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Date: Thu, 12 Mar 2009 17:44:47 -0700
From: Yinghai Lu <yinghai@...nel.org>
To: Jeremy Fitzhardinge <jeremy@...p.org>
CC: "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
the arch/x86 maintainers <x86@...nel.org>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] x86: add brk allocator for very early allocations
Jeremy Fitzhardinge wrote:
> Yinghai Lu wrote:
>> could have more explanation about the 1M size.
>> because initial_pg_tables will sit in it. please consider to add
>> something like
>>
>> in head_32.S
>>
>> LOW_PAGES = (KERNEL_IMAGE_SIZE + PAGE_SIZE_asm - 1)>>PAGE_SHIFT
>>
>> #if PTRS_PER_PMD > 1
>> PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PMD) + PTRS_PER_PGD
>> #else
>> PAGE_TABLE_SIZE = (LOW_PAGES / PTRS_PER_PGD)
>> #endif
>> ALLOCATOR_SLOP = 4
>>
>
> OK, how does this look:
>
> The following changes since commit
> 21e8ba72daf5d7f0af33968f873499c85f96ccef:
> Jeremy Fitzhardinge (1):
> x86: use brk allocation for DMI
>
> are available in the git repository at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git push/x86/brk
>
> Jeremy Fitzhardinge (1):
> x86: allow extend_brk users to reserve brk space
>
> Yinghai Lu (1):
> x86-32: compute initial mapping size more accurately
>
> arch/x86/include/asm/page_32_types.h | 5 +++++
> arch/x86/include/asm/setup.h | 30 ++++++++++++++++++++++++++++++
> arch/x86/kernel/head_32.S | 4 +++-
> arch/x86/kernel/setup.c | 2 ++
> arch/x86/kernel/vmlinux_32.lds.S | 4 +++-
> arch/x86/kernel/vmlinux_64.lds.S | 4 +++-
> 6 files changed, 46 insertions(+), 3 deletions(-)
>
> git diff 21e8ba72daf5d7f0af33968f873499c85f96ccef..push/x86/brk
> diff --git a/arch/x86/include/asm/page_32_types.h
> b/arch/x86/include/asm/page_32_types.h
> index f1e4a79..0f915ae 100644
> --- a/arch/x86/include/asm/page_32_types.h
> +++ b/arch/x86/include/asm/page_32_types.h
> @@ -39,6 +39,11 @@
> #define __VIRTUAL_MASK_SHIFT 32
> #endif /* CONFIG_X86_PAE */
>
> +/*
> + * Kernel image size is limited to 512 MB (see in
> arch/x86/kernel/head_32.S)
> + */
> +#define KERNEL_IMAGE_SIZE (512 * 1024 * 1024)
> +
> #ifndef __ASSEMBLY__
>
> /*
> diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h
> index 366d366..61b126b 100644
> --- a/arch/x86/include/asm/setup.h
> +++ b/arch/x86/include/asm/setup.h
> @@ -104,6 +104,29 @@ extern struct boot_params boot_params;
> extern unsigned long _brk_end;
> void *extend_brk(size_t size, size_t align);
>
> +/*
> + * Reserve space in the brk section. The name must be unique within
> + * the file, and somewhat descriptive. The size is in bytes. Must be
> + * used at file scope.
> + *
> + * (This uses a temp function to wrap the asm so we can pass it the
> + * size parameter; otherwise we wouldn't be able to. We can't use a
> + * "section" attribute on a normal variable because it always ends up
> + * being @progbits, which ends up allocating space in the vmlinux
> + * executable.)
