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author | Bjorn Helgaas <bjorn.helgaas@hp.com> | 2006-01-08 01:04:13 -0800 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-01-08 20:14:02 -0800 |
commit | 80851ef2a5a404e6054211ca96ecd5ac4b06d297 (patch) | |
tree | dcacd2a475adc28c540b6012b58f1af9783778c1 /drivers/char/sonypi.c | |
parent | 44ac8413901167589226abf824d994aa57e4fd28 (diff) |
[PATCH] /dev/mem: validate mmap requests
Add a hook so architectures can validate /dev/mem mmap requests.
This is analogous to validation we already perform in the read/write
paths.
The identity mapping scheme used on ia64 requires that each 16MB or
64MB granule be accessed with exactly one attribute (write-back or
uncacheable). This avoids "attribute aliasing", which can cause a
machine check.
Sample problem scenario:
- Machine supports VGA, so it has uncacheable (UC) MMIO at 640K-768K
- efi_memmap_init() discards any write-back (WB) memory in the first granule
- Application (e.g., "hwinfo") mmaps /dev/mem, offset 0
- hwinfo receives UC mapping (the default, since memmap says "no WB here")
- Machine check abort (on chipsets that don't support UC access to WB
memory, e.g., sx1000)
In the scenario above, the only choices are
- Use WB for hwinfo mmap. Can't do this because it causes attribute
aliasing with the UC mapping for the VGA MMIO space.
- Use UC for hwinfo mmap. Can't do this because the chipset may not
support UC for that region.
- Disallow the hwinfo mmap with -EINVAL. That's what this patch does.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Cc: Hugh Dickins <hugh@veritas.com>
Cc: "Luck, Tony" <tony.luck@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers/char/sonypi.c')
0 files changed, 0 insertions, 0 deletions