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