Remove the string length prefix

This is the final stage of discontinuing the string length prefix code.
It removes the actual storage allocation for the 2-byte string length
prefix, and updates all code that adjusted pointers because of the
prefix.  The dt_strlen_store() function is gone.

This change affects the offset calculation for variab;e storage when a
string is involved.  Test results for gvar/tst.undecl-offset.r are
updated to reflect this.

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

bpf/basename.S

@@ -1,10 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 
-#define DT_STRLEN_BYTES		2
-
 #define BPF_FUNC_probe_read_str	45
 
 /*
@@ -24,9 +22,6 @@ dt_basename :
 	mov	SRC, %r1
 	mov	DST, %r2
 
-	/* ignore the string-length prefix */
-	add	SRC, DT_STRLEN_BYTES
-
 	/* r0 = bpf_probe_read_str(dst, STRSZ + 1, src) */
 	mov	%r1, DST
 	lddw	%r2, STRSZ
@@ -83,21 +78,14 @@ dt_basename :
 	mov	LEN, 0
 	/* bgn++ */
 	add	BGN, 1
-	/* bpf_probe_read_str(dst + DT_STRLEN_BYTES, len + 1, &src[bgn]) */
+	/* bpf_probe_read_str(dst, len + 1, &src[bgn]) */
 	mov	%r1, DST
-	add	%r1, DT_STRLEN_BYTES
 	mov	%r2, LEN
 	add	%r2, 1
 	mov	%r3, SRC
 	add	%r3, BGN
 	call	BPF_FUNC_probe_read_str
 
-.Lcoda:
-	/* dt_strlen_store(len, dst) */
-	mov	%r1, LEN
-	mov	%r2, DST
-	call	dt_strlen_store
-
 	/* return */
 	exit
 
@@ -106,18 +94,18 @@ dt_basename :
 	 * The output string is simply ".\0".
 	 */
 	mov	LEN, 1
-	stb	[DST+DT_STRLEN_BYTES], '.'
-	stb	[DST+(DT_STRLEN_BYTES+1)], 0
-	ja	.Lcoda
+	stb	[DST+0], '.'
+	stb	[DST+1], 0
+	exit
 
 .Lslash:
 	/*
 	 * The output string is simply "/\0".
 	 */
 	mov	LEN, 1
-	stb	[DST+DT_STRLEN_BYTES], '/'
-	stb	[DST+(DT_STRLEN_BYTES+1)], 0
-	ja	.Lcoda
+	stb	[DST+0], '/'
+	stb	[DST+1], 0
+	exit
 #undef SRC
 #undef DST
 #undef BGN

bpf/dirname.S

@@ -1,10 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 
-#define DT_STRLEN_BYTES		2
-
 #define BPF_FUNC_probe_read_str	45
 
 /*
@@ -23,9 +21,6 @@ dt_dirname :
 	mov	SRC, %r1
 	mov	DST, %r2
 
-	/* ignore the string-length prefix */
-	add	SRC, DT_STRLEN_BYTES
-
 	/* r0 = bpf_probe_read_str(dst, STRSZ + 1, src) */
 	mov	%r1, DST
 	lddw	%r2, STRSZ
@@ -100,20 +95,13 @@ dt_dirname :
 	 * The output string is up to the end of the dirname.
 	 */
 
-	/* bpf_probe_read_str(dst + DT_STRLEN_BYTES, len + 1, src) */
+	/* bpf_probe_read_str(dst, len + 1, src) */
 	mov	%r1, DST
-	add	%r1, DT_STRLEN_BYTES
 	mov	%r2, LEN
 	add	%r2, 1
 	mov	%r3, SRC
 	call	BPF_FUNC_probe_read_str
 
-.Lcoda:
-	/* dt_strlen_store(len, dst) */
-	mov	%r1, LEN
-	mov	%r2, DST
-	call	dt_strlen_store
-
 	/* return */
 	exit
 
@@ -122,18 +110,18 @@ dt_dirname :
 	 * The output string is simply ".".
 	 */
 	mov	LEN, 1
-	stb	[DST+DT_STRLEN_BYTES], '.'
-	stb	[DST+(DT_STRLEN_BYTES+1)], 0
-	ja	.Lcoda
+	stb	[DST+0], '.'
+	stb	[DST+1], 0
+	exit
 
 .Lslash:
 	/*
 	 * The output string is simply "/".
 	 */
 	mov	LEN, 1
-	stb	[DST+DT_STRLEN_BYTES], '/'
-	stb	[DST+(DT_STRLEN_BYTES+1)], 0
-	ja	.Lcoda
+	stb	[DST+0], '/'
+	stb	[DST+1], 0
+	exit
 #undef SRC
 #undef DST
 #undef LEN

bpf/index.S

@@ -1,10 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 
-#define DT_STRLEN_BYTES		2
-
 #define BPF_FUNC_probe_read	4
 #define BPF_FUNC_probe_read_str	45
 
