Re: exercising current aarch64 kprobe support with systemtap

[William Cohen <wcohen at redhat dot com>]

On 06/13/2016 12:10 PM, William Cohen wrote:
> I dummied up the hw_addr_*.stp tests to not run.  The test made it further, but then got stuck spewing out:
> 
> [ 1648.037580] Unexpected kernel single-step exception at EL1
> [ 1648.043060] Unexpected kernel single-step exception at EL1
> [ 1648.048540] Unexpected kernel single-step exception at EL1

I was able to get the start of when it starting spewning the single-step exception at EL1:

[root@amd-seattle-03 systemtap]# [  793.930801] Scheduler tracepoints stat_sleep, stat_iowait, stat_blocked and stat_runtime require the kernel parameter schedstats=enabled or kernel.sched_schedstats=1
[  793.965896] hrtimer: interrupt took 422795 ns
[  887.063206] ------------[ cut here ]------------
[  887.067856] WARNING: CPU: 1 PID: 21315 at mm/page_counter.c:26 page_counter_cancel+0x5c/0x68
[  887.076288] Modules linked in: stap_e307cc4760ef17e67f4e7cdd288c9472_1_21004(OE) vfat fat amd_xgbe i2c_designware_platform ipmi_si ptp i2c_designware_core i2c_core spi_pl022 sbsa_gwdt ccp ipmi_msghandler pps_core crc32_arm64 ghash_ce nfsd auth_rpcgss nfs_acl lockd grace sunrpc xfs libcrc32c [last unloaded: stap_d8856f77dba73cfbeacac8b8ae0b9f60__20838]
[  887.107716] 
[  887.109202] CPU: 1 PID: 21315 Comm: echo Tainted: G        W IOE   4.7.0-rc1panand+ #5
[  887.117123] Hardware name: AMD Overdrive/Supercharger/Default string, BIOS ROD1001A 02/09/2016
[  887.125738] Unexpected kernel single-step exception at EL1
[  887.131241] Unexpected kernel single-step exception at EL1


-Will
> 
> 
> This happens during the "systemtap.onthefly/kprobes_onthefly.exp" tests  and can be reliably triggered running that portion of the systemtap tests with:
> 
> make installcheck RUNTESTFLAGS="--debug systemtap.onthefly/kprobes_onthefly.exp"
> 
> 
> Seems like the tests get past the following and then start spewing the error message:
> 
> Executing: kill -KILL 22311
> kill: kill: sending signal to 22311 failed: No such process
> PASS: kprobes_onthefly - otf_stress_hard_iter_2000 (survived)
> 
> However the testsuite doesn't seem to make it through to print out the next test:
> 
> PASS: hrtimer_onthefly - otf_stress_max_iter_5000 (survived)
> 
> Note that this kernel (clone of https://github.com/pratyushanand/linux on test_upstream_arm64_devel branch) does have the patch to avoid having the atomic region search go before the start of a function by look for the "stp x29, x30, [sp, -#xx]!"
> 
> -Will
>