kbuild: fix modpost warnings for xtensa

The Xtensa architecture places literal pools in sections separate
from the instructions. The corresponsing text sections, therefore,
reference the .literal section, and we have to suppress those
warnings.

The naming convention defines the name for a literal
section as .SECTION.literal, unless .SECTION is .text. In that case
the name is only .literal. Using strncmp() instead of strcmp()
to compare the from-section with .SECTION.init.refok in pattern 0
should not cause any regressions for other architectures.

We also need to suppress warnings for two informational
sections (.xt.lit and .xt.prop) used by the Xtensa architecture.
Signed-off-by: Chris Zankel <chris@zankel.net>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>

scripts/mod/modpost.c

@@ -640,7 +640,7 @@ static int data_section(const char *name)
  * Pattern 0:
  *   Do not warn if funtion/data are marked with __init_refok/__initdata_refok.
  *   The pattern is identified by:
- *   fromsec = .text.init.refok | .data.init.refok
+ *   fromsec = .text.init.refok* | .data.init.refok*
  *
  * Pattern 1:
  *   If a module parameter is declared __initdata and permissions=0
@@ -675,11 +675,18 @@ static int data_section(const char *name)
  *   This pattern is identified by
  *   refsymname = __init_begin, _sinittext, _einittext
  *
+ * Pattern 5:
+ *   Xtensa uses literal sections for constants that are accessed PC-relative.
+ *   Literal sections may safely reference their text sections.
+ *   (Note that the name for the literal section omits any trailing '.text')
+ *   tosec = <section>[.text]
+ *   fromsec = <section>.literal
  **/
 static int secref_whitelist(const char *modname, const char *tosec,
 			    const char *fromsec, const char *atsym,
 			    const char *refsymname)
 {
+	int len;
 	const char **s;
 	const char *pat2sym[] = {
 		"driver",
@@ -701,8 +708,8 @@ static int secref_whitelist(const char *modname, const char *tosec,
 	};
 
 	/* Check for pattern 0 */
-	if ((strcmp(fromsec, ".text.init.refok") == 0) ||
-	    (strcmp(fromsec, ".data.init.refok") == 0))
+	if ((strncmp(fromsec, ".text.init.refok", strlen(".text.init.refok")) == 0) ||
+	    (strncmp(fromsec, ".data.init.refok", strlen(".data.init.refok")) == 0))
 		return 1;
 
 	/* Check for pattern 1 */
@@ -728,6 +735,15 @@ static int secref_whitelist(const char *modname, const char *tosec,
 		if (strcmp(refsymname, *s) == 0)
 			return 1;
 
+	/* Check for pattern 5 */
+	if (strrcmp(tosec, ".text") == 0)
+		len = strlen(tosec) - strlen(".text");
+	else
+		len = strlen(tosec);
+	if ((strncmp(tosec, fromsec, len) == 0) && (strlen(fromsec) > len) &&
+	    (strcmp(fromsec + len, ".literal") == 0))
+		return 1;
+
 	return 0;
 }
 
@@ -856,9 +872,9 @@ static void warn_sec_mismatch(const char *modname, const char *fromsec,
 		refsymname = elf->strtab + refsym->st_name;
 
 	/* check whitelist - we may ignore it */
-	if (before &&
-	    secref_whitelist(modname, secname, fromsec,
-			     elf->strtab + before->st_name, refsymname))
+	if (secref_whitelist(modname, secname, fromsec,
+			     before ? elf->strtab + before->st_name : "",
+	                     refsymname))
 		return;
 
 	if (before && after) {
@@ -1111,6 +1127,8 @@ static int initexit_section_ref_ok(const char *name)
 		".smp_locks",
 		".stab",
 		".m68k_fixup",
+		".xt.prop",		/* xtensa informational section */
+		".xt.lit",		/* xtensa informational section */
 		NULL
 	};
 	/* Start of section names */