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Message-ID: <20090429204846.GA655@uranus.ravnborg.org>
Date: Wed, 29 Apr 2009 22:48:46 +0200
From: Sam Ravnborg <sam@...nborg.org>
To: Ralf Baechle <ralf@...ux-mips.org>
Cc: linux-kernel@...r.kernel.org
Subject: Re: [PATCH, RFC] Fix bogus modpost warnings
On Wed, Apr 29, 2009 at 02:32:11PM +0200, Ralf Baechle wrote:
> Trying to build the current kernel with gcc 4.4.0 will result in a large
> number of apparently bogus warnings like these:
>
> WARNING: crypto/cryptd.o (.text.T.349): unexpected section name.
> The (.[number]+) following section name are ld generated and not expected.
> Did you forget to use "ax"/"aw" in a .S file?
> Note that for example <linux/init.h> contains
> section definitions for use in .S files.
>
> WARNING: drivers/block/pktcdvd.o (.text.T.772): unexpected section name.
> The (.[number]+) following section name are ld generated and not expected.
> Did you forget to use "ax"/"aw" in a .S file?
> Note that for example <linux/init.h> contains
> section definitions for use in .S files.
>
> emitted by modpost. This is because with -ffunction-sections gcc may now
> generate some section names like .text.T.772 itself instead of like in
> the past deriving those from the function's name like .text.ipgre_close.
>
> Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
> ---
>
> For now I see this patch as a proposal only. I'm also not sure if with
> this addition check there are still section names left for which the if
> condition would ever be true. Data sections maybe?
Anders Kaseorg already wrote a better patch to fix this - appended below.
Could you please give it a try and let me know it it
works for you too.
It is about to be applied to kbuild-next - I have just been sidetracked
by other stuff.
Sam
From: Anders Kaseorg <andersk@....edu>
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.
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@....edu>
---
scripts/mod/modpost.c | 49 ++++++++++++++++++-------------------------------
1 files changed, 18 insertions(+), 31 deletions(-)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index f39132b..3e6ff75 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -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)
-{
- const char *e = sec + strlen(sec) - 1;
- if (match(sec, section_white_list))
- return 1;
-
- 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);
- }
+static void check_section(const char *modname, struct elf_info *elf,
+ Elf_Shdr *sechdr)
+{
+ const char *sec = sech_name(elf, sechdr);
+
+ 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;
}
@@ -1377,7 +1363,7 @@ 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++) {
@@ -1421,7 +1407,7 @@ 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++) {
@@ -1484,6 +1470,7 @@ 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]);
--
1.6.2.1
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