RFR(M): 8140482: Various minor code improvements (runtime)

[Lindenmaier, Goetz]

Oh, sure, this is to be removed.
I updated the webrev in-place.
http://cr.openjdk.java.net/~goetz/webrevs/8140482-covRt/webrev.04/

Best regards,
  Goetz.



> -----Original Message-----
> From: Dmitry Samersoff [mailto:dmitry.samersoff at oracle.com]
> Sent: Freitag, 6. November 2015 18:56
> To: Lindenmaier, Goetz; 'hotspot-runtime-dev at openjdk.java.net'
> Subject: Re: RFR(M): 8140482: Various minor code improvements (runtime)
> 
> Goetz,
> 
> Looks good for me except one small nit:
> 
> os_linux.cpp: 5937 is not necessary.
> 
> -Dmitry
> 
> On 2015-11-06 19:18, Lindenmaier, Goetz wrote:
> > Hi,
> >
> > Thanks for looking at this again!
> > New webrev:
> > http://cr.openjdk.java.net/~goetz/webrevs/8140482-covRt/webrev.04/
> >
> > I copied out the remaining issues,
> > Hope this makes the mail better readable:
> >
> >>>> 2. ps_core.c
> >>
> >> If you don't trust ELF header, it might be better to write
> >>
> >> 822 interp_name[exec_php->p_filesz] = '\0';
> > Done.
> > I figured the function is indented by 3, I fixed that, too.
> >
> >>>> os_linux.cpp
> >>
> >> It might be better to further refactor this code to avoid scanner
> complains.
> >>
> > Yes that's a good idea.  I also return early if the file was not opened,
> > and only do core_pattern[ret] = '\0'; in the else branch.
> >
> >>>> xmlstream.cpp:
> >>>>
> >>>> 354:
> >>
> >> Could you add
> >>  int format_len == strlen(format);
> >> and then use memcpy and calculated offsets/sizes here instead of strn* ?
> >
> > I optimized it. One strlen is sufficient.
> >
> > I also ran another scan, which is fine.
> >
> > Best regards,
> >   Goetz.
> >
> >
> >
> >> -----Original Message-----
> >> From: Dmitry Samersoff [mailto:dmitry.samersoff at oracle.com]
> >> Sent: Freitag, 6. November 2015 11:27
> >> To: Lindenmaier, Goetz; 'hotspot-runtime-dev at openjdk.java.net'
> >> Subject: Re: RFR(M): 8140482: Various minor code improvements
> (runtime)
> >>
> >> Goetz,
> >>
> >> Thank you for this work.
> >>
> >> Please, see below inline.
> >>
> >>
> >> On 2015-11-06 00:36, Lindenmaier, Goetz wrote:
> >>> Hi Dmitry,
> >>>
> >>> Finally I have a new webrev:
> >>> http://cr.openjdk.java.net/~goetz/webrevs/8140482-covRt/webrev.03/
> >>> I ran the scan again, twice, which take a while.  See coments below.
> >>>
> >>>> 1. libproc_impl.c
> >>>>
> >>>> it might be better to check that strlen(alt_root) + strlen(name) is less
> >>>> than PATH_MAX at ll. 50 and return an error. Then we can safely leave
> >>>> strcat staff as it is.
> >>> Yes, that would look better, but the scan does not grok it. It still
> >>> complains: "You might overrun the 4097 byte fixed-size string alt_path
> by
> >> copying s without checking the length."
> >>> I would like to keep my changes.
> >>
> >> OK.
> >>
> >>>
> >>>> 2. ps_core.c
> >>>>
> >>>> if interpreter name is truncated for some reason, we have no chance to
> >>>> open it and can't continue.
> >>>>
> >>>> So it might be better to check if exec_php->p_filesz > BUF_SIZE and
> >>>> return an error immediately.
> >>>>
> >>>> Also, please add a comment that BUF_SIZE is (PATH_MAX +
> NAME_MAX
> >> + 1)
> >>> I added what you asked for.  But that does not solve my issue. If there is
> >>> no nul in ph->core->exec_fd the code fails.  So I also left my code in
> there.
