On Thu, Apr 12, 2018 at 8:37 PM, Michael Kerrisk (man-pages)
> Hi John,
> On 12 April 2018 at 20:33, John Hubbard <jhubb...@nvidia.com> wrote:
>> On 04/12/2018 08:39 AM, Jann Horn wrote:
>>> Clarify that MAP_FIXED is appropriate if the specified address range has
>>> been reserved using an existing mapping, but shouldn't be used otherwise.
>>> Signed-off-by: Jann Horn <ja...@google.com>
>>> man2/mmap.2 | 19 +++++++++++--------
>>> 1 file changed, 11 insertions(+), 8 deletions(-)
>>> diff --git a/man2/mmap.2 b/man2/mmap.2
>>> For example, suppose that thread A looks through
>>> @@ -284,13 +285,15 @@ and the PAM libraries
>>> .UR http://www.linux-pam.org
>>> .UE .
>>> -Newer kernels
>>> -(Linux 4.17 and later) have a
>>> +For cases in which the specified memory region has not been reserved using
>>> +existing mapping, newer kernels (Linux 4.17 and later) provide an option
>>> .B MAP_FIXED_NOREPLACE
>>> -option that avoids the corruption problem; if available,
>>> -.B MAP_FIXED_NOREPLACE
>>> -should be preferred over
>>> -.BR MAP_FIXED .
>>> +that should be used instead; older kernels require the caller to use
>>> +.I addr
>>> +as a hint (without
>>> +.BR MAP_FIXED )
>> Here, I got lost: the sentence suddenly jumps into explaining non-MAP_FIXED
>> behavior, in the MAP_FIXED section. Maybe if you break up the sentence, and
>> possibly omit non-MAP_FIXED discussion, it will help.
> Hmmm -- true. That piece could be a little clearer.
How about something like this?
For cases in which MAP_FIXED can not be used because
the specified memory
region has not been reserved using an existing mapping,
(Linux 4.17 and later) provide an option
should be used instead. Older kernels require the
caller to use addr as a hint and take appropriate action if
the kernel places the new mapping at a different address.
John, Michael, what do you think?
> Jann, I've already pushed the existing patch. Do you want to add a patch on