From 5e6c1b2c91af547ad53faafeec20cddaedf7aaa4 Mon Sep 17 00:00:00 2001
From: Zhipeng Xie <xiezhipeng1@huawei.com>
Date: Wed, 26 Feb 2020 20:28:13 -0500
Subject: [PATCH 13/23] Add running kernel symbol table to help symbol lookup

For some duplicate symbols whose section have no other
symbols, we need running kernel symbol table to help
symbol lookup.

Signed-off-by: Zhipeng Xie <xiezhipeng1@huawei.com>
---
 kpatch-build/create-diff-object.c |  7 ++-
 kpatch-build/lookup.c             | 74 ++++++++++++++++++++++++++++++-
 kpatch-build/lookup.h             |  3 +-
 3 files changed, 81 insertions(+), 3 deletions(-)

diff --git a/kpatch-build/create-diff-object.c b/kpatch-build/create-diff-object.c
index 73c557b..c5320d4 100644
--- a/kpatch-build/create-diff-object.c
+++ b/kpatch-build/create-diff-object.c
@@ -3597,6 +3597,7 @@ int main(int argc, char *argv[])
 	struct sym_compare_type *base_locals, *sym_comp;
 	char *no_profiling_calls = NULL;
 	char *gcc_add_option = NULL, *mlongcall = NULL;
+	char *kallsyms;
 
 	arguments.debug = 0;
 	argp_parse (&argp, argc, argv, 0, NULL, &arguments);
@@ -3710,8 +3711,12 @@ int main(int argc, char *argv[])
 	 */
 	kpatch_elf_teardown(kelf_patched);
 
+	kallsyms = getenv("KALLSYMS");
+	if (kallsyms)
+		log_debug("kallsyms file:%s\n", kallsyms);
+
 	/* create symbol lookup table */
-	lookup = lookup_open(parent_symtab, mod_symvers, hint, base_locals);
+	lookup = lookup_open(parent_symtab, mod_symvers, hint, base_locals, kallsyms);
 	for (sym_comp = base_locals; sym_comp && sym_comp->name; sym_comp++) {
 		free(sym_comp->name);
 	}
diff --git a/kpatch-build/lookup.c b/kpatch-build/lookup.c
index 1dd183f..03a5b32 100644
--- a/kpatch-build/lookup.c
+++ b/kpatch-build/lookup.c
@@ -45,6 +45,7 @@ struct object_symbol {
 	char *name;
 	int type, bind;
 	int sec_index;
+	unsigned long kaddr;
 };
 
 struct export_symbol {
@@ -284,6 +285,57 @@ static void symtab_read(struct lookup_table *table, char *path)
 	fclose(file);
 }
 
+static void ksymtab_read(struct lookup_table *table, char *path)
+{
+	FILE *file;
+	struct object_symbol *sym, *sym1, *sym2;
+	unsigned long value;
+	int i, j, idx;
+	char line[256], name[256], type[256], mod[256];
+
+	idx =  0;
+	file = fopen(path, "r");
+	if (file == NULL)
+		ERROR("fopen");
+
+	while (fgets(line, 256, file)) {
+		if (sscanf(line, "%lx %s %s [%s]\n",
+			   &value, type, name, mod) != 4)
+			continue;
+
+		if (name[0] == '$')
+			continue;
+
+		i = idx;
+		for_each_obj_symbol_continue(i, sym, table) {
+			if (!strncmp(sym->name, name, KSYM_NAME_LEN-1)) {
+				sym->kaddr = value;
+				idx = i + 1;
+				break;
+			}
+		}
+	}
+
+	for_each_obj_symbol(i, sym1, table) {
+		if (sym1->kaddr == 0)
+			continue;
+		for_each_obj_symbol(j, sym2, table) {
+			if (sym2->kaddr == 0)
+				continue;
+			if (sym1 == sym2)
+				continue;
+			if (sym1->sec_index != sym2->sec_index)
+				continue;
+			if ((long)sym1->value - (long)sym2->value ==
+				(long)sym1->kaddr - (long)sym2->kaddr)
+				continue;
+
+			ERROR("base mismatch(symbol offset)");
+		}
+	}
+	fclose(file);
+}
+
 /*
  * Symvers file format is the following for kernels v5.3 and newer:
  * <CRC>	<Symbol>	<Namespace>	<Module>	<Export Type>
@@ -352,7 +404,8 @@ static void symvers_read(struct lookup_table *table, char *path)
 }
 
 struct lookup_table *lookup_open(char *symtab_path, char *symvers_path,
-				 char *hint, struct sym_compare_type *locals)
+				 char *hint, struct sym_compare_type *locals,
+				 char *kallsyms)
 {
 	struct lookup_table *table;
 
@@ -363,6 +416,8 @@ struct lookup_table *lookup_open(char *symtab_path, char *symvers_path,
 
 	symtab_read(table, symtab_path);
 	symvers_read(table, symvers_path);
+	if (kallsyms)
+		ksymtab_read(table, kallsyms);
 	find_local_syms(table, hint, locals);
 
 	return table;
@@ -609,6 +664,23 @@ int lookup_ref_symbol_offset(struct lookup_table *table, char *name,
 		}
 	}
 
+	if (orig_sym->kaddr == 0)
+		return 1;
+
+	/*find a unique symbol has kaddr*/
+	for_each_obj_symbol(i, sym, table) {
+		if (!strcmp(sym->name, name) || sym->type == STT_FILE ||
+				sym->kaddr == 0 || strchr(sym->name, '.'))
+			continue;
+
+		if (!lookup_is_duplicate_symbol(table, sym->name, objname, 1)) {
+			refsym->name = sym->name;
+			refsym->value = 0;
+			*offset = (long)orig_sym->kaddr - (long)sym->kaddr;
+			return 0;
+		}
+	}
+
 	return 1;
 }
 
diff --git a/kpatch-build/lookup.h b/kpatch-build/lookup.h
index 6f640fd..daeea73 100644
--- a/kpatch-build/lookup.h
+++ b/kpatch-build/lookup.h
@@ -23,7 +23,8 @@ struct lookup_refsym {
 };
 
 struct lookup_table *lookup_open(char *symtab_path, char *symvers_path,
-				 char *hint, struct sym_compare_type *locals);
+				 char *hint, struct sym_compare_type *locals,
+				 char *kallsyms);
 void lookup_close(struct lookup_table *table);
 int lookup_local_symbol(struct lookup_table *table, char *name,
                         struct lookup_result *result);
-- 
2.18.1