ZLO creating RWE segments

To investigate.

To close this issue, one must create all cfar packages, and confirm no RWE segments in any library.

zipr.cpp:643

m_zipr_scoops.insert(new_padding_scoop);
m_firp->GetAddresses().insert(new_padding_scoop_start_addr);
m_firp->GetAddresses().insert(new_padding_scoop_end_addr);

@whh8b is this right? we are only adding the addresses to the IR, not the scoop itself

Issue appears to be that zipr.cpp:640-ish is filling gaps between non-executable scoops, and assigning executable spaces on the same page as non-executable data scoops.

assigned to @whh8b

to dup the issue:

cd cfar/testing_harness/cfar_atds*/apache_prefork/
$PSZ apache_GCC_6.4.0/variant-1/lib/httpd-kudu-canonical ./xxx  --backend zipr --step p1transform=on --step move_globals=on --step-option 'zipr:--large_only:nog_on true' --step-option move_globals:-d --step-option move_globals:.interp --step-option 'zipr:--add-sections true --bss-opts false' 
eu-readelf -l ./xxx|grep RWE

I will start to look at this tonight. Thanks!

That should be

$PSZ apache.../bin/...

instead of referencing the program in the lib directory.

I cannot reproduce this. I ran the command that you gave me and was able to execute ./xxx. I'm sorry to be dumb, but I don't really know where to go from here.

assigned to @jdh8d and unassigned @whh8b

None of the commands I gave indicated to run xxx, just use readelf on it and see if any segments are RWE. It won't run w/o the proper library path and loaded libraries.

assigned to @whh8b and unassigned @jdh8d

Sorry. I was just trying to take the next step and assumed that you meant it didn't work when run. I apologize. Although, I was able to get it to run by just pointing it to one of the configs in the source directory.

No, it was running but RWE is a no no.

mentioned in commit e515da44

@jdh8d Check out rwe_fix branch for my suggested fix. Unfortunately you cannot merge this directly without seeing an error in apache_prefork. Here's why: With this addition, those gaps are forced to be full sized. As a result, there is no room to place the phdrs.

I was able to verify that the fix worked by putting in a temporary workaround in my local environment that shrank those non-executable scoops to an arbitrary size (6 bytes).

Let me know what you think! Will

assigned to @jdh8d and unassigned @whh8b

Also, if you tell me how to

To close this issue, one must create all cfar packages, and confirm no RWE segments in any library.

I can verify that the fix works.

Also, if you tell me how to

To close this issue, one must create all cfar packages, and confirm no RWE segments in any library.

I can verify that the fix works.

git clone --recursive allpnp/cfar.git
cd cfar
. set_env_vars
./get_packages.sh
./build-all.sh
cd testing_harness
./setup.sh
./destroy.sh; ./cfar_atd*/apache_prefork/test_apache_e1.sh ./cfar_atd*/apache_prefork/apache_GCC_6.4.0
cd VGT
nohup ./harness -b -t -r&
tail -f nohup.out

@jdh8d Check out rwe_fix branch for my suggested fix. Unfortunately you cannot merge this directly without seeing an error in apache_prefork. Here's why: With this addition, those gaps are forced to be full sized. As a result, there is no room to place the phdrs.

I was able to verify that the fix worked by putting in a temporary workaround in my local environment that shrank those non-executable scoops to an arbitrary size (6 bytes).

I think the phdr placement issue is related to how the fix is implemented. http://git.zephyr-software.com/allzp/zipr/compare/master...rwe_fix?w=1

I think the non-executable scoops that're being inserted for gap-filling are taking up the space for the phdrs. I recommend we don't fill gaps between RW pages. Only if the gap is bounded on one side by a R-- or R-X page. Also, being careful not to gap-fill onto the RW-side of the page.