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?
On Nov 5, 9:24 pm, Washington Ratso <jobhunt...@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.
On Nov 6, 1:59 am, David Schwartz <dav...@webmaster.com> wrote:
> On Nov 5, 9:24 pm, Washington Ratso <jobhunt...@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.) "
On Nov 5, 9:24 pm, Washington Ratso <jobhunt...@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.
Shankar <shanka...@gmail.com> writes: > On Nov 5, 9:24 pm, Washington Ratso <jobhunt...@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)
>> On Nov 5, 9:24 pm, Washington Ratso <jobhunt...@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).
Also, MAP_SHARED is the only way to get changes written back into a memory-mapped file, so sometimes you need MAP_SHARED with PROT_WRITE even if you don't want shared memory (simultaneously accessible by multiple processes). It's kind of a misleading name.
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