Add support for aarch64

[chenlei0x]

Hi,

I have tried to send this patch to mailing-list.

We are trying to add aarch64 support for kpatch.

kernel-patch directory contains the patch that should be applied to kernel(tested on 4.14)
User should do that before using kpatch.

Need your comments, thanks.

[jpoimboe]

Thanks for sharing this @betacoo. The create-diff-object changes look reasonable. However, I don't think we want to support out-of-tree kernel patches. Also, kpatch.ko is pretty much deprecated in favor of CONFIG_LIVEPATCH upstream.

There has been some arm64 activity in the upstream kernel for livepatch and objtool. So hopefully Linux arm64 CONFIG_LIVEPATCH will be a reality in the near future. Then we can revisit these create-diff-object changes. At that point we will also need some integration and unit tests.

[joe-lawrence]

Hi @betacoo, fwiw, the arm64-support.patch doesn't apply cleanly to upstream v4.14:

% git checkout v4.14
HEAD is now at bebc6082da0a Linux 4.14

% patch --dry-run -p1 < ~/src/kpatch/github-kpatch/kernel-patch/arm64-support.patch 
checking file arch/arm64/Kconfig
checking file arch/arm64/Makefile
Hunk #1 succeeded at 82 with fuzz 1 (offset -1 lines).
checking file arch/arm64/include/asm/ftrace.h
checking file arch/arm64/include/asm/module.h
Hunk #1 FAILED at 32.
1 out of 1 hunk FAILED
checking file arch/arm64/kernel/Makefile
checking file arch/arm64/kernel/arm64ksyms.c
checking file arch/arm64/kernel/entry-ftrace.S
Hunk #2 succeeded at 130 (offset 1 line).
Hunk #3 succeeded at 170 (offset 1 line).
Hunk #4 succeeded at 328 (offset 1 line).
checking file arch/arm64/kernel/ftrace.c
Hunk #2 FAILED at 110.
Hunk #3 FAILED at 130.
Hunk #4 succeeded at 165 (offset -2 lines).
Hunk #5 succeeded at 215 (offset -2 lines).
2 out of 5 hunks FAILED
checking file arch/arm64/kernel/module-plts.c
Hunk #1 FAILED at 190.
1 out of 1 hunk FAILED
checking file arch/arm64/kernel/module.c
checking file drivers/firmware/efi/libstub/Makefile
Hunk #1 FAILED at 11.
1 out of 1 hunk FAILED
checking file include/asm-generic/vmlinux.lds.h
can't find file to patch at input line 719
Perhaps you used the wrong -p or --strip option?
The text leading up to this was:
--------------------------
|diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
|index 4be464a..29aad2a 100644
|--- a/include/linux/compiler_types.h
|+++ b/include/linux/compiler_types.h
--------------------------
File to patch:

It looks like include/linux/compiler_types.h only goes back to v4.15. Is arm64-support.patch based on another upstream release or perhaps a distro-kernel?

[chenlei0x]

Thanks for sharing this @betacoo. The create-diff-object changes look reasonable. However, I don't think we want to support out-of-tree kernel patches. Also, kpatch.ko is pretty much deprecated in favor of CONFIG_LIVEPATCH upstream.

There has been some arm64 activity in the upstream kernel for livepatch and objtool. So hopefully Linux arm64 CONFIG_LIVEPATCH will be a reality in the near future. Then we can revisit these create-diff-object changes. At that point we will also need some integration and unit tests.

@jpoimboe
Thanks for your review.
I know it's not a good way to maintain an Out-of-tree kernel patch. But it will work when a kernel runs without LIVEPATCH support.

It seems that I should close this PR....

[chenlei0x]

Hi @joe-lawrence
I'm using 4.14.134 kernel version for testing.
This is the download link
https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.14.134.tar.xz

[joe-lawrence]

Hi @joe-lawrence
I'm using 4.14.134 kernel version for testing.
This is the download link
https://cdn.kernel.org/pub/linux/kernel/v4.x/linux-4.14.134.tar.xz

Thanks for the link to that specific stable kernel version. The patch now applies, however doesn't build for me:

arch/arm64/kernel/ftrace.c: In function ‘install_ftrace_trampoline’:
arch/arm64/kernel/ftrace.c:85:15: error: too many arguments to function ‘get_plt_entry’
  trampoline = get_plt_entry(*addr, mod_trampoline);
               ^~~~~~~~~~~~~
In file included from ./include/linux/module.h:24,
                 from arch/arm64/kernel/ftrace.c:13:
./arch/arm64/include/asm/module.h:64:32: note: declared here
 static inline struct plt_entry get_plt_entry(u64 val)
                                ^~~~~~~~~~~~~

Do I need to backport further patches to 4.14.134?

[chenlei0x]

@joe-lawrence @jpoimboe
Sorry for the trouble.
This is our base kernel version, we have already back-ported many patches.
I have to admit that maintaining a kernel patch in this project is really ugly.
It's time to close this pr and dig into kernel live patch.

Thanks for your review.