mmap returning MAP_FAILED

[Washington Ratso]

I am running Linux 2.6.26 on an MPC8248. In my application, mmap is
returning MAP_FAILED. The arguments to mmap are start = 0, length =
2680, prot = 3, flags = MAP_SHARED, fd = 5, offset = 0. errno = 22
"Invalid argument"

I looked at the man page for mmap and don't see a reason why this is
happening. Any ideas?

[David Schwartz]

I am running Linux 2.6.26 on an MPC8248.   In my application, mmap is
returning MAP_FAILED.  The arguments to mmap are start = 0, length =
2680, prot = 3, flags = MAP_SHARED, fd = 5, offset = 0.  errno = 22
"Invalid argument"
I looked at the man page for mmap and don't see a reason why this is
happening.  Any ideas?

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

[Washington Ratso]

Post by David Schwartz

I am running Linux 2.6.26 on an MPC8248.   In my application, mmap is
returning MAP_FAILED.  The arguments to mmap are start = 0, length =
2680, prot = 3, flags = MAP_SHARED, fd = 5, offset = 0.  errno = 22
"Invalid argument"
I looked at the man page for mmap and don't see a reason why this is
happening.  Any ideas?

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

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 = open(filename, flags, 0644);

where filename = "/var/lib/oprofile/samples//current/{kern}/no-vmlinux/
{dep}/{kern}/no-vmlinux/TIMER.0.0.all.all.all"
where flags = 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 http://www.ecst.csuchico.edu/~beej/guide/ipc/mmap.html,
"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.) "

[David Schwartz]

I am trying to get oprofile to work.  The file I am opening is a
data->fd = open(filename, flags, 0644);
where filename = "/var/lib/oprofile/samples//current/{kern}/no-vmlinux/
{dep}/{kern}/no-vmlinux/TIMER.0.0.all.all.all"
where flags = 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.

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

DS

[Cliff Brake]

I am trying to get oprofile to work.  The file I am opening is a

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

Cliff

[Shankar]

I am running Linux 2.6.26 on an MPC8248.   In my application, mmap is
returning MAP_FAILED.  The arguments to mmap are start = 0, length =
2680, prot = 3, flags = MAP_SHARED, fd = 5, offset = 0.  errno = 22
"Invalid argument"
I looked at the man page for mmap and don't see a reason why this is
happening.  Any ideas?

prot=3 => 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

[Joe Pfeiffer]

Post by Shankar

I am running Linux 2.6.26 on an MPC8248.   In my application, mmap is
returning MAP_FAILED.  The arguments to mmap are start = 0, length =
2680, prot = 3, flags = MAP_SHARED, fd = 5, offset = 0.  errno = 22
"Invalid argument"
I looked at the man page for mmap and don't see a reason why this is
happening.  Any ideas?

prot=3 => 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.

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).

[karthikbalaguru]

Post by Shankar

I am running Linux 2.6.26 on an MPC8248.   In my application, mmap is
returning MAP_FAILED.  The arguments to mmap are start = 0, length =
2680, prot = 3, flags = MAP_SHARED, fd = 5, offset = 0.  errno = 22
"Invalid argument"
I looked at the man page for mmap and don't see a reason why this is
happening.  Any ideas?

prot=3 => 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.

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 ->
http://docs.blackfin.uclinux.org/doku.php?id=:mmap#mmap_kernel_code_example_2
http://www.opengroup.org/onlinepubs/007908775/xsh/mmap.html

Karthik Balaguru


Karthik Balaguru