Hi Will, On Monday 05 January 2015 09:36 PM, William Cohen wrote:
Hi All, Pratyush has been implementing uprobes support for aarch64 and has posted a set of patches (http://comments.gmane.org/gmane.linux.ports.arm.kernel/382237) for review. The really new Linux kernels requires a patch to the systemtap runtime because the f_dentry macro has been removed. With the patched systemtap I was able to run the systemtap testsuite and get some test results exercising the uprobes support: https://web.elastic.org/~dejazilla/viewsummary.php?summary=%3D%27%3C54A9E21C.2080504%40redhat.com%3E%27 There looked to be a localized fixes for plt support to eliminate the unsupported systemtap.base/list.exp plt-* tests. A number of the tests appear to fail because of userspace arguments cannot be found for sdt probes. The uprobe patches still need some refinement. On a number of systemtap "make installcheck" runs the kernel would get stuck spewing out: Unexpected kernel single-step exception at EL1
There are at least two functions of arm64/uprobe implementation uprobe_breakpoint_handler and uprobe_single_step_handler, where a kprobe insertion might be causing above issue. Currently I have qualified these functions with __kprobe, so that one can not insert a kprobe there. With this you should not be able to see the above message.
However, I am still investigating if a kprobe insertion be allowed to these functions or any other function which is called directly from debug exception handler (do_debug_exception)
Update code is here: https://github.com/pratyushanand/linux.git : ml_arm64_uprobe_devel_v2 ~Pratyush
However, things are looking better for user-space probing on arm64. -Will
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