get system call table in x86-64 Linux

http://bbs.chinaunix.net/thread-2143235-1-1.html Linux System Call Table http://bluemaster.iu.hio.no/edu/dark/lin-asm/syscalls.html #include <linux/kernel.h> #include <linux/init.h> #include <linux/module.h> #include <asm/uaccess.h> #include <asm/fcntl.h> #include <asm/unistd.h> #include <asm/ia32_unistd.h> #include <asm/msr.h> #define THIS_DESCRIPTION "Dynamically get sys_call_table/ia32_sys_call_table in kernel module.\n\t\tI don't think there would be anyone who won't enable CONFIG_IA32_EMULATION these days.\n\t\tso you can add the unessary check if you really want to." MODULE_DESCRIPTION( THIS_DESCRIPTION ); MODULE_AUTHOR("albcamus <[email protected]>"); MODULE_LICENSE("GPL"); /** * TODO: if you want shut this up, comment the following line. */ #define BY_IDT_DEBUG #ifdef BY_IDT_DEBUG #define dbgprint(format,args...) \                  printk("get_syscall: function:%s-L%d: "format, __FUNCTION__, __LINE__, ## args); #else #define dbgprint(format,args...)  do {} while(0); #endif /** * sys call table */ void ** my_ia32_syscall_table; void ** my_syscall_table; /** * 10 bytes  -- please refer to AMD64 Architecture Programmer's  *         Manuals for more information. */ struct idtr {     unsigned short limit;     unsigned long base; //in 64bit mode, base address is 8 bytes } __attribute__ ((packed)); /** * in long mode -- 64bit mode and compatity mode,  * every IDT entry has a 16-byte size */ struct idt {     u16 offset_low;     u16 segment;     unsigned ist : 3, zero0 : 5, type : 5, dpl :2, p : 1;     u16 offset_middle;     u32 offset_high;     u32 zero1; } __attribute__ ((packed)); /** * Return the first appearence of NEEDLE in HAYSTACK.  -- copied from PHRACK * */ static void *memmem(const void *haystack, size_t haystack_len,             const void *needle, size_t needle_len) {/*{{{*/     const char *begin;     const char *const last_possible         = (const char *) haystack + haystack_len - needle_len;     if (needle_len == 0)         /* The first occurrence of the empty string is deemed to occur at            the beginning of the string.  */         return (void *) haystack;     /* Sanity check, otherwise the loop might search through the whole        memory.  */     if (__builtin_expect(haystack_len < needle_len, 0))         return NULL;     for (begin = (const char *) haystack; begin <= last_possible;          ++begin)         if (begin[0] == ((const char *) needle)[0]             && !memcmp((const void *) &begin[1],                    (const void *) ((const char *) needle + 1),                    needle_len - 1))             return (void *) begin;     return NULL; }/*}}}*/ /** * Find the location of ia32_sys_call_table */ static unsigned long get_syscall_table_ia32(void) {/*{{{*/ #define OFFSET_SYSCALL 100    /* from system_call/ia32_syscall, we'll read first 150 bytes */     struct idtr idtr;     struct idt idt;     unsigned long sys_call_off;     unsigned long retval;     char sc_asm[OFFSET_SYSCALL], *p;     /* well, let's read IDTR */     asm("sidt %0"         :"=m"(idtr)         : );     dbgprint("idtr base at %p\n", (void *)idtr.base);     /**      * Read in IDT for vector 0x80 (syscall)       */     memcpy(&idt, (char *) idtr.base + 16 * 0x80, sizeof(idt));      sys_call_off =  ( ( (unsigned long)idt.offset_high ) << 32 ) |          ( ((idt.offset_middle << 16 ) | idt.offset_low) & 0x00000000ffffffff );      dbgprint("sys_call_off at %p\n", (void *)sys_call_off);     /* we have syscall routine address now, look for syscall table        dispatch (indirect call) */     memcpy(sc_asm, (void *)sys_call_off, OFFSET_SYSCALL);     /**      * ia32_call > ia32_tracesys > ia32_do_syscall > 'call *ia32_sys_call_table(,%rax,8)'      * Find callq *ia32_sys_call_table(,%rax,8)      *      * (gdb) disassemble ia32_syscall      * Dump of assembler code for function ia32_syscall:      * 0xffffffff81066b98 <ia32_syscall+0>:    swapgs      * 0xffffffff81066b9b <ia32_syscall+3>:    sti      * 0xffffffff81066b9c <ia32_syscall+4>:    mov    %eax,%eax      * 0xffffffff81066b9e <ia32_syscall+6>:    push   %rax      * 0xffffffff81066b9f <ia32_syscall+7>:    cld      * 0xffffffff81066ba0 <ia32_syscall+8>:    sub    $0x48,%rsp      * 0xffffffff81066ba4 <ia32_syscall+12>:   mov    %rdi,0x40(%rsp)      * 0xffffffff81066ba9 <ia32_syscall+17>:   mov    %rsi,0x38(%rsp)      * 0xffffffff81066bae <ia32_syscall+22>:   mov    %rdx,0x30(%rsp)      * 0xffffffff81066bb3 <ia32_syscall+27>:   mov    %rcx,0x28(%rsp)      * 0xffffffff81066bb8 <ia32_syscall+32>:   mov    %rax,0x20(%rsp)      * 0xffffffff81066bbd <ia32_syscall+37>:   mov    %gs:0x10,%r10      * 0xffffffff81066bc6 <ia32_syscall+46>:   sub    $0x1fd8,%r10      * 0xffffffff81066bcd <ia32_syscall+53>:   orl    $0x2,0x14(%r10)      * 0xffffffff81066bd2 <ia32_syscall+58>:   testl  $0x181,0x10(%r10)      * 0xffffffff81066bda <ia32_syscall+66>:   jne    0xffffffff81066c04 <ia32_tracesys>      * End of assembler dump.      * (gdb) disassemble ia32_tracesys      * Dump of assembler code for function ia32_tracesys:      * 0xffffffff81066c04 <ia32_tracesys+0>:   sub    $0x30,%rsp      * 0xffffffff81066c08 <ia32_tracesys+4>:   mov    %rbx,0x28(%rsp)      * 0xffffffff81066c0d <ia32_tracesys+9>:   mov    %rbp,0x20(%rsp)      * 0xffffffff81066c12 <ia32_tracesys+14>:  mov    %r12,0x18(%rsp)      * 0xffffffff81066c17 <ia32_tracesys+19>:  mov    %r13,0x10(%rsp)      * 0xffffffff81066c1c <ia32_tracesys+24>:  mov    %r14,0x8(%rsp)      * 0xffffffff81066c21 <ia32_tracesys+29>:  mov    %r15,(%rsp)      * 0xffffffff81066c25 <ia32_tracesys+33>:  movq   $0xffffffffffffffda,0x50(%rsp)      * 0xffffffff81066c2e <ia32_tracesys+42>:  mov    %rsp,%rdi      * 0xffffffff81066c31 <ia32_tracesys+45>:  callq  0xffffffff81073a02 <syscall_trace_enter>      * 0xffffffff81066c36 <ia32_tracesys+50>:  mov    0x30(%rsp),%r11      * 0xffffffff81066c3b <ia32_tracesys+55>:  mov    0x38(%rsp),%r10      * 0xffffffff81066c40 <ia32_tracesys+60>:  mov    0x40(%rsp),%r9      * 0xffffffff81066c45 <ia32_tracesys+65>:  mov    0x48(%rsp),%r8      * 0xffffffff81066c4a <ia32_tracesys+70>:  mov    