I'm new in plugin ecosystem, so I have some misunderstanding. You wrote that to comprehend mutexes we just need a data formatter, but how can we get the raw data of all mutexes in our OS? I thought I was supposed to write a generic code that will use a user-defined (specific for each OS) way to collect all mutexes and then use some data formatter to show them.
On Thu, Nov 1, 2018 at 2:31 AM Jim Ingham <jing...@apple.com> wrote: > As Jason pointed out, we also have the SystemRuntime Plugin. That is > intended to provide extra runtime available information based on the > current system. For instance, on Darwin we use it to present the > libdispatch queue view of threads on the system, and to decorate threads > that are doing work on behalf of some queue with the state of the thread > that enqueued the work at the time the work item was enqueued. > > If for instance you had a way to gather all the locks in the process > (something we've been asked to do but I don't know how to do it on > Darwin...), that would be the place to put that functionality. > > Jim > > > > On Oct 31, 2018, at 4:05 PM, Jim Ingham via lldb-dev < > lldb-dev@lists.llvm.org> wrote: > > > > Right now, the OS plugin only supports the job of adding threads. And > that makes more sense as a plugin, because for instance if you had a > cooperative threading scheme that you were laying on top of the system > threads in a User Space process, you can use the Operating System plugin to > show you the cooperative threads. This is not an abstract example... I > think it should stay with just that job. > > > > The place where lldb holds this sort of knowledge is supposed to be in > the Platform class. So for instance, to comprehend mutexes you really just > need a data formatter. The trick is that it has to be a data formatter > that is provided by the platform. Similarly you want to have frame > recognizers for interesting lower-level calls in the system. The machinery > will shortly be there to do that, but loading the particular recognizers > will either need to be done by hand, or coordinated by the Platform. In > general, I think most of the kinds of re-presentation you need to do to > make OS objects and processes more comprehensible can be built as general > mechanisms like the above. Then the Platform can coordinate providing the > set of more general transformations that are appropriate to the Platform > you are targeting. > > > > Jim > > > > > > > >> On Oct 31, 2018, at 3:44 PM, Alexander Polyakov <polyakov....@gmail.com> > wrote: > >> > >> So, if I understand you write, I can look at OS plugin and add a > support of mutexes or memory pages for example? > >> > >> чт, 1 нояб. 2018 г. в 1:05, Jim Ingham <jing...@apple.com>: > >> lldb has one feature - the "Operating System Plugin" that is > specifically designed for debugging threads in kernel contexts. The OS > plugin allows a kernel to present it's notion of threads into > lldb_private::Threads. The xnu kernel macros have an implementation of > this, as do some other embedded OS'es. lldb actually gets used pretty > extensively for debugging xnu - the Darwin kernel. > >> > >> Kuba is adding the notion of "Frame recognizers" which can give > significance to particular functions when they appear on the stack (for > instance displaying the first argument of read, etc. as a file handle even > if you have no debug information for it.) That's another way that you > could express your understanding of the OS you are running on for debugger > users. Greg wrote a data formatter for the Darwin implementation of > pthread_mutex that shows the thread that has the lock and some other > information like that. So data formatters are also a way lldb can express > knowledge of the host OS. > >> > >> Jim > >> > >>> On Oct 31, 2018, at 12:52 PM, Leonard Mosescu via lldb-dev < > lldb-dev@lists.llvm.org> wrote: > >>> > >>> Conceptually it's different levels of abstraction: a user-mode > debugger handles processes, threads as first class concepts. In kernel-mode > (or kernel land), these are just data structures that the code (the kernel) > is managing. From a more pragmatic perspective, the difference is in where > the debugging hooks are implemented and what interfaces are exposed (for > example a kernel mode debugger can normally "poke" around any piece of > memory and it has to be aware of things like VA mappings, while a user-mode > debugger is only allowed to control a limited slice of the system - ex. > control a sub-process through something like ptrace) > >>> > >>> Unless you're specifically looking at kernel debugging I'd stay away > from that. For one thing, LLDB is mostly used as an user-mode debugger so > the impact of any improvements would be bigger. > >>> > >>> Regarding the value of OS-awareness for user-mode debugging, I agree > with Zach - for example windbg provides both kernel mode and user mode > !locks commands. The only suggestion I'd add is to consider an expanded > view of the "OS" to include runtime components which may not be technically > part of what most people think of as the "OS": user-mode loaders and high > level things like std::mutex, etc. > >>> > >>> On Wed, Oct 31, 2018 at 12:29 PM, Alexander Polyakov < > polyakov....