module: reduce symbol table for loaded modules (v2)
Discard all symbols not interesting for kallsyms use: absolute,
section, and in the common case (!KALLSYMS_ALL) data ones.
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/kernel/module.c b/kernel/module.c
index e6bc4b2..97f4d5e 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1862,13 +1862,68 @@
return '?';
}
+static bool is_core_symbol(const Elf_Sym *src, const Elf_Shdr *sechdrs,
+ unsigned int shnum)
+{
+ const Elf_Shdr *sec;
+
+ if (src->st_shndx == SHN_UNDEF
+ || src->st_shndx >= shnum
+ || !src->st_name)
+ return false;
+
+ sec = sechdrs + src->st_shndx;
+ if (!(sec->sh_flags & SHF_ALLOC)
+#ifndef CONFIG_KALLSYMS_ALL
+ || !(sec->sh_flags & SHF_EXECINSTR)
+#endif
+ || (sec->sh_entsize & INIT_OFFSET_MASK))
+ return false;
+
+ return true;
+}
+
+static unsigned long layout_symtab(struct module *mod,
+ Elf_Shdr *sechdrs,
+ unsigned int symindex,
+ const Elf_Ehdr *hdr,
+ const char *secstrings)
+{
+ unsigned long symoffs;
+ Elf_Shdr *symsect = sechdrs + symindex;
+ const Elf_Sym *src;
+ unsigned int i, nsrc, ndst;
+
+ /* Put symbol section at end of init part of module. */
+ symsect->sh_flags |= SHF_ALLOC;
+ symsect->sh_entsize = get_offset(mod, &mod->init_size, symsect,
+ symindex) | INIT_OFFSET_MASK;
+ DEBUGP("\t%s\n", secstrings + symsect->sh_name);
+
+ src = (void *)hdr + symsect->sh_offset;
+ nsrc = symsect->sh_size / sizeof(*src);
+ for (ndst = i = 1; i < nsrc; ++i, ++src)
+ if (is_core_symbol(src, sechdrs, hdr->e_shnum))
+ ++ndst;
+
+ /* Append room for core symbols at end of core part. */
+ symoffs = ALIGN(mod->core_size, symsect->sh_addralign ?: 1);
+ mod->core_size = symoffs + ndst * sizeof(Elf_Sym);
+
+ return symoffs;
+}
+
static void add_kallsyms(struct module *mod,
Elf_Shdr *sechdrs,
+ unsigned int shnum,
unsigned int symindex,
unsigned int strindex,
+ unsigned long symoffs,
const char *secstrings)
{
- unsigned int i;
+ unsigned int i, ndst;
+ const Elf_Sym *src;
+ Elf_Sym *dst;
mod->symtab = (void *)sechdrs[symindex].sh_addr;
mod->num_symtab = sechdrs[symindex].sh_size / sizeof(Elf_Sym);
@@ -1878,12 +1933,32 @@
for (i = 0; i < mod->num_symtab; i++)
mod->symtab[i].st_info
= elf_type(&mod->symtab[i], sechdrs, secstrings, mod);
+
+ mod->core_symtab = dst = mod->module_core + symoffs;
+ src = mod->symtab;
+ *dst = *src;
+ for (ndst = i = 1; i < mod->num_symtab; ++i, ++src) {
+ if (!is_core_symbol(src, sechdrs, shnum))
+ continue;
+ dst[ndst] = *src;
+ ++ndst;
+ }
+ mod->core_num_syms = ndst;
}
#else
+static inline unsigned long layout_symtab(struct module *mod,
+ Elf_Shdr *sechdrs,
+ unsigned int symindex,
+ const Elf_Hdr *hdr,
+ const char *secstrings)
+{
+}
static inline void add_kallsyms(struct module *mod,
Elf_Shdr *sechdrs,
+ unsigned int shnum,
unsigned int symindex,
unsigned int strindex,
+ unsigned long symoffs,
const char *secstrings)
{
}
@@ -1959,6 +2034,9 @@
struct module *mod;
long err = 0;
void *percpu = NULL, *ptr = NULL; /* Stops spurious gcc warning */
+#ifdef CONFIG_KALLSYMS
+ unsigned long symoffs;
+#endif
mm_segment_t old_fs;
DEBUGP("load_module: umod=%p, len=%lu, uargs=%p\n",
@@ -2041,8 +2119,7 @@
sechdrs[infoindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
sechdrs[versindex].sh_flags &= ~(unsigned long)SHF_ALLOC;
#ifdef CONFIG_KALLSYMS
- /* Keep symbol and string tables for decoding later. */
- sechdrs[symindex].sh_flags |= SHF_ALLOC;
+ /* Keep string table for decoding later. */
sechdrs[strindex].sh_flags |= SHF_ALLOC;
#endif
@@ -2109,6 +2186,7 @@
this is done generically; there doesn't appear to be any
special cases for the architectures. */
layout_sections(mod, hdr, sechdrs, secstrings);
+ symoffs = layout_symtab(mod, sechdrs, symindex, hdr, secstrings);
/* Do the allocs. */
ptr = module_alloc_update_bounds(mod->core_size);
@@ -2313,7 +2391,8 @@
percpu_modcopy(mod->percpu, (void *)sechdrs[pcpuindex].sh_addr,
sechdrs[pcpuindex].sh_size);
- add_kallsyms(mod, sechdrs, symindex, strindex, secstrings);
+ add_kallsyms(mod, sechdrs, hdr->e_shnum, symindex, strindex,
+ symoffs, secstrings);
if (!mod->taints) {
struct _ddebug *debug;
@@ -2491,6 +2570,10 @@
/* Drop initial reference. */
module_put(mod);
trim_init_extable(mod);
+#ifdef CONFIG_KALLSYMS
+ mod->num_symtab = mod->core_num_syms;
+ mod->symtab = mod->core_symtab;
+#endif
module_free(mod, mod->module_init);
mod->module_init = NULL;
mod->init_size = 0;