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-me... 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