[lttng-dev] [PATCH lttng-modules v3 2/5] Extract the FD sets in select and pselect6

Julien Desfossez jdesfossez at efficios.com
Fri Apr 15 19:31:10 UTC 2016


Instead of extracting the user-space pointers of the 3 fd_set, we now
extract the bitmask of the FDs in the sets (in, out, ex) in the form of
an array of uint8_t (1024 FDs is the limit in the kernel).

In this example, we select in input FDs 5 to 19 (0xFFFF0), it returns
that one FD is ready: FD 12 (0x1000).

syscall_entry_select: {
  n = 20,
  _fdset_in_length = 3, fdset_in = [ [0] = 0xF0, [1] = 0xFF, [2] = 0xF ],
  _fdset_out_length = 0, fdset_out = [ ],
  _fdset_ex_length = 0, fdset_ex = [ ],
  tvp = 0
 }

syscall_exit_select: {
  ret = 1,
  _fdset_in_length = 3, fdset_in = [ [0] = 0x0, [1] = 0x10, [2] = 0x0 ],
  _fdset_out_length = 0, fdset_out = [ ],
  _fdset_ex_length = 0, fdset_ex = [ ],
  tvp = 0
}

Signed-off-by: Julien Desfossez <jdesfossez at efficios.com>
---
 .../syscalls/headers/syscalls_pointers_override.h  | 218 +++++++++++++++++++++
 1 file changed, 218 insertions(+)

diff --git a/instrumentation/syscalls/headers/syscalls_pointers_override.h b/instrumentation/syscalls/headers/syscalls_pointers_override.h
index bf5c632..64c0474 100644
--- a/instrumentation/syscalls/headers/syscalls_pointers_override.h
+++ b/instrumentation/syscalls/headers/syscalls_pointers_override.h
@@ -53,4 +53,222 @@ SC_LTTNG_TRACEPOINT_EVENT(pipe2,
 	)
 )
 
