The purpose of kpatch_regenerate_special_section() is fairly opaque without
spending a good amount of time and having quite a lot of knowledge about what
the special sections contains.
Introduce some comments in order to give context and describe the expected
functionality.
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
---
create-diff-object.c | 33 +++++++++++++++++++++++++++++++++
1 file changed, 33 insertions(+)
diff --git a/create-diff-object.c b/create-diff-object.c
index d8a2afbf2774..6a751bf3b789 100644
--- a/create-diff-object.c
+++ b/create-diff-object.c
@@ -1210,6 +1210,12 @@ static void kpatch_regenerate_special_section(struct
kpatch_elf *kelf,
src_offset = 0;
dest_offset = 0;
+
+ /*
+ * Special sections processed here are array objects, hence in order to
+ * detect whether a special section needs processing attempt to get the
+ * element size. Returning a size of 0 means no processing required.
+ */
group_size = special->group_size(kelf, src_offset);
if (group_size == 0) {
log_normal("Skipping regeneration of a special section: %s\n",
@@ -1246,6 +1252,33 @@ static void kpatch_regenerate_special_section(struct
kpatch_elf *kelf,
if (src_offset + group_size > sec->base->sh.sh_size)
group_size = sec->base->sh.sh_size - src_offset;
+ /*
+ * Special sections handled perform a bunch of different tasks,
+ * but they all have something in common: they are array like
+ * sections that reference functions in the object file being
+ * processed.
+ *
+ * .bug_frames.* relocations reference the symbol (plus offset)
+ * where the exception is triggered from.
+ *
+ * .altinstructions relocations contain references to
+ * coordinates where the alternatives are to be applied, plus
+ * coordinates that point to the replacement code in
+ * .altinstr_replacement.
+ *
+ * .ex_table relocations contain references to the coordinates
+ * where the fixup code should be executed, plus relocation
+ * coordinates that point to the text code to execte living in
+ * the .fixup section.
+ *
+ * .livepatch.hooks.* relocations point to the hook
+ * functions.
+ *
+ * Such dependencies allow to make a decision on whether an
+ * element in the array needs including in the livepatch: if
+ * the symbol pointed by the relocation is new or has changed
+ * the array element needs including.
+ */
include = should_keep_rela_group(sec, src_offset, group_size);
if (!include)
--
2.44.0
