AMD ta buga wani rahoto da ke nazarin amincin fasahar haɓakawa ta PSF (Tsarin Kayayyakin Kasuwanci) wanda aka aiwatar a cikin jerin na'urori na Zen 3. Fasahar PSF, amma a aikace, har yanzu ba a sami samfuran lambar da ke iya kai hari ba kuma ana kimanta haɗarin gabaɗaya a matsayin maras muhimmanci.
Bari mu tuna cewa harin Specter-v4 (Speculative Store Bypass) ya dogara ne akan maido da bayanan da suka zauna a cikin cache na processor bayan watsar da sakamakon hasashe na aiwatar da ayyuka yayin aiwatar da canza rubutu da karanta ayyukan ta amfani da adireshin kai tsaye. Lokacin da aikin karantawa ya bi aikin rubutawa (misali, mov [rbx + rcx], 0x0; mov rax, [rdx + rsi]), ana iya sanin kashe adireshin karantawa saboda irin ayyukan da ake yi (karanta ayyukan suna aiki. ana yin su akai-akai kuma ana iya karantawa daga cache) kuma mai sarrafa na'ura na iya yin hasashen karantawa kafin ya rubuta ba tare da jira a ƙididdige lissafin indirection na rubutun ba.
Wannan fasalin yana ba da umarnin karantawa don samun damar tsohuwar ƙima a wasu adireshi yayin da ba a gama aikin kantin ba tukuna. Idan akwai kuskuren tsinkaya, za a watsar da aikin hasashe da bai yi nasara ba, amma alamun aiwatar da shi za su kasance a cikin cache na processor kuma ana iya dawo da su ta hanyar ɗayan hanyoyin tantance abubuwan da ke cikin cache dangane da nazarin canje-canjen samun damar shiga. lokaci zuwa cache da bayanan da ba a adana ba.
Ƙara zuwa na'urori masu sarrafawa na AMD Zen 3, PSF yana inganta STLF (Store-To-Load-Forwarding), wanda ke gudanar da ayyukan karantawa ta hanyar tsinkaya dangantaka tsakanin ayyukan karatu da rubutu. Lokacin amfani da classic STLF, mai sarrafa na'ura yana yin aiki na "load" akan bayanan da aka tura kai tsaye daga umarnin "store" na baya, ba tare da jira a zahiri a rubuta sakamakon zuwa ƙwaƙwalwar ajiya ba, amma yana tabbatar da cewa adiresoshin da aka yi amfani da su a cikin "loading" da "store" umarni sun dace. Haɓakawa na PSF yana sa bincika adireshi hasashe kuma yana yin aikin "kayan aiki" kafin a ƙididdige bayanin adireshin idan an aiwatar da wani kantin sayar da / kaya da ke sarrafa adireshi ɗaya a baya. Idan tsinkayar ta gaza, jihar za ta koma baya, amma bayanan sun kasance a cikin cache.
Harin PSF yana yiwuwa ne kawai a cikin tsarin matakin gata guda ɗaya, yana rufe mahallin tsari na yanzu kuma ana toshe shi ta hanyoyin keɓewar sararin samaniya ko injinan akwatin sandbox na hardware. A wannan yanayin, hanyoyin sandboxing na software a cikin matakai na iya yuwuwa matsalar ta shafa. Harin yana haifar da barazana ga tsarin kamar masu bincike, na'urori masu kama da kisa, da JITs waɗanda ke aiwatar da lambar ɓangare na uku a cikin tsari guda ɗaya (harrin na iya ba da damar lambar yashi marar aminci don samun damar yin amfani da wasu bayanan tsari).
AMD ta samar da hanyoyi da dama don kashe PSF gaba ɗaya ko zaɓi, amma, idan aka yi la'akari da ƙarancin haɗarin da yawancin aikace-aikacen ke da shi, ta ba da shawarar barin wannan haɓakawa ta hanyar tsoho. Don kare hanyoyin da aka ware daga aiwatar da lambar da ba a amince da ita ba, an ba da shawarar kashe PSF ta hanyar saita bits ɗin MSR na "SSBD" da "PSFD", gami da na zaren mutum ɗaya. Ga kernel, Linux An shirya faci-faci ta hanyar amfani da zaɓuɓɓukan layin umarni "psfd" da "nopsfd" waɗanda ke sarrafa kunnawa da kashe PSF.
source: budenet.ru
