{"id":99293,"date":"2021-02-28T10:22:45","date_gmt":"2021-02-28T08:22:45","guid":{"rendered":"https:\/\/prohoster.info\/blog\/novosti-interneta\/v-yadro-linux-5-12-prinyata-podsistema-kfence-dlya-vyyavleniya-oshibok-pri-rabote-s-pamyatyu"},"modified":"2021-02-28T10:22:45","modified_gmt":"2021-02-28T08:22:45","slug":"v-yadro-linux-5-12-prinyata-podsistema-kfence-dlya-vyyavleniya-oshibok-pri-rabote-s-pamyatyu","status":"publish","type":"post","link":"https:\/\/prohoster.info\/hr\/blog\/news\/v-yadro-linux-5-12-prinyata-podsistema-kfence-dlya-vyyavleniya-oshibok-pri-rabote-s-pamyatyu","title":{"rendered":"U Linux jezgru 5.12 prihva\u0107en je KFence podsustav za otkrivanje gre\u0161aka u radu s memorijom","gt_translate_keys":[{"key":"rendered","format":"text"}]},"content":{"rendered":"

U sklopu razvijanog Linux kernela 5.12 implementiran je mehanizam KFence (Kernel Electric Fence), koji provjerava rad s memorijom, hvataju\u0107i izlaze iz granica bafera, pristupe memoriji nakon osloba\u0111anja i druge sli\u010dne gre\u0161ke. <\/p>\n

Sli\u010dna funkcionalnost ve\u0107 je postojala u jezgru kao opcija za sastavljanje KASAN (kernel address sanitizer, koristi Address Sanitizer u modernim gcc i clang) \u2014 me\u0111utim, bila je prvenstveno namijenjena za debugging. KFence podsustav se razlikuje od KASAN visokom brzinom rada, \u0161to omogu\u0107ava kori\u0161tenje ove mogu\u0107nosti \u010dak i na jezgrama u radnim sustavima. <\/p>\n

Primjena na radnim sustavima omogu\u0107it \u0107e otkrivanje gre\u0161aka u radu s memorijom koje se ne javljaju tijekom testnih pokretanja i pojavljuju se samo pod radnim optere\u0107enjima ili pri dugotrajnom radu (s velikim uptime-om). Osim toga, primjena KFence na radnim sustavima \u0107e zna\u010dajno pove\u0107ati broj ma\u0161ina uklju\u010denih u provjeru rada kernela s memorijom. <\/p>\n

Minimalni tro\u0161kovi, koji ne ovise o optere\u0107enju, posti\u017eu se u KFence-u pomo\u0107u umetanja stranica za\u0161tite (guard pages) u hrpu kroz fiksne intervale. Nakon isteka vremena sljede\u0107eg intervala za\u0161tite, KFence kroz standardni sustav raspodjele memorije (SLAB ili SLUB allocator) dodaje novu stranicu za\u0161tite iz KFence objektnog bazena i po\u010dinje novo mjerenje vremena. Svaki KFence objekt smje\u0161ten je na posebnoj memorijskoj stranici, a memorijske stranice lijevo i desno od granica \u010dine stranice za\u0161tite (guard pages), \u010dija se veli\u010dina bira nasumi\u010dno. <\/p>\n

Na taj na\u010din, stranice s objektima odvajaju se jedna od druge stranicama za\u0161tite, koje su pode\u0161ene da generiraju \u201epage fault\u201d pri svakom pristupu. Za otkrivanje operacija pisanja izvan granica bafera unutar stranica s objektima dodatno se koriste \u201ecrvene zone\u201d na osnovu uzoraka, koje zauzimaju memoriju koja se ne koristi od objektima, a ostaje nakon poravnanja veli\u010dine stranica memorije. \u2014+\u2014\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014\u2014+ | xxxxxxxxx | O : | xxxxxxxxx | : O | xxxxxxxxx | | xxxxxxxxx | B : | xxxxxxxxx | : B | xxxxxxxxx | | x GUARD x | J : RED- | x GUARD x | RED- : J | x GUARD x | | xxxxxxxxx | E : ZONE | xxxxxxxxx | ZONE : E | xxxxxxxxx | | xxxxxxxxx | C : | xxxxxxxxx | : C | xxxxxxxxx | | xxxxxxxxx | T : | xxxxxxxxx | : T | xxxxxxxxx | \u2014+\u2014\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014\u2014+\u2014\u2014\u2014+ <\/p>\n

