Messages in this thread | | | From | Michael Ellerman <> | Subject | Re: [PATCH 1/3] powerpc/uaccess: Switch __put_user_size_allowed() to __put_user_asm_goto() | Date | Wed, 04 Nov 2020 00:21:44 +1100 |
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Andreas Schwab <schwab@linux-m68k.org> writes: > # > # Automatically generated file; DO NOT EDIT. > # Linux/powerpc 5.10.0-rc1 Kernel Configuration > # > CONFIG_CC_VERSION_TEXT="gcc-4.9 (SUSE Linux) 4.9.3"
So it seems to be a combination of GCC 4.9 and ...
> # CONFIG_PPC_RADIX_MMU is not set
That ^, which specifically causes PPC_KUAP=n.
When PPC_KUAP=y allow_user_access() inlines an isync and mtspr, both of which contain a memory clobber, and that seems to hide the bug.
I think for now we just have to stop using asm goto for put_user() on GCC 4.9.
I'll send a patch for that.
cheers
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