Re: [PATCH v4 1/2] module: add elf_check_module_arch for module specific elf arch checks

Jessica Yu
2021-06-16T12:54:22Z

+++ Nicholas Piggin [16/06/21 11:18 +1000]:
>Excerpts from Jessica Yu's message of June 15, 2021 10:17 pm:
>> +++ Nicholas Piggin [15/06/21 12:05 +1000]:
>>>Excerpts from Jessica Yu's message of June 14, 2021 10:06 pm:
>>>> +++ Nicholas Piggin [11/06/21 19:39 +1000]:
>>>>>The elf_check_arch() function is used to test usermode binaries, but
>>>>>kernel modules may have more specific requirements. powerpc would like
>>>>>to test for ABI version compatibility.
>>>>>
>>>>>Add an arch-overridable function elf_check_module_arch() that defaults
>>>>>to elf_check_arch() and use it in elf_validity_check().
>>>>>
>>>>>Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
>>>>>[np: split patch, added changelog]
>>>>>Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
>>>>>---
>>>>> include/linux/moduleloader.h | 5 +++++
>>>>> kernel/module.c | 2 +-
>>>>> 2 files changed, 6 insertions(+), 1 deletion(-)
>>>>>
>>>>>diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
>>>>>index 9e09d11ffe5b..fdc042a84562 100644
>>>>>--- a/include/linux/moduleloader.h
>>>>>+++ b/include/linux/moduleloader.h
>>>>>@@ -13,6 +13,11 @@
>>>>> * must be implemented by each architecture.
>>>>> */
>>>>>
>>>>>+// Allow arch to optionally do additional checking of module ELF header
>>>>>+#ifndef elf_check_module_arch
>>>>>+#define elf_check_module_arch elf_check_arch
>>>>>+#endif
>>>>
>>>> Hi Nicholas,
>>>>
>>>> Why not make elf_check_module_arch() consistent with the other
>>>> arch-specific functions? Please see module_frob_arch_sections(),
>>>> module_{init,exit}_section(), etc in moduleloader.h. That is, they are
>>>> all __weak functions that are overridable by arches. We can maybe make
>>>> elf_check_module_arch() a weak symbol, available for arches to
>>>> override if they want to perform additional elf checks. Then we don't
>>>> have to have this one-off #define.
>>>
>>>
>>>Like this? I like it. Good idea.
>>
>> Yeah! Also, maybe we can alternatively make elf_check_module_arch() a
>> separate check entirely so that the powerpc implementation doesn't
>> have to include that extra elf_check_arch() call. Something like this maybe?
>
>Yeah we can do that. Would you be okay if it goes via powerpc tree? If
>yes, then we should get your Ack (or SOB because it seems to be entirely
>your patch now :D)

This can go through the powerpc tree. Will you do another respin
of this patch? And yes, feel free to take my SOB for this one -

Signed-off-by: Jessica Yu <jeyu@kernel.org>

Thanks!

Jessica