From: Ross Lagerwall <ross.lagerwall@citrix.com>
Date: Thu, 10 Nov 2016 10:58:45 +0000 (+0000)
Subject: Fix patch creation with GCC 6.1+
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=2af6f1aa6233;p=livepatch-build-tools.git

Fix patch creation with GCC 6.1+

GCC 6.1+ fixed https://gcc.gnu.org/bugzilla/show_bug.cgi?id=192 which
means that .rodata.str1.[0-9]+ sections are now split by function.  We
could probably be smarter about including just the sections we need, but
for now, simply include the string sections for all functions as is done
for previous versions of GCC.

Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
Reported-by: M A Young <m.a.young@durham.ac.uk>
---

diff --git a/create-diff-object.c b/create-diff-object.c
index bda0014..217e58f 100644
--- a/create-diff-object.c
+++ b/create-diff-object.c
@@ -41,6 +41,7 @@
 #include <sys/stat.h>
 #include <fcntl.h>
 #include <stdlib.h>
+#include <stdbool.h>
 #include <string.h>
 #include <libgen.h>
 #include <argp.h>
@@ -1223,6 +1224,47 @@ static void kpatch_process_special_sections(struct kpatch_elf *kelf)
 	}
 }
 
+/* Returns true if s is a string of only numbers with length > 0. */
+static bool isnumber(const char *s)
+{
+	do {
+		if (!*s || !isdigit(*s))
+			return false;
+	} while (*++s);
+
+	return true;
+}
+
+/*
+ * String sections are always included even if unchanged.
+ * The format is either:
+ * .rodata.<func>.str1.[0-9]+ (new in GCC 6.1.0)
+ * or .rodata.str1.[0-9]+ (older versions of GCC)
+ * For the new format we could be smarter and only include the needed
+ * strings sections.
+ */
+static bool should_include_str_section(const char *name)
+{
+#define GCC_5_SECTION_NAME ".rodata.str1."
+#define GCC_6_SECTION_NAME ".str1."
+	const char *s;
+
+	if (strncmp(name, ".rodata.", 8))
+		return false;
+
+	/* Check if name matches ".rodata.str1.[0-9]+" */
+	if (!strncmp(name, GCC_5_SECTION_NAME, strlen(GCC_5_SECTION_NAME)))
+		return isnumber(name + strlen(GCC_5_SECTION_NAME));
+
+	/* Check if name matches ".rodata.<func>.str1.[0-9]+" */
+	s = strstr(name, GCC_6_SECTION_NAME);
+	if (!s)
+		return false;
+	return isnumber(s + strlen(GCC_6_SECTION_NAME));
+#undef GCC_5_SECTION_NAME
+#undef GCC_6_SECTION_NAME
+}
+
 static void kpatch_include_standard_elements(struct kpatch_elf *kelf)
 {
 	struct section *sec;
@@ -1232,7 +1274,7 @@ static void kpatch_include_standard_elements(struct kpatch_elf *kelf)
 		if (!strcmp(sec->name, ".shstrtab") ||
 		    !strcmp(sec->name, ".strtab") ||
 		    !strcmp(sec->name, ".symtab") ||
-		    !strncmp(sec->name, ".rodata.str1.", 13)) {
+		    should_include_str_section(sec->name)) {
 			sec->include = 1;
 			if (sec->secsym)
 				sec->secsym->include = 1;