[RFC PATCH RESEND 24/28] arm64/mm: try VMA lock-based page fault handling first
From: Suren Baghdasaryan <surenb@google.com>
Date: 2022-09-01 17:38:19
Also in:
linux-arm-kernel, linux-mm, lkml
Subsystem:
arm64 port (aarch64 architecture), the rest · Maintainers:
Catalin Marinas, Will Deacon, Linus Torvalds
Attempt VMA lock-based page fault handling first, and fall back to the existing mmap_lock-based handling if that fails. Signed-off-by: Suren Baghdasaryan <surenb@google.com> --- arch/arm64/mm/fault.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+)
diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c
index c33f1fad2745..f05ce40ff32b 100644
--- a/arch/arm64/mm/fault.c
+++ b/arch/arm64/mm/fault.c@@ -525,6 +525,9 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, unsigned long vm_flags; unsigned int mm_flags = FAULT_FLAG_DEFAULT; unsigned long addr = untagged_addr(far); +#ifdef CONFIG_PER_VMA_LOCK + struct vm_area_struct *vma; +#endif if (kprobe_page_fault(regs, esr)) return 0;
@@ -575,6 +578,36 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); +#ifdef CONFIG_PER_VMA_LOCK + if (!(mm_flags & FAULT_FLAG_USER) || atomic_read(&mm->mm_users) == 1) + goto lock_mmap; + + vma = find_and_lock_anon_vma(mm, addr); + if (!vma) + goto lock_mmap; + + if (!(vma->vm_flags & vm_flags)) { + vma_read_unlock(vma); + goto lock_mmap; + } + fault = handle_mm_fault(vma, addr & PAGE_MASK, + mm_flags | FAULT_FLAG_VMA_LOCK, regs); + vma_read_unlock(vma); + + if (!(fault & VM_FAULT_RETRY)) { + count_vm_vma_lock_event(VMA_LOCK_SUCCESS); + goto done; + } + count_vm_vma_lock_event(VMA_LOCK_RETRY); + + /* Quick path to respond to signals */ + if (fault_signal_pending(fault, regs)) { + if (!user_mode(regs)) + goto no_context; + return 0; + } +lock_mmap: +#endif /* CONFIG_PER_VMA_LOCK */ /* * As per x86, we may deadlock here. However, since the kernel only * validly references user space from well defined areas of the code,
@@ -618,6 +651,9 @@ static int __kprobes do_page_fault(unsigned long far, unsigned long esr, } mmap_read_unlock(mm); +#ifdef CONFIG_PER_VMA_LOCK +done: +#endif /* * Handle the "normal" (no error) case first. */
--
2.37.2.789.g6183377224-goog