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

Commit Message

Wieczorkiewicz, Pawel Aug. 20, 2019, 12:07 p.m. UTC

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 <[e-mail]>
Reviewed-by: Andra-Irina Paraschiv <[e-mail]>
Reviewed-by: Bjoern Doebel <[e-mail]>
Reviewed-by: Norbert Manthey <[e-mail]>
---
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(-)

Patch

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);