mirror_zfs/config/kernel-flush_dcache_page.m4
Low-power 589f59b52a
Workaround for Linux PowerPC GPL-only cpu_has_feature()
Linux since 4.7 makes interface 'cpu_has_feature' to use jump labels on
powerpc if CONFIG_JUMP_LABEL_FEATURE_CHECKS is enabled, in this case
however the inline function references GPL-only symbol
'cpu_feature_keys'.

ZFS currently uses 'cpu_has_feature' either directly or indirectly from
several places; while it is unknown how this issue didn't break ZFS on
64-bit little-endian powerpc, it is known to break ZFS with many Linux
versions on both 32-bit and 64-bit big-endian powerpc.

Until this issue is fixed in Linux, we have to workaround it by
overriding affected inline functions without depending on
'cpu_feature_keys'.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: WHR <msl0000023508@gmail.com>
Closes #14590
2023-03-10 09:35:00 -08:00

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dnl #
dnl # Starting from Linux 5.13, flush_dcache_page() becomes an inline
dnl # function and may indirectly referencing GPL-only cpu_feature_keys on
dnl # powerpc
dnl #
dnl #
dnl # Checking if flush_dcache_page is exported GPL-only
dnl #
AC_DEFUN([ZFS_AC_KERNEL_SRC_FLUSH_DCACHE_PAGE], [
ZFS_LINUX_TEST_SRC([flush_dcache_page], [
#include <asm/cacheflush.h>
], [
flush_dcache_page(0);
], [], [ZFS_META_LICENSE])
])
AC_DEFUN([ZFS_AC_KERNEL_FLUSH_DCACHE_PAGE], [
AC_MSG_CHECKING([whether flush_dcache_page() is GPL-only])
ZFS_LINUX_TEST_RESULT([flush_dcache_page_license], [
AC_MSG_RESULT(no)
], [
AC_MSG_RESULT(yes)
AC_DEFINE(HAVE_FLUSH_DCACHE_PAGE_GPL_ONLY, 1,
[flush_dcache_page() is GPL-only])
])
])