From: Dmitry V. Levin <ldv@altlinux.org>
Date: Wed, 29 Mar 2017 17:55:35 +0000 (+0000)
Subject: aarch64: workaround gcc+kernel bug
X-Git-Tag: v4.17~142
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=a8d2417e97e71ae01095bee1a1e563b07f2d6b41;p=strace

aarch64: workaround gcc+kernel bug

Due to a subtle gcc bug that leads to miscompiled aarch64 kernels,
the 3rd argument of sched_getattr syscall is not quite 32-bit
on aarch64 as on other architectures.  For more details see
https://sourceforge.net/p/strace/mailman/message/35721703/

* defs.h (print_abnormal_hi): New prototype.
* util.c (print_abnormal_hi): New function.
* sched.c (SYS_FUNC(sched_getattr)) [AARCH64]: Use it.
* tests/sched_xetattr.c (main) [__arm64__ || __aarch64__]: Test it.
---

diff --git a/defs.h b/defs.h
index 793971e8..b2be75b9 100644
--- a/defs.h
+++ b/defs.h
@@ -550,6 +550,7 @@ extern void print_symbolic_mode_t(unsigned int);
 extern void print_numeric_umode_t(unsigned short);
 extern void print_numeric_long_umask(unsigned long);
 extern void print_dev_t(unsigned long long dev);
+extern void print_abnormal_hi(kernel_ulong_t);
 
 extern void
 dumpiov_in_msghdr(struct tcb *, kernel_ulong_t addr, kernel_ulong_t data_size);
diff --git a/sched.c b/sched.c
index 409fb67a..e0ee98ea 100644
--- a/sched.c
+++ b/sched.c
@@ -176,7 +176,19 @@ SYS_FUNC(sched_getattr)
 			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]);
+		tprints(", ");
+#ifdef AARCH64
+		/*
+		 * Due to a subtle gcc bug that leads to miscompiled aarch64
+		 * kernels, the 3rd argument of sched_getattr is not quite 32-bit
+		 * as on other architectures.  For more details see
+		 * https://sourceforge.net/p/strace/mailman/message/35721703/
+		 */
+		if (syserror(tcp))
+			print_abnormal_hi(tcp->u_arg[2]);
+#endif
+		tprintf("%u", size);
+		tprintf(", %u", (unsigned int) tcp->u_arg[3]);
 	}
 
 	return 0;
diff --git a/tests/sched_xetattr.c b/tests/sched_xetattr.c
index 4b381d25..a9bd2baa 100644
--- a/tests/sched_xetattr.c
+++ b/tests/sched_xetattr.c
@@ -81,8 +81,14 @@ main(void)
 	printf("sched_getattr(%d, NULL, 0, 0) = %s\n", (int) bogus_pid, errstr);
 
 	sys_sched_getattr(-1U, (unsigned long) attr, bogus_size, bogus_flags);
-	printf("sched_getattr(-1, %p, %u, %u) = %s\n",
-	       attr, (unsigned) bogus_size, (unsigned) bogus_flags, errstr);
+	printf("sched_getattr(-1, %p, %s%u, %u) = %s\n",
+	       attr,
+# if defined __arm64__ || defined __aarch64__
+	       "0xdefaced<<32|",
+# else
+	       "",
+# endif
+	       (unsigned) bogus_size, (unsigned) bogus_flags, errstr);
 
 	sys_sched_getattr(0, (unsigned long) efault, sizeof(*attr), 0);
 	printf("sched_getattr(0, %p, %u, 0) = %s\n",
@@ -103,20 +109,31 @@ main(void)
 	       attr->sched_period,
 	       (unsigned) sizeof(*attr));
 
+# if defined __arm64__ || defined __aarch64__
+	long rc =
+# endif
 	sys_sched_getattr(F8ILL_KULONG_MASK, (unsigned long) attr,
 			  F8ILL_KULONG_MASK | sizeof(*attr), F8ILL_KULONG_MASK);
-	printf("sched_getattr(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 "}, %u, 0) = 0\n",
-	       attr->sched_flags ? "SCHED_FLAG_RESET_ON_FORK" : "0",
-	       attr->sched_nice,
-	       attr->sched_priority,
-	       attr->sched_runtime,
-	       attr->sched_deadline,
-	       attr->sched_period,
-	       (unsigned) sizeof(*attr));
+# if defined __arm64__ || defined __aarch64__
+	if (rc) {
+		printf("sched_getattr(0, %p, 0xffffffff<<32|%u, 0) = %s\n",
+		       attr, (unsigned) sizeof(*attr), errstr);
+	} else
+# endif
+	{
+		printf("sched_getattr(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 "}, %u, 0) = 0\n",
+		       attr->sched_flags ? "SCHED_FLAG_RESET_ON_FORK" : "0",
+		       attr->sched_nice,
+		       attr->sched_priority,
+		       attr->sched_runtime,
+		       attr->sched_deadline,
+		       attr->sched_period,
+		       (unsigned) sizeof(*attr));
+	}
 
 	sys_sched_setattr(bogus_pid, 0, 0);
 	printf("sched_setattr(%d, NULL, 0) = %s\n", (int) bogus_pid, errstr);
diff --git a/util.c b/util.c
index f05d4efd..9144efb6 100644
--- a/util.c
+++ b/util.c
@@ -1535,6 +1535,17 @@ printargs_d(struct tcb *tcp)
 	return RVAL_DECODED;
 }
 
+/* Print abnormal high bits of a kernel_ulong_t value. */
+void
+print_abnormal_hi(const kernel_ulong_t val)
+{
+	if (current_klongsize > 4) {
+		const unsigned int hi = (unsigned int) ((uint64_t) val >> 32);
+		if (hi)
+			tprintf("%#x<<32|", hi);
+	}
+}
+
 #if defined _LARGEFILE64_SOURCE && defined HAVE_OPEN64
 # define open_file open64
 #else