module: keep percpu symbols in module's symtab (e0224418) · Commits · 戴 / test

Currently, percpu symbols from .data..percpu ELF section of a module are not copied over and stored in final symtab array of struct module. Consequently such symbol cannot be returned via kallsyms API (for example kallsyms_lookup_name). This can be especially confusing when the percpu symbol is exported. Only its __ksymtab et al. are present in its symtab. The culprit is in layout_and_allocate() function where SHF_ALLOC flag is dropped for .data..percpu section. There is in fact no need to copy the section to final struct module, because kernel module loader allocates extra percpu section by itself. Unfortunately only symbols from SHF_ALLOC sections are copied due to a check in is_core_symbol(). The patch changes is_core_symbol() function to copy over also percpu symbols (their st_shndx points to .data..percpu ELF section). We do it only if CONFIG_KALLSYMS_ALL is set to be consistent with the rest of the function (ELF section is SHF_ALLOC but !SHF_EXECINSTR). Finally elf_type() returns type 'a' for a percpu symbol because its address is absolute. Signed-off-by:

Miroslav Benes <mbenes@suse.cz> Signed-off-by:

Rusty Russell <rusty@rustcorp.com.au> Signed-off-by:

Jiri Kosina <jkosina@suse.cz>

kernel/module.c

+11 −4

Original line number	Diff line number	Diff line
		@@ -2383,7 +2383,7 @@ static char elf_type(const Elf_Sym sym, const struct load_info info)
		}
		if (sym->st_shndx == SHN_UNDEF)
		return 'U';
		if (sym->st_shndx == SHN_ABS)
		if (sym->st_shndx == SHN_ABS \|\| sym->st_shndx == info->index.pcpu)
		return 'a';
		if (sym->st_shndx >= SHN_LORESERVE)
		return '?';
		@@ -2412,7 +2412,7 @@ static char elf_type(const Elf_Sym sym, const struct load_info info)
		}

		static bool is_core_symbol(const Elf_Sym src, const Elf_Shdr sechdrs,
		unsigned int shnum)
		unsigned int shnum, unsigned int pcpundx)
		{
		const Elf_Shdr *sec;

		@@ -2421,6 +2421,11 @@ static bool is_core_symbol(const Elf_Sym src, const Elf_Shdr sechdrs,
		\|\| !src->st_name)
		return false;

		#ifdef CONFIG_KALLSYMS_ALL
		if (src->st_shndx == pcpundx)
		return true;
		#endif

		sec = sechdrs + src->st_shndx;
		if (!(sec->sh_flags & SHF_ALLOC)
		#ifndef CONFIG_KALLSYMS_ALL
		@@ -2458,7 +2463,8 @@ static void layout_symtab(struct module mod, struct load_info info)
		/* Compute total space required for the core symbols' strtab. */
		for (ndst = i = 0; i < nsrc; i++) {
		if (i == 0 \|\|
		is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum)) {
		is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum,
		info->index.pcpu)) {
		strtab_size += strlen(&info->strtab[src[i].st_name])+1;
		ndst++;
		}
		@@ -2500,7 +2506,8 @@ static void add_kallsyms(struct module mod, const struct load_info info)
		src = mod->symtab;
		for (ndst = i = 0; i < mod->num_symtab; i++) {
		if (i == 0 \|\|
		is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum)) {
		is_core_symbol(src+i, info->sechdrs, info->hdr->e_shnum,
		info->index.pcpu)) {
		dst[ndst] = src[i];
		dst[ndst++].st_name = s - mod->core_strtab;
		s += strlcpy(s, &mod->strtab[src[i].st_name],

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