[lttng-dev] [PATCH lttng-modules v4 5/5] Extract the payload of epoll_wait/epoll_pwait
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Fri Apr 15 21:55:44 UTC 2016
----- On Apr 15, 2016, at 5:49 PM, Julien Desfossez ju at klipix.org wrote:
> On 15-Apr-2016 09:41:04 PM, Mathieu Desnoyers wrote:
>> ----- On Apr 15, 2016, at 4:37 PM, Julien Desfossez jdesfossez at efficios.com
>> wrote:
>>
>> > When epoll_wait returns, extract the content of the "events" field
>> > (events set and data payload).
>> >
>> > Here is an example output:
>> > syscall_entry_epoll_wait: { epfd = 3, maxevents = 32, timeout = 100 }
>> > syscall_exit_epoll_wait: { ret = 1, fds_length = 1,
>> > fds = [ [0] = { raw_events = 0x1,
>> > events = { EPOLLIN = 1, EPOLLPRI = 0, EPOLLOUT = 0, EPOLLERR = 0,
>> > padding = 0 },
>> > data_union = { u64 = 0x100000005, fd = 5 } } ]
>> > }
>> >
>> > Signed-off-by: Julien Desfossez <jdesfossez at efficios.com>
>> > ---
>> > .../syscalls/headers/syscalls_pointers_override.h | 190 +++++++++++++++++++++
>> > 1 file changed, 190 insertions(+)
>> >
>> > diff --git a/instrumentation/syscalls/headers/syscalls_pointers_override.h
>> > b/instrumentation/syscalls/headers/syscalls_pointers_override.h
>> > index 9bb6a01..301b338 100644
>> > --- a/instrumentation/syscalls/headers/syscalls_pointers_override.h
>> > +++ b/instrumentation/syscalls/headers/syscalls_pointers_override.h
>> > @@ -799,4 +799,194 @@ SC_LTTNG_TRACEPOINT_EVENT_CODE(epoll_ctl,
>> > )
>> > #endif /* defined(CONFIG_X86_32) || defined(CONFIG_X86_64) ||
>> > defined(CONFIG_ARM64) || defined(CONFIG_ARM) */
>> >
>> > +#ifndef ONCE_LTTNG_TRACE_EPOLL_H
>> > +#define ONCE_LTTNG_TRACE_EPOLL_H
>> > +
>> > +static struct lttng_event_field lttng_epoll_wait_fields[] = {
>> > + [0] = {
>> > + .name = "data_union",
>> > + .type = {
>> > + .atype = atype_struct,
>> > + .u._struct.nr_fields = ARRAY_SIZE(lttng_epoll_data_fields),
>> > + .u._struct.fields = lttng_epoll_data_fields,
>> > + }
>> > + },
>> > + [1] = {
>> > + .name = "raw_events",
>> > + .type = __type_integer(uint32_t, 0, 0, 0, __BYTE_ORDER, 16, none),
>> > + },
>> > + [2] = {
>> > + .name = "events",
>> > + .type = {
>> > + .atype = atype_struct,
>> > + .u._struct.nr_fields = ARRAY_SIZE(lttng_epoll_ctl_events_fields),
>> > + .u._struct.fields = lttng_epoll_ctl_events_fields,
>> > + }
>> > + },
>> > +};
>> > +
>> > +static struct lttng_type lttng_epoll_wait_elem = {
>> > + .atype = atype_struct,
>> > + .u._struct.nr_fields = ARRAY_SIZE(lttng_epoll_wait_fields),
>> > + .u._struct.fields = lttng_epoll_wait_fields,
>> > +};
>> > +
>> > +#endif /* ONCE_LTTNG_TRACE_EPOLL_H */
>> > +
>> > +#if defined(CONFIG_X86_32) || defined(CONFIG_X86_64)
>> > +#define OVERRIDE_32_epoll_wait
>> > +#define OVERRIDE_64_epoll_wait
>> > +SC_LTTNG_TRACEPOINT_EVENT_CODE(epoll_wait,
>> > + TP_PROTO(sc_exit(long ret,) int epfd, struct epoll_event __user * uevents,
>> > + int maxevents, int timeout),
>> > + TP_ARGS(sc_exit(ret,) epfd, uevents, maxevents, timeout),
>> > + TP_locvar(
>> > + sc_out(
>> > + int fds_length;
>>
>> Why is it signed ?