> + */
> +#define RESERVE_BRK(name,sz) \
> + static void __section(.discard) __used \
> + __brk_reservation_fn_##name##__(void) { \
> + asm volatile ( \
> + ".pushsection .brk_reservation,\"aw\",@nobits;" \
> + "__brk_reservation_" #name "__:" \
> + " 1:.skip %c0;" \
> + " .size __brk_reservation_" #name "__, . - 1b;" \
> + " .popsection" \
> + : : "i" (sz)); \
> + }
> +
> #ifdef __i386__
>
> void __init i386_start_kernel(void);
> @@ -115,6 +138,13 @@ void __init x86_64_start_reservations(char
> *real_mode_data);
>
> #endif /* __i386__ */
> #endif /* _SETUP */
> +#else
> +#define RESERVE_BRK(name,sz) \
> + .pushsection .brk_reservation,"aw",@nobits; \
> +__brk_reservation_##name##__: \
> +1: .skip sz; \
> + .size __brk_reservation_##name##__,.-1b; \
> + .popsection
> #endif /* __ASSEMBLY__ */
> #endif /* __KERNEL__ */
>
> diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
> index d243437..80dc05e 100644
> --- a/arch/x86/kernel/head_32.S
> +++ b/arch/x86/kernel/head_32.S
> @@ -54,7 +54,7 @@
> *
> * This should be a multiple of a page.
> */
> -LOW_PAGES = 1<<(32-PAGE_SHIFT_asm)
> +LOW_PAGES = (KERNEL_IMAGE_SIZE + PAGE_SIZE_asm - 1)>>PAGE_SHIFT
>
> /*
> * To preserve the DMA pool in PAGEALLOC kernels, we'll allocate
> @@ -75,6 +75,8 @@ ALLOCATOR_SLOP = 4
>
> INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE +
> ALLOCATOR_SLOP)*PAGE_SIZE_asm
no user for INIT_MAP_BEYOND_END any more.
>
> +RESERVE_BRK(pagetables, PAGE_TABLE_SIZE * PAGE_SIZE)
> +
> /*
> * 32-bit kernel entrypoint; only used by the boot CPU. On entry,
> * %esi points to the real-mode code as a 32-bit pointer.
> diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
> index b344908..d633958 100644
> --- a/arch/x86/kernel/setup.c
> +++ b/arch/x86/kernel/setup.c
> @@ -112,6 +112,8 @@
> #define ARCH_SETUP
> #endif
>
> +RESERVE_BRK(dmi_alloc, 65536);
> +
> unsigned int boot_cpu_id __read_mostly;
>
> static __initdata unsigned long _brk_start = (unsigned long)__brk_base;
> diff --git a/arch/x86/kernel/vmlinux_32.lds.S
> b/arch/x86/kernel/vmlinux_32.lds.S
> index 1063fbe..4005279 100644
> --- a/arch/x86/kernel/vmlinux_32.lds.S
> +++ b/arch/x86/kernel/vmlinux_32.lds.S
> @@ -192,7 +192,8 @@ SECTIONS
>
> . = ALIGN(PAGE_SIZE);
> __brk_base = . ;
> - . += 1024 * 1024 ;
> + . += 64 * 1024 ; /* 64k slop space */
> + *(.brk_reservation) /* areas brk users have reserved */
> __brk_limit = . ;
>
> _end = . ;
> @@ -201,6 +202,7 @@ SECTIONS
> /* Sections to be discarded */
> /DISCARD/ : {
> *(.exitcall.exit)
> + *(.discard)
> }
>
> STABS_DEBUG
could add
/*
* Build-time check on the image size:
*/
ASSERT((_end - LOAD_OFFSET <= KERNEL_IMAGE_SIZE),
"kernel image bigger than KERNEL_IMAGE_SIZE")
for 32bit
YH
> diff --git a/arch/x86/kernel/vmlinux_64.lds.S
> b/arch/x86/kernel/vmlinux_64.lds.S
> index b8b83e4..47deee3 100644
> --- a/arch/x86/kernel/vmlinux_64.lds.S
> +++ b/arch/x86/kernel/vmlinux_64.lds.S
> @@ -250,7 +250,8 @@ SECTIONS
>
> . = ALIGN(PAGE_SIZE);
> __brk_base = . ;
> - . += 1024 * 1024 ;
> + . += 64 * 1024 ; /* 64k slop space */
> + *(.brk_reservation) /* areas brk users have reserved */
> __brk_limit = . ;
> }
>
> @@ -260,6 +261,7 @@ SECTIONS
> /DISCARD/ : {
> *(.exitcall.exit)
> *(.eh_frame)
> + *(.discard)
> }
>
> STABS_DEBUG
>
--
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