133 lines
4.5 KiB
C
133 lines
4.5 KiB
C
/************************/
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/** **/
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/** PLT section **/
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/** **/
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/************************/
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// insmod error: module PLT section(s) missing
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__attribute__((section(".plt")))
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char plt = 0;
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__attribute__((section(".init.plt")))
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char initplt = 0;
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__attribute__((section(".text.ftrace_trampoline")))
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char textftrace_trampoline = 0; // TODO: probably irrelevant
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/************************/
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/** **/
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/** .modinfo **/
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/** **/
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/************************/
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// objdump -s -j .modinfo $KMODULE
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#define AUTHOR "someone"
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#define DESCRIPTION "Simple =^.^= kernel module"
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#define NAME "bmod"
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#define LICENSE "GPL"
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#define VERMAGIC "4.14.186-perf-00288-g7df34d2ae6db SMP preempt mod_unload modversions aarch64"
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__attribute__((section(".modinfo")))
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char modinfo_strings[] =
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"author=" AUTHOR "\0"
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"description=" DESCRIPTION "\0"
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"license=" LICENSE "\0"
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"vermagic=" VERMAGIC "\0"
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"name=" NAME "\0"
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;
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/*******************************/
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/** **/
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/** .gnu.linkonce.this_module **/
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/** **/
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/*******************************/
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// 1 - section size
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// objdump -h $KMODULE | grep .gnu.linkonce.this_module
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// .gnu.linkonce.this_module 00000340 0000000000000000 0000000000000000 00109800 2**6
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// ^^^^^^^^ section size
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// 2 - section content
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// objdump -s $KMODULE -j .gnu.linkonce.this_module
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// Contents of section .gnu.linkonce.this_module:
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// 0000 00000000 00000000 00000000 00000000 ................
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// 0010 00000000 00000000 6d657400 00000000 ........met..... // <<-- NAME offset 0x18
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// 0020 00000000 00000000 00000000 00000000 ................
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// 3 - entry points offsets
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// readelf -a $KMODULE -W
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// Relocation section '.rela.gnu.linkonce.this_module' at offset 0x109b40 contains 2 entries:
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// <--- Offset ---> Info Type Symbol's Value Symbol's Name + Addend
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// 0000000000000150 000006c500000101 R_AARCH64_ABS64 0000000000000000 init_module + 0
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// 0000000000000310 000006ee00000101 R_AARCH64_ABS64 0000000000000000 cleanup_module + 0
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#define L_ONCE_SIZE 0x340
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#define L_ONCE_OFFSET_NAME 0x18
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#define L_ONCE_OFFSET_INIT 0x150
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#define L_ONCE_OFFSET_CLEANUP 0x310
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int init_module(void);
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void cleanup_module(void);
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__attribute__((section(".gnu.linkonce.this_module"), aligned(8)))
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struct module {
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char __pad0[L_ONCE_OFFSET_NAME];
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char name[sizeof(NAME)];
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char __pad1[L_ONCE_OFFSET_INIT - L_ONCE_OFFSET_NAME - sizeof(NAME)];
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int (*init_module)(void);
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char __pad2[L_ONCE_OFFSET_CLEANUP - L_ONCE_OFFSET_INIT - sizeof(void*)];
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void (*cleanup_module)(void);
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char __pad3[L_ONCE_SIZE - L_ONCE_OFFSET_CLEANUP - sizeof(void*)];
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} __attribute__((packed))
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__this_module = {
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.name = NAME,
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.init_module = &init_module,
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.cleanup_module = &cleanup_module,
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};
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/*******************************/
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/** **/
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/** __versions **/
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/** **/
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/*******************************/
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// objdump -s $KMODULE -j '__versions' #dump binary
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// modprobe --dump-modversions $KMODULE #dump readable
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char __attribute__((section("__versions"))) ____versions[] = {
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/* module_layout */ // <<-- MUST BE PROVIDED
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0xe8, 0xd6, 0xfc, 0x68, 0x00, 0x00, 0x00, 0x00, 0x6d, 0x6f, 0x64, 0x75, 0x6c, 0x65, 0x5f, 0x6c,
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0x61, 0x79, 0x6f, 0x75, 0x74, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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/* printk */
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0xa1, 0x58, 0x55, 0x98, 0x00, 0x00, 0x00, 0x00, 0x70, 0x72, 0x69, 0x6e, 0x74, 0x6b, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
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};
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/*
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* The Module
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*/
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// load: insmod module_name.ko
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// logs: dmesg | grep insmod
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// unload: rmmod MODULE_NAME # from .gnu.linkonce.this_module section
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int printk(const char *fmt, ...);
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#define MTAG "["NAME"] "
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int init_module(void) {
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printk( MTAG"Hello, world!\n");
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return 0;
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}
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void cleanup_module(void) {
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printk( MTAG"Goodbye, world!\n");
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}
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