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Re: [Xen-devel] [livepatch-build-tools part2 v2 5/6] create-diff-object: Add new entries to special sections array array

  • To: "Wieczorkiewicz, Pawel" <wipawel@xxxxxxxxx>
  • From: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
  • Date: Fri, 16 Aug 2019 15:19:46 +0100
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  • Cc: "Pohlack, Martin" <mpohlack@xxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, xen-devel <xen-devel@xxxxxxxxxxxxx>
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On 8/16/19 1:06 PM, Wieczorkiewicz, Pawel wrote:

On 16. Aug 2019, at 11:40, Ross Lagerwall <ross.lagerwall@xxxxxxxxxx <mailto:ross.lagerwall@xxxxxxxxxx>> wrote:

On 8/8/19 1:35 PM, Pawel Wieczorkiewicz wrote:


  * The rela groups in the .fixup section vary in size.  The beginning of each   * .fixup rela group is referenced by the .ex_table section. To find the size @@ -1072,6 +1090,18 @@ static struct special_section special_sections[] = {
.name= ".altinstructions",
.group_size= altinstructions_group_size,
+.name= ".altinstr_replacement",
+.group_size= undefined_group_size,
+.name= ".livepatch.hooks.load",
+.group_size= livepatch_hooks_group_size,
+.name= ".livepatch.hooks.unload",
+.group_size= livepatch_hooks_group_size,

Unless I'm misunderstanding something, I can't see how kpatch_regenerate_special_section would work with .altinstr_replacement having a group size of 0. It looks to me like the for loop in that function would become an infinite loop (due to incrementing by group_size) and should_keep_rela_group would always return false.

AFAICS, the group_size 0 sections are never actually processed by the kpatch_regenerate_special_section(). They are not RELA sections and the following check excludes them from this processing:

OK, that makes sense.

Ross Lagerwall

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