[lttng-dev] [PATCH lttng-modules v3 5/5] Extract the payload of epoll_wait/epoll_pwait

[Julien Desfossez]

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 74596f6..e272bff 100644
--- a/instrumentation/syscalls/headers/syscalls_pointers_override.h
+++ b/instrumentation/syscalls/headers/syscalls_pointers_override.h
@@ -725,4 +725,194 @@ 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;
+			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;
+
+			if (maxevents > 0) {
+				tp_locvar->events = kmalloc(
+					maxevents * sizeof(struct epoll_event),
+					GFP_KERNEL);
+				if (!tp_locvar->events) {
+					tp_locvar->fds_length = 0;
+				}
+			}
+
+			if (ret > 0 && maxevents > 0 && tp_locvar->events) {
+				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_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 =
+						&lttng_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_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)
+					}
+				)
+			)
+		)
+	),
+	TP_code_post(
+		sc_out(
+			if (maxevents > 0 && tp_locvar->events) {
+				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 =
+						&lttng_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