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charset="utf-8" Enable x86 support for handling page faults in an mshare region by redirecting page faults to operate on the mshare mm_struct and vmas contained in it. Some permissions checks are done using vma flags in architecture-specfic fault handling code so the actual vma needed to complete the handling is acquired before calling handle_mm_fault(). Because of this an ARCH_SUPPORTS_MSHARE config option is added. Signed-off-by: Anthony Yznaga --- arch/Kconfig | 3 +++ arch/x86/Kconfig | 1 + arch/x86/mm/fault.c | 40 +++++++++++++++++++++++++++++++++++++++- mm/Kconfig | 2 +- 4 files changed, 44 insertions(+), 2 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index d1b4ffd6e085..2e10a11fc442 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -1676,6 +1676,9 @@ config HAVE_ARCH_PFN_VALID config ARCH_SUPPORTS_DEBUG_PAGEALLOC bool =20 +config ARCH_SUPPORTS_MSHARE + bool + config ARCH_SUPPORTS_PAGE_TABLE_CHECK bool =20 diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 58d890fe2100..1ad252eec417 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -124,6 +124,7 @@ config X86 select ARCH_SUPPORTS_ATOMIC_RMW select ARCH_SUPPORTS_DEBUG_PAGEALLOC select ARCH_SUPPORTS_HUGETLBFS + select ARCH_SUPPORTS_MSHARE if X86_64 select ARCH_SUPPORTS_PAGE_TABLE_CHECK if X86_64 select ARCH_SUPPORTS_NUMA_BALANCING if X86_64 select ARCH_SUPPORTS_KMAP_LOCAL_FORCE_MAP if NR_CPUS <=3D 4096 diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 998bd807fc7b..2a7df3aa13b4 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -1215,6 +1215,8 @@ void do_user_addr_fault(struct pt_regs *regs, struct mm_struct *mm; vm_fault_t fault; unsigned int flags =3D FAULT_FLAG_DEFAULT; + bool is_shared_vma; + unsigned long addr; =20 tsk =3D current; mm =3D tsk->mm; @@ -1328,6 +1330,12 @@ void do_user_addr_fault(struct pt_regs *regs, if (!vma) goto lock_mmap; =20 + /* mshare does not support per-VMA locks yet */ + if (vma_is_mshare(vma)) { + vma_end_read(vma); + goto lock_mmap; + } + if (unlikely(access_error(error_code, vma))) { bad_area_access_error(regs, error_code, address, NULL, vma); count_vm_vma_lock_event(VMA_LOCK_SUCCESS); @@ -1356,17 +1364,38 @@ void do_user_addr_fault(struct pt_regs *regs, lock_mmap: =20 retry: + addr =3D address; + is_shared_vma =3D false; vma =3D lock_mm_and_find_vma(mm, address, regs); if (unlikely(!vma)) { bad_area_nosemaphore(regs, error_code, address); return; } =20 + if (unlikely(vma_is_mshare(vma))) { + fault =3D find_shared_vma(&vma, &addr); + + if (fault) { + mmap_read_unlock(mm); + goto done; + } + + if (!vma) { + mmap_read_unlock(mm); + bad_area_nosemaphore(regs, error_code, address); + return; + } + + is_shared_vma =3D true; + } + /* * Ok, we have a good vm_area for this memory access, so * we can handle it.. */ if (unlikely(access_error(error_code, vma))) { + if (unlikely(is_shared_vma)) + mmap_read_unlock(vma->vm_mm); bad_area_access_error(regs, error_code, address, mm, vma); return; } @@ -1384,7 +1413,14 @@ void do_user_addr_fault(struct pt_regs *regs, * userland). The return to userland is identified whenever * FAULT_FLAG_USER|FAULT_FLAG_KILLABLE are both set in flags. */ - fault =3D handle_mm_fault(vma, address, flags, regs); + fault =3D handle_mm_fault(vma, addr, flags, regs); + + /* + * If the lock on the shared mm has been released, release the lock + * on the task's mm now. + */ + if (unlikely(is_shared_vma) && (fault & (VM_FAULT_COMPLETED | VM_FAULT_RE= TRY))) + mmap_read_unlock(mm); =20 if (fault_signal_pending(fault, regs)) { /* @@ -1412,6 +1448,8 @@ void do_user_addr_fault(struct pt_regs *regs, goto retry; } =20 + if (unlikely(is_shared_vma)) + mmap_read_unlock(vma->vm_mm); mmap_read_unlock(mm); done: if (likely(!(fault & VM_FAULT_ERROR))) diff --git a/mm/Kconfig b/mm/Kconfig index 8b50e9785729..824da2a481f9 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -1402,7 +1402,7 @@ config FIND_NORMAL_PAGE =20 config MSHARE bool "Mshare" - depends on MMU + depends on MMU && ARCH_SUPPORTS_MSHARE help Enable msharefs: A pseudo filesystem that allows multiple processes to share kernel resources for mapping shared pages. A file created on --=20 2.47.1