On Mon, 2019-09-30 at 14:59 +0900, Masahiro Yamada wrote: > KernelCI reports that bcm2835_defconfig is no longer booting since > commit ac7c3e4ff401 ("compiler: enable CONFIG_OPTIMIZE_INLINING > forcibly"): > > https://lkml.org/lkml/2019/9/26/825 > > I also received a regression report from Nicolas Saenz Julienne: > > https://lkml.org/lkml/2019/9/27/263 > > This problem has cropped up on arch/arm/config/bcm2835_defconfig > because it enables CONFIG_CC_OPTIMIZE_FOR_SIZE. The compiler tends > to prefer not inlining functions with -Os. I was able to reproduce > it with other boards and defconfig files by manually enabling > CONFIG_CC_OPTIMIZE_FOR_SIZE. > > The __get_user_check() specifically uses r0, r1, r2 registers. > So, uaccess_save_and_enable() and uaccess_restore() must be inlined > in order to avoid those registers being overwritten in the callees. > > Prior to commit 9012d011660e ("compiler: allow all arches to enable > CONFIG_OPTIMIZE_INLINING"), the 'inline' marker was always enough for > inlining functions, except on x86. > > Since that commit, all architectures can enable CONFIG_OPTIMIZE_INLINING. > So, __always_inline is now the only guaranteed way of forcible inlining. > > I want to keep as much compiler's freedom as possible about the inlining > decision. So, I changed the function call order instead of adding > __always_inline around. > > Call uaccess_save_and_enable() before assigning the __p ("r0"), and > uaccess_restore() after evacuating the __e ("r0"). > > Fixes: 9012d011660e ("compiler: allow all arches to enable > CONFIG_OPTIMIZE_INLINING") > Reported-by: "kernelci.org bot" > Reported-by: Nicolas Saenz Julienne > Signed-off-by: Masahiro Yamada > --- Thanks! Tested-by: Nicolas Saenz Julienne