Ukujonga ukuxhaphaza ukuba semngciphekweni

Njengoko bendijonge phambili ekuqhubekeni ndixoxa ngesi sihloko, mandikuxelele kancinci ngembali, ithiyori kunye nokuziqhelanisa nobuthathaka. Sonke sivile ngoku ukuba iziphene zokhuseleko zinokubiza imali eninzi, sonke siyazi ukuba kufuneka sigcine isoftware yethu ihlaziyiwe, sonke siyazi ukuba uhlaziyo oluninzi lubangelwa ziimpazamo kwezokhuseleko. Kodwa namhlanje ndiza kukuxelela kancinci malunga nendlela ezi mpazamo zifunyanwa kwaye zixhatshazwe ngayo.Kodwa ngaphambi koku siza kucacisa iinkcukacha ezimbalwa ukuze sibe nokujonga ngcono.

Ngaphambi kokuba uqale

Kuqala ndifuna ukukuxelela ukuba siza kugxila kukungakhuseleki kokuqala endikufundileyo ukuxhaphaza, okwaziwayo Ukuphuphuma kwebhafu, kobu buthathaka sithatha ithuba lokungabikho kokuqinisekiswa kwememori ukwenza izinto ezimnandi 🙂 Kodwa masicacise kancinci ngayo.

Oku akuyi kuba yimeko yokwenyani yehlabathi

Andinakho ukubanika ithuba lokubafundisa ukophula nayiphi na inkqubo abayibonayo 🙂 kuqala kuba kuyingozi kwiikhompyuter zabo, okwesibini kuba oko kuya kuthatha ngaphezulu kwesabelo sam esiqhelekileyo samagama.

Siya kuhambo oluya kwii-80s

Into endizokubonisa yona ndingayenza kwiLaptop yam, kodwa oko akuthethi ukuba inokwenziwa namhlanje ngendlela elula - uninzi lwezi ngcinga sele luxhatshazwe amaxesha amaninzi kangangokuba iindlela ezintsha zokukhusela kunye neendlela ezintsha zokuphepha ziye zavela 😛 kodwa loo nto isibuyisela endaweni enye, akukho sithuba sokwazi ukuxela konke oko 🙂

Isenokungasebenzi kwiprosesa yakho

Nangona ndiza kusebenzisa umzekelo olula, ndifuna ukuba icace kwasekuqaleni ukuba iinkcukacha zoku zininzi kwaye zahlukahlukene kangangokuba zinokuphuma ngokufanayo nam, ukuba ufuna ukuzama desired Kodwa unokucinga ukuba andinakucacisa ukuba kwesi sithuba, ngakumbi kuba ngale ntetho sele ndithathe ngaphezu kwamagama angama-300, ke siye ngqo kwindawo yethu.

Yintoni i Ukugcwala kweBuffer

Ukuphendula oku kufuneka kuqala siqonde isiqingatha sokuqala sale ndibaniselwano.

Iibuffers

Njengoko yonke into imalunga nememori kwikhompyuter, kusengqiqweni ukuba kufuneka kubekho uhlobo oluthile lwesikhongozeli solwazi. Xa sithetha ngayo igalelo o iziphumo, size ngqo kwingcinga buffers. Ukuyigcina imfutshane, a buffer Indawo yememori yobungakanani obuchaziweyo apho siza kugcina ubuninzi bolwazi, ngokulula 🙂

Ukugcwala kuyenzeka, njengoko igama lisitsho, xa i-buffer igcwalisa ngolwazi oluninzi kunokuba inako ukuphatha. Kodwa kutheni oku kubalulekile?

Stack

Ikwabizwa ngokuba zizistiki, ziluhlobo lwedatha ebambekayo esinakho isitaki ulwazi, uphawu lwabo oluphambili kukuba banoku-odolwa I-LIFO (Okokugqibela kuQala ngokuPhuma). Masicinge okomzuzwana malunga nesitaki samacwecwe, sizibeka ngaphezulu nganye nganye, emva koko sizikhuphe nganye nganye ukusuka phezulu, oku kwenza ipleyiti yokugqibela esiyibekileyo (leyo iphezulu) yipleyiti yokuqala Ukuba siza kukhupha ipleyiti enye ngexesha kwaye sithathe isigqibo sokwenza ngoluhlobo: P.

Ngoku ukuba uyazi le migaqo mibini, kufuneka siyibeke ngokulandelelana. Izitaki zibalulekile kuba inkqubo nganye esiyiqhubayo inezayo isitokhwe sokubulala. Kodwa lo mfumba une- uphawu oluthile, ikhula phantsi. Inye kuphela into ekufuneka uyazi malunga noku kukuba ngelixa inkqubo iqhubeka, xa umsebenzi ubizwa, isitaki sisuka kwinani X kwimemori lisiya kwinani (Xn). Kodwa ukuze siqhubeke kufuneka siqonde umbono omnye.

