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i386/msr: Extract and improve MSR support detection code

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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>
This commit is contained in:
Daniel Kiper 2024-10-06 17:14:44 +03:00
parent 929fafdf5e
commit 1b1061409d
3 changed files with 39 additions and 32 deletions
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21
grub-core/commands/i386/rdmsr.c
View File

@ -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"));

21
grub-core/commands/i386/wrmsr.c
View File

@ -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"));

29
include/grub/i386/msr.h
View File

@ -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#.