Re: [Xen-devel] [PATCH v2 11/12] livepatch: Add metadata runtime retrieval mechanism

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, Aug 27, 2019 at 08:46:23AM +0000, Pawel Wieczorkiewicz wrote:
> Extend the livepatch list operation to fetch also payloads' metadata.
> This is achieved by extending the sysctl list interface with 2 extra
> guest handles:
> * metadata     - an array of arbitrary size strings
> * metadata_len - an array of metadata strings' lengths (uin32_t each)
> 
> Payloads' metadata is a string of arbitrary size and does not have an
> upper bound limit. It may also vary in size between payloads.
> 
> In order to let the userland allocate enough space for the incoming
> data add a metadata total size field to the list sysctl operation and
> fill it with total size of all payloads' metadata.
> 
> Extend the libxc to handle the metadata back-to-back data transfers
> as well as metadata length array data transfers.
> 
> The xen-livepatch userland tool is extended to always display the
> metadata for each received module. The metadata is received with the
> following format: key=value\0key=value\0...key=value\0. The format is
> modified to the following one: key=value;key=value;...key=value.
> The new format allows to easily parse the metadata for a given module
> by a machine.
> 
> Signed-off-by: Pawel Wieczorkiewicz <wipawel@amazon.de>
> Reviewed-by: Andra-Irina Paraschiv <andraprs@amazon.com>
> Reviewed-by: Martin Pohlack <mpohlack@amazon.de>
> Reviewed-by: Norbert Manthey <nmanthey@amazon.de>
> ---
> Changed since v1:
>   * added corresponding documentation
>   * make metadata optional (do not display it when given payload
>     does not have it)
> 
>  docs/misc/livepatch.pandoc    | 31 ++++++++++++++++-----
>  tools/libxc/include/xenctrl.h | 22 +++++++++++----
>  tools/libxc/xc_misc.c         | 64 +++++++++++++++++++++++++++++++++++--------
>  tools/misc/xen-livepatch.c    | 43 +++++++++++++++++++++++------
>  xen/common/livepatch.c        | 22 +++++++++++----
>  xen/include/public/sysctl.h   | 19 +++++++++----
>  6 files changed, 157 insertions(+), 44 deletions(-)

And it may be worth folding this in:

diff --git a/xen/test/livepatch/Makefile b/xen/test/livepatch/Makefile
index a7857d3a2e..3f088e74b2 100644
--- a/xen/test/livepatch/Makefile
+++ b/xen/test/livepatch/Makefile
@@ -79,9 +79,17 @@ config.h: xen_hello_world_func.o
 xen_hello_world.o: config.h
 
 .PHONY: $(LIVEPATCH)
-$(LIVEPATCH): xen_hello_world_func.o xen_hello_world.o note.o xen_note.o
+$(LIVEPATCH): xen_hello_world_func.o xen_hello_world.o note.o xen_note.o modinfo.o
        $(LD) $(LDFLAGS) $(build_id_linker) -r -o $(LIVEPATCH) $^
 
+.PHONY: modinfo.o
+modinfo.o:
+       (set -e; \
+        printf "LIVEPATCH_RULEZ\0") > $@.bin
+       $(OBJCOPY) $(OBJCOPY_MAGIC) \
+                  --rename-section=.data=.modinfo,alloc,load,readonly,data,contents -S $@.bin $@
+       #rm -f $@.bin
+
 #
 # This target is only accessible if CONFIG_LIVEPATCH is defined, which
 # depends on $(build_id_linker) being available. Hence we do not

.. which the test-case can test for.

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