Re: [Xen-devel] [livepatch-hooks-2 PATCH 2/4] create-diff-object: Add support for applied/reverted marker

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On 8/14/19 4:38 AM, Pawel Wieczorkiewicz wrote:
> With version 2 of a payload structure additional field is supported
> to track whether given function has been applied or reverted.
> There also comes additional 8-byte alignment padding to reserve
> place for future flags and options.
>
> The new fields are zero-out upon .livepatch.funcs section creation.
>
> Signed-off-by: Pawel Wieczorkiewicz <wipawel@xxxxxxxxx>
> ---
>   common.h             | 2 ++
>   create-diff-object.c | 4 +++-
>   2 files changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/common.h b/common.h
> index 06e19e7..d8cde35 100644
> --- a/common.h
> +++ b/common.h
> @@ -124,6 +124,8 @@ struct livepatch_patch_func {
>         uint32_t old_size;
>         uint8_t version;
>         unsigned char pad[31];
So the 31 pad is for this purpose - that you can make it smaller. Why 
not use that?
> +       uint8_t applied;
> +       uint8_t _pad[7];
>   };
>   
>   struct special_section {
> diff --git a/create-diff-object.c b/create-diff-object.c
> index 263c7d2..534516b 100644
> --- a/create-diff-object.c
> +++ b/create-diff-object.c
> @@ -2009,8 +2009,10 @@ static void livepatch_create_patches_sections(struct 
> kpatch_elf *kelf,
>                         funcs[index].old_size = result.size;
>                         funcs[index].new_addr = 0;
>                         funcs[index].new_size = sym->sym.st_size;
> -                       funcs[index].version = 1;
> +                       funcs[index].version = 2;
>                         memset(funcs[index].pad, 0, sizeof funcs[index].pad);
> +                       funcs[index].applied = 0;
> +                       memset(funcs[index]._pad, 0, sizeof funcs[index]._pad);
>   
>   			/*
>                          * Add a relocation that will populate

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