{"id":16389,"date":"2022-10-15T11:39:08","date_gmt":"2022-10-15T06:09:08","guid":{"rendered":"https:\/\/jassweb.com\/solved\/solved-finding-address-of-variable-in-shared-library\/"},"modified":"2022-10-15T11:39:08","modified_gmt":"2022-10-15T06:09:08","slug":"solved-finding-address-of-variable-in-shared-library","status":"publish","type":"post","link":"https:\/\/jassweb.com\/solved\/solved-finding-address-of-variable-in-shared-library\/","title":{"rendered":"[Solved] Finding address of variable in shared library"},"content":{"rendered":"

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If you are on a Linux system with a GNU libc<\/a>, and if the variable is a known name inside the dynamic symbol table of some dynamically linked<\/a> library, i.e. ELF<\/a> shared object, and if you can change the code of the main program (or some shared object dynamically linked by it, perhaps playing LD_PRELOAD<\/code> tricks) you could use the dladdr(3)<\/a> function (given a pointer, dladdr<\/code> gives you a Dl_info<\/code> structure with symbol and shared object names close to the given pointer).<\/p>\n

Since dynamically linked shared object libraries are often mmap(2)<\/a>-ed at non predictable addresses (e.g. because of ASLR<\/a>) you need to do that at runtime. (See also \/proc\/self\/maps<\/code> from inside your process; read proc(5)<\/a> etc…)<\/p>\n

Read Drepper’s paper: How to write Shared Libraries<\/em><\/a>; be aware of VDSO<\/a>…<\/p>\n

Notice that a given *.so<\/code> file has several mmap<\/code>-ed segments, and that some of its (file) data is not<\/em> mmap<\/code>-ed! Use pmap(1)<\/a> to find out.<\/p>\n<\/p><\/div>\n

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3<\/span> <\/p><\/div>\n<\/div>\n

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solved Finding address of variable in shared library <\/p>\n","protected":false},"excerpt":{"rendered":"

[ad_1] If you are on a Linux system with a GNU libc, and if the variable is a known name inside the dynamic symbol table of some dynamically linked library, i.e. ELF shared object, and if you can change the code of the main program (or some shared object dynamically linked by it, perhaps playing … Read more<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[320],"tags":[2097,2697,424,4164],"class_list":["post-16389","post","type-post","status-publish","format-standard","hentry","category-solved","tag-gdb","tag-linker","tag-linux","tag-shared-libraries"],"yoast_head":"\n[Solved] Finding address of variable in shared library - JassWeb<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/jassweb.com\/solved\/solved-finding-address-of-variable-in-shared-library\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"[Solved] Finding address of variable in shared library - JassWeb\" \/>\n<meta property=\"og:description\" content=\"[ad_1] If you are on a Linux system with a GNU libc, and if the variable is a known name inside the dynamic symbol table of some dynamically linked library, i.e. ELF shared object, and if you can change the code of the main program (or some shared object dynamically linked by it, perhaps playing ... 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