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From: Ian Campbell <Ian.Campbell@citrix.com> Under Xen the toolstack is responsible for managing the domains in the system, e.g. creating, destroying, and otherwise manipulating them. To do this it uses a number of ioctls on the /proc/xen/privcmd device. Most of these (the MMAPBATCH ones) simply set things up such that a subsequenct mmap call will map the desired guest memory. Since valgrind has no way of knowing what the memory contains we assume that it is all initialised (to do otherwise would require valgrind to be observing the complete state of the system and not just the given process). The most interesting ioctl is XEN_IOCTL_PRIVCMD_HYPERCALL which allows the toolstack to make arbitrary hypercalls. Although the mechanism here is specific to the OS of the guest running the toolstack the hypercalls themselves are defined solely by the hypervisor. Therefore I have split support for this ioctl into a part in syswrap-linux.c which handles the ioctl itself and passes things onto a new syswrap-xen.c which handles the specifics of the hypercalls themselves. Porting this to another OS should just be a matter of wiring up syswrap-$OS.c to decode the ioctl and call into syswrap-xen.c. In the future we may want to split this into syswrap-$ARCH-xen.c but for now this is x86 only. The hypercall coverage here is pretty small but is enough to get reasonable(-ish) results out of the xl toolstack when listing, creating and destroying domains. One issue is that the hypercalls which are exlusively used by the toolstacks (as opposed to those used by guest operating systems) are not considered a stable ABI, since the hypervisor and the lowlevel tools are considered a matched pair. This covers the sysctl and domctl hypercalls which are a fairly large chunk of the support here. I'm not sure how to solve this without invoking a massive amount of duplication. Right now this targets the Xen unstable interface (which will shortly be released as Xen 4.2), perhaps I can get away with deferring this problem until the first change . On the plus side the vast majority of hypercalls are not of interest to the toolstack (they are used by guests) so we can get away without implementing them. Note: a hypercall only reads as many words from the ioctl arg struct as there are actual arguments to that hypercall and the toolstack only initialises the arguments which are used. However there is no space in the DEFN_PRE_TEMPLATE prototype to allow this to be communicated from syswrap-xen.c back to syswrap-linux.c. Since a hypercall can have at most 5 arguments I have hackily stolen ARG8 for this purpose. git-svn-id: svn://svn.valgrind.org/valgrind/trunk@12963
On 4 Apr 06, the debuginfo reader (m_debuginfo) was majorly cleaned up
and restructured. It has been a bit of a tangle for a while. The new
structure looks like this:
debuginfo.c
readelf.c
readdwarf.c readstabs.c
storage.c
Each .c can only call those below it on the page.
storage.c contains the SegInfo structure and stuff for
maintaining/searching arrays of symbols, line-numbers, and Dwarf CF
info records.
readdwarf.c and readstabs.c parse the relevant kind of info and
call storage.c to store the results.
readelf.c reads ELF format, hands syms directly to storage.c,
then delegates to readdwarf.c/readstabs.c for debug info. All
straightforward.
debuginfo.c is the top-level file, and is quite small.
There are 3 goals to this:
(1) Generally tidy up something which needs tidying up
(2) Introduce more modularity, so as to make it easier to add
readers for other formats, if needed
(3) Simplify the stabs reader.
Rationale for (1) and (2) are obvious.
Re (3), the stabs reader has for a good year contained a sophisticated
and impressive parser for stabs strings, with the aim of recording in
detail the types of variables (I think) (Jeremy's work). Unfortunately
that has caused various segfaults reading stabs info in the past few months
(#77869, #117936, #119914, #120345 and another to do with deeply nested
template types).
The worst thing is that it is the stabs type reader that is crashing,
not the stabs line-number reader, but the type info is only used by
Helgrind, which is looking pretty dead at the moment. So I have lifed
out the type-reader code and put it in UNUSED_STABS.txt for safe
storage, just leaving the line-number reader in place.
If Helgrind ever does come back to life we will need to reinstate the
type storage/reader stuff but with DWARF as its primary target.
Placing the existing stabs type-reader in hibernation improves
stability whilst retaining the development effort/expertise that went
into it for possible future reinstatement.