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    SubjectRe: [PATCH] arm64: increase stack size for KASAN_EXTRA
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    On Tue, 2018-12-11 at 13:42 +0100, Arnd Bergmann wrote:
    > On Fri, Dec 7, 2018 at 11:35 PM Qian Cai <cai@lca.pw> wrote:
    > >
    > > If the kernel is configured with KASAN_EXTRA, the stack size is
    > > increasted significantly due to enable this option will set
    > > -fstack-reuse to "none" in GCC [1]. As the results, it could trigger
    > > stack overrun quite often with 32k stack size compiled using GCC 8. For
    > > example, this reproducer
    > >
    > > size
    > > 7536 shrink_inactive_list
    > > 7440 shrink_page_list
    > > 6560 fscache_stats_show
    > > 3920 jbd2_journal_commit_transaction
    > > 3216 try_to_unmap_one
    > > 3072 migrate_page_move_mapping
    > > 3584 migrate_misplaced_transhuge_page
    > > 3920 ip_vs_lblcr_schedule
    > > 4304 lpfc_nvme_info_show
    > > 3888 lpfc_debugfs_nvmestat_data.constprop
    > >
    > > There are other 49 functions are over 2k in size while compiling kernel
    > > with "-Wframe-larger-than=" on this machine. Hence, it is too much work
    > > to change Makefiles for each object to compile without
    > > -fsanitize-address-use-after-scope individually.
    > >
    > > [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715#c23
    >
    > Could you clarify: are the numbers you see with or without the bugfix
    > from that bugzilla?
    >

    The numbers were from GCC8 which does NOT contain this patch [1].

    GCC9 is awesome which reduced the numbers in half even for KASAN_EXTRA. Only
    thing is that GCC9 has not been officially released yet, so it is a bit
    inconvenient for users need to compile the compiler by themselves first.

    I am fine either way to drop this patch or keep it until GCC9 is GA.

    [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81715#c35

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