Gulu la ofufuza ochokera ku mayunivesite aku China ndi ku America apeza chiwopsezo chatsopano mu ma processor a Intel omwe amatsogolera ku kutayikira kwa chidziwitso chokhudza zotsatira za ntchito zongopeka kudzera munjira za chipani chachitatu, zomwe zingagwiritsidwe ntchito, mwachitsanzo, kukonza njira yolumikizirana yobisika. pakati pa njira kapena kuzindikira kutayikira panthawi ya Meltdown.
Chofunikira cha chiwopsezo ndikuti kusintha kwa purosesa ya EFLAGS processor register, yomwe idachitika chifukwa cha kuphatikizika kwa malangizo, kumakhudza nthawi yotsatiridwa ya malangizo a JCC (kudumpha pamene mikhalidwe yodziwika yakwaniritsidwa). Ntchito zongopeka sizimalizidwa ndipo zotsatira zake zimatayidwa, koma kusintha kwa EFLAGS komwe kunatayidwa kungadziwike posanthula nthawi yochitira malangizo a JCC. Kuyerekeza koyerekeza koyerekeza kusanachitike, ngati kufananizako kukuyenda bwino, kumabweretsa kuchedwa pang'ono komwe kungayesedwe ndikugwiritsidwa ntchito ngati mawonekedwe kuti agwirizane ndi zomwe zili.
Mosiyana ndi kuukira ena ofanana kudzera njira wachitatu chipani, njira yatsopano si kusanthula kusintha kwa nthawi kupeza cached ndi sanali cached deta ndipo sikutanthauza siteji ya bwererani kaundula EFLAGS ku boma loyamba, zomwe zimapangitsa kuti zikhale zovuta kuzindikira ndi kuletsa kuukira. Monga chiwonetsero, ochita kafukufuku adagwiritsa ntchito njira ina ya Meltdown attack, pogwiritsa ntchito njira yatsopano kuti adziwe zambiri za zotsatira za ntchito yongopeka. Kugwiritsiridwa ntchito kwa njira yokonzekera kutulutsa chidziwitso panthawi ya Meltdown kwawonetsedwa bwino pamakina omwe ali ndi Intel Core i7-6700 ndi i7-7700 CPU m'malo okhala ndi Ubuntu 22.04 ndi Linux 5.15 kernel. Padongosolo lomwe lili ndi Intel i9-10980XE CPU, kuwukirako kudachita bwino pang'ono.
Chiwopsezo cha Meltdown chimachokera ku mfundo yakuti panthawi yongopeka ya malangizo, purosesa imatha kupeza malo achinsinsi, ndikutaya zotsatira zake, popeza mwayi wokhazikitsidwa umaletsa mwayi woterewu kuchokera kwa wogwiritsa ntchito. Mu pulogalamu, chipika chopangidwa mongopeka chimasiyanitsidwa ndi code yayikulu ndikudumpha kokhazikika, komwe nthawi zonse kumayaka moto, koma chifukwa chakuti mawu okhazikika amagwiritsa ntchito mtengo wowerengeka womwe purosesa sakudziwa panthawi yoyeserera. kuphedwa, zosankha zonse za nthambi zimachitidwa mongoyerekeza.
M'gulu lakale la Meltdown, popeza cache yomweyi imagwiritsidwa ntchito pochita zinthu mongoyerekeza ngati malangizo omwe amaperekedwa nthawi zonse, ndizotheka panthawi yongopeka kuyika zolembera mu cache zomwe zikuwonetsa zomwe zili m'malo okumbukira otsekedwa, ndiyeno. mu code yomwe nthawi zambiri imagwira kuti mudziwe tanthauzo lake mwa kusanthula nthawi yofikira ku data yosungidwa komanso yosasungidwa. Kusintha kwatsopano kumagwiritsa ntchito kusintha kwa regista ya EFLAGS ngati chikhomo cha kutayikira. Mu chiwonetsero cha Covert Channel, njira imodzi idasinthira zomwe zidatumizidwa kuti zisinthe zomwe zili mu kaundula wa EFLAGS, ndipo njira ina idasinthiratu kusintha kwa nthawi ya JCC kuti akonzenso zomwe zidatumizidwa ndi njira yoyamba.
Source: opennet.ru