kpatch/0019-create-diff-object-add-jump-label-support.patch

From c0b20224cf1b081fba152cb4944d762515561d89 Mon Sep 17 00:00:00 2001
From: Zhipeng Xie <xiezhipeng1@huawei.com>
Date: Mon, 2 Mar 2020 04:35:07 -0500
Subject: [PATCH 19/23] create-diff-object: add jump label support

This patch processes the __jump_table special section, and
only the jump_lable used by the changed functions will be
included in __jump_table section and solve this limitation.
(The livepatch in kernel should also be modified that processing
the tracepoint again after the dynamic relocation by livepatch.)

Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
---
 kpatch-build/create-diff-object.c | 47 +------------------------------
 1 file changed, 1 insertion(+), 46 deletions(-)

diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
index 457d517..4fa4488 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -2140,7 +2140,6 @@ static void kpatch_regenerate_special_section(struct kpatch_elf *kelf,
 	struct rela *rela, *safe;
 	char *src, *dest;
 	unsigned int group_size, src_offset, dest_offset, include;
-	int jump_table = !strcmp(special->name, "__jump_table");
 
 	LIST_HEAD(newrelas);
 
@@ -2180,49 +2179,6 @@ static void kpatch_regenerate_special_section(struct kpatch_elf *kelf,
 		if (!include)
 			continue;
 
-		/*
-		 * Jump labels (aka static keys or static branches) aren't
-		 * actually supported for the time being.  Warn on all
-		 * non-tracepoint jump labels when they occur in a replacement
-		 * function.  An inert tracepoint is harmless enough, but a
-		 * broken static key can cause unexpected behavior.
-		 *
-		 * Here we hard-code knowledge about the contents of the
-		 * jump_label struct.  It has three fields: code, target, and
-		 * key.
-		 */
-		if (jump_table) {
-			struct rela *code, *key;
-			int i = 0;
-
-			list_for_each_entry(rela, &sec->relas, list) {
-				if (rela->offset >= src_offset &&
-				    rela->offset < src_offset + group_size) {
-					if (i == 0)
-						code = rela;
-					else if (i == 2)
-						key = rela;
-					i++;
-				}
-			}
-
-			if (i != 3)
-				ERROR("BUG: __jump_table has an unexpected format");
-
-			/* inert tracepoints are harmless */
-			if (!strncmp(key->sym->name, "__tracepoint_", 13))
-				continue;
-
-			/* inert dynamic debug printks are harmless */
-			if (is_dynamic_debug_symbol(key->sym))
-				continue;
-
-			ERROR("Found a jump label at %s()+0x%lx, using key %s.  Jump labels aren't currently supported.  Use static_key_enabled() instead.",
-			      code->sym->name, code->addend, key->sym->name);
-
-			continue;
-		}
-
 		/*
 		 * Copy all relas in the group.  It's possible that the relas
 		 * aren't sorted (e.g. .rela.fixup), so go through the entire
@@ -2659,8 +2615,7 @@ static void kpatch_process_special_sections(struct kpatch_elf *kelf)
 	 * jump labels and enable tracepoints in a patched function.
 	 */
 	list_for_each_entry(sec, &kelf->sections, list) {
-		if (strcmp(sec->name, "__jump_table") &&
-		    strcmp(sec->name, "__tracepoints") &&
+		if (strcmp(sec->name, "__tracepoints") &&
 		    strcmp(sec->name, "__tracepoints_ptrs") &&
 		    strcmp(sec->name, "__tracepoints_strings"))
 			continue;
-- 
2.18.1