How to allocate memory in Linux dynamically (like malloc)

flat assembler
Message board for the users of flat assembler.

Index > Linux > How to allocate memory in Linux dynamically (like malloc)

Author

Thread

Ton

Joined: 06 Jan 2005
Posts: 22

Ton 10 Feb 2005, 08:30

Dear all,

In fasm I can allocate memory with e.g.
a0 rd 1024h

But how can I do this dynamically using system calls. Basically I need a
malloc(3), and free(3). I couldn't find the clue in the system call list, there is
no *alloc* there.

Best Regards,
Ton

10 Feb 2005, 08:30

Endre

Joined: 29 Dec 2003
Posts: 215
Location: Budapest, Hungary

Endre 10 Feb 2005, 12:11

You have an excellent example: Take a look into the source of fasm. You will find it.

10 Feb 2005, 12:11

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8435
Location: Kraków, Poland

Tomasz Grysztar 10 Feb 2005, 12:18

It's syscall 45, called sys_brk, which resizes the memory block allocated for your program (the program resides on the bottom of this block, and with sys_brk you just move the top of it).

10 Feb 2005, 12:18

Dryobates

Joined: 13 Jul 2003
Posts: 46
Location: Poland

Dryobates 10 Feb 2005, 16:11

sys_brk is old style. Now it's preffered sys_mmap with anon mapping.

_________________
There's one more bug... Smile

10 Feb 2005, 16:11

Tomasz Grysztar

Joined: 16 Jun 2003
Posts: 8435
Location: Kraków, Poland

Tomasz Grysztar 10 Feb 2005, 16:21

However brk syscall is common for the Linux and all BSD systems (I'm not sure about BeOS), so I preferred it.

10 Feb 2005, 16:21

Ton

Joined: 06 Jan 2005
Posts: 22

Ton 10 Feb 2005, 16:52

Thanks for the pointers. Iĺl give it a try.

--
Ton

10 Feb 2005, 16:52

scientica
Retired moderator

Joined: 16 Jun 2003
Posts: 689
Location: Linköping, Sweden

scientica 11 Feb 2005, 12:48

there's also malloc and free in linux Smile

try: man 3 malloc

11 Feb 2005, 12:48

Dryobates

Joined: 13 Jul 2003
Posts: 46
Location: Poland

Dryobates 11 Feb 2005, 22:08

scientica wrote:

there's also malloc and free in linux
try: man 3 malloc

But then he need link with libc...

_________________
There's one more bug... Smile

11 Feb 2005, 22:08

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum