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Date: Thu, 12 Mar 2009 16:59:09 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Yinghai Lu <yinghai@...nel.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
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
+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
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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