I`m still reading all the resources, but I found a few more. http://www.ualberta.ca/CNS/RESEARCH/LinuxClusters/mem.html
I didn`t find a few answers yet, but how a module is loaded ? When you do a insmod the kernel take some pages and load all the module's sections to these pages ? How this work ? Where I can find more information about memory allocation for a new module. If I don`t find, I will read the source code for that part, but I try to find a better way to learn. I know that source code is the best and updated, but takes more time too. And when I do a int inside my module I suppose that my int will be inside that pages that kernel allocated for my new module. Right ?? But if I do this inside kernel code ? It's compiler task do allocate this memory in sections ? How the kernel runs ? Like my module is driven by kernel, but how kernel driven it's self ??? Thanks -- Lucas Tanure +55 (19) 988176559 On Tue, Aug 5, 2014 at 12:31 AM, Peter Teoh <[email protected]> wrote: > And Q2: > > Just want to comment that the load address has to be fixed initially, > because unlike normal ELF, after loading ELF, there is a relocation tasks > done by the linker. In vmlinuz we cannot have relocation, before > executing the kernel is the BIOS / uboot / bootloader etc. One possible > answer. Others: > > https://groups.google.com/forum/#!topic/comp.os.linux.embedded/0-SAzCqQKFM > > And perhaps some of the links below may help you: > > http://jianggmulab.blogspot.sg/2010_01_01_archive.html > > > http://stackoverflow.com/questions/5647279/why-does-the-module-start-from-address-0xbf000000 > > http://www.arm.linux.org.uk/developer/memory.txt > > http://en.wikipedia.org/wiki/High_memory > > bottomline: keep googling. > > Q6 and 7 makes no sense to me....sorry. > > > > On Mon, Aug 4, 2014 at 11:22 PM, Lucas Tanure <[email protected]> wrote: > >> Thanks! >> >> A quick look in all of that show me that there a lot of information >> about how kernel manage memory. >> But, I will find the answer for question 2, 6 and 7 in it ? >> >> Thanks! >> -- >> Lucas Tanure >> +55 (19) 988176559 >> >> >> On Sun, Aug 3, 2014 at 8:58 PM, Peter Teoh <[email protected]> >> wrote: >> > I like your curiosities and interests in Linux >> > kernel. >> http://virtuallyhyper.com/2013/07/rhcsa-and-rhce-chapter-10-the-kernel/ >> > >> > Instead of answering one by one, I think I will just identify the >> knowledge >> > you are lacking: >> > >> > Memory management (from both x86/intel and linux kernel perspective). >> > >> > There are many many resources out there for you in these area, eg: >> > >> > http://en.wikipedia.org/wiki/Page_table >> > http://en.wikipedia.org/wiki/X86-64 >> > >> > (both boring, but just understand it well enough) >> > >> > http://wiki.osdev.org/Paging (good explanation....understand it very >> very >> > well). >> > >> > The ultimate classic ebook: >> > >> > https://www.kernel.org/doc/gorman/pdf/understand.pdf >> > >> > And this blog site has tons of good info on intel/memory etc: >> > >> > >> http://duartes.org/gustavo/blog/post/cpu-rings-privilege-and-protection/ >> > http://duartes.org/gustavo/blog/post/anatomy-of-a-program-in-memory/ >> > >> > http://virtuallyhyper.com/2013/07/rhcsa-and-rhce-chapter-10-the-kernel/ >> > >> > http://www.cse.psu.edu/~anand/spring01/linux/memory.ppt >> > >> > One more thing: >> > >> > "readelf -S -W vmlinux" shows u the sections and the address where the >> > different sections are supposed to be loaded in memory. If u replace >> the >> > vmlinux with the kernel module, eg: ip_tables.ko, then it says: >> > >> > starting at offset 0x328c blah blah.... >> > >> > so the loaded address is with respect to ZERO, but then the actual >> module >> > address is: >> > >> > sudo cat /proc/modules |grep ip_table >> > >> > ip_tables 18106 1 iptable_filter, Live 0xf8bf5000 >> > >> > So all the output from your readelf, just add 0xf8bf5000 to it and you >> will >> > get the actual virtual address of that section IN MEMORY. >> > >> > Just only in memory. In file, the file offset of the section is >> different. >> > And many parts inside the ELF is also different from memory too: you >> will >> > need to add the virtual load address (above) to the offset as specified >> > inside the relocation tables (objdump -r), and for each section there >> is a >> > separate relocation table (all independent from another, meaning that >> the >> > different section CAN BE loaded to different parts in memory). >> > >> > Thanks. >> > >> > >> > On Sun, Aug 3, 2014 at 11:59 PM, Lucas Tanure <[email protected]> wrote: >> >> >> >> Hi, >> >> >> >> I'm looking for some site, pdf, book etc, that can answer this >> questions. >> >> For now I have : >> >> >> >> >> http://unix.stackexchange.com/questions/5124/what-does-the-virtual-kernel-memory-layout-in-dmesg-imply >> >> >> >> >> >> I want to understand a few things about the memory and the execution >> >> of Linux kernel. >> >> Taking from a X86 and grub I have: >> >> >> >> 1) Grub loads kernel and root file system in memory, and the vmlinux >> >> has the code to decompress it self, right ? linux >> >> >> >> 2) The address of load kernel is always the same ? And It's at >> >> compilation time that is chosen ? >> >> >> >> 2a) The kernel takes places in 3g-4g memory place, and user space from >> 0 >> >> to 3gb. >> >> But if the pc has only 256mb of memory ? >> >> And when pc has 16gb of memory, the user space will be split in two ? >> >> >> >> 2b) And if kernel has soo many modules that needs more than 1gb to run >> ? >> >> >> >> 2c) How we configure all of that memory configs ? make menuconfig and >> >> friends ? >> >> >> >> 3) The function A will call functon B. B is at 0xGGGGGG in .text >> >> section, but kernel was loaded in address 0xJJJJJJJJJJ, how A will >> >> find B ? >> >> >> >> 4) Please consider this: >> >> $ readelf -S -W vmlinux >> >> There are 37 section headers, starting at offset 0xe05718: >> >> >> >> Section Headers: >> >> [Nr] Name Type Address >> >> Off Size ES Flg Lk Inf Al >> >> [ 0] NULL >> >> 0000000000000000 000000 000000 00 0 0 0 >> >> [ 1] .text PROGBITS >> >> ffffffff81000000 200000 53129a 00 AX 0 0 4096 >> >> [ 2] .notes NOTE >> >> ffffffff8153129c 73129c 0001d8 00 AX 0 0 4 >> >> [ 3] __ex_table PROGBITS ffffffff81531480 >> >> 731480 002018 00 A 0 0 8 >> >> [ 4] .rodata PROGBITS >> >> ffffffff81600000 800000 1655ee 00 A 0 0 64 >> >> [ 5] __bug_table PROGBITS ffffffff817655f0 >> >> 9655f0 005424 00 A 0 0 1 >> >> [ 6] .pci_fixup PROGBITS ffffffff8176aa18 >> >> 96aa18 002f88 00 A 0 0 8 >> >> [ 7] .tracedata PROGBITS ffffffff8176d9a0 >> >> 96d9a0 00003c 00 A 0 0 1 >> >> [ 8] __ksymtab PROGBITS ffffffff8176d9e0 >> >> 96d9e0 00e710 00 A 0 0 16 >> >> [ 9] __ksymtab_gpl PROGBITS ffffffff8177c0f0 >> >> 97c0f0 00a150 00 A 0 0 16 >> >> [10] __kcrctab PROGBITS ffffffff81786240 >> >> 986240 007388 00 A 0 0 8 >> >> [11] __kcrctab_gpl PROGBITS ffffffff8178d5c8 >> >> 98d5c8 0050a8 00 A 0 0 8 >> >> [12] __ksymtab_strings PROGBITS ffffffff81792670 >> >> 992670 01cb42 00 A 0 0 1 >> >> [13] __init_rodata PROGBITS ffffffff817af1c0 >> >> 9af1c0 0000e8 00 A 0 0 32 >> >> [14] __param PROGBITS ffffffff817af2a8 >> >> 9af2a8 000b00 00 A 0 0 8 >> >> [15] __modver PROGBITS ffffffff817afda8 >> >> 9afda8 000258 00 A 0 0 8 >> >> [16] .data PROGBITS >> >> ffffffff81800000 a00000 0e1180 00 WA 0 0 4096 >> >> [17] .vvar PROGBITS >> >> ffffffff818e2000 ae2000 