[Xen-devel] [livepatch-build-tools part2 v3 5/6] create-diff-object: Add new entries to special sections array

[Pawel Wieczorkiewicz <wipawel@xxxxxxxxx>]

Handle .livepatch.hooks* and .altinstr_replacement sections as the
special sections with assigned group_size resolution function.
By default each .livepatch.hooks* sections' entry is 8 bytes long (a
pointer). The .altinstr_replacement section has undefined group_size.

Allow to specify different .livepatch.hooks* section entry size using
shell environment variable HOOK_STRUCT_SIZE.

Add an explicit check to kpatch_regenerate_special_section() skipping
regeneration of special sections, whose group_size is 0.

Signed-off-by: Pawel Wieczorkiewicz <wipawel@xxxxxxxxx>
Reviewed-by: Andra-Irina Paraschiv <andraprs@xxxxxxxxxx>
Reviewed-by: Bjoern Doebel <doebel@xxxxxxxxx>
Reviewed-by: Norbert Manthey <nmanthey@xxxxxxxxx>
---
v3:
* Added an explicit check to kpatch_regenerate_special_section()
 skipping regeneration of special sections, whose group_size is 0.
v2:
* Applied suggestions from Ross and neccessary changes enforced by
 previous patch of the series:
 - fixed indentation
 - used log_debug() instead of printf()
 - added aux. function undefined_group_size() returning 0 for a
   undefined group_size
 - added .altinstr_replacement to the special_sections array and
   fixed its group_size to undefined (0).
---
 create-diff-object.c | 42 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 39 insertions(+), 3 deletions(-)

diff --git a/create-diff-object.c b/create-diff-object.c
index c6183c3..0d231d5 100644
--- a/create-diff-object.c
+++ b/create-diff-object.c
@@ -995,6 +995,24 @@ static int altinstructions_group_size(struct kpatch_elf 
*kelf, int offset)
        return size;
 }
 
+static int livepatch_hooks_group_size(struct kpatch_elf *kelf, int offset)
+{
+       static int size = 0;
+       char *str;
+       if (!size) {
+               str = getenv("HOOK_STRUCT_SIZE");
+               size = str ? atoi(str) : 8;
+       }
+
+       log_debug("livepatch_hooks_size=%d\n", size);
+       return size;
+}
+
+static int undefined_group_size(struct kpatch_elf *kelf, int offset)
+{
+       return 0;
+}
+
 /*
  * 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,
+       },
        {},
 };
 
@@ -1142,6 +1172,15 @@ static void kpatch_regenerate_special_section(struct 
kpatch_elf *kelf,
 
        LIST_HEAD(newrelas);
 
+       src_offset = 0;
+       dest_offset = 0;
+       group_size = special->group_size(kelf, src_offset);
+       if (group_size == 0) {
+               log_normal("Skipping regeneration of a special section: %s\n",
+                          special->name);
+               return;
+       }
+
        src = sec->base->data->d_buf;
        /* alloc buffer for new base section */
        dest = malloc(sec->base->sh.sh_size);
@@ -1156,9 +1195,6 @@ static void kpatch_regenerate_special_section(struct 
kpatch_elf *kelf,
                }
        }
 
-       group_size = 0;
-       src_offset = 0;
-       dest_offset = 0;
        for ( ; src_offset < sec->base->sh.sh_size; src_offset += group_size) {
 
                group_size = special->group_size(kelf, src_offset);
-- 
2.16.5




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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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