mmap returning MAP_FAILED

=3D

=3D 22

It would help if you told us what you were trying to do. What is file descriptor 5 and how was it opened? Also, I doubt '2680' is a multiple of your page size, so you cannot create a 2,680-byte mapping.

DS

=3D

o =3D 22

I am trying to get oprofile to work. The file I am opening is a sample file. Here is the code for the open:

data->fd =3D open(filename, flags, 0644);

where filename =3D "/var/lib/oprofile/samples//current/{kern}/no-vmlinux/ {dep}/{kern}/no-vmlinux/TIMER.0.0.all.all.all" where flags =3D O_CREAT | O_RDWR

The file /var/lib/oprofile/samples//current/{kern}/no-vmlinux/{dep}/ {kern}/no-vmlinux/TIMER.0.0.all.all.all does exist.

I changed the length to the page size and it made no difference. According to

"This can be any length you want. (Aside: if len not a multiple of the virtual memory page size, you will get a blocksize that is rounded up to that size. The extra bytes will be 0, and any changes you make to them will not modify the file.) "

What exactly do you think mapping a zero-length file would do?

DS

=3D

=3D 22

prot=3D3 =3D> would mean PROT_READ|PROT_WRITE

MAP_SHARED I think is a invalid mode if you are trying to map it that way, Probably you may want to remove PROT_WRITE and see whats happening.

Thanks

Shankar Easwaran

That would do terrible things to the utility of shared memory -- no, MAP_SHARED and PROT_WRITE are compatible. Maybe you're thinking of MAP_SHARED and MAP_ANONYMOUS (which didn't used to be compatible, but is since 2.4).

--
As we enjoy great advantages from the inventions of others, we should
be glad of an opportunity to serve others by any invention of ours;
and this we should do freely and generously. (Benjamin Franklin)

Make sure you are not logging data to a JFFS2 file system. JFFS2 does not support MMAP.

Cliff

=3D

o =3D 22

No. It is feasible. The parameter prot determines whether read, write, execute, or some combination of accesses are permitted to the data being mapped. The prot should be either PROT_NONE or the bitwise inclusive OR of one or more of the other flags listed below - PROT_READ Data can be read. PROT_WRITE Data can be written. PROT_EXEC Data can be executed. PROT_NONE Data cannot be accessed.

Check the below links w.r.t mmap ->

le_2

Karthik Balaguru

Karthik Balaguru