arm64/__mc_ex_table: fix __mc_ex_table do_sort() issue

hulk inclusion
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5GB28
CVE: NA

-------------------------------

If ARCH_HAS_MC_EXTABLE is not set then the _mc_ex_table is empty.

There is a logic error in do_sort(). _mc_ex_table is different from
_ex_table. _ex_table is always not empty, while _mc_ex_table may be empty.
If _mc_ex_table is empty, there is a issue with setting the initial value
of mc_extable_index to 0.

Fixes: 8bb071c9 ("arm64: extable: add new extable type "__mc_ex_table"")
Signed-off-by: NTong Tiangen <tongtiangen@huawei.com>
Reviewed-by: NKefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

scripts/sorttable.h

@@ -227,7 +227,6 @@ static int do_sort(Elf_Ehdr *ehdr,
 	Elf_Rel *mc_relocs = NULL;
 	int mc_relocs_size = 0;
 	char *mc_extab_image = NULL;
-	int mc_extab_index = 0;
 
 	shstrndx = r2(&ehdr->e_shstrndx);
 	if (shstrndx == SHN_XINDEX)
@@ -245,11 +244,6 @@ static int do_sort(Elf_Ehdr *ehdr,
 			extab_index = i;
 		}
 
-		if (!strcmp(secstrings + idx, "__mc_ex_table")) {
-			mc_extab_sec = s;
-			mc_extab_index = i;
-		}
-
 		if (!strcmp(secstrings + idx, ".symtab"))
 			symtab_sec = s;
 		if (!strcmp(secstrings + idx, ".strtab"))
@@ -262,11 +256,15 @@ static int do_sort(Elf_Ehdr *ehdr,
 			relocs_size = _r(&s->sh_size);
 		}
 
-		if ((r(&s->sh_type) == SHT_REL ||
-		     r(&s->sh_type) == SHT_RELA) &&
-		    r(&s->sh_info) == mc_extab_index) {
-			mc_relocs = (void *)ehdr + _r(&s->sh_offset);
-			mc_relocs_size = _r(&s->sh_size);
+		if (!strcmp(secstrings + idx, "__mc_ex_table")) {
+			mc_extab_sec = s;
+
+			if ((r(&s->sh_type) == SHT_REL ||
+				r(&s->sh_type) == SHT_RELA) &&
+				r(&s->sh_info) == i) {
+				mc_relocs = (void *)ehdr + _r(&s->sh_offset);
+				mc_relocs_size = _r(&s->sh_size);
+			}
 		}
 
 		if (r(&s->sh_type) == SHT_SYMTAB_SHNDX)