gABI extension proposal: PT_SHMMAP

[Suprateeka R Hegde]

On 07-Jun-2017 10:40 PM, H. Peter Anvin wrote:
> Any particular reason that you feel this is not generally useful?

1. The use case provided looks extremely specific to Linux. AFAIK, none
of the unix like HP-UX, Solaris or AIX need this requirement.

2. This looks so specific to a runtime loader that it can be as well
handled as a special case in GNU mmap system (may be in ld.so).

3. Assuming Cary is right in understanding that you want a writable but
still sharable page, such features are not even provided by some of the
legacy unix kernels.

4. Eventually there can be many such flags if we start going with
specific claims. For instance there was a request for
PF_NOREAD/SHF_NOREAD that would help some archs (STM?) to protect code
from being read.

5. Why dont we try to fit this proposal under the bigger one - program
properties - proposed by H.J. ? The theme there is to pass such
information to runtime.

6. Lastly, the proposal looks incomplete:
5-a. The hex value for the proposed flag is missing
5-b. The proposal should be sent to Generic SYS-V ABI group and not
GNU-GABI alone.
5-c. The complete semantics of this flag in a standard form. The
semantics should talk about what is mandatory, what is optional. Is the
current/existing UNIX should be changed to honor this flag or is this
optional?

--
Supra