How to use mprotect/make a code segment memory writable? [solved]
lazarus / 32-Linux

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pik33 · 2019-07-08 15:13

I have an asm code (ARM, RPi) which I want to move from a bare metal
environment to Lazarus/Linux on RPi. It writes values to the procedure
area so the program causes the exception.

Is there any way to set a code area memory writable (while linking or
runtime)?

I read the ld linker has -N option which does this but I don't know if
Lazarus (2.0.0) uses LD and if yes, how to pass the parameter to the
linker. I tried -k in option with no success (a lot of linker errors)

Edit: I found a mprotect system call. How to use it in Lazarus?

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pik33 · 2019-07-09 07:32

Solved

Code: [Select]function
Do_SysCall(sysnr,param1,param2,param3:cardinal):integer; external name
'FPC_SYSCALL3';

function fpmprotect(addr,size,prot:cardinal):longint;

begin
 result:=Do_SysCall(125,addr,size,prot);
end;

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marcov · 2019-07-09 09:22

The do_syscalls are available via unit syscall, so you don't need to
declare it with external