From 62125c1bf327ba04df7a3cafb22c92df935fb0f3 Mon Sep 17 00:00:00 2001
From: Zhipeng Xie <[email protected]>
Date: Wed, 26 Feb 2020 20:28:13 -0500
Subject: [PATCH 11/38] 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 <[email protected]>
---
 kpatch-build/lookup.c | 73 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 73 insertions(+)

diff --git a/kpatch-build/lookup.c b/kpatch-build/lookup.c
index 9eb3e73..87f315a 100644
--- a/kpatch-build/lookup.c
+++ b/kpatch-build/lookup.c
@@ -46,6 +46,7 @@ struct object_symbol {
 	char *name;
 	int type, bind;
 	int sec_index;
+	unsigned long kaddr;
 };
 
 struct export_symbol {
@@ -439,10 +440,62 @@ static void symvers_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->addr - (long)sym2->addr ==
+				(long)sym1->kaddr - (long)sym2->kaddr)
+				continue;
+
+			ERROR("base mismatch(symbol offset)");
+		}
+	}
+	fclose(file);
+}
+
 struct lookup_table *lookup_open(char *symtab_path, char *objname,
 				 char *symvers_path, struct kpatch_elf *kelf)
 {
 	struct lookup_table *table;
+	char *kallsyms;
 
 	table = malloc(sizeof(*table));
 	if (!table)
@@ -452,6 +505,9 @@ struct lookup_table *lookup_open(char *symtab_path, char *objname,
 	table->objname = objname;
 	symtab_read(table, symtab_path);
 	symvers_read(table, symvers_path);
+	kallsyms = getenv("KALLSYMS");
+	if (kallsyms)
+		ksymtab_read(table, kallsyms);
 
 	find_local_syms_multiple(table, kelf);
 
@@ -717,6 +773,23 @@ int lookup_ref_symbol_offset(struct lookup_table *table,
 		}
 	}
 
+	if (orig_sym->kaddr == 0)
+		return 1;
+
+	/*find a unique symbol has kaddr*/
+	for_each_obj_symbol(i, sym, table) {
+		if (!strcmp(sym->name, lookup_sym->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->addr = 0;
+			*offset = (long)orig_sym->kaddr - (long)sym->kaddr;
+			return 0;
+		}
+	}
+
 	return 1;
 }
 
-- 
2.33.0