module: Add comments describing how the "strmap" logic works
Signed-off-by: Kevin Cernekee <cernekee@gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/kernel/module.c b/kernel/module.c
index 178333c..cf9f1b6 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2193,6 +2193,13 @@
src = (void *)info->hdr + symsect->sh_offset;
nsrc = symsect->sh_size / sizeof(*src);
+
+ /*
+ * info->strmap has a '1' bit for each byte of .strtab we want to
+ * keep resident in mod->core_strtab. Everything else in .strtab
+ * is unreferenced by the symbols in mod->core_symtab, and will be
+ * discarded when add_kallsyms() compacts the string table.
+ */
for (ndst = i = 1; i < nsrc; ++i, ++src)
if (is_core_symbol(src, info->sechdrs, info->hdr->e_shnum)) {
unsigned int j = src->st_name;
@@ -2215,6 +2222,8 @@
/* Append room for core symbols' strings at end of core part. */
info->stroffs = mod->core_size;
+
+ /* First strtab byte (and first symtab entry) are zeroes. */
__set_bit(0, info->strmap);
mod->core_size += bitmap_weight(info->strmap, strsect->sh_size);
}