linux/scripts/genksyms/keywords.c
Masahiro Yamada 69a94abb82 export.h, genksyms: do not make genksyms calculate CRC of trimmed symbols
Arnd Bergmann reported false-positive modpost warnings detected by his
randconfig testing of linux-next.

Actually, this happens under the combination of CONFIG_MODVERSIONS
and CONFIG_TRIM_UNUSED_KSYMS since commit 15bfc2348d ("modpost:
check for static EXPORT_SYMBOL* functions").

For example, arch/arm/config/multi_v7_defconfig + CONFIG_MODVERSIONS
+ CONFIG_TRIM_UNUSED_KSYMS produces the following false-positives:

WARNING: "__lshrdi3" [vmlinux] is a static (unknown)
WARNING: "__ashrdi3" [vmlinux] is a static (unknown)
WARNING: "__aeabi_lasr" [vmlinux] is a static (unknown)
WARNING: "__aeabi_llsr" [vmlinux] is a static (unknown)
WARNING: "ftrace_set_clr_event" [vmlinux] is a static (unknown)
WARNING: "__muldi3" [vmlinux] is a static (unknown)
WARNING: "__aeabi_ulcmp" [vmlinux] is a static (unknown)
WARNING: "__ucmpdi2" [vmlinux] is a static (unknown)
WARNING: "__aeabi_lmul" [vmlinux] is a static (unknown)
WARNING: "__bswapsi2" [vmlinux] is a static (unknown)
WARNING: "__bswapdi2" [vmlinux] is a static (unknown)
WARNING: "__ashldi3" [vmlinux] is a static (unknown)
WARNING: "__aeabi_llsl" [vmlinux] is a static (unknown)

The root cause of the problem is not in the modpost, but in the
implementation of CONFIG_TRIM_UNUSED_KSYMS.

If there is at least one untrimmed symbol in the file, genksyms is
invoked to calculate CRC of *all* the exported symbols in that file
even if some of them have been trimmed due to no caller existing.

As a result, .tmp_*.ver files contain CRC of trimmed symbols, thus
unneeded, orphan __crc* symbols are added to objects. It had been
harmless until recently.

With commit 15bfc2348d ("modpost: check for static EXPORT_SYMBOL*
functions"), it is now harmful because the bogus __crc* symbols make
modpost call sym_update_crc() to add the symbols to the hash table,
but there is no one that clears the ->is_static member.

I gave Fixes to the first commit that uncovered the issue, but the
potential problem has long existed since commit f235541699
("export.h: allow for per-symbol configurable EXPORT_SYMBOL()").

Fixes: 15bfc2348d ("modpost: check for static EXPORT_SYMBOL* functions")
Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Tested-by: Arnd Bergmann <arnd@arndb.de>
2019-09-14 11:40:13 +09:00

76 lines
2.1 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
static struct resword {
const char *name;
int token;
} keywords[] = {
{ "__GENKSYMS_EXPORT_SYMBOL", EXPORT_SYMBOL_KEYW },
{ "__asm", ASM_KEYW },
{ "__asm__", ASM_KEYW },
{ "__attribute", ATTRIBUTE_KEYW },
{ "__attribute__", ATTRIBUTE_KEYW },
{ "__const", CONST_KEYW },
{ "__const__", CONST_KEYW },
{ "__extension__", EXTENSION_KEYW },
{ "__inline", INLINE_KEYW },
{ "__inline__", INLINE_KEYW },
{ "__signed", SIGNED_KEYW },
{ "__signed__", SIGNED_KEYW },
{ "__typeof", TYPEOF_KEYW },
{ "__typeof__", TYPEOF_KEYW },
{ "__volatile", VOLATILE_KEYW },
{ "__volatile__", VOLATILE_KEYW },
{ "__builtin_va_list", VA_LIST_KEYW },
{ "__int128", BUILTIN_INT_KEYW },
{ "__int128_t", BUILTIN_INT_KEYW },
{ "__uint128_t", BUILTIN_INT_KEYW },
// According to rth, c99 defines "_Bool", __restrict", __restrict__", "restrict". KAO
{ "_Bool", BOOL_KEYW },
{ "_restrict", RESTRICT_KEYW },
{ "__restrict__", RESTRICT_KEYW },
{ "restrict", RESTRICT_KEYW },
{ "asm", ASM_KEYW },
// attribute commented out in modutils 2.4.2. People are using 'attribute' as a
// field name which breaks the genksyms parser. It is not a gcc keyword anyway.
// KAO. },
// { "attribute", ATTRIBUTE_KEYW },
{ "auto", AUTO_KEYW },
{ "char", CHAR_KEYW },
{ "const", CONST_KEYW },
{ "double", DOUBLE_KEYW },
{ "enum", ENUM_KEYW },
{ "extern", EXTERN_KEYW },
{ "float", FLOAT_KEYW },
{ "inline", INLINE_KEYW },
{ "int", INT_KEYW },
{ "long", LONG_KEYW },
{ "register", REGISTER_KEYW },
{ "short", SHORT_KEYW },
{ "signed", SIGNED_KEYW },
{ "static", STATIC_KEYW },
{ "struct", STRUCT_KEYW },
{ "typedef", TYPEDEF_KEYW },
{ "typeof", TYPEOF_KEYW },
{ "union", UNION_KEYW },
{ "unsigned", UNSIGNED_KEYW },
{ "void", VOID_KEYW },
{ "volatile", VOLATILE_KEYW },
};
#define NR_KEYWORDS (sizeof(keywords)/sizeof(struct resword))
static int is_reserved_word(register const char *str, register unsigned int len)
{
int i;
for (i = 0; i < NR_KEYWORDS; i++) {
struct resword *r = keywords + i;
int l = strlen(r->name);
if (len == l && !memcmp(str, r->name, len))
return r->token;
}
return -1;
}