-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Mulyadi Santosa wrote: > Hi... > > On Thu, Nov 6, 2008 at 10:42 PM, Giannis Kozyrakis <trv@xxxxxxxxxxx> wrote: >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA1 >> >> Hello, >> >> I've recently begun to study kernel modules, and how they changed >> between kernel 2.4 and 2.6, with respect to symbol exporting options. >> >> In kernel 2.4, there was a /proc/ksyms file. This file, if I understand >> correctly, was a method to access the kernel's public symbol table. This >> table had all the public kernel's symbols (variables, functions..) and >> its associated global addresses, along with some othere usefull stuff, >> like a CRC value, and the module exporting every specific symbol. >> >> Fine until this point. >> >> In 2.6 kernels, /proc/ksyms disappeared. Many suggest that it was >> replaced by /proc/kallsyms file. BUT this file seems to be something >> completely different, and I haven't figured out in what way it is different. >> >> So, some questions to anyone that knows more on this: >> >> 1. Is my description of the functionality of /proc/ksyms in 2.4 kernels >> correct? >> >> 2. What exactly the /proc/kallsyms file contains? Why this file exists >> and how is it used? >> >> 3. Why was there this change in name and behavior of this file? >> >> 4. If one wants to find out what are the exported symbols from some >> module, how can he achive this? >> >> >> - From what I understand about /proc/kallsyms, it contains even the >> symbols that are not exported using EXPORT_SYMBOL(symbol_name). >> /proc/ksyms, contained every symbol appart from those that were not >> exported (considering the export all default policy in 2.4, in contrast >> with the export none policy of 2.6) > > I think you're correct. kallsyms contains symbols located in text > section, bss section, data section... be it local or global. however, > I do see that my kernel (Ubuntu's 2.6.22-14 generic) is configured > with CONFIG_KALLSYMS_ALL=y, so maybe that explains why I saw abundant > symbol names. > > Using kallsyms, i saw that every symbols name are suffixed with module > name where they belong to. So simply grepping module name will tell > you which ones are exported (you probably just want to see the global > ones.....T, B and D). > > Kallsyms itself, AFAIK, is either a special section in kernel memory > layout...or special linked list that contains those symbols. > Therefore, it has constructor, destructor and accessor functions. > > regards, > > Mulyadi. > Hello Mulyadi, First, thank you very much for your answer. About CONFIG_KALLSYMS=y option: "Say Y here to let the kernel print out symbolic crash information and symbolic stack backtraces. This increases the size of the kernel somewhat, as all symbols have to be loaded into the kernel image." I don't think this option has something to do with /proc/kallsyms file.. Or I don't know their relation. I don't know the exact format of the /proc/kallsyms file, so I don't really know what the T, B and D you say refer to. I have to dig further obviously :) Any references to search further? Thanks again! -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iEYEARECAAYFAkkUusIACgkQusj5FmsVhIc1JgCgk6sJkjNiD0FC0xs3pi9hY4Cy AYYAni5h5W8hrMut/gaxil5KBwUdhD7U =Vumz -----END PGP SIGNATURE----- -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
