kbuild, kallsyms: Ignore source file weak symbols

With LTO gcc-nm generates some strange weak symbols for each source
file. These are outside the normal kernel range and confuse
kallsyms, resulting in incorrect kallsyms tables.

Just ignore them as they are not needed for symbolization.

Signed-off-by: Andi Kleen <[email protected]>
Signed-off-by: Adam W. Willis <[email protected]>

scripts/kallsyms.c

@@ -109,7 +109,7 @@ static int check_symbol_range(const char *sym, unsigned long long addr,
 
 static int read_symbol(FILE *in, struct sym_entry *s)
 {
-	char sym[500], stype;
+	char sym[500], stype, *p;
 	int rc;
 
 	rc = fscanf(in, "%llx %c %499s\n", &s->addr, &stype, sym);
@@ -150,6 +150,17 @@ static int read_symbol(FILE *in, struct sym_entry *s)
 	/* exclude debugging symbols */
 	else if (stype == 'N' || stype == 'n')
 		return -1;
+	/* gcc-nm produces extra weak symbols for C files
+	 * in the form
+	 * 000000000003aa8b W version.c.36323a88
+	 * ignore they are outside the supported range
+	 * and confuse the symbol generation, and they
+	 * are not useful for symbolization.
+	 */
+	else if ((stype = 'W' || stype == 'w') &&
+		(p = strstr(sym, ".c.")) &&
+		isxdigit(p[3]))
+		return -1;
 	/* exclude s390 kasan local symbols */
 	else if (!strncmp(sym, ".LASANPC", 8))
 		return -1;