test: Switch kernel pointer in tracemem() test

The tracemem() test dumped a portion of kernel memory, comparing
different tracemem() output for the same kernel memory for consistency.
Since it was looking at task_struct for the current thread, however,
the underlying data could conceivably change as the test ran, leading
to inconsistency and a false negative.

Change the kernel memory to be the first 14 bytes of `linux_banner,
which should remain "Linux version ".

Signed-off-by: Eugene Loh <eugene.loh@oracle.com>
Reviewed-by: Kris Van Hees <kris.van.hees@oracle.com>

test/unittest/tracemem/tst.tracemem.d

@@ -13,53 +13,19 @@
 
 #pragma D option quiet
 
-long long *p;
-
 BEGIN {
-	/* pick some pointer to kernel memory */
-	p = (long long *) curthread;
-
-	/* dump memory at this pointer */
-	printf("%16.16x %16.16x\n", p[ 0], p[ 1]);
-	printf("%16.16x %16.16x\n", p[ 2], p[ 3]);
-	printf("%16.16x %16.16x\n", p[ 4], p[ 5]);
-	printf("%16.16x %16.16x\n", p[ 6], p[ 7]);
-	printf("%16.16x %16.16x\n", p[ 8], p[ 9]);
-	printf("%16.16x %16.16x\n", p[10], p[11]);
-	printf("%16.16x %16.16x\n", p[12], p[13]);
-	printf("%16.16x %16.16x\n", p[14], p[15]);
-	printf("%16.16x %16.16x\n", p[16], p[17]);
-	printf("%16.16x %16.16x\n", p[18], p[19]);
-	printf("%16.16x %16.16x\n", p[20], p[21]);
-	printf("%16.16x %16.16x\n", p[22], p[23]);
-	printf("%16.16x %16.16x\n", p[24], p[25]);
-	printf("%16.16x %16.16x\n", p[26], p[27]);
-	printf("%16.16x %16.16x\n", p[28], p[29]);
-	printf("%16.16x %16.16x\n", p[30], p[31]);
-
-	/* try tracemem() with this same pointer but various sizes */
-
-	tracemem(p, 256);	/* 256 bytes */
-
-	tracemem(p, 256,  -1);	/* 256 bytes (arg2 < 0) */
-
-	tracemem(p, 256,   0);	/*   0 bytes */
-
-	tracemem(p, 256,  32);	/*  32 bytes */
-
-	tracemem(p, 256,  64);	/*  64 bytes */
-
-	tracemem(p, 256, 128);	/* 128 bytes */
-
-	tracemem(p, 256, 256);	/* 256 bytes */
-
-	tracemem(p, 256, 320);	/* 256 bytes (arg1 <= arg2) */
-
-	tracemem(p, 256, (unsigned char) 0x80);
-				/* 128 bytes */
-
-	tracemem(p, 256, (signed char) 0x80);
-				/* 256 bytes (arg2 < 0) */
+	p = (char *)`linux_banner;	/* first 14 chars are "Linux version " */
+
+	/* try tracemem() with various sizes */
+
+	tracemem(p, 14);		/* "Linux version ": 14 bytes */
+	tracemem(p, 14, -1);		/* "Linux version ": 14 bytes (arg2 < 0) */
+	tracemem(p, 14,  0);		/*                    0 bytes */
+	tracemem(p, 14,  2);		/* "Li"            :  2 bytes */
+	tracemem(p, 14,  7);		/* "Linux v"       :  7 bytes */
+	tracemem(p, 14, 12);		/* "Linux versio"  : 12 bytes */
+	tracemem(p, 14, 14);		/* "Linux version ": 14 bytes */
+	tracemem(p, 14, 15);		/* "Linux version ": 14 bytes (arg1 <= arg2) */
 
 	exit(0);
 }

test/unittest/tracemem/tst.tracemem.r

@@ -1,9 +1,22 @@
-256 bytes
-256 bytes
-32 bytes
-64 bytes
-128 bytes
-256 bytes
-256 bytes
-128 bytes
-256 bytes
+
+             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  0123456789abcdef
+         0: 4c 69 6e 75 78 20 76 65 72 73 69 6f 6e 20        Linux version 
+
+             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  0123456789abcdef
+         0: 4c 69 6e 75 78 20 76 65 72 73 69 6f 6e 20        Linux version 
+
+             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  0123456789abcdef
+         0: 4c 69                                            Li
+
+             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  0123456789abcdef
+         0: 4c 69 6e 75 78 20 76                             Linux v
+
+             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  0123456789abcdef
+         0: 4c 69 6e 75 78 20 76 65 72 73 69 6f              Linux versio
+
+             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  0123456789abcdef
+         0: 4c 69 6e 75 78 20 76 65 72 73 69 6f 6e 20        Linux version 
+
+             0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f  0123456789abcdef
+         0: 4c 69 6e 75 78 20 76 65 72 73 69 6f 6e 20        Linux version 
+