@@ -84,10 +82,6 @@ dt_index_match:
  *     uint64_t r0, tlen;
  *     uint64_t buflen;
  *
- *     // ignore length prefix
- *     s += DT_STRLEN_BYTES;
- *     t += DT_STRLEN_BYTES;
- *
  *     // determine actual start index
  *     if (start < 0) start = 0;
  *
@@ -135,9 +129,6 @@ dt_index_match:
 	.global	dt_index
 	.type	dt_index, @function
 dt_index:
-	add	%r1, DT_STRLEN_BYTES		/* s += DT_STRLEN_BYTES */
-	add	%r2, DT_STRLEN_BYTES		/* t += DT_STRLEN_BYTES */
-
 	jsge	%r3, 0, 1
 	mov	%r3, 0				/* if (start < 0) start = 0 */
 

bpf/lltostr.S

@@ -1,9 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 
-#define DT_STRLEN_BYTES		2
 #define BPF_FUNC_probe_read	4
 #define MAXCHARS		19
 
@@ -46,9 +45,6 @@
  *
  *     LEN = min(IDX, STRSZ)
  *
- *     dt_strlen_store(LEN, STR)
- *     STR += DT_STRLEN_BYTES
- *
  *     // copy to output string
  *     bpf_probe_read(STR, LEN, %fp + -IDX)
  *
@@ -140,12 +136,6 @@ dt_lltostr:
 	jle	LEN, %r1, 1
 	mov	LEN, %r1			/* LEN = min(IDX, STRSZ) */
 
-	mov	%r1, LEN
-	mov	%r2, STR
-	call	dt_strlen_store			/* dt_strlen_store(LEN, STR) */
-
-	add	STR, DT_STRLEN_BYTES		/* STR += DT_STRLEN_BYTES */
-
 	mov	%r1, STR
 	mov	%r2, LEN
 	mov	%r3, %fp

bpf/rindex.S

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 
 /*
@@ -17,8 +17,6 @@
  *   - In the call to rindex.S, start<0 means to use the default.
  */
 
-#define DT_STRLEN_BYTES		2
-
 #define BPF_FUNC_probe_read	4
 #define BPF_FUNC_probe_read_str	45
 
@@ -29,10 +27,6 @@
  *     uint64_t r0, tlen;
  *     uint64_t buflen;
  *
- *     // ignore length prefix
- *     s += DT_STRLEN_BYTES;
- *     t += DT_STRLEN_BYTES;
- *
  *     // round buflen for dt_index_match()
  *     buflen = STRSZ rounded up to multiple of 8;
  *
@@ -82,9 +76,6 @@
 	.global	dt_rindex
 	.type	dt_rindex, @function
 dt_rindex:
-	add	%r1, DT_STRLEN_BYTES		/* s += DT_STRLEN_BYTES */
-	add	%r2, DT_STRLEN_BYTES		/* t += DT_STRLEN_BYTES */
-
 	lddw	%r6, STRSZ
 	add	%r6, 7
 	and	%r6, -8

bpf/strchr.S

@@ -1,10 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 
-#define DT_STRLEN_BYTES		2
-
 #define BPF_FUNC_probe_read	4
 #define BPF_FUNC_probe_read_str	45
 
@@ -24,7 +22,7 @@
  *     [%fp-32]=tmp
  *
  *     // make temporary copy of string and get string length
- *     r6 = bpf_probe_read_str(dst, STRSZ, src + DT_STRLEN_BYTES);
+ *     r6 = bpf_probe_read_str(dst, STRSZ, src);
  *     r6--;
  *
  *     // xor the char with every byte;  a match results in NULL byte
@@ -40,12 +38,9 @@
  *     // determine length of output string
  *     r6 -= r8;
  *     if (r6 <= 0) return -1;
- *     dt_strlen_store(r6, dst);
  *
  *     // write output string
- *     r8 += DT_STRLEN_BYTES;
- *     bpf_probe_read(dst + DT_STRLEN_BYTES, r6, src + r8);
- *     r6 += DT_STRLEN_BYTES;
+ *     bpf_probe_read(dst, r6, src + r8);
  *     dst[r6] = '\0';
  *
  *     return 0;
@@ -75,8 +70,7 @@ dt_strchr :
 	ldxdw	%r1, [%fp+-24]
 	lddw	%r2, STRSZ
 	ldxdw	%r3, [%fp+-8]
-	add	%r3, DT_STRLEN_BYTES
-	call	BPF_FUNC_probe_read_str	/* r6 = bpf_probe_read_str(dst, STRSZ, src + DT_STRLEN_BYTES) */
+	call	BPF_FUNC_probe_read_str	/* r6 = bpf_probe_read_str(dst, STRSZ, src) */
 	mov	%r6, %r0
 
