Re: [Xen-devel] [PATCH v3 16/18] livepatch: ARM32 support.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 11.09.16 at 22:35, <konrad.wilk@xxxxxxxxxx> wrote:
> The patch piggybacks on: livepatch: Initial ARM64 support, which
> brings up all of the neccessary 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.
> 
> Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

The little bit of non-ARM parts:
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>


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