RFR(xs): 8216559: [JFR] Native libraries not correctly parsed from /proc/self/maps

[Severin Gehwolf]

Hi,

On Fri, 2019-01-11 at 08:43 -0800, Markus Gronlund wrote:
> Hi Severin,
> 
> Looks good, thanks for fixing.

Thanks for the review, Markus!

Any other reviewers or is this trivial enough for me to push with 1
review?

Thanks,
Severin

> Markus
> 
> -----Original Message-----
> From: Severin Gehwolf <sgehwolf at redhat.com> 
> Sent: den 11 januari 2019 14:35
> To: hotspot-dev <hotspot-dev at openjdk.java.net>; 
> hotspot-jfr-dev at openjdk.java.net
> Subject: RFR(xs): 8216559: [JFR] Native libraries not correctly
> parsed from /proc/self/maps
> 
> Hi,
> 
> Could I please get a review of this tiny fix for native libraries
> parsing from /proc/<pid>/maps? It's a Linux-only change and seems to
> surface only on certain systems (with 3-digit device ids in /proc).
> The issue has been noticed since TestNativeLibrariesEvent.java was
> failing for me.
> 
> What's the problem? The Linux impl of os::get_loaded_modules_info
> reads /proc/self/maps and scans each line into variables via
> sscanf(). The format for the device pointer allowed up to 5
> characters. In my case it was 6 characters long. As a result, the
> last digit of the device id got interpreted as inode value and the
> inode value as name. Thus, the failing test was showing strange
> library names like "25847051".
> 
> According to the spec, major:minor device numbers may be up to 3-
> digits in length. Hence, I propose to change the format from '%5s' to
> '%7s': 3 digits for major/minor each, plus one for ':'.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8216559
> webrev: 
> http://cr.openjdk.java.net/~sgehwolf/webrevs/JDK-8216559/webrev.01/
> 
> Testing: jdk_jfr tests on Linux x86_64 including
> TestNativeLibrariesEvent.java
>          which now passes.
> 
> Thoughts?
> 
> Thanks,
> Severin
>