PING: RFR(S): 8240360: NativeLibraryEvent has wrong library name on Linux
Yasumasa Suenaga
suenaga at oss.nttdata.com
Mon Mar 23 12:25:11 UTC 2020
Hi Denghui,
On 2020/03/23 18:08, Denghui Dong wrote:
> Hi Yasumasa,
>
> Thanks for the review.
>
> I agree with you that it's necessary to filter those lines in which the file is not a shared object by check the exec bit.
> I think we should create another bug to trace the problem that you mentioned.
I filed it:
https://bugs.openjdk.java.net/browse/JDK-8241439
I think we might use dl_iterate_phdr() for the fix. I will try it.
> BTW, Could you sponsor it?
Sure, but you need to get one more reviewer before pushing.
Thanks,
Yasumasa
> Thanks,
> Denghui Dong
>
> ------------------------------------------------------------------
> From:Yasumasa Suenaga <suenaga at oss.nttdata.com>
> Send Time:2020年3月23日(星期一) 16:31
> To:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>; hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net>
> Subject:Re: PING: RFR(S): 8240360: NativeLibraryEvent has wrong library name on Linux
>
> Hi Denghui,
>
> Your change looks good.
>
> However, we might need to update os::get_loaded_modules_info() more.
> Currently, we would get multiple jdk.NativeLibrary events from 1 library 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
> }
>
> :
>
> ```
>
> In addition, we would get the events even if they are not shared library as below:
>
> ```
> jdk.NativeLibrary {
> startTime = 16:59:06.621
> name = "/home/ysuenaga/OpenJDK/jdk/build/linux-x86_64-server-fastdebug/images/jdk/lib/server/cl
> asses.jsa"
> baseAddress = 0x800000000
> topAddress = 0x800007000
> }
> ```
>
> os::get_loaded_modules_info() has introduced in JDK-8056242, and it says this function is for dll/so/dylibs.
> In fact, os::get_loaded_modules_info() uses EnumProcessModules() in Windows.
>
> So I think we need to check exec bit, and merge same library to one event.
> But I think it is another issue, and I'm not sure my think is correct.
>
> Thus I agree with your change now.
>
>
> Thanks,
>
> Yasumasa (ysuenaga)
>
>
> On 2020/03/20 11:12, Denghui Dong wrote:
> > PING: Could you review it?
> >
> > Webrev: http://cr.openjdk.java.net/~ddong/8240360/webrev.01/
> > JBS: https://bugs.openjdk.java.net/browse/JDK-8240360
> >
> > In Linux, EventNativeLibrary has a wrong name if the target library is located in a device whose device number (major or minor) exceeds the range of two digits.
> >
> > My fix is small, use "%*s" to ignore perms, offset and device.
> >
> > --- old/src/hotspot/os/linux/os_linux.cpp 2020-03-10 14:35:41.224134041 +0800
> > +++ new/src/hotspot/os/linux/os_linux.cpp 2020-03-10 14:35:41.090129104 +0800
> > @@ -2078,20 +2078,18 @@
> >
> > // Read line by line from 'file'
> > while (fgets(line, sizeof(line), procmapsFile) != NULL) {
> > - u8 base, top, offset, inode;
> > - char permissions[5];
> > - char device[6];
> > + u8 base, top, inode;
> > char name[sizeof(line)];
> >
> > - // Parse fields from line
> > - int matches = sscanf(line, UINT64_FORMAT_X "-" UINT64_FORMAT_X " %4s " UINT64_FORMAT_X " %5s " INT64_FORMAT " %s",
> > - &base, &top, permissions, &offset, device, &inode, name);
> > - // the last entry 'name' is empty for some entries, so we might have 6 matches instead of 7 for some lines
> > - if (matches < 6) continue;
> > - if (matches == 6) name[0] = '\0';
> > + // Parse fields from line, discard perms, offset and device
> > + int matches = sscanf(line, UINT64_FORMAT_X "-" UINT64_FORMAT_X " %*s %*s %*s " INT64_FORMAT " %s",
> > + &base, &top, &inode, name);
> > + // the last entry 'name' is empty for some entries, so we might have 3 matches instead of 4 for some lines
> > + if (matches < 3) continue;
> > + if (matches == 3) name[0] = '\0';
> >
> > - // Filter by device id '00:00' so that we only get file system mapped files.
> > - if (strcmp(device, "00:00") != 0) {
> > + // Filter by inode 0 so that we only get file system mapped files.
> > + if (inode != 0) {
> >
> > // Call callback with the fields of interest
> > if(callback(name, (address)base, (address)top, param)) {
> >
> >
> > Thanks,
> > Denghui Dong
> >
> >
> >
> > ------------------------------------------------------------------
> > From:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>
> > Send Time:2020年3月10日(星期二) 14:16
> > To:hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net>
> > Subject:Re: RFR(S): 8240360: NativeLibraryEvent has wrong library name on Linux
> >
> > Hi,
> > I used a new way to fix this problem.
> > Ignore "perms", "offset" and "device" fields by "%*s" so that we don't need to be concerned about the length of the device,
> > and use "inode" instead of "device" for filtering.
> >
> > Webrev: http://cr.openjdk.java.net/~ddong/8240360/webrev.01/
> >
> > Could you review it?
> >
> > Thanks,
> > Denghui Dong
> > ------------------------------------------------------------------
> > From:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>
> > Send Time:2020年3月4日(星期三) 12:05
> > To:hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net>
> > Subject:Re: RFR(S): 8240360: NativeLibraryEvent has wrong library name on Linux
> >
> > Testing: jdk/jfr all passed.
> > ------------------------------------------------------------------
> > From:董登辉(卓昂) <denghui.ddh at alibaba-inc.com>
> > Send Time:2020年3月3日(星期二) 22:25
> > To:hotspot-jfr-dev <hotspot-jfr-dev at openjdk.java.net>
> > Subject:RFR(S): 8240360: NativeLibraryEvent has wrong library name on Linux
> >
> > Hi team,
> >
> > I found TestNativeLibrariesEvent is always failed in my Linux environment.
> >
> > The root cause is that os::get_loaded_modules_info in os_linux.cpp can not read library name correctly,
> > because the device number in my Linux environment is 103:01, the format passed to sscanf can't identify
> > it.
> >
> > I found the limit of major and minor device number in Linux from
> > https://github.com/torvalds/linux/blob/master/include/linux/kdev_t.h, and made this patch.
> >
> > Please review this small change that fixes this problem.
> >
> > Bug: https://bugs.openjdk.java.net/browse/JDK-8240360
> > Webrev: http://cr.openjdk.java.net/~ddong/8240360/webrev.00/
> >
> >
> > Thanks
> > Denghui Dong
> >
>
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