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Matheus
146 lines
2.2 KiB
NASM
146 lines
2.2 KiB
NASM
section .rodata
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extern syscall_libc_log
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extern syscall_mmap
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extern syscall_arch_ctl
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extern syscall_gettid
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extern syscall_open
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extern syscall_read
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extern syscall_lseek
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extern syscall_close
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extern syscall_isatty
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extern syscall_write
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extern syscall_stat
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extern syscall_fstat
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extern syscall_fork
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extern syscall_execve
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extern syscall_waitpid
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extern syscall_exit
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func_count equ 16
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func_table:
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dq syscall_libc_log
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dq syscall_mmap
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dq syscall_arch_ctl
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dq syscall_gettid
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dq syscall_open
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dq syscall_read
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dq syscall_lseek
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dq syscall_close
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dq syscall_isatty
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dq syscall_write
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dq syscall_stat
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dq syscall_fstat
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dq syscall_fork
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dq syscall_execve
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dq syscall_waitpid
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dq syscall_exit
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section .text
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global asm_syscall_entry
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; the registers for the system call are:
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; RETURN:
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; rax -> ret value
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; rdx -> errno
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; PARAM:
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; rax -> func
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; rdi, rsi, rdx, r10, r8, r9 -> parameters
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; clobbers: rax, rdx, rcx, r11
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asm_syscall_entry:
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swapgs
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xchg rsp, [gs:0] ; get new stack
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push qword [gs:0] ; save old stack
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mov [gs:0], rsp ; return back the kernel stack
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add qword [gs:0], 8 ; fix it
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sti
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; assemble and save context needed for some system calls
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push qword 0x43 ; ss
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push qword [rsp+8] ; rsp
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push r11 ; old rflags
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push qword 0x3b ; cs
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push rcx ; old rip
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push qword 0 ; err
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push rbp
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push rsi
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push rdi
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push r15
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push r14
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push r13
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push r12
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push r11
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push r10
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push r9
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push r8
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push rdx
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push rcx
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push rbx
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push rax
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push qword 0x43 ; ds
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push qword 0x43 ; es
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push qword 0 ; fs
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push qword 0 ; gs
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push qword 0 ; cr2
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mov r11, 0x30 ; kernel data
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mov ds, r11
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mov es, r11
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; system V C abi expects the third param to be in rcx
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; but the param is in rdx because of the syscall instruction
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mov rcx, r10
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; set up context for calls that need it
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cmp rax, 12 ; fork
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jne .not_fork
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mov rdi, rsp
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jmp .do_syscall
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.not_fork:
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.do_syscall:
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call [func_table + rax * 8]
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; restore entry state
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mov r11, 0x43 ; user data
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mov es,r11
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mov ds,r11
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add rsp, 0x30 ; cr2 gs fs es ds rax
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pop rbx
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pop rcx
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add rsp, 8 ; rdx
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pop r8
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pop r9
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pop r10
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pop r11
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pop r12
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pop r13
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pop r14
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pop r15
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pop rdi
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pop rsi
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pop rbp
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add rsp, 0x30 ; err, rip, cs, rflags, rsp, ss
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pop rsp ; actual rsp
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cli
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swapgs
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o64 sysret
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