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41a5c1717b
commit 24d3ba0a7b44c1617c27f5045eecc4f34752ab03 upstream.
The 32-bit ARM kernel stops working if the kernel grows to the point
where veneers for __get_user_* are created.
AAPCS32 [1] states, "Register r12 (IP) may be used by a linker as a
scratch register between a routine and any subroutine it calls. It
can also be used within a routine to hold intermediate values between
subroutine calls."
However, bl instructions buried within the inline asm are unpredictable
for compilers; hence, "ip" must be added to the clobber list.
This becomes critical when veneers for __get_user_* are created because
veneers use the ip register since commit 02e541db05 ("ARM: 8323/1:
force linker to use PIC veneers").
[1]: https://github.com/ARM-software/abi-aa/blob/2023Q1/aapcs32/aapcs32.rst
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Cc: John Stultz <jstultz@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>