[lldb-dev] Do we have any infrastructure for creating mini dump files from a loaded process or from a core file?

Wed Jun 13 15:20:22 PDT 2018

>
> What about the case where you already have a Unix core file and you aren't
> in a debugger but just want to convert it?

Just curious, would a small Python script using the LLDB SB API satisfy
this requirement?

 We could move all the code for consuming and producing Windows minidumps
> and Unix / Mach-O corefiles from LLDB down into LLVMCoreFile, write a
> library like llvm-core that can manipulate or inspect them, then have LLDB
> use it.  Kill 2 birds with one stone that way IMO.
>

I like the idea of factoring out reusable subsystems, and I'd love to see
something along these lines. Just a word of caution though: the hard part
may not be the generation of a "structurally valid" minidump file, but
"parsing" and modeling the process state (figuring out the list of modules
& memory regions, etc. See the Crashpad implementation for details).

On Wed, Jun 13, 2018 at 3:01 PM, Zachary Turner via lldb-dev <
lldb-dev at lists.llvm.org> wrote:

> Yea, I think something like this would actually make a useful llvm
> utility.  Call it llvm-core or something, and it links against the library
> LLVMCoreFile.  We could move all the code for consuming and producing
> Windows minidumps and Unix / Mach-O corefiles from LLDB down into
> LLVMCoreFile, write a library like llvm-core that can manipulate or inspect
> them, then have LLDB use it.  Kill 2 birds with one stone that way IMO.
>
> On Wed, Jun 13, 2018 at 2:56 PM Jason Molenda <jmolenda at apple.com> wrote:
>
>> fwiw I had to prototype a new LC_NOTE load command a year ago in Mach-O
>> core files, to specify where the kernel binary was located.  I wrote a
>> utility to add the data to an existing corefile - both load command and
>> payload - and it was only about five hundred lines of C++.  I didn't link
>> against anything but libc, it's such  a simple task I didn't sweat trying
>> to find an object-file-reader/writer library.  ELF may be more complicated
>> though.
>>
>> > On Jun 13, 2018, at 2:51 PM, Zachary Turner via lldb-dev <
>> lldb-dev at lists.llvm.org> wrote:
>> >
>> > What about the case where you already have a Unix core file and you
>> aren't in a debugger but just want to convert it?  It seems like we could
>> have a standalone utility that did that (one could imagine doing the
>> reverse too).  I'm wondering if it wouldn't be possible to do this as a
>> library or something that didn't have any dependencies on LLDB, that way a
>> standalone tool could link against this library, and so could LLDB.  I
>> think this would improve its usefulness quite a bit.
>> >
>> > On Wed, Jun 13, 2018 at 2:42 PM Greg Clayton <clayborg at gmail.com>
>> wrote:
>> > The goal is to take a live process (regular process just stopped, or a
>> core file) and run "save_minidump ..." as a command and export a minidump
>> file that can be sent elsewhere. Unix core files are too large to always
>> send and they are less useful if they are not examined in the machine that
>> they were produced on. So LLDB gives us the connection to the live process,
>> and we can then create a minidump file. I am going to create a python
>> module that can do this for us.
>> >
>> > Greg
>> >
>> >
>> >> On Jun 13, 2018, at 2:29 PM, Zachary Turner via lldb-dev <
>> lldb-dev at lists.llvm.org> wrote:
>> >>
>> >> Also, if the goal is to have this upstream somewhere, it would be nice
>> to have a tool this be a standalone tool.  This seems like something that
>> you shouldn't be required to start up a debugger to do, and probably
>> doesn't have many (or any for that matters) on the rest of LLDB.
>> >>
>> >> On Wed, Jun 13, 2018 at 1:58 PM Leonard Mosescu <mosescu at google.com>
>> wrote:
>> >> That being said, it's not exactly trivial to produce a good minidump.
>> Crashpad has a native & cross-platform minidump writer, that's what I'd
>> start with.
>> >>
>> >> Addendum: I realized after sending the email that if the goal is to
>> convert core files -> LLDB -> minidump a lot of the complexity found in
>> Crashpad can be avoided, so perhaps writing an LLDB minidump writer from
>> scratch would not be too bad.
>> >>
>> >> On Wed, Jun 13, 2018 at 1:50 PM, Leonard Mosescu <mosescu at google.com>
>> wrote:
>> >> The minidump format is more or less documented in MSDN.
>> >>
>> >> That being said, it's not exactly trivial to produce a good minidump.
>> Crashpad has a native & cross-platform minidump writer, that's what I'd
>> start with.
>> >>
>> >> On Wed, Jun 13, 2018 at 1:38 PM, Adrian McCarthy via lldb-dev <
>> lldb-dev at lists.llvm.org> wrote:
>> >> Zach's right.  On Windows, lldb can produce a minidump, but it just
>> calls out to a Microsoft library to do so.  We don't have any
>> platform-agnostic code for producing a minidump.
>> >>
>> >> I've also pinged another Googler who I know might be interested in
>> converting between minidumps and core files (the opposite direction) to see
>> if he has any additional info.  I don't think he's on lldb-dev, though, so
>> I'll act as a relay if necessary.
>> >>
>> >> On Wed, Jun 13, 2018 at 12:07 PM, Zachary Turner via lldb-dev <
>> lldb-dev at lists.llvm.org> wrote:
>> >> We can’t produce them, but you should check out the source code of
>> google breakpad / crashpad which can.
>> >>
>> >> That said it’s a pretty simple format, there may be enough in our
>> consumer code that should allow you to produce them
>> >>
>> >>
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