sched: enhance decoding of sched_setattr syscall

Implement read/write semantics of struct sched_attr.size argument
of sched_setattr syscall.  Do not print members of struct sched_attr
besides sched_attr.size when the specified structure size is less than
the minimal size allowed by the kernel.

* sched.c (print_sched_attr): Fetch struct sched_attr.size and use it
as the structure size.  Print struct sched_attr.size only when the
structure size is less than SCHED_ATTR_MIN_SIZE.
(SYS_FUNC(sched_setattr)): Call print_sched_attr with zero size
argument.  Print struct sched_attr.size returned by the kernel
on exiting syscall in case of E2BIG. Print the last syscall argument
on exiting syscall.
(SYS_FUNC(sched_getattr)): Do not call print_sched_attr with zero size
argument.
* NEWS: Mention it.
* tests/sched_xetattr.c (main): Check it.

diff --git a/NEWS b/NEWS
index c82eecbecea259580f998a724a1166d8f6c13ded..6c588593f9dd58c5a22cb15268b2141cfc5f1b22 100644 (file)
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,9 @@
 Noteworthy changes in release ?.?? (????-??-??)
 ===============================================
 
+* Improvements
+  * Enhanced decoding of sched_setattr syscall.
+
 Noteworthy changes in release 4.16 (2017-02-14)
 ===============================================
 

diff --git a/sched.c b/sched.c
index a648f863ce310958ecd785639f26cf24eb64a1b4..409fb67ac544f3c73e8b688ef08d0c513890ad46 100644 (file)
--- a/sched.c
+++ b/sched.c
@@ -96,33 +96,73 @@ SYS_FUNC(sched_rr_get_interval)
 
 static void
 print_sched_attr(struct tcb *const tcp, const kernel_ulong_t addr,
-                unsigned int size)
+                unsigned int usize)
 {
        struct sched_attr attr = {};
+       unsigned int size;
+
+       if (usize) {
+               /* called from sched_getattr */
+               size = usize <= sizeof(attr) ? usize : (unsigned) sizeof(attr);
+               if (umoven_or_printaddr(tcp, addr, size, &attr))
+                       return;
+               /* the number of bytes written by the kernel */
+               size = attr.size;
+       } else {
+               /* called from sched_setattr */
+               if (umove_or_printaddr(tcp, addr, &attr.size))
+                       return;
+               usize = attr.size;
+               if (!usize)
+                       usize = SCHED_ATTR_MIN_SIZE;
+               size = usize <= sizeof(attr) ? usize : (unsigned) sizeof(attr);
+               if (size >= SCHED_ATTR_MIN_SIZE) {
+                       if (umoven_or_printaddr(tcp, addr, size, &attr))
+                               return;
+               }
+       }
+
+       tprintf("{size=%u", attr.size);
+
+       if (size >= SCHED_ATTR_MIN_SIZE) {
+               tprints(", sched_policy=");
+               printxval(schedulers, attr.sched_policy, "SCHED_???");
+               tprints(", sched_flags=");
+               printflags64(sched_flags, attr.sched_flags, "SCHED_FLAG_???");
+
+#define PRINT_SCHED_FIELD(field, fmt)                  \
+               tprintf(", " #field "=%" fmt, attr.field)
 
-       if (size > sizeof(attr))
-               size = sizeof(attr);
-       if (umoven_or_printaddr(tcp, addr, size, &attr))
-               return;
-
-       tprintf("{size=%u, sched_policy=", attr.size);
-       printxval(schedulers, attr.sched_policy, "SCHED_???");
-       tprints(", sched_flags=");
-       printflags64(sched_flags, attr.sched_flags, "SCHED_FLAG_???");
-       tprintf(", sched_nice=%d", attr.sched_nice);
-       tprintf(", sched_priority=%u", attr.sched_priority);
-       tprintf(", sched_runtime=%" PRIu64, attr.sched_runtime);
-       tprintf(", sched_deadline=%" PRIu64, attr.sched_deadline);
-       tprintf(", sched_period=%" PRIu64 "}", attr.sched_period);
+               PRINT_SCHED_FIELD(sched_nice, "d");
+               PRINT_SCHED_FIELD(sched_priority, "u");
+               PRINT_SCHED_FIELD(sched_runtime, PRIu64);
+               PRINT_SCHED_FIELD(sched_deadline, PRIu64);
+               PRINT_SCHED_FIELD(sched_period, PRIu64);
+
+               if (usize > size)
+                       tprints(", ...");
+       }
+
+       tprints("}");
 }
 
