From: Marc Dionne <marc.c.dionne@gmail.com>
To: David Howells <dhowells@redhat.com>
Cc: linux-afs@lists.infradead.org,
"Alexey Dobriyan (SK hynix)" <adobriyan@gmail.com>,
"Steven Rostedt (VMware)" <rostedt@goodmis.org>,
Andrew Morton <akpm@linux-foundation.org>,
linux-fsdevel@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v2 1/4] afs: Fix tracepoint string placement with built-in AFS
Date: Mon, 12 Jul 2021 16:27:03 -0300 [thread overview]
Message-ID: <CAB9dFdt5P-6nB0D_nMb-PT+Uv+FtAy811PA_W2fXPZAvPRo0sQ@mail.gmail.com> (raw)
In-Reply-To: <162610726860.3408253.445207609466288531.stgit@warthog.procyon.org.uk>
On Mon, Jul 12, 2021 at 1:28 PM David Howells <dhowells@redhat.com> wrote:
>
> To quote Alexey[1]:
>
> I was adding custom tracepoint to the kernel, grabbed full F34 kernel
> .config, disabled modules and booted whole shebang as VM kernel.
>
> Then did
>
> perf record -a -e ...
>
> It crashed:
>
> general protection fault, probably for non-canonical address 0x435f5346592e4243: 0000 [#1] SMP PTI
> CPU: 1 PID: 842 Comm: cat Not tainted 5.12.6+ #26
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014
> RIP: 0010:t_show+0x22/0xd0
>
> Then reproducer was narrowed to
>
> # cat /sys/kernel/tracing/printk_formats
>
> Original F34 kernel with modules didn't crash.
>
> So I started to disable options and after disabling AFS everything
> started working again.
>
> The root cause is that AFS was placing char arrays content into a
> section full of _pointers_ to strings with predictable consequences.
>
> Non canonical address 435f5346592e4243 is "CB.YFS_" which came from
> CM_NAME macro.
>
> Steps to reproduce:
>
> CONFIG_AFS=y
> CONFIG_TRACING=y
>
> # cat /sys/kernel/tracing/printk_formats
>
> Fix this by the following means:
>
> (1) Add enum->string translation tables in the event header with the AFS
> and YFS cache/callback manager operations listed by RPC operation ID.
>
> (2) Modify the afs_cb_call tracepoint to print the string from the
> translation table rather than using the string at the afs_call name
> pointer.
>
> (3) Switch translation table depending on the service we're being accessed
> as (AFS or YFS) in the tracepoint print clause. Will this cause
> problems to userspace utilities?
>
> Note that the symbolic representation of the YFS service ID isn't
> available to this header, so I've put it in as a number. I'm not sure
> if this is the best way to do this.
>
> (4) Remove the name wrangling (CM_NAME) macro and put the names directly
> into the afs_call_type structs in cmservice.c.
>
> Fixes: 8e8d7f13b6d5a9 ("afs: Add some tracepoints")
> Reported-by: Alexey Dobriyan (SK hynix) <adobriyan@gmail.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> Reviewed-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
> cc: Andrew Morton <akpm@linux-foundation.org>
> cc: linux-afs@lists.infradead.org
> Link: https://lore.kernel.org/r/YLAXfvZ+rObEOdc%2F@localhost.localdomain/ [1]
> Link: https://lore.kernel.org/r/643721.1623754699@warthog.procyon.org.uk/
> Link: https://lore.kernel.org/r/162430903582.2896199.6098150063997983353.stgit@warthog.procyon.org.uk/ # v1
> Link: https://lore.kernel.org/r/162609463957.3133237.15916579353149746363.stgit@warthog.procyon.org.uk/ # v1 (repost)
> ---
>
> fs/afs/cmservice.c | 25 +++++-----------
> include/trace/events/afs.h | 67 +++++++++++++++++++++++++++++++++++++++++---
> 2 files changed, 69 insertions(+), 23 deletions(-)
>
> diff --git a/fs/afs/cmservice.c b/fs/afs/cmservice.c
> index d3c6bb22c5f4..a3f5de28be79 100644
> --- a/fs/afs/cmservice.c
> +++ b/fs/afs/cmservice.c
> @@ -29,16 +29,11 @@ static void SRXAFSCB_TellMeAboutYourself(struct work_struct *);
>
> static int afs_deliver_yfs_cb_callback(struct afs_call *);
>
> -#define CM_NAME(name) \
> - char afs_SRXCB##name##_name[] __tracepoint_string = \
> - "CB." #name
> -
> /*
> * CB.CallBack operation type