001000 00 WA 0 0 16 >> >> [18] .data..percpu PROGBITS 0000000000000000 >> >> c00000 015300 00 WA 0 0 4096 >> >> [19] .init.text PROGBITS >> >> ffffffff818f9000 cf9000 0503ea 00 AX 0 0 16 >> >> [20] .init.data PROGBITS >> >> ffffffff8194a000 d4a000 09e4c8 00 WA 0 0 4096 >> >> [21] .x86_cpu_dev.init PROGBITS ffffffff819e84c8 >> >> de84c8 000018 00 A 0 0 8 >> >> [22] .parainstructions PROGBITS ffffffff819e84e0 >> >> de84e0 00bd3c 00 A 0 0 8 >> >> [23] .altinstructions PROGBITS ffffffff819f4220 >> >> df4220 005f40 00 A 0 0 1 >> >> [24] .altinstr_replacement PROGBITS ffffffff819fa160 >> >> dfa160 001a69 00 AX 0 0 1 >> >> [25] .iommu_table PROGBITS ffffffff819fbbd0 >> >> dfbbd0 0000f0 00 A 0 0 8 >> >> [26] .apicdrivers PROGBITS ffffffff819fbcc0 >> >> dfbcc0 000020 00 WA 0 0 8 >> >> [27] .exit.text PROGBITS ffffffff819fbce0 >> >> dfbce0 0009bc 00 AX 0 0 1 >> >> [28] .smp_locks PROGBITS ffffffff819fd000 >> >> dfd000 005000 00 A 0 0 4 >> >> [29] .data_nosave PROGBITS ffffffff81a02000 >> >> e02000 001000 00 WA 0 0 4 >> >> [30] .bss NOBITS >> >> ffffffff81a03000 e03000 122000 00 WA 0 0 4096 >> >> [31] .brk NOBITS >> >> ffffffff81b25000 e03000 425000 00 WA 0 0 1 >> >> [32] .comment PROGBITS 0000000000000000 >> >> e03000 000027 01 MS 0 0 1 >> >> [33] .debug_frame PROGBITS 0000000000000000 >> >> e03028 002560 00 0 0 8 >> >> [34] .shstrtab STRTAB >> >> 0000000000000000 e05588 00018a 00 0 0 1 >> >> [35] .symtab SYMTAB 0000000000000000 >> >> e06058 1a29f8 18 36 43659 8 >> >> [36] .strtab STRTAB >> >> 0000000000000000 fa8a50 180d92 00 0 0 1 >> >> Key to Flags: >> >> W (write), A (alloc), X (execute), M (merge), S (strings), l (large) >> >> I (info), L (link order), G (group), T (TLS), E (exclude), x >> (unknown) >> >> O (extra OS processing required) o (OS specific), p (processor >> specific) >> >> >> >> So the vmlinux is loaded in memory like a dd ? >> >> >> >> 5) In my function A, inside the module that I wrote, a non-initialized >> >> variable will take place in non-initialized section that was loaded in >> >> memory ? >> >> Or my modules has a new sections for it's own use, and my module is >> >> loaded my memory like a process, with all his sections? >> >> So how another module or kernel code will fin my exported >> >> variable/function ? >> >> >> >> >> >> 6) Let's suppose: >> >> I have a int variable, with 17 as content, and the address is 0xGGGGGG. >> >> If I stop the linux in this time, read my memory at address 0xGGGGGG I >> >> will got 17, right ? >> >> 0xGGGGGGG will be bigger than 0xc0000000 always, right ? >> >> >> >> >> >> 7) Now take int from question and change for: >> >> struct mystruct * foo = (struct mystruct* ) kmalloc(sizeof(struct >> >> mystruct)); >> >> >> >> I will be able to read at address 0xGGGGGG the struct that created, >> >> and it address will be greater than 0xc0000000, right ? >> >> But for this struct, the memory will be allocated for ever, until I >> >> free the pointer, right ? >> >> >> >> >> >> >> >> Well, this just a start. I really want to understand how kernel is >> >> run, loaded etc. Any help is appreciate, answering my questions, links >> >> to read, books to read. >> >> Actually, I didn't find any book with that kind of information . >> >> >> >> >> >> -- >> >> Lucas Tanure >> >> +55 (19) 988176559 >> >> >> >> -- >> >> To unsubscribe, send a message with 'unsubscribe linux-mm' in >> >> the body to [email protected]. For more info on Linux MM, >> >> see: http://www.linux-mm.org/ . >> >> Don't email: <a href=mailto:"[email protected]";> [email protected] </a> >> > >> > >> > >> > >> > -- >> > Regards, >> > Peter Teoh >> > > > > -- > Regards, > Peter Teoh >
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