On 12-08-16, Baoquan He wrote:
> In early boot code level2_kernel_pgt is used to map kernel text. And its
> size varies according to KERNEL_IMAGE_SIZE and fixed at compiling time.
> In fact we can make it always takes 512 entries of one whople page table,
> because later function cleanup_highmap will clean up the unused entries.
> With the help of this change kernel text mapping size can be decided at
> runtime later, 512M if kaslr is disabled, 1G if kaslr is enabled.
s/whople/whole
> Signed-off-by: Baoquan He <b...@redhat.com>
> ---
> arch/x86/include/asm/page_64_types.h | 3 ++-
> arch/x86/kernel/head_64.S | 15 ++++++++-------
> arch/x86/mm/init_64.c | 2 +-
> 3 files changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/arch/x86/include/asm/page_64_types.h
> b/arch/x86/include/asm/page_64_types.h
> index 9215e05..62a20ea 100644
> --- a/arch/x86/include/asm/page_64_types.h
> +++ b/arch/x86/include/asm/page_64_types.h
> @@ -56,8 +56,9 @@
> * are fully set up. If kernel ASLR is configured, it can extend the
> * kernel page table mapping, reducing the size of the modules area.
> */
> +#define KERNEL_MAPPING_SIZE_EXT (1024 * 1024 * 1024)
> #if defined(CONFIG_RANDOMIZE_BASE)
> -#define KERNEL_IMAGE_SIZE (1024 * 1024 * 1024)
> +#define KERNEL_IMAGE_SIZE KERNEL_MAPPING_SIZE_EXT
> #else
> #define KERNEL_IMAGE_SIZE (512 * 1024 * 1024)
> #endif
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index b4421cc..c4b40e7c9 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -453,17 +453,18 @@ NEXT_PAGE(level3_kernel_pgt)
>
> NEXT_PAGE(level2_kernel_pgt)
> /*
> - * 512 MB kernel mapping. We spend a full page on this pagetable
> - * anyway.
> + * Kernel image size is limited to 512 MB. The kernel code+data+bss
> + * must not be bigger than that.
> *
> - * The kernel code+data+bss must not be bigger than that.
> + * We spend a full page on this pagetable anyway, so take the whole
> + * page here so that the kernel mapping size can be decided at runtime,
> + * 512M if no kaslr, 1G if kaslr enabled. Later cleanup_highmap will
> + * clean up those unused entries.
> *
> - * (NOTE: at +512MB starts the module area, see MODULES_VADDR.
> - * If you want to increase this then increase MODULES_VADDR
> - * too.)
> + * The module area starts after kernel mapping area.
> */
> PMDS(0, __PAGE_KERNEL_LARGE_EXEC,
> - KERNEL_IMAGE_SIZE/PMD_SIZE)
> + PTRS_PER_PMD)
>
> NEXT_PAGE(level2_fixmap_pgt)
> .fill 506,8,0
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 14b9dd7..e95b977 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -307,7 +307,7 @@ void __init init_extra_mapping_uc(unsigned long phys,
> unsigned long size)
> void __init cleanup_highmap(void)
> {
> unsigned long vaddr = __START_KERNEL_map;
> - unsigned long vaddr_end = __START_KERNEL_map + KERNEL_IMAGE_SIZE;
> + unsigned long vaddr_end = __START_KERNEL_map + KERNEL_MAPPING_SIZE_EXT;
> unsigned long end = roundup((unsigned long)_brk_end, PMD_SIZE) - 1;
> pmd_t *pmd = level2_kernel_pgt;
>
> --
> 2.5.5
>
