bootguard-status

Print the Intel Boot Guard state of the running system, decoded from MSR_BOOT_GUARD_SACM_INFO (MSR 0x13a).

It reports whether Boot Guard is enabled and, if so, whether the boot was verified, measured, or both.

Usage

# bootguard-status

Requires root and /dev/cpu/0/msr, which needs CONFIG_X86_MSR. Run modprobe msr if the driver is built as a module.

Example

SACM_INFO:       0x0000000300000050 (MSR 0x13a)
Boot Guard:      enabled
Verified boot:   yes
Measured boot:   no
TPM (per ACM):   none
NEM:             disabled
Force anchor:    yes
Key revoked:     no
Undecoded bits:  0x0000000200000000

Bits whose meaning is not known are printed as raw values.

On systems with Boot Guard-capable silicon but no profile fused, it prints Boot Guard: not enabled (no profile fused) and stops there.

How it works

The startup ACM records what it did in MSR 0x13a before handing control to the IBB. The register remains readable at runtime.

The tool reads eight bytes from offset 0x13a in /dev/cpu/0/msr and decodes the fields. It does not use MEI/HECI, access the SPI flash, or write anything to the system.

TPM (per ACM) refers to the TPM the ACM found and used, not simply whether the system has a TPM. For example, a system with a working TPM 2.0 still reports none when measured boot is disabled, since the ACM did not use it.

License

BSD-2-Clause