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Re: arm64 kprobes/systemtap support progress
- From: William Cohen <wcohen at redhat dot com>
- To: systemtap at sourceware dot org
- Cc: "dave. >> Dave Long" <dave dot long at linaro dot org>
- Date: Wed, 05 Nov 2014 12:12:49 -0500
- Subject: Re: arm64 kprobes/systemtap support progress
- Authentication-results: sourceware.org; auth=none
- References: <54569BF6 dot 7070909 at redhat dot com>
On 11/02/2014 04:02 PM, William Cohen wrote:
> Hi All,
>
> Dave Long has been working on getting arm64 kprobes support merged into the upstream kernels. The kprobes64 branch of the git tree at
> https://git.linaro.org/people/dave.long/linux.git
>
A bit more poking around with the arm64 kprobe support and found that it does not work well with smp at the moment. There appears to be some issues in linux/arch/arm64/kernel/insn.c and getting the processors to patch in the kprobe breakpoint. After booting the machine in uniprocessor mode (kernel boot parameter maxcpus=1) the kprobes were much more stable. I was able to run the systemtap syscall tests with:
make installcheck RUNTESTFLAGS="--debug systemtap.syscall/*syscall.exp"
There were a lot of failures on arm64 due to a number of the syscalls being remapped. An incomplete list of the syscall mappings:
open -> openat
chmod -> fchmodat
chown -> fchown
lchown -> fchownat
mkdir -> mkdirat
rmdir -> unlinkat
dup2 -> dup3
inotify_init -> inotify_init1
link -> linkat
readlink -> readlinkat
symlink -> symlinkat
Thus, get the following mediocre results from the syscall tests:
=== systemtap Summary ===
# of expected passes 110
# of unexpected failures 70
# of untested testcases 2
# of unsupported tests 4
I am getting more adventurous and trying to run more of the systemtap testsuite to see what other things are not right on arm64.
-Will