+#if defined(CONFIG_X86_32) || defined(CONFIG_X86_64)
+#define OVERRIDE_32_select
+#define OVERRIDE_64_select
+SC_LTTNG_TRACEPOINT_EVENT_CODE(select,
+	TP_PROTO(sc_exit(long ret,) int n, fd_set __user * inp, fd_set __user * outp,
+		fd_set __user * exp, struct timeval * tvp),
+	TP_ARGS(sc_exit(ret,) n, inp, outp, exp, tvp),
+	TP_locvar(
+		uint8_t fds_in[__FD_SETSIZE / (8 * sizeof(uint8_t))],
+			fds_out[__FD_SETSIZE / (8 * sizeof(uint8_t))],
+			fds_ex[__FD_SETSIZE / (8 * sizeof(uint8_t))];
+		int nb_in, nb_out, nb_ex;
+	),
+	TP_code_pre(
+		sc_in(
+		{
+			unsigned long nr_bytes;
+			int err;
+
+			if (n <= 0) {
+				nr_bytes = 0;
+			} else {
+				nr_bytes = DIV_ROUND_UP((unsigned int) n, BITS_PER_BYTE);
+				/* On error or bogus input, don't copy anything. */
+				if (nr_bytes > (__FD_SETSIZE / (8 * sizeof(uint8_t)))) {
+					nr_bytes = 0;
+				}
+			}
+			tp_locvar->nb_in = 0;
+			tp_locvar->nb_out = 0;
+			tp_locvar->nb_ex = 0;
+			if (inp) {
+				err = copy_from_user(tp_locvar->fds_in, inp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_in = nr_bytes;
+			}
+			if (outp) {
+				err = copy_from_user(tp_locvar->fds_out, outp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_out = nr_bytes;
+			}
+			if (exp) {
+				err = copy_from_user(tp_locvar->fds_ex, exp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_ex = nr_bytes;
+			}
+		}
+		skip_code:
+		)
+		sc_out(
+		{
+			unsigned long nr_bytes;
+			int err;
+
+			tp_locvar->nb_in = 0;
+			tp_locvar->nb_out = 0;
+			tp_locvar->nb_ex = 0;
+			if (ret <= 0)
+				goto skip_code;
+
+			if (n <= 0) {
+				nr_bytes = 0;
+			} else {
+				nr_bytes = DIV_ROUND_UP((unsigned int) n, BITS_PER_BYTE);
+				/* On error or bogus input, don't copy anything. */
+				if (nr_bytes > (__FD_SETSIZE / (8 * sizeof(uint8_t)))) {
+					nr_bytes = 0;
+				}
+			}
+			if (inp) {
+				err = copy_from_user(tp_locvar->fds_in, inp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_in = nr_bytes;
+			}
+			if (outp) {
+				err = copy_from_user(tp_locvar->fds_out, outp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_out = nr_bytes;
+			}
+			if (exp) {
+				err = copy_from_user(tp_locvar->fds_ex, exp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_ex = nr_bytes;
+			}
+		}
+		skip_code:
+		)
+	),
+	TP_FIELDS(
+		sc_exit(ctf_integer(long, ret, ret))
+		sc_in(ctf_integer(int, n, n))
+		sc_inout(ctf_sequence_hex(uint8_t, fdset_in,
+				tp_locvar->fds_in, uint8_t, tp_locvar->nb_in))
+		sc_inout(ctf_sequence_hex(uint8_t, fdset_out,
+				tp_locvar->fds_out, uint8_t, tp_locvar->nb_out))
+		sc_inout(ctf_sequence_hex(uint8_t, fdset_ex,
+				tp_locvar->fds_ex, uint8_t, tp_locvar->nb_ex))
+		sc_inout(ctf_integer(struct timeval *, tvp, tvp))
+	),
+	TP_code_post()
+)
+#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_pselect6
+#define OVERRIDE_64_pselect6
+SC_LTTNG_TRACEPOINT_EVENT_CODE(pselect6,
+	TP_PROTO(sc_exit(long ret,) int n, fd_set __user * inp, fd_set __user * outp,
+		fd_set __user * exp, struct timeval * tvp, void * sig),
+	TP_ARGS(sc_exit(ret,) n, inp, outp, exp, tvp, sig),
+	TP_locvar(
+		uint8_t fds_in[__FD_SETSIZE / (8 * sizeof(uint8_t))],
+			fds_out[__FD_SETSIZE / (8 * sizeof(uint8_t))],
+			fds_ex[__FD_SETSIZE / (8 * sizeof(uint8_t))];
+		int nb_in, nb_out, nb_ex;
+	),
+	TP_code_pre(
+		sc_in(
+		{
+			unsigned long nr_bytes;
+			int err;
+
+			if (n <= 0) {
+				nr_bytes = 0;
+			} else {
+				nr_bytes = DIV_ROUND_UP((unsigned int) n, BITS_PER_BYTE);
+				/* On error or bogus input, don't copy anything. */
+				if (nr_bytes > (__FD_SETSIZE / (8 * sizeof(uint8_t)))) {
+					nr_bytes = 0;
+				}
+			}
+			tp_locvar->nb_in = 0;
+			tp_locvar->nb_out = 0;
+			tp_locvar->nb_ex = 0;
+			if (inp) {
+				err = copy_from_user(tp_locvar->fds_in, inp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_in = nr_bytes;
+			}
+			if (outp) {
+				err = copy_from_user(tp_locvar->fds_out, outp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_out = nr_bytes;
+			}
+			if (exp) {
+				err = copy_from_user(tp_locvar->fds_ex, exp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_ex = nr_bytes;
+			}
+		}
+		skip_code:
+		)
+		sc_out(
+		{
+			unsigned long nr_bytes;
+			int err;
+
+			tp_locvar->nb_in = 0;
+			tp_locvar->nb_out = 0;
+			tp_locvar->nb_ex = 0;
+			if (ret <= 0)
+				goto skip_code;
+
+			if (n <= 0) {
+				nr_bytes = 0;
+			} else {
+				nr_bytes = DIV_ROUND_UP((unsigned int) n, BITS_PER_BYTE);
+				/* On error or bogus input, don't copy anything. */
+				if (nr_bytes > (__FD_SETSIZE / (8 * sizeof(uint8_t)))) {
+					nr_bytes = 0;
+				}
+			}
+			if (inp) {
+				err = copy_from_user(tp_locvar->fds_in, inp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_in = nr_bytes;
+			}
+			if (outp) {
+				err = copy_from_user(tp_locvar->fds_out, outp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_out = nr_bytes;
+			}
+			if (exp) {
+				err = copy_from_user(tp_locvar->fds_ex, exp, nr_bytes);
+				if (err < 0)
+					goto skip_code;
+				tp_locvar->nb_ex = nr_bytes;
+			}
+		}
+		skip_code:
+		)
+	),
+	TP_FIELDS(
+		sc_exit(ctf_integer(long, ret, ret))
+		sc_in(ctf_integer(int, n, n))
+		sc_inout(ctf_sequence_hex(uint8_t, fdset_in,
+				tp_locvar->fds_in, uint8_t, tp_locvar->nb_in))
+		sc_inout(ctf_sequence_hex(uint8_t, fdset_out,
+				tp_locvar->fds_out, uint8_t, tp_locvar->nb_out))
+		sc_inout(ctf_sequence_hex(uint8_t, fdset_ex,
+				tp_locvar->fds_ex, uint8_t, tp_locvar->nb_ex))
+		sc_inout(ctf_integer(struct timeval *, tvp, tvp))
+	),
+	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



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