>>
>> > + struct epoll_event *events;
>> > + )
>> > + ),
>> > + TP_code_pre(
>> > + BUILD_BUG_ON(((ARRAY_SIZE(lttng_epoll_ctl_events_fields) - 1) +
>> > + EPOLL_FLAGS_PADDING_SIZE) !=
>> > + sizeof(uint8_t) * BITS_PER_BYTE);
>> > + sc_out({
>> > + int err;
>> > +
>> > + tp_locvar->fds_length = 0;
>> > + tp_locvar->events = NULL;
>> > +
>> > + if (maxevents <= 0)
>> > + goto skip_code;
>> > +
>> > + tp_locvar->events = kmalloc(
>>
>> How should we handle negative or very large maxevents values ?
> A negative value is catched by the if just before.
> For very large value, I thought we could rely on kmalloc to fail and
> handle the failure, is it ok ?
No, I think it may trigger dmesg warnings in some configurations.
> If the resulting event is too large for the subbuffer, it will just be
> discarded right ?
Yes.
Thanks,
Mathieu
>
> Thanks,
>
> Julien
>
>>
>> > + maxevents * sizeof(struct epoll_event),
>> > + GFP_KERNEL);
>> > + if (!tp_locvar->events)
>> > + goto skip_code;
>> > +
>> > + if (ret > 0) {
>> > + tp_locvar->fds_length = ret;
>> > + err = copy_from_user(tp_locvar->events,
>> > + uevents, maxevents * sizeof(struct epoll_event));
>> > + if (err) {
>> > + tp_locvar->fds_length = 0;
>> > + }
>> > + }
>> > + }
>> > + skip_code:
>> > + )
>> > + ),
>> > + TP_FIELDS(
>> > + sc_exit(ctf_integer(long, ret, ret))
>> > + sc_in(ctf_integer(int, epfd, epfd))
>> > + sc_in(ctf_integer(int, maxevents, maxevents))
>> > + sc_in(ctf_integer(int, timeout, timeout))
>> > + sc_out(ctf_integer(unsigned int, fds_length, tp_locvar->fds_length))
>> > + sc_out(
>> > + ctf_custom_field(
>> > + ctf_custom_type(
>> > + .atype = atype_sequence_compound,
>> > + .u.sequence_compound.length_name =
>> > + "fds_length",
>> > + .u.sequence_compound.elem_type =
>> > + <tng_epoll_wait_elem,
>> > + ),
>> > + fds,
>> > + ctf_custom_code(
>> > + uint32_t i;
>> > +
>> > + ctf_align(uint64_t)
>> > + for (i = 0; i < tp_locvar->fds_length; i++) {
>>
>> Comparison of unsigned (i) with signed (tp_locvar->fds_length).
>>
>> > + ctf_integer_bitfield_type(uint32_t,
>> > + cpu_to_le32(tp_locvar->events[i].events))
>> > + ctf_integer_bitfield_type(uint8_t,
>> > + (uint8_t) cpu_to_le32(tp_locvar->events[i].events))
>> > + ctf_integer_type(uint64_t, tp_locvar->events[i].data)
>> > + ctf_integer_type(int, tp_locvar->events[i].data)
>>
>> ^ fix order of fields (as you pointed out).
