| Summary: | www-servers/nginx-1.7.2 on ABI_X86=x32 - if compiled with -O2, crash when closing TCP connexion. | ||
|---|---|---|---|
| Product: | Gentoo Linux | Reporter: | Thibaud CANALE <thican> |
| Component: | [OLD] Server | Assignee: | Tiziano Müller (RETIRED) <dev-zero> |
| Status: | RESOLVED TEST-REQUEST | ||
| Severity: | normal | CC: | bugs, proxy-maint |
| Priority: | Normal | ||
| Version: | unspecified | ||
| Hardware: | All | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Package list: | Runtime testing required: | --- | |
| Bug Depends on: | |||
| Bug Blocks: | 393673 | ||
| Attachments: |
emerge --info
gdb /usr/sbin/nginx /tmp/cores/core build.log with -O2 build.log with -O0 |
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Description
Thibaud CANALE
2014-07-13 15:16:54 UTC
Please make sure that you have debug symbols installed for nginx (with FEATURES="splitdebug compressdebug"), then enable coredumps (using `ulimit -c unlimited`), restart nginx (which should pickup the new ulimit, check with `cat /proc/$(pidof nginx)/limits`) and check before it crashes where the coredump will go (`ls -l /proc/$(pidof nginx)/cwd`). After that, use `gdb /usr/sbin/nginx /your-core-dump-file` to load the coredump, and generate a backtrace using the `bt` command withing gdb. Post the result here. Hello Tiziano, Sorry, I am sure I am missing a step, but I didn't found any coredump where it should be (where the symlink is /proc/.../cwd --> /). As you said, I did: 1. FEATURES="splitdebug compressdebug" emerge nginx 2. ulimit -c unlimited 3. restarting nginx, with rc-service or directly 4. checking the symlink /proc/.../cwd 5. crashing it. 6. nothing found where it should be. Thanks for your support. I found this document on the wiki, I keep you update: https://wiki.gentoo.org/wiki/Project:Hardened/Debugging Created attachment 380744 [details] gdb /usr/sbin/nginx /tmp/cores/core Ok, finally, here I am. Because /proc/<pid>/cwd is a symlink to / with root:root 755, and the process has nginx:www-data rights, I needed to create a directory to store and redefine the variable /proc/sys/kernel/core_pattern with sysctl: # mkdir /tmp/cores/ # chown root:root /tmp/cores/ # chmod 1773 /tmp/cores/ # sysctl kernel.core_pattern kernel.core_pattern = core # sysctl -w kernel.core_pattern="/tmp/cores/core" kernel.core_pattern = /tmp/cores/core Other detail, when I was only doing `ulimit -c unlimited`, it was still: # cat /proc/<pid>/limits Limit Soft Limit Hard Limit Units ../.. Max core file size 0 unlimited bytes So, I see we should use `ulimit -Sc unlimited`. And now it works :-) (Note: I followed https://wiki.gentoo.org/wiki/Project:Hardened/Debugging but I was unable to revealed the "??" in line 0) PS: I didn't found any lib named linux_vdso.so.1 related to "warning: Could not load shared library symbols for linux-vdso.so.1." message (cf. attachment). hmm, I don't see any obvious problems with the code at the positions given by the backtrace, but then I'm not the x32 specialist. Do you mind rebuild nginx again without the optimization flags (no "-O2" and the like) such that we get a a view on the values __len=<optimized out>, __src=<optimized out>, __dest=<optimized out> passed to memcpy? Can you possibly also attach the full build log? Maybe the compiler has some warnings for us. The problem is that I don't have access to a x32 system. If I'm still clueless after this I will have to open a bug report at upstream. Oh! Extraordinary, I figured that using -O0 is not crashing the process anymore. I was using -O2, like every package on my system, only nginx was crashing with this. I am sending build logs as attachments. Thanks for support. Created attachment 380954 [details]
build.log with -O2
CFLAGS="-march=corei7-avx -O2 -pipe -ggdb"
Created attachment 380956 [details]
build.log with -O0
As you can see in the build.log, there is a lot of lines with 2 instructions "-Ox":
x86_64-pc-linux-gnux32-gcc -c -march=corei7-avx -O2 -pipe -ggdb -O0 ...
The fact is I used /etc/portage/package.env and a file related to, with those informations:
in /etc/portage/make.conf: CFLAGS="-march=corei7-avx -O2 -pipe -ggdb"
in /etc/portage/env/: CFLAGS="${CFLAGS} -O0"
TBH, at the moment it seems to me like gcc is doing something strange here. Maybe the x32-porting people have some more insight. You could also try to set CFLAGS to "-O2" only (without the march) and then play around with the optimization flags (not only -Ox but the ones enabled by -O1/-O2) to see which one is causing the issue. Hello, (In reply to Tiziano Müller from comment #9) > TBH, at the moment it seems to me like gcc is doing something strange here. > Maybe the x32-porting people have some more insight. > You could also try to set CFLAGS to "-O2" only (without the march) and then > play around with the optimization flags (not only -Ox but the ones enabled > by -O1/-O2) to see which one is causing the issue. So, as requested, I set CFLAGS without the march (but still with "-pipe -ggdb"), and I have the same error and the same backtrace. Unfortunately, I don't understand your request about "play around with the optimization flags (not only -Ox but the ones enabled by -O1/-O2)" Other information, I "succeeded" to rise another segmentation fault simply by executing /usr/sbin/nginx with the wrong right on /var/log/nginx/ (like a simple user). here the backtrace for this error (using -O2): #0 0xf64c1650 in ?? () from /libx32/libc.so.6 #1 0x56575914 in memcpy (__len=2027, __src=<optimized out>, __dest=<optimized out>) at /usr/include/bits/string3.h:51 #2 ngx_vslprintf (buf=<optimized out>, last=<optimized out>, fmt=0x56620a36 "V] ", args=args@entry=0xffffcc6c) at src/core/ngx_string.c:238 #3 0x56575cba in ngx_slprintf (buf=<optimized out>, last=last@entry=0xffffd560 "0", fmt=fmt@entry=0x56620a33 " [%V] ") at src/core/ngx_string.c:139 #4 0x56571237 in ngx_log_error_core (level=level@entry=1, log=<optimized out>, err=0, fmt=fmt@entry=0x5662c4fe "%*s") at src/core/ngx_log.c:104 #5 0x56581cf0 in ngx_conf_log_error (level=level@entry=1, cf=cf@entry=0xffffdd80, err=13, fmt=fmt@entry=0x56620fdc "open() \"%s\" failed") at src/core/ngx_conf_file.c:926 #6 0x56582550 in ngx_conf_parse (cf=cf@entry=0xffffdd80, filename=filename@entry=0x56870df8) at src/core/ngx_conf_file.c:125 #7 0x56580092 in ngx_init_cycle (old_cycle=<optimized out>) at src/core/ngx_cycle.c:264 #8 0x5656fc76 in main (argc=<optimized out>, argv=<optimized out>) at src/core/nginx.c:333 As you can notice, we have the same requests from #4 to #0 between the previous backtrace attachment 380744 [details] and this. Thanks again for support. @Thibaud: are you able to reproduce on newer versions? Please report back, if it's still an issue. |
