Subject: [Bug 215389] pagealloc: memory corruption at building glibc-2.33 and running its' testsuite

From: [email-masked]
Date: Tue, 25 Jan 2022 22:23:59 +0000

https://bugzilla.kernel.org/show_bug.cgi?id=215389

--- Comment #6 from Erhard F. ([email-masked]) ---
Created attachment 300318
  --> https://bugzilla.kernel.org/attachment.cgi?id=300318&action=edit
bisect.log

Ok, finally got it. Interesting find:

 # git bisect bad
db972a3787d12b1ce9ba7a31ec376d8a79e04c47 is the first bad commit
commit db972a3787d12b1ce9ba7a31ec376d8a79e04c47
Author: Christophe Leroy <[email-masked]>
Date:   Tue Dec 8 05:24:19 2020 +0000

    powerpc/powermac: Fix low_sleep_handler with CONFIG_VMAP_STACK

    low_sleep_handler() can't restore the context from standard
    stack because the stack can hardly be accessed with MMU OFF.

    Store everything in a global storage area instead of storing
    a pointer to the stack in that global storage area.

    To avoid a complete churn of the function, still use r1 as
    the pointer to the storage area during restore.

    Fixes: cd08f109e262 ("powerpc/32s: Enable CONFIG_VMAP_STACK")
    Reported-by: Giuseppe Sacco <[email-masked]>
    Signed-off-by: Christophe Leroy <[email-masked]>
    Tested-by: Giuseppe Sacco <[email-masked]>
    Signed-off-by: Michael Ellerman <[email-masked]>
    Link:
https://lore.kernel.org/r/e3e0d804[email-masked]

 arch/powerpc/platforms/Kconfig.cputype  |   2 +-
 arch/powerpc/platforms/powermac/sleep.S | 132 ++++++++++++++------------------
 2 files changed, 60 insertions(+), 74 deletions(-)

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