[livepatch-expect,1/2] create-diff-object: Add support for expectations

Commit Message

Wieczorkiewicz, Pawel Aug. 14, 2019, 11:24 a.m. UTC

Extend livepatch_patch_func to support a new field: expect. This new
field describes the expected data, its length and whether expectation
is enabled. The expectation's data is of opaque padding size.

Bump the payload version for hotpatches built with expectations.
The expectations are supported starting from version 3 of the payload.

By default the expectation field is zero-out and the expectation is
disabled unless explicitly specified in the patch.

Signed-off-by: Pawel Wieczorkiewicz <[e-mail]>
---
 common.h             | 11 ++++++++++-
 create-diff-object.c |  3 ++-
 2 files changed, 12 insertions(+), 2 deletions(-)

Patch

diff --git a/common.h b/common.h
index d8cde35..7c6fb73 100644
--- a/common.h
+++ b/common.h
@@ -115,6 +115,14 @@  struct kpatch_elf {
 };
 
 #define PATCH_INSN_SIZE 5
+#define MAX_REPLACEMENT_SIZE 31
+struct livepatch_expectation {
+	uint8_t enabled : 1;
+	uint8_t len : 5;
+	uint8_t pad : 2;
+	uint8_t data[MAX_REPLACEMENT_SIZE];
+};
+typedef struct livepatch_expectation livepatch_expectation_t;
 
 struct livepatch_patch_func {
 	char *name;
@@ -123,9 +131,10 @@  struct livepatch_patch_func {
 	uint32_t new_size;
 	uint32_t old_size;
 	uint8_t version;
-	unsigned char pad[31];
+	unsigned char pad[MAX_REPLACEMENT_SIZE];
 	uint8_t applied;
 	uint8_t _pad[7];
+	livepatch_expectation_t expect;
 };
 
 struct special_section {
diff --git a/create-diff-object.c b/create-diff-object.c
index 534516b..c7431cc 100644
--- a/create-diff-object.c
+++ b/create-diff-object.c
@@ -2009,10 +2009,11 @@  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 = 2;
+			funcs[index].version = 3;
 			memset(funcs[index].pad, 0, sizeof funcs[index].pad);
 			funcs[index].applied = 0;
 			memset(funcs[index]._pad, 0, sizeof funcs[index]._pad);
+			memset(&funcs[index].expect, 0, sizeof funcs[index].expect);
 
 			/*
 			 * Add a relocation that will populate