 	jsle	%r6, 0, .Lerror
@@ -119,20 +113,11 @@ dt_strchr :
 
 	jsle	%r6, 0, .Lerror		/* if (r6 <= 0) return -1 */
 
-	mov	%r1, %r6
-	ldxdw	%r2, [%fp+-24]
-	call	dt_strlen_store		/* dt_strlen_store(r6, dst) */
-
-	add	%r8, DT_STRLEN_BYTES	/* r8 += DT_STRLEN_BYTES */
-
 	ldxdw	%r1, [%fp+-24]
-	add	%r1, DT_STRLEN_BYTES
 	mov	%r2, %r6
 	ldxdw	%r3, [%fp+-8]
 	add	%r3, %r8
-	call	BPF_FUNC_probe_read	/* bpf_probe_read(dst + DT_STRLEN_BYTES, r6, src + r8) */
-
-	add	%r6, DT_STRLEN_BYTES	/* r6 += DT_STRLEN_BYTES */
+	call	BPF_FUNC_probe_read	/* bpf_probe_read(dst, r6, src + r8) */
 
 	ldxdw	%r1, [%fp+-24]
 	add	%r1, %r6		/* dst[r6] = '\0' */

bpf/strcmp.S

@@ -1,10 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 /*
- * Copyright (c) 2021, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2022, Oracle and/or its affiliates. All rights reserved.
  */
 
-#define DT_STRLEN_BYTES		2
-
 #define BPF_FUNC_probe_read	4
 #define BPF_FUNC_probe_read_str	45
 
@@ -70,8 +68,8 @@ dt_strcmp_not :
  *     r8 = STRSZ
  *
  *     // make temporary copies of strings
- *     r6 = bpf_probe_read_str(tmp1, STRSZ, s + DT_STRLEN_BYTES);
- *     r7 = bpf_probe_read_str(tmp2, STRSZ, t + DT_STRLEN_BYTES);
+ *     r6 = bpf_probe_read_str(tmp1, STRSZ, s);
+ *     r7 = bpf_probe_read_str(tmp2, STRSZ, t);
  *     tmp1[r6] = '\0';
  *     tmp2[r7] = '\0';
  *
@@ -88,7 +86,6 @@ dt_strcmp_not :
  *     // based on this location, judge if the strings are >, <, or ==
  *     if (r0 > r6) goto Lsame;
  *     if (r0 > r7) goto Lsame;
- *     r0 += DT_STRLEN_BYTES;
  *     if (s[r0] > t[r0]) return +1;
  *     if (s[r0] < t[r0]) return +1;
  *
@@ -114,17 +111,15 @@ dt_strcmp :
 	ldxdw	%r1, [%fp+-24]
 	mov	%r2, %r8
 	ldxdw	%r3, [%fp+-8]
-	add	%r3, DT_STRLEN_BYTES
-	call	BPF_FUNC_probe_read_str	/* r6 = bpf_probe_read_str(tmp1, STRSZ, s + DT_STRLEN_BYTES) */
+	call	BPF_FUNC_probe_read_str	/* r6 = bpf_probe_read_str(tmp1, STRSZ, s) */
 	mov	%r6, %r0
 	jle	%r6, %r8, 1
 	mov	%r6, %r8
 
 	ldxdw	%r1, [%fp+-32]
 	mov	%r2, %r8
 	ldxdw	%r3, [%fp+-16]
-	add	%r3, DT_STRLEN_BYTES
-	call	BPF_FUNC_probe_read_str	/* r7 = bpf_probe_read_str(tmp2, STRSZ, t + DT_STRLEN_BYTES) */
+	call	BPF_FUNC_probe_read_str	/* r7 = bpf_probe_read_str(tmp2, STRSZ, t) */
 	mov	%r7, %r0
 	jle	%r7, %r8, 1
 	mov	%r7, %r8
@@ -155,7 +150,6 @@ dt_strcmp :
 
 	jsle	%r0, 0, .L0		/* help the BPF verifier */
 	lddw	%r8, STRSZ
-	sub	%r8, DT_STRLEN_BYTES
 	jlt	%r0, %r8, 1
 	mov	%r0, %r8
 
@@ -164,8 +158,6 @@ dt_strcmp :
 	jgt	%r0, %r6, .Lsame	/* if (r0 > r6) goto Lsame */
 	jgt	%r0, %r8, .Lsame	/* if (r0 > r8) goto Lsame */
 
-	add	%r0, DT_STRLEN_BYTES	/* r0 += DT_STRLEN_BYTES */
-
 	ldxdw	%r4, [%fp+-8]
 	add	%r4, %r0
 	ldxb	%r4, [%r4+0]		/* s[r0] */