> >>
> >> If you don't trust ELF header, it might be better to write
> >>
> >> 822 interp_name[exec_php->p_filesz] = '\0';
> >>
> >>
> >>>> 3. os_linux.cpp
> >>>>
> >>>> 4257:
> >>>>
> >>>> I'm OK with this change but we should revisit the use of MAXSIGNUM
> >> under
> >>>> Linux and probably define it to _NSIG for the rest of VM
> >>> I opened an extra issue for this (for the change in SR_initialize() I
> removed.)
> >>> https://bugs.openjdk.java.net/browse/JDK-8141529
> >>
> >> OK
> >>
> >>>
> >>>> 5944:
> >>>>
> >>>> What is the reason of the change? core_pattern is initialized to zero at
> >>>> ll. 5939.
> >>> If the file is corrupted, there might be more than 128 chars in it.
> >>>
> >>>> It might be better to check that ret is less than corep_pattern_len and
> >>>> then use ret instead of strlen at ll. 5948
> >>
> >>> That's a good point.  It also saves the cost of strlen(). I now return if
> >>> too many chars were read.
> >>> But with removing writing \'0' the scan now complains, again:
> >> "string_null_argument: Function read does not terminate string
> >> *core_pattern.",
> >>> And further down at the next strlen: "Passing unterminated string
> >> core_pattern to strlen, which expects a null-terminated string."
> >>> I'd like to add the \'0' again.
> >>
> >> It might be better to further refactor this code to avoid scanner
> complains.
> >>
> >> 5937:
> >>
> >> if (ret <= 0 || ret >= core_pattern_len || *core_pattern == '\n') {
> >>    return -1;
> >> }
> >>
> >> after that ifs at 5942 and 5991 is not necessary and we can make scanner
> >> happy as
> >>
> >> 5943
> >>
> >> core_pattern[ret] = '\0';
> >> if (core_pattern[ret-1] == '\n') core_pattern[ret-1] = '\0'
> >>
> >>
> >>>> deoptimization.cpp:
> >>>>
> >>>> 2085, 2182:
> >>>>
> >>>> jio_snprintf always return -1 and always null-terminate string in case
> >>>> of overflow.  So original code is incorrect and we can just remove it.
> >>> Good point.  I think I fixed jio_snprintf at some point :) Should have
> known.
> >>
> >> OK.
> >>
> >> PS:
> >> Be careful fixing jio_snprintf because posix versions of vsnprintf
> >> returns the number of charаcters to be written but windows version
> >> returns -1 in case of overflow
> >>
> >> Correct solution that uses vsnptrinf(NULL, 0 ... ) and _vscprintf to
> >> check overflow explicitly obviously will have performance impact.
> >>
> >>
> >>>
> >>>> attachListener.hpp:
> >>>>
> >>>> 125,143:
> >>>>
> >>>> It might be better to calculate strlen(name) once, than use memcpy.
> >>> Fixed.
> >>
> >> OK.
> >>
> >>>
> >>>> heapDumper.cpp:
> >>>>
> >>>> 1983:
> >>>>
> >>>>    we checked that HeapDumpPath fits in the buffer at ll 1973, so we can
> >>>> safely use strcpy() here.
> >>> I had removed my fix as David asked for it. I change it to strcpy.
> >>
> >> OK.
> >>
> >>>
> >>>> xmlstream.cpp:
> >>>>
> >>>> 354:
> >>>>
> >>>>    What is the reason of this change? we checked that string fits to
> >>>> buffer at ll 348.
> >>> A guarantee can be overruled with SuppressErrorAt. Also in the opt
> build.
> >>> So the code is also reachable with bad values.
> >>
> >> This code is executed in a loop so I would prefer to don't have extra
> >> strlen calls here.
> >>
> >> Could you add
> >>
> >>  int format_len == strlen(format);
> >>
> >> and then use memcpy and calculated offsets/sizes here instead of strn* ?
> >>
> >> -Dmitry
> >>
> >>
> >>> Best regards,
> >>>   Goetz.
