Re: [PATCH v4 3/3] arm64: apply __ro_after_init to some objects

[Mark Rutland]

On Mon, Aug 15, 2016 at 02:45:46PM +0800, Jisheng Zhang wrote:
> These objects are set during initialization, thereafter are read only.
> 
> Previously I only want to mark vdso_pages, vdso_spec, vectors_page and
> cpu_ops as __read_mostly from performance point of view. Then inspired
> by Kees's patch[1] to apply more __ro_after_init for arm, I think it's
> better to mark them as __ro_after_init. What's more, I find some more
> objects are also read only after init. So apply __ro_after_init to all
> of them.
> 
> This patch also removes global vdso_pagelist and tries to clean up
> vdso_spec[] assignment code.
> 
> [1] http://www.spinics.net/lists/arm-kernel/msg523188.html
> 
> Signed-off-by: Jisheng Zhang <jszhang@xxxxxxxxxxx>

This looks good to me. With or without the include cleanup in vdso.c:

Acked-by: Mark Rutland <mark.rutland@xxxxxxx>

Mark.

> ---
>  arch/arm64/kernel/cpu_ops.c |  3 ++-
>  arch/arm64/kernel/kaslr.c   |  3 ++-
>  arch/arm64/kernel/vdso.c    | 30 +++++++++++++++---------------
>  arch/arm64/mm/dma-mapping.c |  3 ++-
>  arch/arm64/mm/init.c        |  5 +++--
>  arch/arm64/mm/mmu.c         |  3 ++-
>  6 files changed, 26 insertions(+), 21 deletions(-)
> 
> diff --git a/arch/arm64/kernel/cpu_ops.c b/arch/arm64/kernel/cpu_ops.c
> index c7cfb8f..e137cea 100644
> --- a/arch/arm64/kernel/cpu_ops.c
> +++ b/arch/arm64/kernel/cpu_ops.c
> @@ -17,6 +17,7 @@
>   */
>  
>  #include <linux/acpi.h>
> +#include <linux/cache.h>
>  #include <linux/errno.h>
>  #include <linux/of.h>
>  #include <linux/string.h>
> @@ -28,7 +29,7 @@ extern const struct cpu_operations smp_spin_table_ops;
>  extern const struct cpu_operations acpi_parking_protocol_ops;
>  extern const struct cpu_operations cpu_psci_ops;
>  
> -const struct cpu_operations *cpu_ops[NR_CPUS];
> +const struct cpu_operations *cpu_ops[NR_CPUS] __ro_after_init;
>  
>  static const struct cpu_operations *dt_supported_cpu_ops[] __initconst = {
>  	&smp_spin_table_ops,
> diff --git a/arch/arm64/kernel/kaslr.c b/arch/arm64/kernel/kaslr.c
> index b054691..769f24e 100644
> --- a/arch/arm64/kernel/kaslr.c
> +++ b/arch/arm64/kernel/kaslr.c
> @@ -6,6 +6,7 @@
>   * published by the Free Software Foundation.
>   */
>  
> +#include <linux/cache.h>
>  #include <linux/crc32.h>
>  #include <linux/init.h>
>  #include <linux/libfdt.h>
> @@ -20,7 +21,7 @@
>  #include <asm/pgtable.h>
>  #include <asm/sections.h>
>  
> -u64 __read_mostly module_alloc_base;
> +u64 __ro_after_init module_alloc_base;
>  u16 __initdata memstart_offset_seed;
>  
>  static __init u64 get_kaslr_seed(void *fdt)
> diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
> index 10ad8ab..6225612 100644
> --- a/arch/arm64/kernel/vdso.c
> +++ b/arch/arm64/kernel/vdso.c
> @@ -18,12 +18,13 @@
>   * Author: Will Deacon <will.deacon@xxxxxxx>
>   */
>  
> -#include <linux/kernel.h>
> +#include <linux/cache.h>
>  #include <linux/clocksource.h>
>  #include <linux/elf.h>
>  #include <linux/err.h>
>  #include <linux/errno.h>
>  #include <linux/gfp.h>
> +#include <linux/kernel.h>
>  #include <linux/mm.h>
>  #include <linux/sched.h>
>  #include <linux/signal.h>
> @@ -37,8 +38,7 @@
>  #include <asm/vdso_datapage.h>
>  
>  extern char vdso_start, vdso_end;
> -static unsigned long vdso_pages;
> -static struct page **vdso_pagelist;
