On 10/7/2024 9:05 PM, Leo Yan wrote: > > Hi Julien, > > On Wed, Sep 25, 2024 at 03:13:56PM +0200, Julien Meunier wrote: >> The previous implementation limited the tracing capabilities when perf >> was run in the init PID namespace, making it impossible to trace >> applications in non-init PID namespaces. >> >> This update improves the tracing process by verifying the event owner. >> This allows us to determine whether the user has the necessary >> permissions to trace the application. > > The original commit aab473867fed is not for constraint permission. It is > about PID namespace mismatching issue. > > E.g. Perf runs in non-root namespace, thus it records process info in the > non-root PID namespace. On the other hand, Arm CoreSight traces PID for > root namespace, as a result, it will lead mess when decoding. > > With this change, I am not convinced that Arm CoreSight can trace PID for > non-root PID namespace. Seems to me, the concerned issue is still existed > - it might cause PID mismatching issue between hardware trace data and > Perf's process info. I thought again and found I was wrong with above conclusion. This patch is a good fixing for the perf running in root namespace to profile programs in non-root namespace. Sorry for noise. Maybe it is good to improve a bit comments to avoid confusion. See below. [...] >> diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c >> index bf01f01964cf..8365307b1aec 100644 >> --- a/drivers/hwtracing/coresight/coresight-etm4x-core.c >> +++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c >> @@ -695,7 +695,7 @@ static int etm4_parse_event_config(struct coresight_device *csdev, >> >> /* Only trace contextID when runs in root PID namespace */ We can claim the requirement for the *tool* running in root PID namespae. /* Only trace contextID when the tool runs in root PID namespace */ >> if ((attr->config & BIT(ETM_OPT_CTXTID)) && >> - task_is_in_init_pid_ns(current)) >> + task_is_in_init_pid_ns(event->owner)) >> /* bit[6], Context ID tracing bit */ >> config->cfg |= TRCCONFIGR_CID; >> >> @@ -710,7 +710,7 @@ static int etm4_parse_event_config(struct coresight_device *csdev, >> goto out; >> } >> /* Only trace virtual contextID when runs in root PID namespace */ Ditto. /* Only trace virtual contextID when the tool runs in root PID namespace */ With above change: Reviewed-by: Leo Yan <leo.yan@xxxxxxx> >> - if (task_is_in_init_pid_ns(current)) >> + if (task_is_in_init_pid_ns(event->owner)) >> config->cfg |= TRCCONFIGR_VMID | TRCCONFIGR_VMIDOPT; >> } >> >> -- >> 2.34.1 >> >>
