Edit report at https://bugs.php.net/bug.php?id=80243&edit=1
ID: 80243
Comment by: brainpower at mailbox dot org
Reported by: jens-erik dot riedel at kippdata dot de
Summary: OPCache JIT segfaults at startup
Status: Open
Type: Bug
Package: JIT
Operating System: RHEL 8.0
PHP Version: 8.0.0rc1
Block user comment: N
Private report: N
New Comment:
https://gist.github.com/brainpower/d85cc63d6820dd2fb65d12ca52f5f957
Here's stepping through dasm_setup() up to the point where D->section is broken.
As I thought, it seems something is wrong with the memsets in there...
I've added the configure command to the gist, too.
Maybe some feature I've enabled messes with things.
Previous Comments:
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[2020-10-20 14:10:23] nikic@php.net
Would it be possible for you to set a break point on dasm_setup, step through it, and check that
D->section is initialized at the end?
In the meantime, I've done a php-8.0.0RC2 build on CentOS 7 (rather than Ubuntu 20.04) and
wasn't able to reproduce the issue there either.
------------------------------------------------------------------------
[2020-10-20 13:25:53] brainpower at mailbox dot org
Lots of other members of D are zeroed, not sure if that's ok or not:
Program received signal SIGSEGV, Segmentation fault.
dasm_put (Dst=Dst@entry=0x7fffffffcc00, start=start@entry=5) at
/root/shmbuild/src/php-8.0.0RC2/ext/opcache/jit/dynasm/dasm_x86.h:176
176 int pos = sec->pos, ofs = sec->ofs, mrm = -1;
(gdb) print D->section
$1 = (dasm_Section *) 0x0
(gdb) print D->sections[0]
$2 = {rbuf = 0x0, buf = 0x0, bsize = 0, pos = 0, epos = 0, ofs = 0}
(gdb) print &D->sections[0]
$3 = (dasm_Section *) 0x7ffff3608150
(gdb) print D->maxsection
$4 = 0
(gdb) print D->status
$5 = 0
(gdb) print D->actionlist
$6 = (dasm_ActList) 0x0
(gdb) print D->lglabels
$7 = (int *) 0x0
(gdb) print D->lgsize
$8 = 0
(gdb) print D->pclabels
$9 = (int *) 0x0
(gdb) print D->pcsize
$10 = 0
(gdb) print D->globals
$11 = (void **) 0x0
(gdb) print D->psize
$12 = 0
(gdb) print D->codesize
$13 = 0
(gdb)
Maybe dasm_setup didn't run? Or some errand memset() overwrote the wrong thing(s)?
------------------------------------------------------------------------
[2020-10-20 10:20:47] nikic@php.net
D->section is initialized by dasm_setup(), and that does get called directly before the stub is
compiled. Not clear to me how it ends up being NULL.
------------------------------------------------------------------------
[2020-10-19 15:51:10] ricardo at banak dot com
And same in PHP 8.0.0RC2
------------------------------------------------------------------------
[2020-10-19 15:48:52] ricardo at banak dot com
It also happens in Centos 8 and Centos 7.
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