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usermode linux without MMU - fosdem2026 kernel ...

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Avatar for Hajime Tazaki Hajime Tazaki
February 01, 2026
Technology
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usermode linux without MMU - fosdem2026 kernel devroom

Avatar for Hajime Tazaki

Hajime Tazaki

February 01, 2026

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Transcript

  1. usermode linux without MMU  1 

  2. Overview CONFIG_MMU=n 2 

  3. nommu port of UML !MMU 3 

  4. User Mode Linux (UML) 4 

  5. UML (cont'd) mm/nommu.c 5 

  6. hard to find bugs of nommu diff --git a/mm/nommu.c b/mm/nommu.c

    index 385b0c15add8..0c708f85408d 100644 --- a/mm/nommu.c +++ b/mm/nommu.c @@ -573,7 +573,7 @@ static int delete_vma_from_mm(struct vm_area_struct *vma) VMA_ITERATOR(vmi, vma->vm_mm, vma->vm_start); vma_iter_config(&vmi, vma->vm_start, vma->vm_end); - if (vma_iter_prealloc(&vmi, vma)) { + if (vma_iter_prealloc(&vmi, NULL)) { pr_warn("Allocation of vma tree for process %d failed\n", current->pid); return -ENOMEM; 6 

  7. alternatives 7 

  8. implementation (nommu UML) 8 

  9. implementation CONFIG_MMU=n 9 

  10. nommu architecture 10 

  11. nommu UML binfmt_elf_fdpic 11 

  12. how syscall works syscall SIGSYS rip fs fp current sys_call_table

    12 

  13. limitations exit(2) 13 

  14. integration busybox-nommu musl-nommu 00:02 14 

  15. showcases 15 

  16. testing usecase 16 

  17. Identity added: /home/tazaki/.ssh/id_rsa (tazaki@ikb-07-27) ikb-h07-29-noble:~/work/nabla-linux/linux-um-nommu% 00:01 (none):/# /r 00:05 17

  18. KUnit test Identity added: /home/tazaki/.ssh/id_rsa (tazaki@ikb-07-27) ikb-h07-29-noble:~/work/nabla-linux/linux-um-nommu% 00:03 18 

  19. performance 19 

  20. discussion: what was this ? 20 

  21. summary 21 