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SMAP

Architecture referenceFeex

Dem still dey call am OS Guard (SMAP)

SMAP, Supervisor-Mode Access Prevention, dey stop supervisor from accessing user-accessible pages unless di architecture override conditions apply. E dey different from SMEP, wey dem commonly brand as Intel OS Guard.

Wetin you need know

SMAP, Supervisor-Mode Access Prevention, dey stop supervisor from accessing user-accessible pages unless di architecture override conditions apply. E dey different from SMEP, wey dem commonly brand as Intel OS Guard.

How e dey work

Di OS fit enable SMAP so dat privileged data access wey dem no plan into user mappings go cause fault. Kernel routines wey intentionally copy user data dey use access windows wey dem control well under di architecture rules. Execution permission na different matter wey mechanisms like SMEP and NX dey handle.

Where e dey useful

Kernel routine wey receive user pointer must validate and access am using im OS established user-copy facilities. SMAP na defense boundary around such accesses, e no be replacement for length checks, lifetime handling, or correct privilege decisions.

How to check support and enablement

CPUID.07H.00H:EBX bit 20 dey enumerate SMAP, while CR4.SMAP dey control enablement. SMEP dey use different bit. Check OS documentation and status interfaces; no disable di protection as generic troubleshooting step for 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

Di imported label OS Guard (SMAP) no mean say SMEP and SMAP na di same thing or say dem enable both of dem. Processor capability no dey show di protection state of one particular kernel, guest, or driver.

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.

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.

Sources and verification

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

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