0x58(%rsp),%rcx      * 0xffffffff81066c4f <ia32_tracesys+75>:  mov    0x60(%rsp),%rdx      * 0xffffffff81066c54 <ia32_tracesys+80>:  mov    0x68(%rsp),%rsi      * 0xffffffff81066c59 <ia32_tracesys+85>:  mov    0x70(%rsp),%rdi      * 0xffffffff81066c5e <ia32_tracesys+90>:  mov    0x78(%rsp),%rax      * 0xffffffff81066c63 <ia32_tracesys+95>:  mov    (%rsp),%r15      * 0xffffffff81066c67 <ia32_tracesys+99>:  mov    0x8(%rsp),%r14      * 0xffffffff81066c6c <ia32_tracesys+104>: mov    0x10(%rsp),%r13      * 0xffffffff81066c71 <ia32_tracesys+109>: mov    0x18(%rsp),%r12      * 0xffffffff81066c76 <ia32_tracesys+114>: mov    0x20(%rsp),%rbp      * 0xffffffff81066c7b <ia32_tracesys+119>: mov    0x28(%rsp),%rbx      * 0xffffffff81066c80 <ia32_tracesys+124>: add    $0x30,%rsp      * 0xffffffff81066c84 <ia32_tracesys+128>: jmpq   0xffffffff81066bdc <ia32_do_syscall>      * End of assembler dump.      * (gdb) disassemble ia32_do_syscall      * Dump of assembler code for function ia32_do_syscall:      * 0xffffffff81066bdc <ia32_do_syscall+0>: cmp    $0x13d,%eax      * 0xffffffff81066be1 <ia32_do_syscall+5>: ja     0xffffffff81066c89 <ia32_badsys>      * 0xffffffff81066be7 <ia32_do_syscall+11>:        mov    %edi,%r8d      * 0xffffffff81066bea <ia32_do_syscall+14>:        mov    %ebp,%r9d      * 0xffffffff81066bed <ia32_do_syscall+17>:        xchg   %ecx,%esi      * 0xffffffff81066bef <ia32_do_syscall+19>:        mov    %ebx,%edi      * 0xffffffff81066bf1 <ia32_do_syscall+21>:        mov    %edx,%edx      * 0xffffffff81066bf3 <ia32_do_syscall+23>:        callq  *0xffffffff812e7c70(,%rax,8)      * End of assembler dump.      * (gdb) x/xw ia32_do_syscall+23      * 0xffffffff81066bf3 <ia32_do_syscall+23>:        0x70c514ff      * (gdb)      *      */     p = (char *) memmem(sc_asm, OFFSET_SYSCALL, "\xff\x14\xc5", 3);     if (p == NULL) {         printk("opcode not found, meats that we cannot find sys_call_table.\n");         return 0;     }     retval = *(unsigned long *) (p + 3);     return retval; #undef OFFSET_SYSCALL }/*}}}*/ /** * Find the location of long-mode sys_call_table */ static unsigned long get_syscall_table_long(void) {/*{{{*/ #define OFFSET_SYSCALL 150     unsigned long syscall_long, retval;     char sc_asm[OFFSET_SYSCALL];     rdmsrl(MSR_LSTAR, syscall_long);     dbgprint("long mode: system_call is at %p\n", (void *)syscall_long);     memcpy(sc_asm, (char *)syscall_long, OFFSET_SYSCALL);     /**      * Find callq *sys_call_table(,%rax,8)       * -------------------------------------      * (gdb) disassemble system_call      * Dump of assembler code for function system_call:      * 0xffffffff81063750 <system_call+0>:     swapgs      * 0xffffffff81063753 <system_call+3>:     mov    %rsp,%gs:0x18      * 0xffffffff8106375c <system_call+12>:    mov    %gs:0x10,%rsp      * 0xffffffff81063765 <system_call+21>:    sti      * 0xffffffff81063766 <system_call+22>:    sub    $0x50,%rsp      * 0xffffffff8106376a <system_call+26>:    mov    %rdi,0x40(%rsp)      * 0xffffffff8106376f <system_call+31>:    mov    %rsi,0x38(%rsp)      * 