kpatch-elf: Fix rela->string calculation

On s390x, .L1^B19 -> .rodata.str (bug_table) .LC0 -> .rodata.str1.2 In these cases, return true and rela->string should point to rela->sym->sec->data->d_buf + value of the associated symbol. Previous result: offset 68, type 26, .LC0 + 2 (string = NETDEV_UP) offset 78, type 26, .LC17 + 2 (string = NETDEV_UP) offset 88, type 26, .LC2 + 2 (string = NETDEV_UP) After fix: offset 68, type 26, .LC0 + 2 (string = NETDEV_UP) offset 78, type 26, .LC17 + 2 (string = NETDEV_NOTIFY_PEERS) offset 88, type 26, .LC2 + 2 (string = NETDEV_REBOOT) Signed-off-by: Sumanth Korikkar <[email protected]>
dynup · Sep 20, 2021 · c6f87d6 · c6f87d6
1 parent 9d71c8d
commit c6f87d6
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Showing 2 changed files with 26 additions and 1 deletion.
diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
@@ -510,6 +510,10 @@ static bool rela_equal(struct rela *rela1, struct rela *rela2)
 	if (!rela_toc1 || !rela_toc2)
 		return false;
 
+	/*
+	 * For LC symbol, comparision is performed using rela->string.
+	 * rela->string is initialized appropriately based on LC symbol or not.
+	 */
 	if (rela_toc1->string)
 		return rela_toc2->string && !strcmp(rela_toc1->string, rela_toc2->string);
 

diff --git a/kpatch-build/kpatch-elf.c b/kpatch-build/kpatch-elf.c
@@ -151,6 +151,24 @@ int offset_of_string(struct list_head *list, char *name)
 	return index;
 }
 
+/*
+ * Check if the symbol name contains LC or L1^B.
+ *
+ * On s390x,
+ * .L1^B19 -> .rodata.str (bug_table)
+ * .LC0 -> .rodata.str1.2
+ *
+ *  In these cases, return true and rela->string should point to
+ *  rela->sym->sec->data->d_buf + value of the associated symbol.
+ */
+
+static bool lc_string(struct rela *rela) {
+	if (!strncmp(rela->sym->name, ".LC", 3) || !strncmp(rela->sym->name, ".L1", 3))
+		return true;
+	else
+		return false;
+}
+
 void kpatch_create_rela_list(struct kpatch_elf *kelf, struct section *sec)
 {
 	int index = 0, skip = 0;
@@ -193,7 +211,10 @@ void kpatch_create_rela_list(struct kpatch_elf *kelf, struct section *sec)
 			ERROR("could not find rela entry symbol\n");
 		if (rela->sym->sec &&
 		    (rela->sym->sec->sh.sh_flags & SHF_STRINGS)) {
-			rela->string = rela->sym->sec->data->d_buf + rela->addend;
+			if (lc_string(rela))
+				rela->string = rela->sym->sec->data->d_buf + rela->sym->sym.st_value;
+			else
+				rela->string = rela->sym->sec->data->d_buf + rela->addend;
 			if (!rela->string)
 				ERROR("could not lookup rela string for %s+%ld",
 				      rela->sym->name, rela->addend);