kpatch/0030-kpatch-update-sympos-for-duplicate-symbols-in-vmlinu.patch

From 8f5c1ff32fcc519bf061f68a481116f622b9cef8 Mon Sep 17 00:00:00 2001
From: Zhipeng Xie <xiezhipeng1@huawei.com>
Date: Fri, 10 Sep 2021 04:34:40 -0400
Subject: [PATCH] kpatch: update sympos for duplicate symbols in vmlinux

kallsyms in vmlinux is sorted by address, so symbol order
in vmlinux is different from /proc/kallsyms, update sympos
when patching duplicate symbol function.

Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
Signed-off-by: hubin57 <hubin57@huawei.com>
---
 kpatch-build/create-diff-object.c | 26 ++++++--------------------
 kpatch-build/lookup.c             | 24 ++++++++++++++++++++++++
 kpatch-build/lookup.h             |  2 ++
 3 files changed, 32 insertions(+), 20 deletions(-)

diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
index afd5e3b..ff2b0e4 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -2813,26 +2813,12 @@ static void kpatch_create_patches_sections(struct kpatch_elf *kelf,
 			funcs[index].new_size = sym->sym.st_size;
 			funcs[index].sympos = result.pos;
 			if (lookup_is_duplicate_symbol(table, sym->name, objname, result.pos)) {
-				struct lookup_refsym refsym;
-				long offset;
-
-				if (lookup_ref_symbol_offset(table, sym->name, &refsym,
-							objname, &offset))
-					ERROR("unresolvable ambiguity on symbol %s\n", sym->name);
-
-				funcs[index].ref_offset = offset;
-
-				/*
-				 * Add a relocation that will populate
-				 * the funcs[index].ref_name field.
-				 */
-				ALLOC_LINK(rela, &relasec->relas);
-				rela->sym = strsym;
-				rela->type = absolute_rela_type;
-				rela->addend = offset_of_string(&kelf->strings, refsym.name);
-				rela->offset = (unsigned int)(index * sizeof(*funcs) +
-					offsetof(struct kpatch_patch_func, ref_name));
-
+				if (!strcmp(objname, "vmlinux")) {
+					result.pos = get_vmlinux_duplicate_symbol_pos(table, sym->name, result.value);
+					log_debug("update %s sympos from %ld to %ld\n",
+							sym->name, funcs[index].sympos, result.pos);
+					funcs[index].sympos = result.pos;
+				}
 			}
 
 
diff --git a/kpatch-build/lookup.c b/kpatch-build/lookup.c
index 888bcc9..aa8527d 100644
--- a/kpatch-build/lookup.c
+++ b/kpatch-build/lookup.c
@@ -526,6 +526,30 @@ int lookup_global_symbol(struct lookup_table *table, char *name,
 	return 1;
 }
 
+/*
+ * In case sometimes the sympos of duplicate symbols are different in vmlinux and 
+ * /proc/kallsyms, and causes lookup_local_symbol to save wrong sympos in result, 
+ * this function returns correct sympos of the symbol, by comparing
+ * address value with the symbol in vmlinux symbol table.
+ */
+unsigned long get_vmlinux_duplicate_symbol_pos(struct lookup_table *table, 
+                                               char *name, unsigned long value)
+{
+	struct object_symbol *sym;
+	unsigned long pos = 1;
+	int i;
+
+	for_each_obj_symbol(i, sym, table) {
+		if (strcmp(sym->name, name))
+			continue;
+
+		if (sym->value < value)
+			pos++;
+	}
+
+	return pos;
+}
+
 int lookup_is_exported_symbol(struct lookup_table *table, char *name)
 {
 	struct export_symbol *sym, *match = NULL;
diff --git a/kpatch-build/lookup.h b/kpatch-build/lookup.h
index daeea73..c745366 100644
--- a/kpatch-build/lookup.h
+++ b/kpatch-build/lookup.h
@@ -37,5 +37,7 @@ int lookup_is_duplicate_symbol(struct lookup_table *table, char *name,
 int lookup_ref_symbol_offset(struct lookup_table *table, char *name,
 		struct lookup_refsym *refsym, char *objname,
 			 long *offset);
+unsigned long get_vmlinux_duplicate_symbol_pos(struct lookup_table *table, char *name,
+                         unsigned long value);
 
 #endif /* _LOOKUP_H_ */
-- 
2.27.0