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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2017-02-24 14:57:42 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2017-02-24 17:46:55 -0800
commitc8394812e56fbc334d815226268cea69b447d461 (patch)
tree4edee13e2f73ab1dd7ccea59c73fa2b958c43217
parent0efadf48bca01f17cb64ebceaf528590b2bc7665 (diff)
downloadlinux-c8394812e56fbc334d815226268cea69b447d461.tar.bz2
uprobes: split THPs before trying to replace them
Patch series "Fix few rmap-related THP bugs", v3. The patchset fixes handing PTE-mapped THPs in page_referenced() and page_idle_clear_pte_refs(). To achieve that I've intrdocued new helper -- page_vma_mapped_walk() -- which replaces all page_check_address{,_transhuge}() and covers all THP cases. Patchset overview: - First patch fixes one uprobe bug (unrelated to the rest of the patchset, just spotted it at the same time); - Patches 2-5 fix handling PTE-mapped THPs in page_referenced(), page_idle_clear_pte_refs() and rmap core; - Patches 6-12 convert all page_check_address{,_transhuge}() users (plus remove_migration_pte()) to page_vma_mapped_walk() and drop unused helpers. I think the fixes are not critical enough for stable@ as they don't lead to crashes or hangs, only suboptimal behaviour. This patch (of 12): For THPs page_check_address() always fails. It leads to endless loop in uprobe_write_opcode(). Testcase with huge-tmpfs (uprobes cannot probe anonymous memory). mount -t debugfs none /sys/kernel/debug mount -t tmpfs -o huge=always none /mnt gcc -Wall -O2 -o /mnt/test -x c - <<EOF int main(void) { return 0; } /* Padding to map the code segment with huge pmd */ asm (".zero 2097152"); EOF echo 'p /mnt/test:0' > /sys/kernel/debug/tracing/uprobe_events echo 1 > /sys/kernel/debug/tracing/events/uprobes/enable /mnt/test Let's split THPs before trying to replace. Link: http://lkml.kernel.org/r/20170129173858.45174-2-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Rik van Riel <riel@redhat.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com> Cc: Vladimir Davydov <vdavydov.dev@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--kernel/events/uprobes.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index d416f3baf392..1e65c79e52a6 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -300,8 +300,8 @@ int uprobe_write_opcode(struct mm_struct *mm, unsigned long vaddr,
retry:
/* Read the page with vaddr into memory */
- ret = get_user_pages_remote(NULL, mm, vaddr, 1, FOLL_FORCE, &old_page,
- &vma, NULL);
+ ret = get_user_pages_remote(NULL, mm, vaddr, 1,
+ FOLL_FORCE | FOLL_SPLIT, &old_page, &vma, NULL);
if (ret <= 0)
return ret;