> */
> -static CM_NAME(CallBack);
> static const struct afs_call_type afs_SRXCBCallBack = {
> - .name = afs_SRXCBCallBack_name,
> + .name = "CB.CallBack",
> .deliver = afs_deliver_cb_callback,
> .destructor = afs_cm_destructor,
> .work = SRXAFSCB_CallBack,
> @@ -47,9 +42,8 @@ static const struct afs_call_type afs_SRXCBCallBack = {
> /*
> * CB.InitCallBackState operation type
> */
> -static CM_NAME(InitCallBackState);
> static const struct afs_call_type afs_SRXCBInitCallBackState = {
> - .name = afs_SRXCBInitCallBackState_name,
> + .name = "CB.InitCallBackState",
> .deliver = afs_deliver_cb_init_call_back_state,
> .destructor = afs_cm_destructor,
> .work = SRXAFSCB_InitCallBackState,
> @@ -58,9 +52,8 @@ static const struct afs_call_type afs_SRXCBInitCallBackState = {
> /*
> * CB.InitCallBackState3 operation type
> */
> -static CM_NAME(InitCallBackState3);
> static const struct afs_call_type afs_SRXCBInitCallBackState3 = {
> - .name = afs_SRXCBInitCallBackState3_name,
> + .name = "CB.InitCallBackState3",
> .deliver = afs_deliver_cb_init_call_back_state3,
> .destructor = afs_cm_destructor,
> .work = SRXAFSCB_InitCallBackState,
> @@ -69,9 +62,8 @@ static const struct afs_call_type afs_SRXCBInitCallBackState3 = {
> /*
> * CB.Probe operation type
> */
> -static CM_NAME(Probe);
> static const struct afs_call_type afs_SRXCBProbe = {
> - .name = afs_SRXCBProbe_name,
> + .name = "CB.Probe",
> .deliver = afs_deliver_cb_probe,
> .destructor = afs_cm_destructor,
> .work = SRXAFSCB_Probe,
> @@ -80,9 +72,8 @@ static const struct afs_call_type afs_SRXCBProbe = {
> /*
> * CB.ProbeUuid operation type
> */
> -static CM_NAME(ProbeUuid);
> static const struct afs_call_type afs_SRXCBProbeUuid = {
> - .name = afs_SRXCBProbeUuid_name,
> + .name = "CB.ProbeUuid",
> .deliver = afs_deliver_cb_probe_uuid,
> .destructor = afs_cm_destructor,
> .work = SRXAFSCB_ProbeUuid,
> @@ -91,9 +82,8 @@ static const struct afs_call_type afs_SRXCBProbeUuid = {
> /*
> * CB.TellMeAboutYourself operation type
> */
> -static CM_NAME(TellMeAboutYourself);
> static const struct afs_call_type afs_SRXCBTellMeAboutYourself = {
> - .name = afs_SRXCBTellMeAboutYourself_name,
> + .name = "CB.TellMeAboutYourself",
> .deliver = afs_deliver_cb_tell_me_about_yourself,
> .destructor = afs_cm_destructor,
> .work = SRXAFSCB_TellMeAboutYourself,
> @@ -102,9 +92,8 @@ static const struct afs_call_type afs_SRXCBTellMeAboutYourself = {
> /*
> * YFS CB.CallBack operation type
> */
> -static CM_NAME(YFS_CallBack);
> static const struct afs_call_type afs_SRXYFSCB_CallBack = {
> - .name = afs_SRXCBYFS_CallBack_name,
> + .name = "YFSCB.CallBack",
> .deliver = afs_deliver_yfs_cb_callback,
> .destructor = afs_cm_destructor,
> .work = SRXAFSCB_CallBack,
> diff --git a/include/trace/events/afs.h b/include/trace/events/afs.h
> index 3ccf591b2374..9f73ed2cf061 100644
> --- a/include/trace/events/afs.h
> +++ b/include/trace/events/afs.h
> @@ -174,6 +174,34 @@ enum afs_vl_operation {
> afs_VL_GetCapabilities = 65537, /* AFS Get VL server capabilities */
> };
>
> +enum afs_cm_operation {
> + afs_CB_CallBack = 204, /* AFS break callback promises */
> + afs_CB_InitCallBackState = 205, /* AFS initialise callback state */
> + afs_CB_Probe = 206, /* AFS probe client */
> + afs_CB_GetLock = 207, /* AFS get contents of CM lock table */
> + afs_CB_GetCE = 208, /* AFS get cache file description */
> + afs_CB_GetXStatsVersion = 209, /* AFS get version of extended statistics */
> + afs_CB_GetXStats = 210, /* AFS get contents of extended statistics data */
> + afs_CB_InitCallBackState3 = 213, /* AFS initialise callback state, version 3 */
> + afs_CB_ProbeUuid = 214, /* AFS check the client hasn't rebooted */
> +};
> +
> +enum yfs_cm_operation {
> + yfs_CB_Probe = 206, /* YFS probe client */
> + yfs_CB_GetLock = 207, /* YFS get contents of CM lock table */
