Segfault with 7.4 when using preload feature

[remicollet]

Without swoole

$ touch foo.php
$ php74 -n -d zend_extension=opcache -d extension=ffi -d extension=zstd -d opcache.enable=1 -d opcache.enable_cli=1 -d extension=mysqlnd -d extension=sockets   -d opcache.preload=$PWD/foo.php -v
PHP 7.4.0RC4 (cli) (built: Oct 15 2019 11:28:21) ( NTS )
Copyright (c) The PHP Group
Zend Engine v3.4.0-dev, Copyright (c) Zend Technologies
    with Zend OPcache v7.4.0RC4, Copyright (c), by Zend Technologies

With swoole enabled

$ php74 -n -d zend_extension=opcache -d extension=ffi -d extension=zstd -d opcache.enable=1 -d opcache.enable_cli=1 -d extension=mysqlnd -d extension=sockets  -d extension=swoole -d opcache.preload=$PWD/foo.php -v
Segmentation fault (core dumped)

(gdb) bt
#0  accel_preload (config=<optimized out>) at /usr/src/debug/php74-php-7.4.0~rc4-28.fc29.remi.x86_64/Zend/zend_types.h:442
#1  0x00007ffff6f833b5 in accel_finish_startup () at /usr/src/debug/php74-php-7.4.0~rc4-28.fc29.remi.x86_64/ext/opcache/ZendAccelerator.c:4625
#2  accel_post_startup () at /usr/src/debug/php74-php-7.4.0~rc4-28.fc29.remi.x86_64/ext/opcache/ZendAccelerator.c:3024
#3  0x0000555555923a98 in zend_post_startup () at /usr/src/debug/php74-php-7.4.0~rc4-28.fc29.remi.x86_64/Zend/zend.c:1000
#4  0x00005555558c0fcd in php_module_startup (sf=<optimized out>, additional_modules=<optimized out>, num_additional_modules=<optimized out>) at /usr/src/debug/php74-php-7.4.0~rc4-28.fc29.remi.x86_64/main/main.c:2358
#5  0x00005555559acd51 in php_cli_startup (sapi_module=<optimized out>) at /usr/src/debug/php74-php-7.4.0~rc4-28.fc29.remi.x86_64/sapi/cli/php_cli.c:407
#6  0x000055555578a41e in main (argc=21, argv=0x555555f870e0) at /usr/src/debug/php74-php-7.4.0~rc4-28.fc29.remi.x86_64/sapi/cli/php_cli.c:1319

@dstogov may have some interest for you.

[twose]

Swoole eval some PHP code in RINIT
Is there something wrong with this usage?

[dstogov]

@twose not in general, but it seems preload-er didn't expect this. Do you need to "eval" some code on each request? or only on the first one? In last case, you may use zend_post_startup callback with "virtual" request, in the same way as preloader does.

[twose]

only on the first one

I'll try to fix it

[twose]

Hi @dstogov

I try to hook zend_post_startup_cb, but zend_extension (opcache) always loaded after extension (swoole), and accel_post_startup always call orig_post_startup_cb first

I can't find the right time to load the PHP code unless hook zend_execute_ex

[dstogov]

It shouldn't be a problem if you run some code before opcache. You should just cleanup the data crated during execution.

[twose]

@dstogov
Our PHP code just defines some functions and classes.

if I hook zend_post_startup_cb, the code would be loaded before request startup, compile_globals has not been initialized yet

if I add it to RINIT (before opcache), ZEND_ASSERT(op_array->fn_flags & ZEND_ACC_PRELOADED); failed (The registered classes will be traversed and treated as the part of the preload in accel_preload)

This question plagued us for a long time, we can't find the way to hook the first user's zend_execute, unless we implement a SAPI

[dstogov]

I mean executing your code inside a virtual request, wrapped by php_request_startup() ... php_request_shutdown(), like this is done in accel_finish_startup(). See https://github.com/php/php-src/blob/master/ext/opcache/ZendAccelerator.c#L4643-L4716

However, I may try to set ZEND_COMPILE_PRELOAD flag in CG(compiler_options) a bit early, so you could detect and avoid execution of the code during RINIT of preloader. Anyway, your code will affect the first request.

[twose]

Oh I see! let me have a try, thanks!

[twose]

I read the source code of the preloader today, I have some misunderstandings about it before...

Swoole only supports SAPI CLI, so I think the following code is enough:

sapi_module.deactivate != NULL && sapi_module.register_server_variables != NULL

I will replace it with !(CG(compiler_options) & ZEND_COMPILE_PRELOAD) when you set ZEND_COMPILE_PRELOAD earlier

It works well now

@remicollet @dstogov Thank you for your help!

[dstogov]

OK. If check of SAPI callback is enough for now, lets use this way.
I won't change ZEND_COMPILE_PRELOAD behaviour yet.

[twose]

OK, I see.

[dstogov]

I've changed ZEND_COMPILE_PRELOAD to be set during RINIT as a part of another fix.
See php/php-src@1417352
You may try to use this flag now