> +static unsigned long vdso_pages __ro_after_init;
>  
>  /*
>   * The vDSO data page.
> @@ -53,7 +53,7 @@ struct vdso_data *vdso_data = &vdso_data_store.data;
>  /*
>   * Create and map the vectors page for AArch32 tasks.
>   */
> -static struct page *vectors_page[1];
> +static struct page *vectors_page[1] __ro_after_init;
>  
>  static int __init alloc_vectors_page(void)
>  {
> @@ -110,11 +110,19 @@ int aarch32_setup_vectors_page(struct linux_binprm *bprm, int uses_interp)
>  }
>  #endif /* CONFIG_COMPAT */
>  
> -static struct vm_special_mapping vdso_spec[2];
> +static struct vm_special_mapping vdso_spec[2] __ro_after_init = {
> +	{
> +		.name	= "[vvar]",
> +	},
> +	{
> +		.name	= "[vdso]",
> +	},
> +};
>  
>  static int __init vdso_init(void)
>  {
>  	int i;
> +	struct page **vdso_pagelist;
>  
>  	if (memcmp(&vdso_start, "\177ELF", 4)) {
>  		pr_err("vDSO is not a valid ELF object!\n");
> @@ -138,16 +146,8 @@ static int __init vdso_init(void)
>  	for (i = 0; i < vdso_pages; i++)
>  		vdso_pagelist[i + 1] = pfn_to_page(PHYS_PFN(__pa(&vdso_start)) + i);
>  
> -	/* Populate the special mapping structures */
> -	vdso_spec[0] = (struct vm_special_mapping) {
> -		.name	= "[vvar]",
> -		.pages	= vdso_pagelist,
> -	};
> -
> -	vdso_spec[1] = (struct vm_special_mapping) {
> -		.name	= "[vdso]",
> -		.pages	= &vdso_pagelist[1],
> -	};
> +	vdso_spec[0].pages = &vdso_pagelist[0];
> +	vdso_spec[1].pages = &vdso_pagelist[1];
>  
>  	return 0;
>  }
> diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c
> index c4284c4..5cd202f 100644
> --- a/arch/arm64/mm/dma-mapping.c
> +++ b/arch/arm64/mm/dma-mapping.c
> @@ -20,6 +20,7 @@
>  #include <linux/gfp.h>
>  #include <linux/acpi.h>
>  #include <linux/bootmem.h>
> +#include <linux/cache.h>
>  #include <linux/export.h>
>  #include <linux/slab.h>
>  #include <linux/genalloc.h>
> @@ -30,7 +31,7 @@
>  
>  #include <asm/cacheflush.h>
>  
> -static int swiotlb __read_mostly;
> +static int swiotlb __ro_after_init;
>  
>  static pgprot_t __get_dma_pgprot(unsigned long attrs, pgprot_t prot,
>  				 bool coherent)
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index bbb7ee7..251e082 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -23,6 +23,7 @@
>  #include <linux/swap.h>
>  #include <linux/init.h>
>  #include <linux/bootmem.h>
> +#include <linux/cache.h>
>  #include <linux/mman.h>
>  #include <linux/nodemask.h>
>  #include <linux/initrd.h>
> @@ -55,8 +56,8 @@
>   * executes, which assigns it its actual value. So use a default value
>   * that cannot be mistaken for a real physical address.
>   */
> -s64 memstart_addr __read_mostly = -1;
> -phys_addr_t arm64_dma_phys_limit __read_mostly;
> +s64 memstart_addr __ro_after_init = -1;
> +phys_addr_t arm64_dma_phys_limit __ro_after_init;
>  
>  #ifdef CONFIG_BLK_DEV_INITRD
>  static int __init early_initrd(char *p)
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 4989948..e634a0f 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -17,6 +17,7 @@
>   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>   */
>  
> +#include <linux/cache.h>
>  #include <linux/export.h>
>  #include <linux/kernel.h>
>  #include <linux/errno.h>
> @@ -46,7 +47,7 @@
>  
>  u64 idmap_t0sz = TCR_T0SZ(VA_BITS);
>  
> -u64 kimage_voffset __read_mostly;
> +u64 kimage_voffset __ro_after_init;
>  EXPORT_SYMBOL(kimage_voffset);
>  
>  /*
> -- 
> 2.8.1
>