Re: [Xen-devel] [PATCH v5 05/16] livepatch: Initial ARM64 support.

[Julien Grall <julien.grall@xxxxxxx>]

Hi Konrad,

On 23/09/2016 08:44, Konrad Rzeszutek Wilk wrote:
> Here is the updated patch:
> From deef8f6921c15a4d07209bfba1fc8697dbfeb605 Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Date: Mon, 19 Sep 2016 12:24:09 -0400
> Subject: [PATCH v6] livepatch: Initial ARM64 support.
>
> As compared to x86 the va of the hypervisor .text
> is locked down - we cannot modify the running pagetables
> to have the .ro flag unset. We borrow the same idea that
> alternative patching has - which is to vmap the entire
> .text region and use the alternative virtual address
> for patching.
>
> Since we are doing vmap we may fail, hence the
> arch_livepatch_quiesce was changed (see "x86,arm:
> Change arch_livepatch_quiesce() declaration") to return
> an error value which will be bubbled in payload->rc and
> provided to the user (along with messages in the ring buffer).
>
> The livepatch virtual address space (where the new functions
> are) needs to be close to the hypervisor virtual address
> so that the trampoline can reach it. As such we re-use
> the BOOT_RELOC_VIRT_START which is not used after bootup
> (alternatively we can also use the space after the _end to
> FIXMAP_ADDR(0), but that may be too small).
>
> The ELF relocation engine at the start was coded from
> the "ELF for the ARM 64-bit Architecture (AArch64)"
> (http://infocenter.arm.com/help/topic/com.arm.doc.ihi0056b/IHI0056B_aaelf64.pdf)
> but after a while of trying to write the correct bit shifting
> and masking from scratch I ended up borrowing from Linux, the
> 'reloc_insn_imm' (Linux v4.7 arch/arm64/kernel/module.c function.
> See 257cb251925f854da435cbf79b140984413871ac "arm64: Loadable modules")
>
> And while at it - we also utilize code from Linux to construct
> the right branch instruction (see "arm64/insn: introduce
> aarch64_insn_gen_{nop|branch_imm}() helper functions").
>
> In the livepatch payload loading code we tweak the #ifdef to
> only exclude ARM_32. The exceptions are not part of ARM 32/64 hence
> they are still behind the #ifdef.
>
> We also expand the MAINTAINERS file to include the arm64 and arm32
> platform specific livepatch file.
>
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx> [non-arm parts]
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
You can add my acked-by on this version:

Acked-by: Julien Grall <julien.grall@xxxxxxx>

Regards,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel