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kbuild, modpost: Check the section flags, to catch missing "ax"/"aw"

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When you put
  .section ".foo"
in an assembly file instead of
  .section "foo", "ax"
, one of the possible symptoms is that modpost will see an
ld-generated section name ".foo.1" in section_rel() or section_rela().
But this heuristic has two problems: it will miss a bad section that
has no relocations, and it will incorrectly flag many gcc-generated
sections as bad when compiling with -ffunction-sections
-fdata-sections.

On mips it fixes a lot of bogus warnings with gcc 4.4.0 lije this one:
WARNING: crypto/cryptd.o (.text.T.349): unexpected section name.

So instead of checking whether the section name matches a particular
pattern, we directly check for a missing SHF_ALLOC in the section
flags.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>
Tested-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
This commit is contained in:
Anders Kaseorg 2009-04-23 16:49:33 -04:00 committed by Sam Ravnborg
parent c993971f4a
commit b614a697dc
1 changed files with 17 additions and 30 deletions
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47
scripts/mod/modpost.c
View file

@ -716,41 +716,27 @@ int match(const char *sym, const char * const pat[])
/* sections that we do not want to do full section mismatch check on */
static const char *section_white_list[] =
{ ".debug*", ".stab*", ".note*", ".got*", ".toc*", NULL };
{ ".comment", ".debug*", ".stab*", ".note*", ".got*", ".toc*", NULL };
/*
* Is this section one we do not want to check?
* This is often debug sections.
* If we are going to check this section then
* test if section name ends with a dot and a number.
* This is used to find sections where the linker have
* appended a dot-number to make the name unique.
* This is used to find sections missing the SHF_ALLOC flag.
* The cause of this is often a section specified in assembler
* without "ax" / "aw" and the same section used in .c
* code where gcc add these.
* without "ax" / "aw".
*/
static int check_section(const char *modname, const char *sec)
static void check_section(const char *modname, struct elf_info *elf,
Elf_Shdr *sechdr)
{
const char *e = sec + strlen(sec) - 1;
if (match(sec, section_white_list))
return 1;
const char *sec = sech_name(elf, sechdr);
if (*e && isdigit(*e)) {
/* consume all digits */
while (*e && e != sec && isdigit(*e))
e--;
if (*e == '.' && !strstr(sec, ".linkonce")) {
warn("%s (%s): unexpected section name.\n"
"The (.[number]+) following section name are "
"ld generated and not expected.\n"
"Did you forget to use \"ax\"/\"aw\" "
"in a .S file?\n"
"Note that for example <linux/init.h> contains\n"
"section definitions for use in .S files.\n\n",
modname, sec);
}
if (sechdr->sh_type == SHT_PROGBITS &&
!(sechdr->sh_flags & SHF_ALLOC) &&
!match(sec, section_white_list)) {
warn("%s (%s): unexpected non-allocatable section.\n"
"Did you forget to use \"ax\"/\"aw\" in a .S file?\n"
"Note that for example <linux/init.h> contains\n"
"section definitions for use in .S files.\n\n",
modname, sec);
}
return 0;
}
@ -1358,7 +1344,7 @@ static void section_rela(const char *modname, struct elf_info *elf,
fromsec = sech_name(elf, sechdr);
fromsec += strlen(".rela");
/* if from section (name) is know good then skip it */
if (check_section(modname, fromsec))
if (match(fromsec, section_white_list))
return;
for (rela = start; rela < stop; rela++) {
@ -1402,7 +1388,7 @@ static void section_rel(const char *modname, struct elf_info *elf,
fromsec = sech_name(elf, sechdr);
fromsec += strlen(".rel");
/* if from section (name) is know good then skip it */
if (check_section(modname, fromsec))
if (match(fromsec, section_white_list))
return;
for (rel = start; rel < stop; rel++) {
@ -1465,6 +1451,7 @@ static void check_sec_ref(struct module *mod, const char *modname,
/* Walk through all sections */
for (i = 0; i < elf->hdr->e_shnum; i++) {
check_section(modname, elf, &elf->sechdrs[i]);
/* We want to process only relocation sections and not .init */
if (sechdrs[i].sh_type == SHT_RELA)
section_rela(modname, elf, &elf->sechdrs[i]);