Re: [Xen-devel] [PATCH v5 14/16] livepatch: Initial ARM32 support.

[Julien Grall <julien.grall@xxxxxxx>]

Hi Konrad,

On 27/09/2016 10:50, Konrad Rzeszutek Wilk wrote:
> On Tue, Sep 27, 2016 at 09:39:06AM -0700, Julien Grall wrote:
> > >    - Rebased on "livepatch: Drop _jmp from arch_livepatch_[apply,revert]_jmp"
> > >    - Added explanation for the usage of data cache and why we need to sync it.
> > ... you also replace the clean_and_invalidate to the old_ptr by
> > clean_and_invalidate to the new_ptr.
> Ah yes! I had it in my patch queue but neglected to email it out.
Good, I wanted to make sure you replicate the change requested on ARM64 
to ARM32.
> Here is what I have in the git branch:
>
> From 8bf07ac18e2cfcf304860aa00ab157e1e7f77ed9 Mon Sep 17 00:00:00 2001
> From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Date: Thu, 22 Sep 2016 20:15:09 -0400
> Subject: [PATCH] livepatch: Initial ARM32 support.
>
> The patch piggybacks on: livepatch: Initial ARM64 support, which
> brings up all of the necessary livepatch infrastructure pieces in.
>
> This patch adds three major pieces:
>
>  1) ELF relocations. ARM32 uses SHT_REL instead of SHT_RELA which
>     means the adddendum had to be extracted from within the
>     instruction. Which required parsing BL/BLX, B/BL<cond>,
>     MOVT, and MOVW instructions.
>
>     The code was written from scratch using the ARM ELF manual
>     (and the ARM Architecture Reference Manual)
>
>  2) Inserting an trampoline. We use the B (branch to address)
>     which uses an offset that is based on the PC value: PC + imm32.
>     Because we insert the branch at the start of the old function
>     we have to account for the instruction already being fetched
>     and subtract -8 from the delta (new_addr - old_addr). See
>     ARM DDI 0406C.c, see A2.3 (pg 45) and A8.8.18 pg (pg 334,335)
>
>  3) Allows the test-cases to be built under ARM 32.
>     The "livepatch: tests: Make them compile under ARM64"
>     put in the right infrastructure for it and we piggyback on it.
>
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx> [for non-ARM parts]
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Acked-by: Julien Grall <julien.grall@xxxxxxx>

Regards,

--
Julien Grall

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