Re: [PATCH] riscv: enable BUILDTIME_TABLE_SORT for !MMU

[Jisheng Zhang <jszhang@kernel.org>]

On Tue, Apr 11, 2023 at 10:37:36AM +0100, Conor Dooley wrote:
> Hey Jisheng,
> 
> On Mon, Apr 10, 2023 at 12:43:06AM +0800, Jisheng Zhang wrote:
> > BUILDTIME_TABLE_SORT works for !MMU as well, so enable it.
> > 
> > Tested on QEMU and FPGA.
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> 
> Fails to build for nommu_k210_defconfig:
> 
> make ARCH=riscv CROSS_COMPILE=riscv64-unknown-linux-gnu- O=build -sk -j30
> no __ex_table in file: vmlinux

This failure log makes me carefully go through the ex_table mechanism
again. Now I knew where's the failure from and what should be done:
Because FUTEX is disabled in nommu_k210_defconfig. However, there's a
deeply hidden issue here: there should be no __ex_table section usage
at all in NOMMU case, becaue __ex_table usage relies on MMU to do the
*fixup*, so I need to patch the risc extable part instead.

Thanks

> Failed to sort kernel tables
> make[2]: *** [../scripts/Makefile.vmlinux:35: vmlinux] Error 1
> make[2]: *** Deleting file 'vmlinux'
> make[2]: Target '__default' not remade because of errors.
> make[1]: *** [/home/conor/stuff/linux/Makefile:1250: vmlinux] Error 2
> make[1]: Target '__all' not remade because of errors.
> make: *** [Makefile:226: __sub-make] Error 2
> make: Target '__all' not remade because of errors.
> 
> :(
> 
> > ---
> >  arch/riscv/Kconfig | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index c5e42cc37604..212ea28e346b 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -50,7 +50,7 @@ config RISCV
> >  	select ARCH_WANT_LD_ORPHAN_WARN if !XIP_KERNEL
> >  	select ARCH_WANTS_THP_SWAP if HAVE_ARCH_TRANSPARENT_HUGEPAGE
> >  	select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU
> > -	select BUILDTIME_TABLE_SORT if MMU
> > +	select BUILDTIME_TABLE_SORT
> >  	select CLINT_TIMER if !MMU
> >  	select CLONE_BACKWARDS
> >  	select COMMON_CLK
> > -- 
> > 2.40.0
> >