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linux-next/Documentation/arm/memory.txt

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Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
2005-04-17 06:20:36 +08:00
Kernel Memory Layout on ARM Linux
Russell King <rmk@arm.linux.org.uk>
[ARM] Fix some corner cases in new mm initialisation Document that the VMALLOC_END address must be aligned to 2MB since it must align with a PGD boundary. Allocate the vectors page early so that the flush_cache_all() later will cause any dirty cache lines in the direct mapping will be safely written back. Move the flush_cache_all() to the second local_flush_cache_tlb() and remove the now redundant first local_flush_cache_tlb(). Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2005-11-18 06:43:30 +08:00
November 17, 2005 (2.6.15)
Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
2005-04-17 06:20:36 +08:00
This document describes the virtual memory layout which the Linux
kernel uses for ARM processors. It indicates which regions are
free for platforms to use, and which are used by generic code.
The ARM CPU is capable of addressing a maximum of 4GB virtual memory
space, and this must be shared between user space processes, the
kernel, and hardware devices.
As the ARM architecture matures, it becomes necessary to reserve
certain regions of VM space for use for new facilities; therefore
this document may reserve more VM space over time.
Start End Use
--------------------------------------------------------------------------
ffff8000 ffffffff copy_user_page / clear_user_page use.
For SA11xx and Xscale, this is used to
setup a minicache mapping.
ARM: 5624/1: Document cache aliasing region Augment the memory.txt file for ARM to list the cache aliasing region ffff4000-fffffff. Signed-off-by: Linus Walleij <linus.walleij@stericsson.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2009-07-28 05:11:59 +08:00
ffff4000 ffffffff cache aliasing on ARMv6 and later CPUs.
Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
2005-04-17 06:20:36 +08:00
ffff1000 ffff7fff Reserved.
Platforms must not use this address range.
ffff0000 ffff0fff CPU vector page.
The CPU vectors are mapped here if the
CPU supports vector relocation (control
register V bit.)
[ARM] fixmap support This is the minimum fixmap interface expected to be implemented by architectures supporting highmem. We have a second level page table already allocated and covering 0xfff00000-0xffffffff because the exception vector page is located at 0xffff0000, and various cache tricks already use some entries above 0xffff0000. Therefore the PTEs covering 0xfff00000-0xfffeffff are free to be used. However the XScale cache flushing code already uses virtual addresses between 0xfffe0000 and 0xfffeffff. So this reserves the 0xfff00000-0xfffdffff range for fixmap stuff. The Documentation/arm/memory.txt information is updated accordingly, including the information about the actual top of DMA memory mapping region which didn't match the code. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-17 01:05:53 +08:00
fffe0000 fffeffff XScale cache flush area. This is used
in proc-xscale.S to flush the whole data
ARM: 6225/1: make TCM allocation static and common for all archs This changes the TCM handling so that a fixed area is reserved at 0xfffe0000-0xfffeffff for TCM. This areas is used by XScale but XScale does not have TCM so the mechanisms are mutually exclusive. This change is needed to make TCM detection more dynamic while still being able to compile code into it, and is a must for the unified ARM goals: the current TCM allocation at different places in memory for each machine would be a nightmare if you want to compile a single image for more than one machine with TCM so it has to be nailed down in one place. Signed-off-by: Linus Walleij <linus.walleij@stericsson.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-07-13 04:53:28 +08:00
cache. (XScale does not have TCM.)
fffe8000 fffeffff DTCM mapping area for platforms with
DTCM mounted inside the CPU.
fffe0000 fffe7fff ITCM mapping area for platforms with
ITCM mounted inside the CPU.
[ARM] fixmap support This is the minimum fixmap interface expected to be implemented by architectures supporting highmem. We have a second level page table already allocated and covering 0xfff00000-0xffffffff because the exception vector page is located at 0xffff0000, and various cache tricks already use some entries above 0xffff0000. Therefore the PTEs covering 0xfff00000-0xfffeffff are free to be used. However the XScale cache flushing code already uses virtual addresses between 0xfffe0000 and 0xfffeffff. So this reserves the 0xfff00000-0xfffdffff range for fixmap stuff. The Documentation/arm/memory.txt information is updated accordingly, including the information about the actual top of DMA memory mapping region which didn't match the code. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-17 01:05:53 +08:00
ARM: expand fixmap region to 3MB With commit a05e54c103b0 ("ARM: 8031/2: change fixmap mapping region to support 32 CPUs"), the fixmap region was expanded to 2MB, but it precluded any other uses of the fixmap region. In order to support other uses the fixmap region needs to be expanded beyond 2MB. Fortunately, the adjacent 1MB range 0xffe00000-0xfff00000 is availabe. Remove fixmap_page_table ptr and lookup the page table via the virtual address so that the fixmap region can span more that one pmd. The 2nd pmd is already created since it is shared with the vector page. Signed-off-by: Rob Herring <robh@kernel.org> [kees: fixed CONFIG_DEBUG_HIGHMEM get_fixmap() calls] [kees: moved pte allocation outside of CONFIG_HIGHMEM] Signed-off-by: Kees Cook <keescook@chromium.org> Acked-by: Nicolas Pitre <nico@linaro.org>
2014-07-02 15:01:15 +08:00
ffc00000 ffefffff Fixmap mapping region. Addresses provided
[ARM] fixmap support This is the minimum fixmap interface expected to be implemented by architectures supporting highmem. We have a second level page table already allocated and covering 0xfff00000-0xffffffff because the exception vector page is located at 0xffff0000, and various cache tricks already use some entries above 0xffff0000. Therefore the PTEs covering 0xfff00000-0xfffeffff are free to be used. However the XScale cache flushing code already uses virtual addresses between 0xfffe0000 and 0xfffeffff. So this reserves the 0xfff00000-0xfffdffff range for fixmap stuff. The Documentation/arm/memory.txt information is updated accordingly, including the information about the actual top of DMA memory mapping region which didn't match the code. Signed-off-by: Nicolas Pitre <nico@marvell.com>
2008-09-17 01:05:53 +08:00
by fix_to_virt() will be located here.
