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| Computers Forum Index » Computer Architecture - Embedded » mmap returning MAP_FAILED... |
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| Washington Ratso... |
 Posted: Fri Nov 06, 2009 5:24 am |
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Guest
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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? |
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| Washington Ratso... |
| Posted: Sat Nov 07, 2009 2:10 am |
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Guest
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On Nov 6, 1:59 am, David Schwartz <dav... at (no spam) webmaster.com> wrote:
Quote: On Nov 5, 9:24 pm, Washington Ratso <jobhunt... at (no spam) aol.com> wrote:
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.) " |
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| David Schwartz... |
| Posted: Sat Nov 07, 2009 3:52 am |
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Guest
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On Nov 6, 6:10 pm, Washington Ratso <jobhunt... at (no spam) aol.com> wrote:
Quote: 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.
What exactly do you think mapping a zero-length file would do?
DS |
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| Joe Pfeiffer... |
| Posted: Sun Nov 08, 2009 10:09 pm |
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Shankar <shankarke at (no spam) gmail.com> writes:
Quote: On Nov 5, 9:24 pm, Washington Ratso <jobhunt... at (no spam) aol.com> wrote:
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).
--
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) |
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