Izikhombisi

Lo ngumbono oqhuba uninzi lwabadwelisi benkqubo xa beqala kwihlabathi le-C, eneneni amandla amakhulu enkqubo ye-C kungenxa yokusetyenziswa kwezikhombisi. Ukuyigcina ilula, isikhombisi yalatha kwidilesi yememori. Oku kuvakala kunzima, kodwa akunzima kangako, sonke sine-RAM koomatshini bethu? Ewe, oku kunokuchazwa njenge ilandelelana ibhloko yeebhloko, ezi ndawo zihlala zichazwe kumanani ee-hexadecimal (ukusuka ku-0 ukuya ku-9 emva koko ukusuka ku-A ukuya ku-F, njenge-0x0, 0x1, 0x6, 0xA, 0xF, 0x10). Apha njengenqaku elinomdla, 0x10 Hayi ilingana no 10 😛 ukuba siyiguqulela kwi-decimal ngokulandelelana iyakufana nokuthi 15. Le yinto edida ngaphezulu kwesinye ekuqaleni, kodwa masihle siye kuyo.

Iingxelo

Iiprosesa zisebenza ngenani leefayile iirekhodi, esebenza ukuhambisa indawo ukusuka kwimemori ebonakalayo iye kwiprosesa, kuyilo olusebenzisa ii-bits ezingama-64, inani leerejista likhulu kwaye kunzima ukulichaza apha, kodwa ukufumana umbono, iirejista zifana nezikhombisi, zibonisa phakathi kwezinye izinto , indawo yememori (indawo).

Ngoku ziqhelanise

Ndiyazi ukuba ibinolwazi oluninzi ukuqhubekeka kude kube ngoku, kodwa enyanisweni yimicimbi enzima endizama ukuyicacisa ngendlela elula kakhulu, siza kubona inkqubo encinci esebenzisa i-buffers kwaye siza Yaphule ukuze uqonde oku malunga nokuphuphuma, ngokucacileyo le ayisiyiyo Inkqubo yokwenyani, kwaye siza "kuphepha" uninzi lwezinto ezisetyenziswayo namhlanje, ukubonisa nje ukuba izinto bezisenziwa njani ngaphambili before kwaye ngenxa yokuba ezinye zazo imigaqo-siseko iyimfuneko ukuze ukwazi ukufunda izinto ezinzima ngakumbi

GDB

Inkqubo entle ngokungathandabuzekiyo yenye yezona zisetyenziswa kakhulu ziinkqubo zeC.C phakathi kokulunga kwayo okuninzi sinesibakala sokuba iyasivumela ukuba siyibone yonke le nto kudala sithetha ngayo ukuza kuthi ga ngoku, iirejista, isitaki, iziphathi, njl. Masibone inkqubo esiza kuyisebenzisa njengomzekelo wethu.

sokukhuphela.c

Le yinkqubo elula, siza kusebenzisa ithala leencwadi stdio.h ukuze ukwazi ukufumana ulwazi kwaye ulubonise kwisiphelo sendlela. Sibona umsebenzi obiziweyo return_input evelisa i buffer kubizwa uluhlu, enobude obungama-30 i-byte (uhlobo lwedatha yedatha ngu-1 byte ubude).

Umsebenzi gets(array); Cela ulwazi ngekhonsoli kunye nomsebenzi printf() ibuyisela umxholo woludwe kwaye iwubonise kwiscreen.

Yonke inkqubo ebhalwe ngo-C iqala ngomsebenzi main(), oku kuyakuba kukujongana kuphela nokubiza ukubuya_kungeniswa, ngoku siza kwenza inkqubo.

Masikhe siyithathe kancinci le ndiyenzileyo. Inketho -ggdb ixelela i-gcc ukuba iqulunqe inkqubo kunye ne-gdb ukuze ikwazi ukulungisa ingxaki ngokufanelekileyo. -fno-stack-protector Lukhetho ekucacileyo ukuba bekungafanelekanga ukuba silusebenzisa, kodwa siza kulusebenzisa kuba kungenjalo kuya kubakho ukuvela okugcwala kwesitampu. Ekugqibeleni ndivavanye iziphumo. ./a.out iqhuba nje le ndiyenzileyo nje, ifuna ulwazi kwaye iyibuyise. Ukubaleka 🙂

Izilumkiso

Enye inqaku apha. Ngaba uyazibona izilumkiso? Ngokucacileyo yinto ekufuneka ithathelwe ingqalelo xa sisebenza ngekhowudi okanye sidibanisa, oku kuyacaca kwaye kukho iinkqubo ezimbalwa ezinomsebenzi namhlanje. gets() Kwikhowudi. Olunye uncedo lweGentoo kukuba ngokudibanisa inkqubo nganye, ndiyabona ukuba yintoni engalunganga, inkqubo "efanelekileyo" ayifanelanga ukuba nayo, kodwa uya kumangaliswa ukuba zingaphi iinkqubo ezinkulu ezinezi zilumkiso kuba zikhulu KAKHULU kwaye Kunzima ukugcina umkhondo kubo.imisebenzi eyingozi xa kukho izilumkiso ezininzi ngaxeshanye. Ngoku ukuba siyaqhubeka

Ukulungisa ingxaki kwinkqubo

Ngoku eli candelo linokudideka, kodwa kuba sele ndibhalile kancinci, andinakukwazi ukuchaza yonke into, uxolo ke xa ubona ukuba ndihamba ngokukhawuleza okukhulu

Ukuphelisa ikhowudi

Masiqale ngokujonga inkqubo yethu edityanisiweyo yolwimi.

