I'm trying to access and print the elements of arr found in the data section below in nasm using printf from c, but every time I get (.text+0x4e): undefined reference to `printf.
can anyone tell me the problem?
xor rcx, rcx
print_array:
cmp rcx, r8
jz exit
mov rax, [arr+rcx]
inc r8
push rax ; caller-save register
push rsi ; caller-save register
mov rdi, char_format ; set 1st parameter (format)
mov rsi, r8 ; set 2nd parameter (current_number)
xor rax, rax ; because printf is varargs
call printf ; printf(format, current_number)
pop rsi ; restore caller-save register
pop rax ; restore caller-save register
jmp print_array
exit:
mov rax, 0
pop rbp
section .data
arr: dd 30, 10, 6, 4, 8, 15, 1, 60, 7, 19, 17, 13, 11
ent: dd "enter the number of items", 10
char_format: db "%c", 10, 0
decimal_format: db "%d", 10, 0
string_format: db "%s", 10, 0
Related
assembly language
**main.asm**
%include "lib.asm"
section .text
global _start
_start:
;
; YOUR CODE HERE!
;
; SAMPLE
mov rdi, 65526 ; going to print 65536
call print_num ; print the number
call print_lf ; move to next line
exit:
mov rax, 60 ; exit
mov rdi, 0 ; return code
syscall
I'm working on code to enumerate the PCI bus, but have found that the jz statement for the loop over each device jumps to the wrong location (not even a label). The register function should be getting called for each time cmp ax, 0xffff is inequal, which should be more than once. It is only getting called once.
register: ; eax = edi = config offset of the function
mov dx, ADDR_PRT
add eax, 0x08
in eax, dx
shr eax, 16
mov dx, ax
call checkpoint
mov eax, edi
rmsd: cmp dx, 0x0601 ; mass storage devices
je ahci_register ; register an AHCI controller
ret ; couldn't find it, ignore it
pci_init:
mov edi, 0x80000000
ilp0: mov rax, rdi
mov dx, ADDR_PRT
out dx, eax
mov dx, DATA_PRT
in eax, dx
cmp ax, 0xffff
je ilp0c0
push rdi
mov rax, rdi
call register
pop rdi
ilp0c0: add rdi, 0x100
test edi, 0xff000000 ; code jupms to the line before this
jz ilp0
ret
Code is assembled as a PE file and then linked using lld-link and run using EFI.
I have simple 64 bit assembly program that we are doing for class. It is supposed to take user input (string) and return that string with lowercase letters into uppercase and uppercase into lowercase.
With what I have, it will read anything until it finds a space and this will not read anymore after that. So if I input "test", it will output "TEST". If I input "test Test" it will output "TEST". However, if I add spaces before the first word, it would output the first word but removes the spaces. For example: input " TesT", output: "tESt".
Anyone know how I can go about fixing this?
Here is my whole program:
;Author: Keenan Kaufman
;Date: 10/20/2017
INCLUDELIB msvcrt.lib
printf PROTO
scanf PROTO
exit PROTO
.DATA
CRLF BYTE 0Dh, 0Ah, 0 ;carriage return
msgHeader BYTE "Enter a mixed case string: ", 0
message BYTE 20 DUP(0), 0
target BYTE SIZEOF message DUP(?), 0Dh, 0Ah, 0
msgformat BYTE "%20s", 0
.CODE
main PROC
;Display request for user input
lea rcx, msgHeader
call printf
;obtain user input
lea rcx, msgformat
lea rdx, message
call scanf
lea rsi, message
lea rdi, target
jmp GETNEXT
GETNEXT:
mov al, [rsi]
cmp al, 0
je ENDCASE
cmp al, 'z'
ja NOCHANGE
cmp al, 'A'
jb NOCHANGE
cmp al, 'a'
jae TOUPPER
cmp al, 'Z'
jbe TOLOWER
TOUPPER:
sub al, 32
mov [rdi], al
inc rdi
inc rsi
jmp GETNEXT
TOLOWER:
add al, 32
mov [rdi], al
inc rdi
inc rsi
jmp GETNEXT
NOCHANGE:
mov [rdi], al
inc rdi
inc rsi
jmp GETNEXT
ENDCASE:
jmp FINISH
FINISH:
;Display target
lea rcx, target
call printf
lea rcx, CRLF
call printf
mov rax, 0
call exit
main ENDP
END
Yes, that is a feature of scanf. Here is the Linux man page for scanf which, for the %s format, says:
s
Matches a sequence of non-white-space characters; the next
pointer must be a pointer to the initial element of a character
array that is long enough to hold the input sequence and the
terminating null byte ('\0'), which is added automatically. The
input string stops at white space or at the maximum field width,
whichever occurs first.
