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

["Wieczorkiewicz, Pawel" <wipawel@xxxxxxxxx>]

On 21. Aug 2019, at 20:09, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:

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?

No, I must not use that. The 31 pad should be actually called opaque,

and corresponds to the location where hypervisor stores replaced bytes

of the replaced functions.

+ 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

Best Regards,
Pawel Wieczorkiewicz

Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Ralf Herbrich
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879

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