On Mon, Feb 03, 2014 at 04:28:06PM +0100, Jean Pihet wrote: > Hi Arun, > > On 22 January 2014 06:15, Arun Sharma <a...@sharma-home.net> wrote: > > On Tue, Jan 21, 2014 at 12:16 AM, Jean Pihet <jean.pi...@linaro.org> wrote: > > > >>>> This is the case when e.g. profiling an ARMv7 binary that runs on an > >>>> ARMv8 (aka AARCH64) platform. > >>> > >>> Why not configure libunwind for ARMv7 in that case? > >>> > >>> I'm trying to understand how is your use case different from using > >>> x86_32 libunwind to do local unwinding on a x86_64 machine. > >> Can you give more details on the use case and how to configure > >> libunwind? > > > > You could either build libunwind on a ARMv7 machine and copy it over > > or setup a 32 bit chroot on a 64 bit kernel and compile libunwind > > inside that. > > > >> The provided patches dynamically detect the target binary > >> address size and parse the debug info accordingly, all that in a > >> single library. > > > > This is generally called cross-unwinding in libunwind lingo. Some > > description here: > > > > http://www.nongnu.org/libunwind/man/libunwind%283%29.html#section_4 > > > >> > >> Note: my use case is to call libunwind from the perf utility in order > >> to unwind from the dwarf info. > >> > > > > You could link in two copies of libunwind into the perf binary: > > * libunwind.a for local (host == target) unwinding > > * libunwind-arm.a for 32 bit cross-unwinding > > > > Doing cross-unwinding requires you to write a bunch of "accessors" on > > how to access the address space of a non-local thread. > > > > Something like ./configure --target=arm on aarch64. > > Thanks for the link and info. > > Is there a concrete example of cross-unwinding with multiple targets, > for example on x86_64 using native and x86_32 libunwind libraries > simultaneously? > I am trying to assess the impact of multiple unwinding libs in the perf code. > > Jiri, Arnaldo, > How is that done on x86? I do not think this can be done with the > current perf code, am I correct?
correct, but it sounds cool ;-) jirka -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
