Hello All,
Sorry to interrupt you.
I have been facing a wierd problem on same kernel version
(2.6.5-7.97.smp) but running on different machines 32-bit and 64-bit
(which can run 32-bit also).
I found that every process running in this kernel version has a
virtual address mapping in /proc/<pid>/maps file as follows
<-------------------------------------------------------------------------------------------------->
ffffe000-ffff000 ---p 00000000 00:00 0
<-------------------------------------------------------------------------------------------------->
You can find this vaddr mapping at end of maps file.
on a 64-bit(uname --all == 'Linux host 2.6.5-7.97.smp #1 <time stamp>
x86_64 x86_64 x86_64 GNU/Linux) machine which is running the same
kernel, I try to write the contents of the virtual address on to file
with
(r = write(fd,0xffffe000,4096) ). The write on this machine is
successful. But if I try to write the same segment on 32-bit machine
(uname --all == Linux host 2.6.5-7.97-smp #1 <timestamp> i686 i686
i386 GNU/Linux).
The write on this 32-bit machine fails with EFAULT(14), but if memcpy
to a buffer from this virtual address seems to work fine i.e if I do
'memcpy(buf1,0xffffe000,4096)' it write perfectly the contents of this
virtual address segment into the buf1.
I had a hard time googling about this I could'nt find any information
on why this happens. May be some mm hackers may share some of their
thoughts.
Really appreciate your inputs on this.
Sincerely,
Vamsi kundeti
PS: BTW I'am running suse distribution and will glibc will have any
effect on write behaviour ? (I though that since write is a syscall
the issue might be with the kernel the thus skipping the glibc
details)
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