@gmail.com> wrote: > >>> Looks like I don't completely understand what is the difference > between user-mode and kernel-mode from the debugger's point of view. Could > you please explain me this? > >>> > >>> On Wed, Oct 31, 2018 at 10:22 PM Zachary Turner <ztur...@google.com> > wrote: > >>> I don’t totally agree with this. I think there are a lot of useful os > awareness tasks in user mode. For example, you’re debugging a deadlock and > want to understand the state of other mutexes, who owns them, etc. or you > want to examine open file descriptors. In the case of a heap corruption you > may wish to study the internal structures of your process’s heap, or even > lower level, the os virtual memory page table structures. > >>> > >>> There’s quite a lot you can still do in user mode, but definitely > there is more in kernel mode. As Leonard said, try put WinDbg as a lot of > this stuff already exists so it’s a good reference > >>> On Wed, Oct 31, 2018 at 12:08 PM Alexander Polyakov via lldb-dev < > lldb-dev@lists.llvm.org> wrote: > >>> Hi Leonard, > >>> > >>> I think it will be kernel-mode debugging since debugging an > application in user mode is not an OS awareness imo. Of course, some of > kernel's modules might run in user-mode, but it will be ok I think. > >>> > >>> Thanks for your reference, I'll take a look at it. > >>> > >>> Also, I found out that ARM supports OS awareness in their DS-5 > debugger. They have a mechanism for adding new operating systems. All you > need to do is to describe OS' model (thread's or task's structure for > example). I think that is how it might be done in LLDB. > >>> > >>> On Wed, Oct 31, 2018 at 9:26 PM Leonard Mosescu <mose...@google.com> > wrote: > >>> Hi Alexander, are you interested in user-mode, kernel-mode debugging > or both? > >>> > >>> Fore reference, the current state of the art regarding OS-awareness > debugging is debugging tools for windows (windbg & co.). This is not > surprising since the tools were developed alongside Windows. Obviously they > are specific to Windows, but it's good example of how the OS-awareness > might look like. > >>> > >>> > >>> On Mon, Oct 29, 2018 at 11:37 AM, Alexander Polyakov via lldb-dev < > lldb-dev@lists.llvm.org> wrote: > >>> Hi lldb-dev, > >>> > >>> I'm a senior student at Saint Petersburg State University. The one of > my possible diploma themes is "OS Awareness in LLDB". Generally, the OS > awareness extends a debugger to provide a representation of the OS threads > - or tasks - and other relevant data structures, typically semaphores, > mutexes, or queues. > >>> > >>> I want to ask the community if OS awareness is interesting for LLDB > users and developers? The main goal is to create some base on top of LLDB > that can be extended to support awareness for different operating systems. > >>> > >>> Also, if you have a good article or other useful information about OS > awareness, please share it with me. > >>> > >>> Thanks in advance! > >>> > >>> -- > >>> Alexander > >>> > >>> _______________________________________________ > >>> lldb-dev mailing list > >>> lldb-dev@lists.llvm.org > >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev > >>> > >>> > >>> > >>> > >>> -- > >>> Alexander > >>> _______________________________________________ > >>> lldb-dev mailing list > >>> lldb-dev@lists.llvm.org > >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev > >>> > >>> > >>> -- > >>> Alexander > >>> > >>> _______________________________________________ > >>> lldb-dev mailing list > >>> lldb-dev@lists.llvm.org > >>> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev > >> > >> -- > >> Alexander > > > > _______________________________________________ > > lldb-dev mailing list > > lldb-dev@lists.llvm.org > > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev > > -- Alexander
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