linux-dev/arch/parisc/mm/fault.c, branch linus/master

parisc: Disable debug code regarding cache flushes in handle_nadtlb_fault()

2022-05-17T19:49:06Z

Change the "BUG" to "WARNING" and disable the message because it triggers occasionally in spite of the check in flush_cache_page_if_present. The pte value extracted for the "from" page in copy_user_highpage is racy and occasionally the pte is cleared before the flush is complete. I assume that the page is simultaneously flushed by flush_cache_mm before the pte is cleared as nullifying the fdc doesn't seem to cause problems. I investigated various locking scenarios but I wasn't able to find a way to sequence the flushes. This code is called for every COW break and locks impact performance. This patch is related to the bigger cache flush patch because we need the pte on PA8800/PA8900 to flush using the vma context. I have also seen this from copy_to_user_page and copy_from_user_page. The messages appear infrequently when enabled. Signed-off-by: John David Anglin Signed-off-by: Helge Deller

parisc: Fix handling off probe non-access faults

2022-03-11T18:49:30Z

Currently, the parisc kernel does not fully support non-access TLB fault handling for probe instructions. In the fast path, we set the target register to zero if it is not a shadowed register. The slow path is not implemented, so we call do_page_fault. The architecture indicates that non-access faults should not cause a page fault from disk. This change adds to code to provide non-access fault support for probe instructions. It also modifies the handling of faults on userspace so that if the address lies in a valid VMA and the access type matches that for the VMA, the probe target register is set to one. Otherwise, the target register is set to zero. This was done to make probe instructions more useful for userspace. Probe instructions are not very useful if they set the target register to zero whenever a page is not present in memory. Nominally, the purpose of the probe instruction is determine whether read or write access to a given address is allowed. This fixes a problem in function pointer comparison noticed in the glibc testsuite (stdio-common/tst-vfprintf-user-type). The same problem is likely in glibc (_dl_lookup_address). V2 adds flush and lpa instruction support to handle_nadtlb_fault. Signed-off-by: John David Anglin Signed-off-by: Helge Deller

Merge branch 'akpm' (patches from Andrew)

2022-01-15T18:37:06Z

Merge misc updates from Andrew Morton: "146 patches. Subsystems affected by this patch series: kthread, ia64, scripts, ntfs, squashfs, ocfs2, vfs, and mm (slab-generic, slab, kmemleak, dax, kasan, debug, pagecache, gup, shmem, frontswap, memremap, memcg, selftests, pagemap, dma, vmalloc, memory-failure, hugetlb, userfaultfd, vmscan, mempolicy, oom-kill, hugetlbfs, migration, thp, ksm, page-poison, percpu, rmap, zswap, zram, cleanups, hmm, and damon)" * emailed patches from Andrew Morton : (146 commits) mm/damon: hide kernel pointer from tracepoint event mm/damon/vaddr: hide kernel pointer from damon_va_three_regions() failure log mm/damon/vaddr: use pr_debug() for damon_va_three_regions() failure logging mm/damon/dbgfs: remove an unnecessary variable mm/damon: move the implementation of damon_insert_region to damon.h mm/damon: add access checking for hugetlb pages Docs/admin-guide/mm/damon/usage: update for schemes statistics mm/damon/dbgfs: support all DAMOS stats Docs/admin-guide/mm/damon/reclaim: document statistics parameters mm/damon/reclaim: provide reclamation statistics mm/damon/schemes: account how many times quota limit has exceeded mm/damon/schemes: account scheme actions that successfully applied mm/damon: remove a mistakenly added comment for a future feature Docs/admin-guide/mm/damon/usage: update for kdamond_pid and (mk|rm)_contexts Docs/admin-guide/mm/damon/usage: mention tracepoint at the beginning Docs/admin-guide/mm/damon/usage: remove redundant information Docs/admin-guide/mm/damon/usage: update for scheme quotas and watermarks mm/damon: convert macro functions to static inline functions mm/damon: modify damon_rand() macro to static inline function mm/damon: move damon_rand() definition into damon.h ...

mm: remove redundant check about FAULT_FLAG_ALLOW_RETRY bit

2022-01-15T14:30:27Z

Since commit 4064b9827063 ("mm: allow VM_FAULT_RETRY for multiple times") allowed VM_FAULT_RETRY for multiple times, the FAULT_FLAG_ALLOW_RETRY bit of fault_flag will not be changed in the page fault path, so the following check is no longer needed: flags & FAULT_FLAG_ALLOW_RETRY So just remove it. [akpm@linux-foundation.org: coding style fixes] Link: https://lkml.kernel.org/r/20211110123358.36511-1-zhengqi.arch@bytedance.com Signed-off-by: Qi Zheng Cc: Peter Zijlstra Cc: Ingo Molnar Cc: David Hildenbrand Cc: Kirill Shutemov Cc: Peter Xu Cc: Muchun Song Cc: Chengming Zhou Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

parisc: Enhance page fault termination message

2022-01-07T00:29:21Z

In debugging kernel panics, I believe it is useful to know what type of page fault caused the termination. "Bad Address" is too vague. Signed-off-by: John David Anglin Signed-off-by: Helge Deller

parisc: Don't call faulthandler_disabled() in do_page_fault()

2022-01-07T00:29:21Z

It is dangerous to call faulthandler_disabled() when user_mode(regs) is true. The task pagefault_disabled counter is racy and it is not updated atomically on parisc. As a result, calling faulthandler_disabled() may cause erroneous termination. We now handle execption fixups and termination when user_mode(regs) is false in handle_interruption(). Thus, we can just remove the faulthandler_disabled() check from do_page_fault(). Signed-off-by: John David Anglin Signed-off-by: Helge Deller

parisc: Switch user access functions to signal errors in r29 instead of r8

2022-01-07T00:29:21Z

Use register r29 instead of register r8 to signal faults when accessing user memory. In case of faults, the fixup routine will store -EFAULT in this register. This change saves up to 752 bytes on a 32bit kernel, partly because the compiler doesn't need to save and restore the old r8 value on the stack. bloat-o-meter results for usage with r29 register: add/remove: 0/0 grow/shrink: 23/86 up/down: 228/-980 (-752) bloat-o-meter results for usage with r28 register: add/remove: 0/0 grow/shrink: 28/83 up/down: 296/-956 (-660) Signed-off-by: Helge Deller

parisc: make parisc_acctyp() available outside of faults.c

2021-10-30T21:11:00Z

When adding kfence support, we need to tell kfence_handle_page_fault() if the interrupted assembler statement is a read or write operation. Signed-off-by: Helge Deller

treewide: Use fallthrough pseudo-keyword

2020-08-23T22:36:59Z

Replace the existing /* fall through */ comments and its variants with the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary fall-through markings when it is the case. [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through Signed-off-by: Gustavo A. R. Silva

mm/parisc: use general page fault accounting

2020-08-12T17:58:03Z

Use the general page fault accounting by passing regs into handle_mm_fault(). It naturally solve the issue of multiple page fault accounting when page fault retry happened. Add the missing PERF_COUNT_SW_PAGE_FAULTS perf events too. Note, the other two perf events (PERF_COUNT_SW_PAGE_FAULTS_[MAJ|MIN]) were done in handle_mm_fault(). Signed-off-by: Peter Xu Signed-off-by: Andrew Morton Cc: James E.J. Bottomley Cc: Helge Deller Link: http://lkml.kernel.org/r/20200707225021.200906-16-peterx@redhat.com Signed-off-by: Linus Torvalds