> >>>
> >>>
> >>>>
> >>>> -Dmitry
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>>> On 2015-10-27 10:39, Lindenmaier, Goetz wrote:
> >>>>> Hi,
> >>>>>
> >>>>> SAP requires us to fix a row of issues in hotspot.  I'd like to share these
> >>>>> with openjdk:
> >>>>> http://cr.openjdk.java.net/~goetz/webrevs/8140482-
> covRt/webrev.00
> >>>>>
> >>>>> Please review this change.  I please need a sponsor.
> >>>>>
> >>>>> The fixes in detail:
> >>>>>
> >>>>> libproc_impl.c:
> >>>>> Do strncpy in case getenv returned a bad string.
> >>>>> Strcat could overflow the buffer. Use strncat instead.
> >>>>>
> >>>>> ps_core.c:
> >>>>> Pread not necessarily terminates interp_name which is printed
> >> thereafter.
> >>>>> Increase buffer size by 1 and add '\0'.
> >>>>>
> >>>>> stubRoutines_x86.cpp:
> >>>>> Cast to proper type. This way, left and right of '&' have the same type.
> >>>>>
> >>>>> attachListener_linux.cpp:
> >>>>> Read does not terminate buf. Size for '\0' is already considered.
> >>>>>
> >>>>> os_linux.cpp:
> >>>>> Array sigflags[] has size MAXSIGNUM==32.  _NSIG is bigger than
> >>>>> MAXSIGNUM (_NSIG == 65 on my machine).
> >>>>> sig is checked to be smaller than _NSIG. Later, in set_our_sigflags(),
> >>>>> sig is used to access sigflags[MAXSIGNUM] which can overflow the
> array.
> >>>>> Should we also increase MAXSIGNUM?
> >>>>> os::get_core_path(): read does not terminate string, but strlen is
> >>>>> called on it.  The size already foresees one char for the '\0' byte.
> >>>>>
> >>>>> codeBuffer.cpp:
> >>>>> New_capacity is not initialized. Figure_expanded_capacities() handles
> >> this
> >>>>> correctly, but initializing this is cheap and safe.
> >>>>>
> >>>>> dict.cpp:
> >>>>> If j-- is executed for j==0, the loop aborts because j is unsigned (0-- >=
> b-
> >>>>> _cnt).
> >>>>> Instead, only do j++ if necessary.
> >>>>>
> >>>>> generateOopMap.cpp:
> >>>>> Idx is read from String. This is only called with constant strings, so
> >> compare
> >>>>> should be folded away by optimizing compilers if inlined.
> >>>>>
> >>>>> deoptimization.cpp:
> >>>>> If buflen == 0, buf[-1] is accessed.
> >>>>>
> >>>>> task.cpp:
> >>>>> Fatal can return if -XX:SuppressErrorAt is used. Just don't access the
> >>>>> array in this case.
> >>>>>
> >>>>> attachListener.hpp:
> >>>>> Do strncpy to not overflow buffer. Don't write more chars than
> before.
> >>>>>
> >>>>> heapDumper.cpp:
> >>>>> strncpy does not null terminate.
> >>>>>
> >>>>>
> >>>>> Some of these, as the issue in codeBuffer.cpp, are actually handled
> >>>> correctly.
> >>>>> Nevertheless this is not that obvious so that somebody changing the
> >> code
> >>>>> Could oversee he has to add the initialization.
> >>>>>
> >>>>> Some of these fixes are part of SAP JVM for a long time.  This change
> has
> >>>>> been tested with our nightly build of openJDK.
> >>>>>
> >>>>> Best regards,
> >>>>>   Goetz,.
> >>>>>
> >>>>
> >>>>
> >>>> --
> >>>> Dmitry Samersoff
> >>>> Oracle Java development team, Saint Petersburg, Russia
> >>>> * I would love to change the world, but they won't give me the
> sources.
> >>
> >>
> >> --
> >> Dmitry Samersoff
> >> Oracle Java development team, Saint Petersburg, Russia
> >> * I would love to change the world, but they won't give me the sources.
> 
> 
> --
> Dmitry Samersoff
> Oracle Java development team, Saint Petersburg, Russia
> * I would love to change the world, but they won't give me the sources.