[PATCH v6 1/4] module: add module_elf_check_arch for module-specific checks

[Nicholas Piggin]

The elf_check_arch() function is also used to test compatibility of
usermode binaries. Kernel modules may have more specific requirements,
for example powerpc would like to test for ABI version compatibility.

Add a weak module_elf_check_arch() that defaults to true, and call it
from elf_validity_check().

Cc: Michael Ellerman <m...@ellerman.id.au>
Signed-off-by: Jessica Yu <j...@kernel.org>
[np: added changelog, adjust name, rebase]
Acked-by: Luis Chamberlain <mcg...@kernel.org>
Signed-off-by: Nicholas Piggin <npig...@gmail.com>
---
 include/linux/moduleloader.h |  3 +++
 kernel/module/main.c         | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
index 9e09d11ffe5b..7b4587a19189 100644
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -13,6 +13,9 @@
  * must be implemented by each architecture.
  */
 
+/* arch may override to do additional checking of ELF header architecture */
+bool module_elf_check_arch(Elf_Ehdr *hdr);
+
 /* Adjust arch-specific sections.  Return 0 on success.  */
 int module_frob_arch_sections(Elf_Ehdr *hdr,
                              Elf_Shdr *sechdrs,
diff --git a/kernel/module/main.c b/kernel/module/main.c
index d02d39c7174e..7b3f6fb0d428 100644
--- a/kernel/module/main.c
+++ b/kernel/module/main.c
@@ -1674,6 +1674,11 @@ static int elf_validity_check(struct load_info *info)
                       info->hdr->e_machine);
                goto no_exec;
        }
+       if (!module_elf_check_arch(info->hdr)) {
+               pr_err("Invalid module architecture in ELF header: %u\n",
+                      info->hdr->e_machine);
+               goto no_exec;
+       }
        if (info->hdr->e_shentsize != sizeof(Elf_Shdr)) {
                pr_err("Invalid ELF section header size\n");
                goto no_exec;
@@ -2247,6 +2252,11 @@ static void flush_module_icache(const struct module *mod)
                           (unsigned long)mod->core_layout.base + 
mod->core_layout.size);
 }
 
+bool __weak module_elf_check_arch(Elf_Ehdr *hdr)
+{
+       return true;
+}
+
 int __weak module_frob_arch_sections(Elf_Ehdr *hdr,
                                     Elf_Shdr *sechdrs,
                                     char *secstrings,
-- 
2.37.2