Recent aarch64 kprobes and uprobes patch systemtap testing

[David Long]

On 12/10/2015 03:24 PM, William Cohen wrote:
> Hi All,
>
> Dave Long and Pratyush Anand have been working on kprobe and uprobe patches for aarch64.  I have built a local version the uprobe/upstream_arm64_devel branch of https://github.com/pratyushanand/linux which includes those patches in a linux-4.4.0-rc3 kernel.
>
> The tests seemed to run fairly well and the results have been uploaded to dejazilla:
>
> https://web.elastic.org/~dejazilla/viewsummary.php?summary=%3D%27%3C56698DCC.3090207%40redhat.com%3E%27
>
> 		=== systemtap Summary ===
>
> # of expected passes		6096
> # of unexpected failures	111
> # of unexpected successes	2
> # of expected failures		333
> # of unknown successes		2
> # of known failures		89
> # of untested testcases		97
> # of unsupported tests		27
> runtest completed at Thu Dec 10 05:54:32 2015
>
>
> There are still some areas needing for for aarch64 such as stack backtrace support.
>
> The following failure looks suspect because the child process died:
>
>
> spawn stap -g ./systemtap.examples/process/threadstacks.stp -Gsize=65536 -c /root/systemtap_write/systemtap/testsuite/pthread_stacks.x 1024 0 -d /root/systemtap_write/systemtap/testsuite/pthread_stacks.x
>
> pthread_stacks.x: ./systemtap.base/pthread_stacks.c:67: main: Assertion `rc == 0' failed.
>
> WARNING: Child process exited with signal 6 (Aborted)
>
> pthread_stacks.[3567] overwrote __default_stacksize@0x3ffb3be4338 (8388608->65536)
>
> WARNING: /root/systemtap_write/install/bin/staprun exited with status: 1
>
> Pass 5: run failed.  [man error::pass5]
>
> FAIL: pthread_stacks -Gsize (0 0)
>
> The fslatency-nd and fsslower-nd tests need further investigation:
>
> PASS: ./systemtap.examples/lwtools/fslatency-nd build
> meta taglines 'test_installcheck: stap fslatency-nd.stp 1 1' tag 'test_installcheck' value 'stap fslatency-nd.stp 1 1'
> attempting command stap fslatency-nd.stp 1 1
> OUT ERROR: read fault [man error::fault] at 0x0000000000000034 (addr) near operator '@cast' at fslatency-nd.stp:66:15
> Tracing FS sync reads and writes... Output every 1 secs.
> WARNING: Number of errors: 1, skipped probes: 1
> WARNING: /root/systemtap_write/install/bin/staprun exited with status: 1
> Pass 5: run failed.  [man error::pass5]
> child process exited abnormally
> RC 1
> FAIL: ./systemtap.examples/lwtools/fslatency-nd run
>
> PASS: ./systemtap.examples/lwtools/fsslower-nd build
> meta taglines 'test_installcheck: stap fsslower-nd.stp -c "sleep 1"' tag 'test_installcheck' value 'stap fsslower-nd.stp -c "sleep 1"'
> attempting command stap fsslower-nd.stp -c "sleep 1"
> OUT ERROR: read fault [man error::fault] at 0x0000000000000034 (addr) near operator '@cast' at fsslower-nd.stp:68:15
> Tracing FS sync reads and writes slower than 10 ms... Hit Ctrl-C to end.
> TIME     PID    COMM             FUNC           SIZE     LAT(ms)
> WARNING: Number of errors: 1, skipped probes: 1
> WARNING: /root/systemtap_write/install/bin/staprun exited with status: 1
> Pass 5: run failed.  [man error::pass5]
> child process exited abnormally
> RC 1
> FAIL: ./systemtap.examples/lwtools/fsslower-nd run
>
>
> Also a number of network tests failed like the following
>
>
> TEST PWD=/root/systemtap_write/systemtap/testsuite/systemtap.examples/network
> meta taglines 'test_check: stap -g -p4 netfilter_drop.stp TCP 1' tag 'test_check' value 'stap -g -p4 netfilter_drop.stp TCP 1'
> attempting command stap -g -p4 netfilter_drop.stp TCP 1
> OUT /tmp/stapbIEqFl/stap_0c0db8521e3ea3b2d26dcde208a77baf_21082_src.c:2731:1: error: initialization from incompatible pointer type [-Werror]
>   .hook = enter_netfilter_probe_0,
>   ^
> /tmp/stapbIEqFl/stap_0c0db8521e3ea3b2d26dcde208a77baf_21082_src.c:2731:1: error: (near initialization for 'netfilter_opts_0.hook') [-Werror]
> /tmp/stapbIEqFl/stap_0c0db8521e3ea3b2d26dcde208a77baf_21082_src.c:2732:1: error: unknown field 'owner' specified in initializer
>   .owner = THIS_MODULE,
>   ^
> /tmp/stapbIEqFl/stap_0c0db8521e3ea3b2d26dcde208a77baf_21082_src.c:2732:1: error: initialization from incompatible pointer type [-Werror]
> /tmp/stapbIEqFl/stap_0c0db8521e3ea3b2d26dcde208a77baf_21082_src.c:2732:1: error: (near initialization for 'netfilter_opts_0.dev') [-Werror]
> cc1: all warnings being treated as errors
> make[4]: *** [/tmp/stapbIEqFl/stap_0c0db8521e3ea3b2d26dcde208a77baf_21082_src.o] Error 1
> make[3]: *** [_module_/tmp/stapbIEqFl] Error 2
> WARNING: kbuild exited with status: 2
> Pass 4: compilation failed.  [man error::pass4]
> child process exited abnormally
> RC 1
> FAIL: ./systemtap.examples/network/netfilter_drop build
>
> -Will


Cool. Wish I could make sense of systemtap error messages.

  At Will Deacon's suggested I tested probing the instruction in 
__copy_to_user that can cause a captured kernel exception when an 
application passes in a bad buffer address.  Unfortunately the result 
was a hang.  So copy_to/from user is going to have to be blacklisted for 
now, unless there turns out to be a simple fix. I'm worried there might 
be other places in the kernel where an otherwise probeable instruction 
might be expected to generate an exception.

-dl