To do what you want, read the characters yourself directly from stdin using read(), getc(), or fgets().
I've been trying to learn how to create an IRC bot in assembler from some old sources. Everything is going fine with my learning except for a prefix problem.
The prefix for the bot is:
CommandPrefix equ "^^"
And the length of the prefix is added with:
add eax, 2d
I want to change the prefix to just "^", but I am having trouble with figuring out what "add eax" should be changed too for it to work. Or even if that is the best way to do it. Any help with this would be appreciated.
Here is what the original code looks like to get some idea:
include "win32ax.inc"
entry Bot
CommandPrefix equ "^^"
section '.code' code readable executable
Bot:
invoke WSAStartup,0101h,WSAData
cmp eax, 0
jne Exit
invoke socket,AF_INET,SOCK_STREAM,0
cmp eax, -1
je Exit
mov dword [SocketDesc], eax
invoke inet_addr,IRCServer
mov dword [SockAddr_IP], eax
invoke htons,IRCPort
mov word [SockAddr_Port], ax
invoke connect,dword [SocketDesc],SockAddr,16d
cmp eax, 0
jne Exit
call GenerateNickname
invoke lstrcpy,SendBuffer,"NICK "
invoke lstrcat,SendBuffer,Nickname
call SendLine
invoke lstrcpy,SendBuffer,"USER "
invoke lstrcat,SendBuffer,Nickname
invoke lstrcat,SendBuffer," 8 * :"
invoke lstrcat,SendBuffer,Nickname
call SendLine
GetMotd:
call RecvLine
call HandlePing
mov ecx, 0
IsMotd:
cmp dword [ReturnBuffer + ecx], "MOTD"
je HaveMotd
cmp byte [ReturnBuffer + ecx], 0d
je GetMotd
inc ecx
jmp IsMotd
HaveMotd:
invoke lstrcpy,SendBuffer,"JOIN "
invoke lstrcat,SendBuffer,Channel
invoke lstrcat,SendBuffer," "
call SendLine
RecvCommand:
call RecvLine
call HandlePing
mov ecx, 0
IsCommand:
cmp word [ReturnBuffer + ecx], CommandPrefix
je HaveCommand
cmp byte [ReturnBuffer + ecx], 0
je RecvCommand
inc ecx
jmp IsCommand
HaveCommand:
mov ebx, ReturnBuffer
add ebx, ecx
add ebx, 2d ;add length of command prefix
invoke lstrcpy,CommandBuffer,ebx
call ExecuteCommand
jmp RecvCommand
Suppose I have a block of code like so:
;; outut
mov eax, 4
mov ebx, 1 ; stdout
mov ecx, [ans] ; move biggest element to accumulator
add ecx, 30h ; convert to ascii representation
mov [buff], ecx ; move to memory
mov ecx, buff ; put pointer in ecx for printing
mov edx, 4 ; size, 4 bytes
int 80h ; system call.
When I try to put a comment in the front to comment out a line:
;; outut
;mov eax, 4
mov ebx, 1 ; stdout
mov ecx, [ans] ; move biggest element to accumulator
add ecx, 30h ; convert to ascii representation
mov [buff], ecx ; move to memory
mov ecx, buff ; put pointer in ecx for printing
mov edx, 4 ; size, 4 bytes
int 80h ; system call.
Instead of appearing there where I want it to go, it jumps to here:
;; outut
mov eax, 4 ;
mov ebx, 1 ; stdout
mov ecx, [ans] ; move biggest element to accumulator
add ecx, 30h ; convert to ascii representation
mov [buff], ecx ; move to memory
mov ecx, buff ; put pointer in ecx for printing
mov edx, 4 ; size, 4 bytes
int 80h ; system call.
And no matter what I do, I physically cannot comment out anything.
How can I fix this? It don't remember it always doing this, so i feel like I must have hit some combination of keys and it just happens.
; is bound to asm-comment in assembly mode. You can either do a quoted insert with C-q ; on a case-by-case basis, or remove the binding and just use M-; (comment-dwim) for fancier commenting. If you want to do the latter, set ";" locally to do a self-insert command:
(defun my-hook ()
(local-set-key ";" 'self-insert-command))
(add-hook 'asm-mode-hook 'my-hook)