>>
>> Thanks,
>>
>> Mathieu
>>
>> > + }
>> > + )
>> > + )
>> > + )
>> > + ),
>> > + TP_code_post(
>> > + sc_out(
>> > + kfree(tp_locvar->events);
>> > + )
>> > + )
>> > +)
>> > +#endif /* defined(CONFIG_X86_32) || defined(CONFIG_X86_64) */
>> > +
>> > +#if defined(CONFIG_X86_32) || defined(CONFIG_X86_64) || defined(CONFIG_ARM64)
>> > || defined(CONFIG_ARM)
>> > +#define OVERRIDE_32_epoll_pwait
>> > +#define OVERRIDE_64_epoll_pwait
>> > +SC_LTTNG_TRACEPOINT_EVENT_CODE(epoll_pwait,
>> > + TP_PROTO(sc_exit(long ret,) int epfd, struct epoll_event __user * uevents,
>> > + int maxevents, int timeout, const sigset_t * sigmask, size_t sigsetsize),
>> > + TP_ARGS(sc_exit(ret,) epfd, uevents, maxevents, timeout, sigmask, sigsetsize),
>> > + TP_locvar(
>> > + sc_out(
>> > + int fds_length;
>> > + struct epoll_event events[maxevents];
>> > + )
>> > + ),
>> > + TP_code_pre(
>> > + BUILD_BUG_ON(((ARRAY_SIZE(lttng_epoll_ctl_events_fields) - 1) +
>> > + EPOLL_FLAGS_PADDING_SIZE) !=
>> > + sizeof(uint8_t) * BITS_PER_BYTE);
>> > + sc_out({
>> > + int err;
>> > +
>> > + if (ret > 0) {
>> > + tp_locvar->fds_length = ret;
>> > + err = copy_from_user(tp_locvar->events,
>> > + uevents, maxevents * sizeof(struct epoll_event));
>> > + if (err) {
>> > + tp_locvar->fds_length = 0;
>> > + }
>> > + } else {
>> > + tp_locvar->fds_length = 0;
>> > + }
>> > +
>> > + })
>> > + ),
>> > + TP_FIELDS(
>> > + sc_exit(ctf_integer(long, ret, ret))
>> > + sc_in(ctf_integer(int, epfd, epfd))
>> > + sc_in(ctf_integer(int, maxevents, maxevents))
>> > + sc_in(ctf_integer(int, timeout, timeout))
>> > + sc_in(ctf_integer(const sigset_t *, sigmask, sigmask))
>> > + sc_in(ctf_integer(size_t, sigsetsize, sigsetsize))
>> > +
>> > + sc_out(ctf_integer(unsigned int, fds_length, tp_locvar->fds_length))
>> > + sc_out(
>> > + ctf_custom_field(
>> > + ctf_custom_type(
>> > + .atype = atype_sequence_compound,
>> > + .u.sequence_compound.length_name =
>> > + "fds_length",
>> > + .u.sequence_compound.elem_type =
>> > + <tng_epoll_wait_elem,
>> > + ),
>> > + fds,
>> > + ctf_custom_code(
>> > + uint32_t i;
>> > +
>> > + ctf_align(uint64_t)
>> > + for (i = 0; i < tp_locvar->fds_length; i++) {
>> > + ctf_integer_type(uint64_t, tp_locvar->events[i].data)
>> > + ctf_integer_type(int, tp_locvar->events[i].data)
>> > + ctf_integer_bitfield_type(uint32_t,
>> > + cpu_to_le32(tp_locvar->events[i].events))
>> > + ctf_integer_bitfield_type(uint8_t,
>> > + cpu_to_le32(tp_locvar->events[i].events))
>> > + }
>> > + )
>> > + )
>> > + )
>> > + ),
>> > + TP_code_post()
>> > +)
>> > +#endif /* defined(CONFIG_X86_32) || defined(CONFIG_X86_64) ||
>> > defined(CONFIG_ARM64) || defined(CONFIG_ARM) */
>> > +
>> > #endif /* CREATE_SYSCALL_TABLE */
>> > --
>> > 1.9.1
>>
>> --
>> Mathieu Desnoyers
>> EfficiOS Inc.
> > http://www.efficios.com
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
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