> + yfs_CB_XStatsVersion = 209, /* YFS get version of extended statistics */
> + yfs_CB_GetXStats = 210, /* YFS get contents of extended statistics data */
> + yfs_CB_InitCallBackState3 = 213, /* YFS initialise callback state, version 3 */
> + yfs_CB_ProbeUuid = 214, /* YFS check the client hasn't rebooted */
> + yfs_CB_GetServerPrefs = 215,
> + yfs_CB_GetCellServDV = 216,
> + yfs_CB_GetLocalCell = 217,
> + yfs_CB_GetCacheConfig = 218,
> + yfs_CB_GetCellByNum = 65537,
> + yfs_CB_TellMeAboutYourself = 65538, /* get client capabilities */
> + yfs_CB_CallBack = 64204,
> +};
> +
> enum afs_edit_dir_op {
> afs_edit_dir_create,
> afs_edit_dir_create_error,
> @@ -436,6 +464,32 @@ enum afs_cb_break_reason {
> EM(afs_YFSVL_GetCellName, "YFSVL.GetCellName") \
> E_(afs_VL_GetCapabilities, "VL.GetCapabilities")
>
> +#define afs_cm_operations \
> + EM(afs_CB_CallBack, "CB.CallBack") \
> + EM(afs_CB_InitCallBackState, "CB.InitCallBackState") \
> + EM(afs_CB_Probe, "CB.Probe") \
> + EM(afs_CB_GetLock, "CB.GetLock") \
> + EM(afs_CB_GetCE, "CB.GetCE") \
> + EM(afs_CB_GetXStatsVersion, "CB.GetXStatsVersion") \
> + EM(afs_CB_GetXStats, "CB.GetXStats") \
> + EM(afs_CB_InitCallBackState3, "CB.InitCallBackState3") \
> + E_(afs_CB_ProbeUuid, "CB.ProbeUuid")
> +
> +#define yfs_cm_operations \
> + EM(yfs_CB_Probe, "YFSCB.Probe") \
> + EM(yfs_CB_GetLock, "YFSCB.GetLock") \
> + EM(yfs_CB_XStatsVersion, "YFSCB.XStatsVersion") \
> + EM(yfs_CB_GetXStats, "YFSCB.GetXStats") \
> + EM(yfs_CB_InitCallBackState3, "YFSCB.InitCallBackState3") \
> + EM(yfs_CB_ProbeUuid, "YFSCB.ProbeUuid") \
> + EM(yfs_CB_GetServerPrefs, "YFSCB.GetServerPrefs") \
> + EM(yfs_CB_GetCellServDV, "YFSCB.GetCellServDV") \
> + EM(yfs_CB_GetLocalCell, "YFSCB.GetLocalCell") \
> + EM(yfs_CB_GetCacheConfig, "YFSCB.GetCacheConfig") \
> + EM(yfs_CB_GetCellByNum, "YFSCB.GetCellByNum") \
> + EM(yfs_CB_TellMeAboutYourself, "YFSCB.TellMeAboutYourself") \
> + E_(yfs_CB_CallBack, "YFSCB.CallBack")
> +
> #define afs_edit_dir_ops \
> EM(afs_edit_dir_create, "create") \
> EM(afs_edit_dir_create_error, "c_fail") \
> @@ -569,6 +623,8 @@ afs_server_traces;
> afs_cell_traces;
> afs_fs_operations;
> afs_vl_operations;
> +afs_cm_operations;
> +yfs_cm_operations;
> afs_edit_dir_ops;
> afs_edit_dir_reasons;
> afs_eproto_causes;
> @@ -649,20 +705,21 @@ TRACE_EVENT(afs_cb_call,
>
> TP_STRUCT__entry(
> __field(unsigned int, call )
> - __field(const char *, name )
> __field(u32, op )
> + __field(u16, service_id )
> ),
>
> TP_fast_assign(
> __entry->call = call->debug_id;
> - __entry->name = call->type->name;
> __entry->op = call->operation_ID;
> + __entry->service_id = call->service_id;
> ),
>
> - TP_printk("c=%08x %s o=%u",
> + TP_printk("c=%08x %s",
> __entry->call,
> - __entry->name,
> - __entry->op)
> + __entry->service_id == 2501 ?
> + __print_symbolic(__entry->op, yfs_cm_operations) :
> + __print_symbolic(__entry->op, afs_cm_operations))
> );
>
> TRACE_EVENT(afs_call,
>
>
Reviewed-by: Marc Dionne <marc.dionne@auristor.com>
If you wanted to avoid having the hard coded yfs service ID there, you
could pass in a boolean "is yfs" value and let the caller set it based
on the service ID, or even have two separate trace events. But seems
fine as is.
Marc
next prev parent reply other threads:[~2021-07-12 19:27 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-12 16:27 [PATCH v2 0/4] afs: Miscellaneous fixes David Howells
2021-07-12 16:27 ` [PATCH v2 1/4] afs: Fix tracepoint string placement with built-in AFS David Howells
2021-07-12 19:27 ` Marc Dionne [this message]
2021-07-12 16:27 ` [PATCH v2 2/4] afs: check function return David Howells
2021-07-21 12:59 ` Marc Dionne
2021-07-12 16:28 ` [PATCH v2 3/4] afs: Fix setting of writeback_index David Howells
2021-07-21 12:52 ` Marc Dionne
2021-07-12 16:28 ` [PATCH v2 4/4] afs: Remove redundant assignment to ret David Howells
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