From: Rusty Russell Subject: module: document the use of strmap I have to re-read this code carefully every time to figure out what it's doing. Add some comments for next time. Cc: Jan Beulich Signed-off-by: Rusty Russell --- kernel/module.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/module.c b/kernel/module.c --- a/kernel/module.c +++ b/kernel/module.c @@ -2157,6 +2157,7 @@ static char elf_type(const Elf_Sym *sym, return '?'; } +/* These are the only symbols we save for kallsyms. */ static bool is_core_symbol(const Elf_Sym *src, const Elf_Shdr *sechdrs, unsigned int shnum) { @@ -2191,12 +2192,15 @@ static void layout_symtab(struct module info->index.sym) | INIT_OFFSET_MASK; DEBUGP("\t%s\n", info->secstrings + symsect->sh_name); + /* Look at all symbols in symtab, figure out how many we're keeping. */ src = (void *)info->hdr + symsect->sh_offset; nsrc = symsect->sh_size / sizeof(*src); for (ndst = i = 1; i < nsrc; ++i, ++src) if (is_core_symbol(src, info->sechdrs, info->hdr->e_shnum)) { + /* We are keeping this one! */ unsigned int j = src->st_name; + /* Mark string from strtab as used in strmap bitmap. */ while (!__test_and_set_bit(j, info->strmap) && info->strtab[j]) ++j; @@ -2215,7 +2219,6 @@ static void layout_symtab(struct module /* Append room for core symbols' strings at end of core part. */ info->stroffs = mod->core_size; - __set_bit(0, info->strmap); mod->core_size += bitmap_weight(info->strmap, strsect->sh_size); } @@ -2239,6 +2242,7 @@ static void add_kallsyms(struct module * mod->core_symtab = dst = mod->module_core + info->symoffs; mod->core_strtab = s = mod->module_core + info->stroffs; src = mod->symtab; + /* Always copy first symbol. */ *dst = *src; *s++ = 0; for (ndst = i = 1; i < mod->num_symtab; ++i, ++src) { @@ -2753,6 +2757,7 @@ static struct module *layout_and_allocat special cases for the architectures. */ layout_sections(mod, info); + /* This bitmap is used to track what's used in the strtab. */ info->strmap = kzalloc(BITS_TO_LONGS(info->sechdrs[info->index.str].sh_size) * sizeof(long), GFP_KERNEL); if (!info->strmap) {