 SYS_FUNC(sched_setattr)
 {
-       tprintf("%d, ", (int) tcp->u_arg[0]);
-       print_sched_attr(tcp, tcp->u_arg[1], 0x100);
-       tprintf(", %u", (unsigned int) tcp->u_arg[2]);
+       if (entering(tcp)) {
+               tprintf("%d, ", (int) tcp->u_arg[0]);
+               print_sched_attr(tcp, tcp->u_arg[1], 0);
+       } else {
+               struct sched_attr attr;
 
-       return RVAL_DECODED;
+               if (verbose(tcp) && tcp->u_error == E2BIG
+                   && umove(tcp, tcp->u_arg[1], &attr.size) == 0) {
+                       tprintf(" => {size=%u}", attr.size);
+               }
+
+               tprintf(", %u", (unsigned int) tcp->u_arg[2]);
+       }
+
+       return 0;
 }
 
 SYS_FUNC(sched_getattr)
@@ -130,10 +170,13 @@ SYS_FUNC(sched_getattr)
        if (entering(tcp)) {
                tprintf("%d, ", (int) tcp->u_arg[0]);
        } else {
-               print_sched_attr(tcp, tcp->u_arg[1], tcp->u_arg[2]);
-               tprintf(", %u, %u",
-                       (unsigned int) tcp->u_arg[2],
-                       (unsigned int) tcp->u_arg[3]);
+               const unsigned int size = tcp->u_arg[2];
+
+               if (size)
+                       print_sched_attr(tcp, tcp->u_arg[1], size);
+               else
+                       printaddr(tcp->u_arg[1]);
+               tprintf(", %u, %u", size, (unsigned int) tcp->u_arg[3]);
        }
 
        return 0;

diff --git a/tests/sched_xetattr.c b/tests/sched_xetattr.c
index f3d2b3772c73b150274812dd09cfaaedf5ee49ce..23eb19cfd1587713af1fbf11a8d813f988d74deb 100644 (file)
--- a/tests/sched_xetattr.c
+++ b/tests/sched_xetattr.c
@@ -68,6 +68,7 @@ main(void)
                (kernel_ulong_t) 0xdefaceddeadc0deULL;
 
        struct sched_attr *const attr = tail_alloc(sizeof(*attr));
+       unsigned int *const psize = tail_alloc(sizeof(*psize));
        void *const efault = attr + 1;
 
        sys_sched_getattr(0, 0, 0, 0);
@@ -150,6 +151,38 @@ main(void)
               attr->sched_deadline,
               attr->sched_period);
 
+       *psize = attr->size;
+
+       sys_sched_setattr(0, (unsigned long) psize, 0);
+       printf("sched_setattr(0, %p, 0) = %s\n", psize, errstr);
+
+       attr->size = 0;
+
+       sys_sched_setattr(0, (unsigned long) attr, 0);
+       printf("sched_setattr(0, {size=%u, sched_policy=", attr->size);
+       printxval(schedulers, attr->sched_policy, NULL);
+       printf(", sched_flags=%s, sched_nice=%d, sched_priority=%u"
+              ", sched_runtime=%" PRIu64 ", sched_deadline=%" PRIu64
+              ", sched_period=%" PRIu64 "}, 0) = 0\n",
+              "SCHED_FLAG_RESET_ON_FORK",
+              attr->sched_nice,
+              attr->sched_priority,
+              attr->sched_runtime,
+              attr->sched_deadline,
+              attr->sched_period);
+
+       attr->size = 1;
+
+       sys_sched_setattr(0, (unsigned long) attr, 0);
+       printf("sched_setattr(0, {size=%u} => {size=%u}, 0) = %s\n",
+              1, attr->size, errstr);
+
+       attr->size = SCHED_ATTR_MIN_SIZE - 1;
+
+       sys_sched_setattr(0, (unsigned long) attr, 0);
+       printf("sched_setattr(0, {size=%u} => {size=%u}, 0) = %s\n",
+              SCHED_ATTR_MIN_SIZE - 1, attr->size, errstr);
+
        attr->size = 0x90807060;
        attr->sched_policy = 0xca7faced;
        attr->sched_flags = 0xbadc0ded1057da7aULL;
@@ -163,7 +196,7 @@ main(void)
        printf("sched_setattr(%d, {size=%u, sched_policy=%#x /* SCHED_??? */, "
               "sched_flags=%#" PRIx64 " /* SCHED_FLAG_??? */, "
               "sched_nice=%d, sched_priority=%u, sched_runtime=%" PRIu64 ", "
-              "sched_deadline=%" PRIu64 ", sched_period=%" PRIu64 "}, %u)"
+              "sched_deadline=%" PRIu64 ", sched_period=%" PRIu64 ", ...}, %u)"
               " = %s\n",
               (int) bogus_pid,
               attr->size,