linux-kernel - [PATCH v2 03/10] modpost: remove useless export_from

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Message-Id: <20220405113359.2880241-4-masahiroy@kernel.org>
Date:   Tue,  5 Apr 2022 20:33:51 +0900
From:   Masahiro Yamada <masahiroy@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Michal Marek <michal.lkml@...kovi.net>
Subject: [PATCH v2 03/10] modpost: remove useless export_from_sec()

With commit 1743694eb235 ("modpost: stop symbol preloading for
modversion CRC") applied, now export_from_sec() is useless.

handle_symbol() is called for every symbol in the ELF.

When 'symname' does not start with "__ksymtab", export_from_sec() is
called, and the returned value is stored in 'export'.

It is used in the last part of handle_symbol():

    if (strstarts(symname, "__ksymtab_")) {
            name = symname + strlen("__ksymtab_");
            sym_add_exported(name, mod, export);
    }

'export' is used only when 'symname' starts with "__ksymtab_".

So, the value returned by export_from_sec() is never used.

Remove useless export_from_sec(). This makes further cleanups possible.

I put the temporary code:

    export = export_unknown;

Otherwise, I would get the compiler warning:

    warning: 'export' may be used uninitialized in this function [-Wmaybe-uninitialized]

This is apparently false positive because

    if (strstarts(symname, "__ksymtab_")

... is a stronger condition than:

    if (strstarts(symname, "__ksymtab")

Anyway, this part will be cleaned up by the next commit.

Signed-off-by: Masahiro Yamada <masahiroy@...nel.org>
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>
---

Changes in v2:
  - Fix compiler warning

 scripts/mod/modpost.c | 17 ++---------------
 scripts/mod/modpost.h |  4 ----
 2 files changed, 2 insertions(+), 19 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index ed9d056d2108..eebb32689816 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -369,16 +369,6 @@ static enum export export_from_secname(struct elf_info *elf, unsigned int sec)
 		return export_unknown;
 }
 
-static enum export export_from_sec(struct elf_info *elf, unsigned int sec)
-{
-	if (sec == elf->export_sec)
-		return export_plain;
-	else if (sec == elf->export_gpl_sec)
-		return export_gpl;
-	else
-		return export_unknown;
-}
-
 static const char *namespace_from_kstrtabns(const struct elf_info *info,
 					    const Elf_Sym *sym)
 {
@@ -576,10 +566,7 @@ static int parse_elf(struct elf_info *info, const char *filename)
 				fatal("%s has NOBITS .modinfo\n", filename);
 			info->modinfo = (void *)hdr + sechdrs[i].sh_offset;
 			info->modinfo_len = sechdrs[i].sh_size;
-		} else if (strcmp(secname, "__ksymtab") == 0)
-			info->export_sec = i;
-		else if (strcmp(secname, "__ksymtab_gpl") == 0)
-			info->export_gpl_sec = i;
+		}
 
 		if (sechdrs[i].sh_type == SHT_SYMTAB) {
 			unsigned int sh_link_idx;
@@ -703,7 +690,7 @@ static void handle_symbol(struct module *mod, struct elf_info *info,
 	if (strstarts(symname, "__ksymtab"))
 		export = export_from_secname(info, get_secindex(info, sym));
 	else
-		export = export_from_sec(info, get_secindex(info, sym));
+		export = export_unknown;
 
 	switch (sym->st_shndx) {
 	case SHN_COMMON:
diff --git a/scripts/mod/modpost.h b/scripts/mod/modpost.h
index 0c47ff95c0e2..a85dcec3669a 100644
--- a/scripts/mod/modpost.h
+++ b/scripts/mod/modpost.h
@@ -25,7 +25,6 @@
 #define Elf_Sym     Elf32_Sym
 #define Elf_Addr    Elf32_Addr
 #define Elf_Sword   Elf64_Sword
-#define Elf_Section Elf32_Half
 #define ELF_ST_BIND ELF32_ST_BIND
 #define ELF_ST_TYPE ELF32_ST_TYPE
 
@@ -40,7 +39,6 @@
 #define Elf_Sym     Elf64_Sym
 #define Elf_Addr    Elf64_Addr
 #define Elf_Sword   Elf64_Sxword
-#define Elf_Section Elf64_Half
 #define ELF_ST_BIND ELF64_ST_BIND
 #define ELF_ST_TYPE ELF64_ST_TYPE
 
@@ -138,8 +136,6 @@ struct elf_info {
 	Elf_Shdr     *sechdrs;
 	Elf_Sym      *symtab_start;
 	Elf_Sym      *symtab_stop;
-	Elf_Section  export_sec;
-	Elf_Section  export_gpl_sec;
 	char         *strtab;
 	char	     *modinfo;
 	unsigned int modinfo_len;
-- 
2.32.0