modpost: refactor namespace_from_kstrtabns() to not hard-code section name

Currently, namespace_from_kstrtabns() relies on the fact that
namespace strings are recorded in the __ksymtab_strings section.
Actually, it is coded in include/linux/export.h, but modpost does
not need to hard-code the section name.

Elf_Sym::st_shndx holds the index of the relevant section. Using it is
a more portable way to get the namespace string.

Make namespace_from_kstrtabns() simply call sym_get_data(), and delete
the info->ksymtab_strings .

While I was here, I added more 'const' qualifiers to pointers.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

scripts/mod/modpost.c

@@ -356,10 +356,10 @@ static enum export export_from_sec(struct elf_info *elf, unsigned int sec)
 		return export_unknown;
 }
 
-static const char *namespace_from_kstrtabns(struct elf_info *info,
-					    Elf_Sym *kstrtabns)
+static const char *namespace_from_kstrtabns(const struct elf_info *info,
+					    const Elf_Sym *sym)
 {
-	char *value = info->ksymtab_strings + kstrtabns->st_value;
+	const char *value = sym_get_data(info, sym);
 	return value[0] ? value : NULL;
 }
 
@@ -601,10 +601,6 @@ static int parse_elf(struct elf_info *info, const char *filename)
 			info->export_unused_gpl_sec = i;
 		else if (strcmp(secname, "__ksymtab_gpl_future") == 0)
 			info->export_gpl_future_sec = i;
-		else if (strcmp(secname, "__ksymtab_strings") == 0)
-			info->ksymtab_strings = (void *)hdr +
-						sechdrs[i].sh_offset -
-						sechdrs[i].sh_addr;
 
 		if (sechdrs[i].sh_type == SHT_SYMTAB) {
 			unsigned int sh_link_idx;

scripts/mod/modpost.h

@@ -143,7 +143,6 @@ struct elf_info {
 	Elf_Section  export_gpl_sec;
 	Elf_Section  export_unused_gpl_sec;
 	Elf_Section  export_gpl_future_sec;
-	char	     *ksymtab_strings;
 	char         *strtab;
 	char	     *modinfo;
 	unsigned int modinfo_len;