannot be reused by others. Hence, extract this code to a function and
make it public. By the way, improve a code a bit.

Additionally, use GRUB_ERR_BAD_DEVICE instead of GRUB_ERR_BUG to signal
an error because errors encountered by this new routine are not bugs.

Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Signed-off-by: Sergii Dmytruk <sergii.dmytruk@3mdeb.com>
Reviewed-by: Ross Philipson <ross.philipson@oracle.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

diff --git a/grub-core/commands/i386/rdmsr.c b/grub-core/commands/i386/rdmsr.c
index 89ece7657f27c8408f3977ee71a832f83a0a4559..2e42f6197648f5959b1bd25b736991dad12fd0f4 100644 (file)
--- a/grub-core/commands/i386/rdmsr.c
+++ b/grub-core/commands/i386/rdmsr.c
@@ -42,27 +42,16 @@ static const struct grub_arg_option options[] =
 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_err_t err;
+  grub_uint32_t 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"));
+  err = grub_cpu_is_msr_supported ();
 
-  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 (err != GRUB_ERR_NONE)
+    return grub_error (err, N_("RDMSR is unsupported"));
 
   if (argc != 1)
     return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("one argument expected"));

diff --git a/grub-core/commands/i386/wrmsr.c b/grub-core/commands/i386/wrmsr.c
index cf6bf6c8fe432e7a8583580e39136c8d29514cf3..7fbedaed95ba5e53173d81f5501409804609225a 100644 (file)
--- a/grub-core/commands/i386/wrmsr.c
+++ b/grub-core/commands/i386/wrmsr.c
@@ -36,26 +36,15 @@ static grub_command_t cmd_write;
 static grub_err_t
 grub_cmd_msr_write (grub_command_t cmd __attribute__ ((unused)), int argc, char **argv)
 {
-  grub_uint32_t manufacturer[3], max_cpuid, a, b, c, features, addr;
+  grub_err_t err;
+  grub_uint32_t addr;
   grub_uint64_t value;
   const char *ptr;
 
-  /*
-   * 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"));
+  err = grub_cpu_is_msr_supported ();
 
-  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 (err != GRUB_ERR_NONE)
+    return grub_error (err, N_("WRMSR is unsupported"));
 
   if (argc != 2)
     return grub_error (GRUB_ERR_BAD_ARGUMENT, N_("two arguments expected"));

diff --git a/include/grub/i386/msr.h b/include/grub/i386/msr.h
index 4fba1b8e0d045fcde808618439b89a09ecc0156c..1e838c022f41d1b01a4a28f750fdd9a97e8769d4 100644 (file)
--- a/include/grub/i386/msr.h
+++ b/include/grub/i386/msr.h
@@ -19,6 +19,35 @@
 #ifndef GRUB_I386_MSR_H
 #define GRUB_I386_MSR_H 1
 
+#include <grub/err.h>
+#include <grub/i386/cpuid.h>
+#include <grub/types.h>
+
+static inline grub_err_t
+grub_cpu_is_msr_supported (void)
+{
+  grub_uint32_t eax, ebx, ecx, edx;
+
+  /*
+   * 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_ERR_BAD_DEVICE;
+
+  grub_cpuid (0, eax, ebx, ecx, edx);
+
+  if (eax < 1)
+    return GRUB_ERR_BAD_DEVICE;
+
+  grub_cpuid (1, eax, ebx, ecx, edx);
+
+  if (!(edx & (1 << 5)))
+    return GRUB_ERR_BAD_DEVICE;
+
+  return GRUB_ERR_NONE;
+}
+
 /*
  * TODO: Add a general protection exception handler.
  *       Accessing a reserved or unimplemented MSR address results in a GP#.