Re: [PATCH v2] RISC-V: Always compile mm/init.c with cmodel=medany

[Alan Kao]

Hi Anup,

Sorry for being late to the party.  I think one more thing should
move together with setup_vm():

On Mon, Mar 25, 2019 at 03:37:38AM +0000, Anup Patel wrote:
> The Linux RISC-V 32bit kernel is broken after we moved setup_vm() from
> kernel/setup.c to mm/init.c because Linux RISC-V 32bit kernel by default
> uses cmodel=medlow which results in a non-position-independent setup_vm().
> 
> This patch fixes Linux RISC-V 32bit kernel booting by:
> 1. Forcing cmodel=medany for mm/init.c
> 2. Moving remaing MM-related stuff va_pa_offset, pfn_base and
>    empty_zero_page from kernel/setup.c to mm/init.c
> 
> Fixes: 6f1e9e946f0b ("RISC-V: Move setup_vm() to mm/init.c")
> Suggested-by: Christoph Hellwig <hch@xxxxxx>
> Suggested-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
> Signed-off-by: Anup Patel <anup.patel@xxxxxxx>
> ---
> v2: Removed CFLAGS_setup.o from kernel/Makefile and replaced SoBs
> ---
>  arch/riscv/kernel/Makefile | 2 --
>  arch/riscv/kernel/setup.c  | 8 --------
>  arch/riscv/mm/Makefile     | 2 ++
>  arch/riscv/mm/init.c       | 9 +++++++++
>  4 files changed, 11 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
> index f13f7f276639..8b9780b6bd7f 100644
> --- a/arch/riscv/kernel/Makefile
> +++ b/arch/riscv/kernel/Makefile

earlier in this file, there are four lines about ftrace,

  5 ifdef CONFIG_FTRACE
  6 CFLAGS_REMOVE_ftrace.o = -pg
  7 CFLAGS_REMOVE_setup.o = -pg
  8 endif

removing "-pg" flag from setup.o was necessary for ftrace to work, since
setup_vm() cannot process the trampoline of ftrace properly.

As setup_vm() is being moved to mm/init.c, you may either mark it with a
"notrace" attribute with its declaration, or adding corresponding CFLAGS_REMOVE*
to mm/Makefile.

> @@ -29,8 +29,6 @@ obj-y	+= vdso.o
>  obj-y	+= cacheinfo.o
>  obj-y	+= vdso/
>  
> -CFLAGS_setup.o := -mcmodel=medany
> -
>  obj-$(CONFIG_FPU)		+= fpu.o
>  obj-$(CONFIG_SMP)		+= smpboot.o
>  obj-$(CONFIG_SMP)		+= smp.o
> diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
> index ecb654f6a79e..540a331d1376 100644
> --- a/arch/riscv/kernel/setup.c
> +++ b/arch/riscv/kernel/setup.c
> @@ -48,14 +48,6 @@ struct screen_info screen_info = {
>  };
>  #endif
>  
> -unsigned long va_pa_offset;
> -EXPORT_SYMBOL(va_pa_offset);
> -unsigned long pfn_base;
> -EXPORT_SYMBOL(pfn_base);
> -
> -unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
> -EXPORT_SYMBOL(empty_zero_page);
> -
>  /* The lucky hart to first increment this variable will boot the other cores */
>  atomic_t hart_lottery;
>  unsigned long boot_cpu_hartid;
> diff --git a/arch/riscv/mm/Makefile b/arch/riscv/mm/Makefile
> index eb22ab49b3e0..7307609d405b 100644
> --- a/arch/riscv/mm/Makefile
> +++ b/arch/riscv/mm/Makefile
> @@ -3,3 +3,5 @@ obj-y += fault.o
>  obj-y += extable.o
>  obj-y += ioremap.o
>  obj-y += cacheflush.o
> +
> +CFLAGS_init.o := -mcmodel=medany
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index b379a75ac6a6..7a7c454378cb 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -25,6 +25,10 @@
>  #include <asm/pgtable.h>
>  #include <asm/io.h>
>  
> +unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
> +							__page_aligned_bss;
> +EXPORT_SYMBOL(empty_zero_page);
> +
>  static void __init zone_sizes_init(void)
>  {
>  	unsigned long max_zone_pfns[MAX_NR_ZONES] = { 0, };
> @@ -143,6 +147,11 @@ void __init setup_bootmem(void)
>  	}
>  }
>  
> +unsigned long va_pa_offset;
> +EXPORT_SYMBOL(va_pa_offset);
> +unsigned long pfn_base;
> +EXPORT_SYMBOL(pfn_base);
> +
>  pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
>  pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
>  
> -- 
> 2.17.1
> 
> 
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Alan