Please note: We are aware of an issue affecting replies on the Arm Community forums, which may not be loading as expected.

We apologize for any inconvenience and appreciate your patience while we investigate and work to resolve the issue.

Thank you for your understanding.

  • State Accepted Answer
  • Locked Locked
  • Replies 1 reply
  • Subscribers 347 subscribers
  • Views 3081 views
  • Users 0 members are here
Options
Related
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Linux mmap'ed access with memset() gives an alignment issue on the newer Linux kernels

andreas2025

Hello,

I have a memory area that is marked reserved in the Linux kernel, and I use that area as a shared buffer. I have registered that region in drivers/char/mem.c file and I do mmap'ed to the user.

On 5.4 kernel, I do a GNU C memset() to that region and all works fine. if I upgrade  to 5.10 or 5.15 there is a bus error when accessing byte 3  (byte 0, 1, 2 OK) memset() with count 3 fails. If I avoid to write  to areas ( ! i % 3)  then memset() works. Something has changed, same story with memcpy()

I try to figure out what may have changed in 5.15 kernel and the memset() fails.

Has anyone seen something similar before?

  • +1

    I have managed to find the cause of the problem - The latest kernels have shuffled the contents of the MAIR register. I had a hard coded page configuration using a wrong index in the MAIR register. It was pointing to other things rather NORMAL memory.