Re: RFR: 8241439: jdk.NativeLibraryEvent hooks all opened regular files

[Denghui Dong]

Hi Yasumasa,

I have another question:
if a module is loaded into several discontinuous segments, I think this patch can't cover this situation, am I right?

Denghui


------------------------------------------------------------------
From:Yasumasa Suenaga <suenaga at oss.nttdata.com>
Send Time:2020年4月9日(星期四) 17:05
To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>; Hotspot dev runtime <hotspot-runtime-dev at openjdk.java.net>; hotspot-jfr-dev at openjdk.java.net <hotspot-jfr-dev at openjdk.java.net>; hotspot-jfr-dev <hotspot-jfr-dev-bounces at openjdk.java.net>
Cc:yasuenag at gmail.com <yasuenag at gmail.com>
Subject:Re: RFR: 8241439: jdk.NativeLibraryEvent hooks all opened regular files

Hi Denghui,

Thank you for the comment.
I uploaded new webrev:

   http://cr.openjdk.java.net/~ysuenaga/JDK-8241439/webrev.01/

On 2020/04/09 17:11, Denghui Dong wrote:
> Hi Yasumasa,
> I'm not a reviewer, but the following code looks strange:
> =====
> 2096       if ((base == NULL) && (base < phdr_base)) {
> =====
> 
> if the condition is right, it could be simplified: if (base < phdr_base),
> but IMO, the correct condition should be if (base > phdr_base), I may be wrong. ��

You are right, condition should be (base > phdr_base). We need to store base address to `base` from all PT_LOAD header.
So NULL check is needed because (base > phdr_base) always false without it.


Thanks,

Yasumasa


> Thanks,
> Denghui
> ------------------------------------------------------------------
> From:Yasumasa Suenaga <suenaga at oss.nttdata.com>
> Send Time:2020年4月9日(星期四) 15:01
> To:Hotspot dev runtime <hotspot-runtime-dev at openjdk.java.net>; hotspot-jfr-dev at openjdk.java.net <hotspot-jfr-dev at openjdk.java.net>
> Cc:yasuenag at gmail.com <yasuenag at gmail.com>
> Subject:RFR: 8241439: jdk.NativeLibraryEvent hooks all opened regular files
> 
> Hi all,
> 
> Please review this change:
> 
>     JBS: https://bugs.openjdk.java.net/browse/JDK-8241439
>     webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8241439/webrev.00/
> 
> HotSpot has os::get_loaded_modules_info() to get all loaded native libraries, however it would call callback in twice on same library on Linux. Also it would call callback even if the file is not a library.
> 
> We can see this problem in jdk.NativeLibrary JFR event as below:
> 
> 
> ```
> jdk.NativeLibrary {
>      startTime = 16:59:06.621
>      name = "/usr/lib64/libc-2.30.so"
>      baseAddress = 0x7FDB06ACC000
>      topAddress = 0x7FDB06AF1000
> }
> 
> jdk.NativeLibrary {
>      startTime = 16:59:06.621
>      name = "/usr/lib64/libc-2.30.so"
>      baseAddress = 0x7FDB06AF1000
>      topAddress = 0x7FDB06C40000
> }
> 
>       :
> 
> ```
> 
> ```
> jdk.NativeLibrary {
>      startTime = 16:59:06.621
>      name = "/home/ysuenaga/OpenJDK/jdk/build/linux-x86_64-server-fastdebug/images/jdk/lib/server/classes.jsa"
>      baseAddress = 0x800000000
>      topAddress = 0x800007000
> }
> ```
> 
> This change uses dl_iterate_phdr() to get them, so these problem has gone.
> 
> 
> Thanks,
> 
> Yasumasa
>