From f683c8dc7f321593ac0f59a1c2a623f0586f906b Mon Sep 17 00:00:00 2001
From: Sami Tolvanen <samitolvanen@google.com>
Date: Wed, 14 Feb 2018 10:26:35 -0800
Subject: [PATCH] ANDROID: kallsyms: strip hashes from static functions with
 ThinLTO and CFI

With CONFIG_THINLTO and CFI both enabled, LLVM appends a hash to the
names of all static functions. This breaks userspace tools, so strip
out the hash from output.

Bug: 147422318
Change-Id: Ie19a59d9d0681298be54e73064badc361c0f7014
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
---
 kernel/kallsyms.c | 49 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 44 insertions(+), 5 deletions(-)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 136ce049c4ad2..a76be87d013de 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -271,6 +271,24 @@ int kallsyms_lookup_size_offset(unsigned long addr, unsigned long *symbolsize,
 	       !!__bpf_address_lookup(addr, symbolsize, offset, namebuf);
 }
 
+#if defined(CONFIG_CFI_CLANG) && defined(CONFIG_THINLTO)
+/*
+ * LLVM appends a hash to static function names when ThinLTO and CFI are
+ * both enabled, which causes confusion and potentially breaks user space
+ * tools, so we will strip the postfix from expanded symbol names.
+ */
+static inline void cleanup_symbol_name(char *s)
+{
+	char *res;
+
+	res = strrchr(s, '$');
+	if (res)
+		*res = '\0';
+}
+#else
+static inline void cleanup_symbol_name(char *s) {}
+#endif
+
 /*
  * Lookup an address
  * - modname is set to NULL if it's in the kernel.
@@ -297,7 +315,9 @@ const char *kallsyms_lookup(unsigned long addr,
 				       namebuf, KSYM_NAME_LEN);
 		if (modname)
 			*modname = NULL;
-		return namebuf;
+
+		ret = namebuf;
+		goto found;
 	}
 
 	/* See if it's in a module or a BPF JITed image. */
@@ -310,11 +330,16 @@ const char *kallsyms_lookup(unsigned long addr,
 	if (!ret)
 		ret = ftrace_mod_address_lookup(addr, symbolsize,
 						offset, modname, namebuf);
+
+found:
+	cleanup_symbol_name(namebuf);
 	return ret;
 }
 
 int lookup_symbol_name(unsigned long addr, char *symname)
 {
+	int res;
+
 	symname[0] = '\0';
 	symname[KSYM_NAME_LEN - 1] = '\0';
 
@@ -325,15 +350,23 @@ int lookup_symbol_name(unsigned long addr, char *symname)
 		/* Grab name */
 		kallsyms_expand_symbol(get_symbol_offset(pos),
 				       symname, KSYM_NAME_LEN);
-		return 0;
+		goto found;
 	}
 	/* See if it's in a module. */
-	return lookup_module_symbol_name(addr, symname);
+	res = lookup_module_symbol_name(addr, symname);
+	if (res)
+		return res;
+
+found:
+	cleanup_symbol_name(symname);
+	return 0;
 }
 
 int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
 			unsigned long *offset, char *modname, char *name)
 {
+	int res;
+
 	name[0] = '\0';
 	name[KSYM_NAME_LEN - 1] = '\0';
 
@@ -345,10 +378,16 @@ int lookup_symbol_attrs(unsigned long addr, unsigned long *size,
 		kallsyms_expand_symbol(get_symbol_offset(pos),
 				       name, KSYM_NAME_LEN);
 		modname[0] = '\0';
-		return 0;
+		goto found;
 	}
 	/* See if it's in a module. */
-	return lookup_module_symbol_attrs(addr, size, offset, modname, name);
+	res = lookup_module_symbol_attrs(addr, size, offset, modname, name);
+	if (res)
+		return res;
+
+found:
+	cleanup_symbol_name(name);
+	return 0;
 }
 
 /* Look up a kernel symbol and return it in a text buffer. */