how do I make a syscall 11 (execve) in arm?

Question

Here's my code:

@execve takes 3 arguments (r0,r1,r2)

mov r7,#11 @syscall number for execve
ldr r0,=addr_of_string
sub r1,r1,r1 @so that r1 can get zero 
sub r2,r2,r2 @same for r2
svc #0

end:
mov r7,#1
svc 0

.data
addr_of_string: .asciz "\bin\ls"

It compiles successfully and links successfully but when I execute it, I get :

A NULL argv[0] was passed through an exec system call

What operating system? From looking at the code, it seems to be a 32-bit variety. And judging we are using `svc 0`, I am guessing a Linux variety? I'm no expert here, but having that info should help someone else answer the question easier. Also, I'd expect a simple load of #0 into `r1` and `r2`, not this subtraction fun, but to each their own I guess. — Michael Dorgan, Mar 26 '18 at 17:04
See if this doesn't help: https://stackoverflow.com/questions/42906569/file-path-or-file-descriptor-for-arm-execute-system-call — Michael Dorgan, Mar 26 '18 at 17:10
If you follow the info from the link I gave, can you get your exec function to work properly? — Michael Dorgan, Mar 26 '18 at 17:29
In my case.. r0 = "/bin/ls" r1 = 0 r2 = 0 r7 = #11 But then too..its not working — user7083361, Mar 26 '18 at 18:05
Then, I need to leave it to someone with a bit deeper knowledge than I here. — Michael Dorgan, Mar 26 '18 at 20:33

score 0 · Answer 1 · answered Mar 27 '18 at 03:02

0

Why can the execve system call run "/bin/sh" without any argv arguments, but not "/bin/ls"?

The above thread says that since /bin/ls is a part of gnu coreutils package and they call 'set' [program name] to set it up.

answered Mar 27 '18 at 03:02

user7083361

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score 0 · Answer 2 · answered Mar 27 '18 at 03:23

0

Why can the execve system call run "/bin/sh" without any argv arguments, but not "/bin/ls"?

The above thread says that since /bin/ls is a part of the gnu coreutil package and it has to be setup before calling.

answered Mar 27 '18 at 03:23

user7083361

33
1
1
6

how do I make a syscall 11 (execve) in arm?

2 Answers2