ARM: Add fixed PCI i/o mapping This adds a fixed virtual mapping for PCI i/o addresses. The mapping is located at the last 2MB of vmalloc region (0xfee00000-0xff000000). 2MB is used to align with PMD size, but IO_SPACE_LIMIT is 1MB. The space is reserved after .map_io and can be mapped at any time later with pci_ioremap_io. Platforms which need early i/o mapping (e.g. for vga console) can call pci_map_io_early in their .map_io function. This has changed completely from the 1st implementation which only supported creating the static mapping at .map_io. Signed-off-by: Rob Herring <rob.herring@calxeda.com> Cc: Russell King <linux@arm.linux.org.uk> Acked-by: Nicolas Pitre <nico@linaro.org>
2012-03-01 08:10:58 +08:00
fee00000 feffffff Mapping of PCI I/O space. This is a static
mapping within the vmalloc space.
Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
2005-04-17 06:20:36 +08:00
VMALLOC_START VMALLOC_END-1 vmalloc() / ioremap() space.
Memory returned by vmalloc/ioremap will
be dynamically placed in this region.
ARM: move iotable mappings within the vmalloc region In order to remove the build time variation between different SOCs with regards to VMALLOC_END, the iotable mappings are now allocated inside the vmalloc region. This allows for VMALLOC_END to be identical across all machines. The value for VMALLOC_END is now set to 0xff000000 which is right where the consistent DMA area starts. To accommodate all static mappings on machines with possible highmem usage, the default vmalloc area size is changed to 240 MB so that VMALLOC_START is no higher than 0xf0000000 by default. Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org> Tested-by: Stephen Warren <swarren@nvidia.com> Tested-by: Kevin Hilman <khilman@ti.com> Tested-by: Jamie Iles <jamie@jamieiles.com>
2011-08-25 12:35:59 +08:00
Machine specific static mappings are also
located here through iotable_init().
VMALLOC_START is based upon the value
of the high_memory variable, and VMALLOC_END
ARM: 8432/1: move VMALLOC_END from 0xff000000 to 0xff800000 There is a 12MB unused region in our memory map between the vmalloc and fixmap areas. This became unused with commit e9da6e9905e6, confirmed with commit 64d3b6a3f480. We also have a 8MB guard area before the vmalloc area. With the default 240MB vmalloc area size and the current VMALLOC_END definition, that means the end of low memory ends up at 0xef800000 which is unfortunate for 768MB machines where 8MB of RAM is lost to himem. Let's move VMALLOC_END to 0xff800000 so the guard area won't chop the top of the 768MB low memory area while keeping the default vmalloc area size unchanged and still preserving a gap between the vmalloc and fixmap areas. Signed-off-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2015-09-13 10:25:26 +08:00
is equal to 0xff800000.
Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
2005-04-17 06:20:36 +08:00
PAGE_OFFSET high_memory-1 Kernel direct-mapped RAM region.
This maps the platforms RAM, and typically
maps all platform RAM in a 1:1 relationship.
ARM: 5930/1: Add PKMAP area description to memory.txt. Also adapts delimiters of neighbouring modules area. Tested-by: H Hartley Sweeten <hsweeten@visionengravers.com> Signed-off-by: Andreas Fenkart <andreas.fenkart@streamunlimited.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
2010-02-08 04:48:38 +08:00
PKMAP_BASE PAGE_OFFSET-1 Permanent kernel mappings
One way of mapping HIGHMEM pages into kernel
space.
MODULES_VADDR MODULES_END-1 Kernel module space
Linux-2.6.12-rc2 Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
2005-04-17 06:20:36 +08:00
Kernel modules inserted via insmod are
placed here using dynamic mappings.
00001000 TASK_SIZE-1 User space mappings
Per-thread mappings are placed here via
the mmap() system call.
00000000 00000fff CPU vector page / null pointer trap
CPUs which do not support vector remapping
place their vector page here. NULL pointer
dereferences by both the kernel and user
space are also caught via this mapping.
Please note that mappings which collide with the above areas may result
in a non-bootable kernel, or may cause the kernel to (eventually) panic
at run time.
Since future CPUs may impact the kernel mapping layout, user programs
must not access any memory which is not mapped inside their 0x0001000
to TASK_SIZE address range. If they wish to access these areas, they
must set up their own mappings using open() and mmap().
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