0xffffffff81063774 <system_call+36>:    mov    %rdx,0x30(%rsp)      * 0xffffffff81063779 <system_call+41>:    mov    %rax,0x20(%rsp)      * 0xffffffff8106377e <system_call+46>:    mov    %r8,0x18(%rsp)      * 0xffffffff81063783 <system_call+51>:    mov    %r9,0x10(%rsp)      * 0xffffffff81063788 <system_call+56>:    mov    %r10,0x8(%rsp)      * 0xffffffff8106378d <system_call+61>:    mov    %r11,(%rsp)      * 0xffffffff81063791 <system_call+65>:    mov    %rax,0x48(%rsp)      * 0xffffffff81063796 <system_call+70>:    mov    %rcx,0x50(%rsp)      * 0xffffffff8106379b <system_call+75>:    mov    %gs:0x10,%rcx      * 0xffffffff810637a4 <system_call+84>:    sub    $0x1fd8,%rcx      * 0xffffffff810637ab <system_call+91>:    testl  $0x181,0x10(%rcx)      * 0xffffffff810637b2 <system_call+98>:    jne    0xffffffff81063889 <tracesys>      * 0xffffffff810637b8 <system_call+104>:   cmp    $0x117,%rax      * 0xffffffff810637be <system_call+110>:   ja     0xffffffff8106387b <badsys>      * 0xffffffff810637c4 <system_call+116>:   mov    %r10,%rcx      * 0xffffffff810637c7 <system_call+119>:   callq  *0xffffffff812e6d60(,%rax,8)      * 0xffffffff810637ce <system_call+126>:   mov    %rax,0x20(%rsp)      * End of assembler dump.      * (gdb) x/xw system_call+119      * 0xffffffff810637c7 <system_call+119>:   0x60c514ff      * (gdb)      */     retval = (unsigned long) memmem(sc_asm, OFFSET_SYSCALL, "\xff\x14\xc5", 3);     if ( retval != 0 ) {         dbgprint("long mode : sys_call_table is at %p\n",                  (void *) (* (unsigned long *)(retval+3)) ) ;         retval = (unsigned long) ( * (unsigned long *)(retval+3) );     } else {         printk("long mode : memmem found nothing, returning NULL:( \n");         retval = 0;     }  #undef OFFSET_SYSCALL     return retval; }/*}}}*/ static int get_syscall_init_module(void) {/*{{{*/     printk(KERN_DEBUG "get_syscall: Hi, you fucking linux!\n");     my_ia32_syscall_table = (void **) get_syscall_table_ia32();     if (my_ia32_syscall_table == 0)         return -1;     my_syscall_table = (void **) get_syscall_table_long();     if (my_syscall_table == 0)         return -1;     dbgprint("ia32_sys_call_table address : %p\n", (void *) my_ia32_syscall_table);     dbgprint("long mode : sys_call_table address : %p\n", (void *) my_syscall_table); #define REPLACE_IA32(x) o_sys_##x = my_ia32_syscall_table[__NR_ia32_##x];\     my_ia32_syscall_table[__NR_ia32_##x] = my_sys_##x #define GET_OLD_IA32_SYSCALL_ADDR(x) my_ia32_syscall_table[__NR_ia32_##x] //    dbgprint("sys_read at %p, my_read at %p\n", (void *)GET_OLD_IA32_SYSCALL_ADDR(read), (void *)my_sys_read); //    REPLACE_IA32(read); #undef REPLACE_IA32     return 0; }/*}}}*/ static void get_syscall_exit_module(void) {/*{{{*/     printk(KERN_DEBUG "get_syscall: bye, you fucking linux!\n"); #define RESTORE_IA32(x) my_ia32_syscall_table[__NR_ia32_##x] = o_sys_##x //    RESTORE_IA32(read); #undef RESTORE_IA32 }/*}}}*/ module_init(get_syscall_init_module); module_exit(get_syscall_exit_module); 复制代码 Reference : http://phrack.org/archives/58/p58-0x07