another question - VM mappings

[Wojciech Puchar]

thanks!


On Mon, 13 Apr 2015, Oliver Pinter wrote:

> Under amd64 exists an so called shared-page - similar to linux's vdso
> mechanism - https://github.com/freebsd/freebsd/blob/master/sys/kern/kern_exec.c#L1045
> .
>
> This page is double mapped with user-space and with kernel. From
> security reason it's only RO, otherwise, when mapped with RW or RWX,
> then you could write kernel memory from user-space.
>
> On Mon, Apr 13, 2015 at 9:31 AM, Wojciech Puchar <wojtek at puchar.net> wrote:
>> below is mapping for very simple process (no libc etc)
>>
>> [wojtek at laptop ~]$ procstat -v 917
>>   PID              START                END PRT  RES PRES REF SHD   FL TP
>> PATH
>>   917           0x400000           0x401000 r-x    1    0   1   0 CN-- vn
>> /home/wojtek/test/1
>>   917           0x600000           0x601000 rw-    1    0   1   0 ---- df
>>   917     0x7ffffffdf000     0x7ffffffff000 rw-    1    0   1   0 ---D df
>>   917     0x7ffffffff000     0x800000000000 r-x    0    0  39   0 ---- ph
>>
>>
>> what is "ph" mapping and why read&executable?
>
>