The perm_alloc interface supports architectures to direct writes
intended for an allocation to a separate writable staging area before a
mapping is made live. In order to support this, change modules to write
to the address provided by perm_writable_addr(). Currently this is the
same address of the final allocation, so this patch should not create
any functional change yet.
To facilitate re-direction to separate writable staging areas, create a
helper module_adjust_writable_addr(). This function will return an
allocation's writable address if the parameter address is from a module
that is in the process of being loaded. If the address does not meet that
criteria, simply return the address passed in. This helper, while a
little heavy weight, will allow callers in upcoming patches to simply
retrieve the writable address without context of what module is being
loaded.
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
---
include/linux/module.h | 22 ++++++++++++++++++++++
kernel/module.c | 14 +++++++++-----
2 files changed, 31 insertions(+), 5 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index 9964f909d879..32dd22b2a38a 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -576,6 +576,23 @@ struct perm_allocation *module_get_allocation(struct module *mod, unsigned long
bool module_perm_alloc(struct module_layout *layout);
void module_perm_free(struct module_layout *layout);
+static inline void *module_adjust_writable_addr(void *addr)
+{
+ unsigned long laddr = (unsigned long)addr;
+ struct module *mod;
+
+ mutex_lock(&module_mutex);
+ mod = __module_address(laddr);
+ if (!mod) {
+ mutex_unlock(&module_mutex);
+ return addr;
+ }
+ mutex_unlock(&module_mutex);
+ /* The module shouldn't be going away if someone is trying to write to it */
+
+ return (void *)perm_writable_addr(module_get_allocation(mod, laddr), laddr);
+}
+
static inline bool within_module_core(unsigned long addr,
const struct module *mod)
{
@@ -853,6 +870,11 @@ void *dereference_module_function_descriptor(struct module *mod, void *ptr)
return ptr;
}
+static inline void *module_adjust_writable_addr(void *addr)
+{
+ return addr;
+}
+
#endif /* CONFIG_MODULES */
#ifdef CONFIG_SYSFS
diff --git a/kernel/module.c b/kernel/module.c
index 0b31c44798e2..d0afedd36cea 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -3457,7 +3457,7 @@ static int move_module(struct module *mod, struct load_info *info)
/* Transfer each section which specifies SHF_ALLOC */
pr_debug("final section addresses:\n");
for (i = 0; i < info->hdr->e_shnum; i++) {
- void *dest;
+ void *dest, *wdest;
struct perm_allocation *alloc;
Elf_Shdr *shdr = &info->sechdrs[i];
@@ -3470,9 +3470,10 @@ static int move_module(struct module *mod, struct load_info *info)
else
alloc = get_alloc_from_layout(&mod->core_layout, shdr->sh_entsize);
dest = (void *)perm_alloc_address(alloc) + (shdr->sh_entsize & ~ALL_OFFSET_MASK);
+ wdest = (void *)perm_writable_addr(alloc, (unsigned long)dest);
if (shdr->sh_type != SHT_NOBITS)
- memcpy(dest, (void *)shdr->sh_addr, shdr->sh_size);
+ memcpy(wdest, (void *)shdr->sh_addr, shdr->sh_size);
/* Update sh_addr to point to copy in image. */
shdr->sh_addr = (unsigned long)dest;
pr_debug("\t0x%lx %s\n",
@@ -3645,12 +3646,15 @@ int __weak module_finalize(const Elf_Ehdr *hdr,
static int post_relocation(struct module *mod, const struct load_info *info)
{
+ struct exception_table_entry *extable_writ = module_adjust_writable_addr(mod->extable);
+ void *pcpu = (void *)info->sechdrs[info->index.pcpu].sh_addr;
+ void *percpu_writ = module_adjust_writable_addr(pcpu);
+
/* Sort exception table now relocations are done. */
- sort_extable(mod->extable, mod->extable + mod->num_exentries);
+ sort_extable(extable_writ, mod->extable + mod->num_exentries);
/* Copy relocated percpu area over. */
- percpu_modcopy(mod, (void *)info->sechdrs[info->index.pcpu].sh_addr,
- info->sechdrs[info->index.pcpu].sh_size);
+ percpu_modcopy(mod, percpu_writ, info->sechdrs[info->index.pcpu].sh_size);
/* Setup kallsyms-specific fields. */
add_kallsyms(mod, info);
--
2.20.1
