diff options
Diffstat (limited to 'arch/x86/kernel/msr.c')
| -rw-r--r-- | arch/x86/kernel/msr.c | 69 |
1 files changed, 69 insertions, 0 deletions
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 1547be359d7f..49dcfb85e773 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -42,6 +42,14 @@ static struct class *msr_class; static enum cpuhp_state cpuhp_msr_state; +enum allow_write_msrs { + MSR_WRITES_ON, + MSR_WRITES_OFF, + MSR_WRITES_DEFAULT, +}; + +static enum allow_write_msrs allow_writes = MSR_WRITES_DEFAULT; + static ssize_t msr_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { @@ -70,6 +78,24 @@ static ssize_t msr_read(struct file *file, char __user *buf, return bytes ? bytes : err; } +static int filter_write(u32 reg) +{ + switch (allow_writes) { + case MSR_WRITES_ON: return 0; + case MSR_WRITES_OFF: return -EPERM; + default: break; + } + + if (reg == MSR_IA32_ENERGY_PERF_BIAS) + return 0; + + pr_err_ratelimited("Write to unrecognized MSR 0x%x by %s\n" + "Please report to x86@kernel.org\n", + reg, current->comm); + + return 0; +} + static ssize_t msr_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) { @@ -84,6 +110,10 @@ static ssize_t msr_write(struct file *file, const char __user *buf, if (err) return err; + err = filter_write(reg); + if (err) + return err; + if (count % 8) return -EINVAL; /* Invalid chunk size */ @@ -92,9 +122,13 @@ static ssize_t msr_write(struct file *file, const char __user *buf, err = -EFAULT; break; } + + add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK); + err = wrmsr_safe_on_cpu(cpu, reg, data[0], data[1]); if (err) break; + tmp += 2; bytes += 8; } @@ -242,6 +276,41 @@ static void __exit msr_exit(void) } module_exit(msr_exit) +static int set_allow_writes(const char *val, const struct kernel_param *cp) +{ + /* val is NUL-terminated, see kernfs_fop_write() */ + char *s = strstrip((char *)val); + + if (!strcmp(s, "on")) + allow_writes = MSR_WRITES_ON; + else if (!strcmp(s, "off")) + allow_writes = MSR_WRITES_OFF; + else + allow_writes = MSR_WRITES_DEFAULT; + + return 0; +} + +static int get_allow_writes(char *buf, const struct kernel_param *kp) +{ + const char *res; + + switch (allow_writes) { + case MSR_WRITES_ON: res = "on"; break; + case MSR_WRITES_OFF: res = "off"; break; + default: res = "default"; break; + } + + return sprintf(buf, "%s\n", res); +} + +static const struct kernel_param_ops allow_writes_ops = { + .set = set_allow_writes, + .get = get_allow_writes +}; + +module_param_cb(allow_writes, &allow_writes_ops, NULL, 0600); + MODULE_AUTHOR("H. Peter Anvin <hpa@zytor.com>"); MODULE_DESCRIPTION("x86 generic MSR driver"); MODULE_LICENSE("GPL"); |