U slu\u010daju poku\u0161aja pristupa podru\u010dju izvan granica bafera, operacija zahva\u0107a stranicu za\u0161tite, \u0161to dovodi do generiranja \u201epage fault\u201d, koji KFence presre\u0107e i zapisuje u log podatke o otkrivenom problemu. Po defaultu KFence ne blokira gre\u0161ku i samo ispisuje upozorenje u log, ali postoji opcija \u201epanic_on_warn\u201d, koja omogu\u0107ava da u slu\u010daju otkrivanja gre\u0161ke jezgara pre\u0111e u stanje kvara (panic).
\n
Izvor: opennet.ru<\/a> <\/p>","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"excerpt":{"rendered":"

\u0412 \u0441\u043e\u0441\u0442\u0430\u0432 \u043d\u0430\u0445\u043e\u0434\u044f\u0449\u0435\u0433\u043e\u0441\u044f \u0432 \u0440\u0430\u0437\u0440\u0430\u0431\u043e\u0442\u043a\u0435 \u044f\u0434\u0440\u0430 Linux 5.12 \u0432\u043a\u043b\u044e\u0447\u0435\u043d\u0430 \u0440\u0435\u0430\u043b\u0438\u0437\u0430\u0446\u0438\u044f \u043c\u0435\u0445\u0430\u043d\u0438\u0437\u043c\u0430 KFence (Kernel Electric Fence), \u043a\u043e\u0442\u043e\u0440\u044b\u0439 \u043f\u0440\u043e\u0432\u0435\u0440\u044f\u0435\u0442 \u0440\u0430\u0431\u043e\u0442\u0443 \u0441 \u043f\u0430\u043c\u044f\u0442\u044c\u044e, \u043e\u0442\u043b\u0430\u0432\u043b\u0438\u0432\u0430\u044f \u0432\u044b\u0445\u043e\u0434 \u0437\u0430 \u0433\u0440\u0430\u043d\u0438\u0446\u044b \u0431\u0443\u0444\u0435\u0440\u043e\u0432, \u043e\u0431\u0440\u0430\u0449\u0435\u043d\u0438\u044f \u043a \u043f\u0430\u043c\u044f\u0442\u0438 \u043f\u043e\u0441\u043b\u0435 \u043e\u0441\u0432\u043e\u0431\u043e\u0436\u0434\u0435\u043d\u0438\u044f \u0438 \u0434\u0440\u0443\u0433\u0438\u0435 \u043e\u0448\u0438\u0431\u043a\u0438 \u043f\u043e\u0434\u043e\u0431\u043d\u043e\u0433\u043e \u043a\u043b\u0430\u0441\u0441\u0430. \u041f\u043e\u0434\u043e\u0431\u043d\u0430\u044f \u0444\u0443\u043d\u043a\u0446\u0438\u043e\u043d\u0430\u043b\u044c\u043d\u043e\u0441\u0442\u044c \u0443\u0436\u0435 \u043f\u0440\u0438\u0441\u0443\u0442\u0441\u0442\u0432\u043e\u0432\u0430\u043b\u0430 \u0432 \u044f\u0434\u0440\u0435 \u0432 \u0432\u0438\u0434\u0435 \u043e\u043f\u0446\u0438\u0438 \u0441\u0431\u043e\u0440\u043a\u0438 KASAN (kernel address sanitizer, \u0438\u0441\u043f\u043e\u043b\u044c\u0437\u0443\u0435\u0442 Address Sanitizer \u0432 \u0441\u043e\u0432\u0440\u0435\u043c\u0435\u043d\u043d\u044b\u0445 gcc […]<\/p>\n","protected":false,"gt_translate_keys":[{"key":"rendered","format":"html"}]},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[702],"tags":[],"class_list":["post-99293","post","type-post","status-publish","format-standard","hentry","category-news"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\n","aioseo_head_json":{"title":"\ud83e\udd47 U jezgru Linux 5.12 usvojena je podsustava KFence za prepoznavanje gre\u0161aka tijekom rada s memorijom | ProHoster","description":"U sklopu razvijanog jezgre Linux 5.12 uklju\u010dena je implementacija mehanizma KFence (Kernel Electric Fence) koji provjerava rad s memorijom, hvataju\u0107i izlazak iz granica bafera i pristupe slobodnoj 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