OS Guard and SMEP

Wetin you need know

How e dey work

When OS enable SMEP, instruction fetches for supervisor mode go dey checked against page-table user/supervisor permissions. Dis one dey help prevent kernel control-flow mistake make e no directly run code wey dem map as accessible to user. Di OS still get control over page mappings and im own privileged code.

Where e dey useful

Kernel wey mistakenly push execution go inside user page fit trigger fault under SMEP. Dis na specific execution boundary; e no dey independently verify kernel logic, loaded drivers, or allowed supervisor mappings.

How to check support and enablement

CPUID.07H.00H:EBX bit 7 dey show SMEP; CR4.SMEP na di OS control. SMAP get separate bit and control. Check di running OS documented protection configuration, instead of to try change privileged controls from inside application.

Capability, enablement and enforcement na different ting dem wey person must check separately. Processor fit support protection while di OS, application or virtual-machine policy no turn am on. Database support field no be attestation say running system dey secure.

Wetin di feature no dey guarantee

OS Guard no be Boot Guard. Database field wey write OS Guard (SMAP) dey mix two different architectural concepts together and e no fit prove di two; verify SMEP and SMAP separately. Di feature no dey make vulnerable driver safe.

Compatibility and performance inside real life

Keep di OS, firmware and affected runtime current. If protection show compatibility problem, make you use vendor diagnostics and supported update dem first. Broad protection toggle fit affect oda application dem wey no concern am, so e suppose follow clear deployment and recovery policy.

Practical verification checklist

1. Record di exact processor or platform model plus di application, OS and runtime version dem wey dey involve. Make you keep di exact word dem wey di error or requirement use.
2. Check di manufacturer reference for dat exact model, den inspect di real capability and enabled state inside di environment where di program dey run.
3. Compare every single requirement of di binary or backend wey you choose. Name wey resemble am, alias, or broad technology label no reach.
4. Confirm say di application select di implementation wey dem intend. Use di diagnostics wey dem document and supported fallback if requirement dem no complete.
5. Make only one supported change at a time, den run di same workload again. Keep di original configuration and recovery way ready.

If dem list di feature but software no fit use am

Start from di exact component wey dey fail. Hardware database dey describe capability wey dem record; di operating system or hypervisor fit show different real environment. If illegal-instruction error happen, you still need to check di exact instruction wey cause di fault and di binary build, because corrupt file or anoda instruction wey no dey supported fit give di same kind problem.

Install di application, driver or runtime version wey get support for dat exact platform, and use di vendor documented baseline or fallback build if e need am. Software update no fit create instruction wey di processor no get. Firmware and security-policy change dem suppose follow di system manufacturer procedure and recovery plan, no be just any common optimization advice.

Related feature dem and useful difference dem

SMAP · Execute Disable (NX) · Boot Guard · Control-flow Enforcement (CET)

Sources and scope of dis explanation

Intel 64 and IA-32 Architectures Software Developer's Manual · Intel security features related to transient execution attacks

Dis reference dem establish architectural behavior and software requirement dem. Dem no dey independently verify every feature value for any linked hardware model page. For model support, use dat page manufacturer evidence and check di active system configuration. Dis article no supply benchmark, certification or independent review date.

Related

Dis entities connect to dis article. Type dey show for every link.

Sources and verification

Editorial ownership: Feex. No independent review date dey recorded. How we dey do research.

• Intel 64 and IA-32 Architectures Software Developer's Manual · Volume 1 and 2 describe di named instruction family dem and CPUID; Volume 3 describe state, paging, VMX and protection control dem. Architecture documentation no dey prove say particular model support am.
• Intel security features related to transient execution attacks · E connect Intel OS Guard with SMEP. Dis one different from SMAP, even though some imported feature labels dey mix dose names together.