From: Dmitry V. Levin <ldv@altlinux.org>
Date: Sun, 19 Feb 2017 00:31:40 +0000 (+0000)
Subject: sched: enhance decoding of sched_setattr syscall
X-Git-Tag: v4.17~201
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=556652be53452fabcc26a1b0849c1a3d7133d264;hp=f31755fda2015cbb1aa0686e257118169f102031;p=strace

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 c82eecbe..6c588593 100644
--- 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 a648f863..409fb67a 100644
--- 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 f3d2b377..23eb19cf 100644
--- 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,