Re: [Crash-utility] PATCH 00/10] teach crash to work with "live" ramdump
----- Original Message -----
On 04/26, Dave Anderson wrote:
>
> > Ah. Yes, the usage of CRASHBUILTIN is ugly, and I tried to document this.
> >
> > We need the new (say) RAW_MEM_DUMP flag. We can't use RAMDUMP because it
can
> > be set along with KDUMP.
> >
> > And there is no room in pc->flags, so I decided to abuse CRASHBUILTIN for
now.
>
> I understand.
>
> It's exceeding rare that a new dumpfile type, or a new live system accessor in
> this case, gets introduced. When that happens, we can move deprecated leftovers
> from pc->flags to pc->flags2. So for example, all of these can be moved to
> pc->flags2 in one fell swoop:
>
> REM_NETDUMP
> REM_MCLXCD
> REM_LKCD
> REM_S390D
Yes, yes, sure. But while this is trivial, this needs some tiresome changes.
One-time tiresome changes. I should probably do it anyway. They are a
waste of pc->flags space.
and that is what this part of changelog
The usage of CRASHBUILTIN doesn't look nice, we need to cleanup
this logic. I hope we can do this later, and it seems to me that
the usage of MEMORY_SOURCES/DUMPFILE_TYPES needs some cleanups in
any case.
in 9/10 tried to say ;)
CRASHBUILTIN is used to indicate the the Red Hat /dev/crash driver exists and
the kernel module was built into the kernel -- as opposed to having to load the
crash.ko driver. I'm not sure how that is associated with this facility.
Say, memory_page_size(). It does "switch (pc->flags & MEMORY_SOURCES)"
and it
needs the update if we move (say) NETDUMP in pc->flags2. Trivial, but needs
another patch/discussion/etc.
Who said to move NETDUMP? I only suggested the REM_NETDUMP (and the other REM_xxx)
dumpfiles.
Another problem is that there is no simple/clear way to tell fd_init() paths that
we do not need get_live_memory_source/memory_source_init. Unless we set
REMOTE() == T but we should not do this.
So, if REMOTE() is false, fd_init() calls get_live_memory_source() if
pc->dumpfile is NULL. This is not what RAMDUMP need, so 09/10 has to initialize
pc->dumpfile. At the same time memory_source_init() assumes that if
pc->dumpfile must at least exist if it is non-NULL. Perhaps this needs needs
some cleanups too, but this is off-topic right now.
Right, presumably there would need to be a separate "if (QEMU_ACTIVE())" section
in memory_source_init().
Heh ;). and I think fd_init() is simply wrong. The problem is minor
and off-topic
too, I'll report it later (probably with simple fixes tomorrow). But in short,
you can't use /dev/crash unless you are root, and if you root and /dev/crash
is modular then /dev/crash will be removed and the module will be unloaded when
the crash exits, even if it was not loaded/created by crash. Although I need
to verify this, I can be wrong.
Correct. When it's modular (and it isn't any more), the module is unloaded and
/dev/crash is purposely removed. It works as intended.
Dave