Le yikhowudi yomsebenzi wethu ophambili kwi indibano, yile nto iprosesa yethu iqondayo, umgca ngasekhohlo yidilesi ebonakalayo kwimemori, i <+ n> yaziwa njenge ukucinywa, ngokusisiseko umgama ukusuka ekuqaleni komsebenzi (ophambili) ukuya kwingxelo (eyaziwa njenge ikhowudi ye-opcode). Emva koko sibona uhlobo lomyalelo (Push / mov / callq…) kunye noluhlu olunye nangaphezulu. Isishwankathelo sinokuthi luphawu olulandelwe ngumthombo / imvelaphi kunye nendawo ekuyiwa kuyo. <return_input> ibhekisa kumsebenzi wethu wesibini, masijonge.

Igalelo_lokubuyisela

Oku kunzima ngakumbi, kodwa ndifuna nje ukuba ujonge izinto ezimbalwa, kukho ithegi ebizwa <gets@plt> kunye ne-opcode yokugqibela ebizwa ngokuba retq ibonisa ukuphela komsebenzi. Siza kubeka iindawo ezimbalwa zokuphumla, enye isebenze gets kunye nenye kwifayile ye- retq.

Run

Ngoku siza kuqhuba inkqubo ukubona ukuba isenzo siqala njani.

Siyabona ukuba utolo oluncinci luvela lubonisa i-opcode apho sikhona, ndifuna ukuba baqwalasele umkhombandlela 0x000055555555469bLe yidilesi emva komnxeba oya kuwo return_input ekusebenzeni main , oku kubalulekile njengoko kulapho inkqubo inokubuya khona xa ugqibile ukufumana ifayile ye negalelo, masingene emsebenzini. Ngoku siza kujonga imemori ngaphambi kokungena emsebenzini gets.

Ndibuyisele umsebenzi ophambili kuwe, kwaye ndibonisile ikhowudi ebendibhekisa kuyo, njengoko ubona, ngenxa ye- ukunyaniseka yahlulwe yangamacandelo amabini, ndifuna ukuba baqwalasele umkhombandlela 0x7fffffffdbf0 (owokuqala ukusuka ekhohlo emva komyalelo x/20x $rspkuba le yindawo ekufuneka siyisebenzisile ukukhangela iziphumo, masiqhubeke:

Ukophula inkqubo

Ndizicacisile ezo 0x44444444kuba ngabameli be-Ds zethu ngoku siqale ukongeza negalelo kwinkqubo, kwaye njengoko ubona, siyimigca emibini kuphela kwidilesi yethu, siya kuyizalisa de sibe siphambi kweedilesi esizibonakalisileyo kwinyathelo elidlulileyo.

Ukutshintsha indlela yokubuyela

Ngoku sikwazile ukungena kweli candelo lekhowudi apho libonisa khona ukubuya komsebenzi, masibone ukuba kwenzeka ntoni xa sitshintsha idilesi 🙂 endaweni yokuya kwindawo ye-opcode elandela leyo besinayo umzuzwana, ucinga ntoni ukuba sibuyela ku return_input? Kodwa oku, kuyimfuneko ukubhala idilesi esiyifunayo kubhinari, siza kuyenza nomsebenzi printf ukusuka bash 🙂

Ngoku silufumene ulwazi kabini-ngokuqinisekileyo inkqubo ayenzelwanga loo nto, kodwa sikwazile ukophula ikhowudi kwaye sayenza ukuba iphinde iphinde ibe yinto engafanelekanga ukuba yenziwe.

Ukucinga

Olu tshintsho lulula lungaqwalaselwa njenge ukuxhaphaza esisiseko 🙂 ukwazile ukwaphula inkqubo kwaye wenza into esifuna ukuba ayenze.

Eli linyathelo nje lokuqala kuluhlu olungenasiphelo lwezinto ozibonayo kunye nokongeza, kukho iindlela zokongeza izinto ezingaphezulu kokuphinda-phinda iodolo, kodwa ngeli xesha ndibhale kakhulu kwaye yonke into enxulumene nayo iqokobhe sisifundo sokubhala ngaphezulu kwamanqaku, zingathi iincwadi ezigqibeleleyo. Uxolo ukuba khange ndikwazi ukuphinda ndifunde kancinane kwizihloko endiya kuzithanda, kodwa ngokuqinisekileyo kuyakubakho ithuba 🙂 Ukubulisa kunye nombulelo wokufika apha.