diff --git a/btf_encoder.c b/btf_encoder.c
index b124ec2..80e8969 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -36,6 +36,7 @@ struct funcs_layout {
 struct elf_function {
 	const char	*name;
 	unsigned long	 addr;
+	unsigned long	 size;
 	unsigned long	 sh_addr;
 	bool		 generated;
 };
@@ -98,6 +99,7 @@ static int collect_function(struct btf_elf *btfe, GElf_Sym *sym,
 
 	functions[functions_cnt].name = name;
 	functions[functions_cnt].addr = elf_sym__value(sym);
+	functions[functions_cnt].size = elf_sym__size(sym);
 	functions[functions_cnt].sh_addr = sh.sh_addr;
 	functions[functions_cnt].generated = false;
 	functions_cnt++;
@@ -236,6 +238,39 @@ get_kmod_addrs(struct btf_elf *btfe, __u64 **paddrs, __u64 *pcount)
 	return 0;
 }
 
+static int is_ftrace_func(struct elf_function *func, __u64 *addrs, __u64 count)
+{
+	__u64 start = func->addr;
+	__u64 addr, end = func->addr + func->size;
+
+	/*
+	 * The invariant here is addr[r] that is the smallest address
+	 * that is >= than function start addr. Except the corner case
+	 * where there is no such r, but for that we have a final check
+	 * in the return.
+	 */
+	size_t l = 0, r = count - 1, m;
+
+	/* make sure we don't use invalid r */
+	if (count == 0)
+		return false;
+
+	while (l < r) {
+		m = l + (r - l) / 2;
+		addr = addrs[m];
+
+		if (addr >= start) {
+			/* we satisfy invariant, so tighten r */
+			r = m;
+		} else {
+			/* m is not good enough as l, maybe m + 1 will be */
+			l = m + 1;
+		}
+	}
+
+	return start <= addrs[r] && addrs[r] < end;
+}
+
 static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl)
 {
 	__u64 *addrs, count, i;
@@ -283,10 +318,11 @@ static int setup_functions(struct btf_elf *btfe, struct funcs_layout *fl)
 		 * functions[x]::addr is relative address within section
 		 * and needs to be relocated by adding sh_addr.
 		 */
-		__u64 addr = kmod ? func->addr + func->sh_addr : func->addr;
+		if (kmod)
+			func->addr += func->sh_addr;
 
 		/* Make sure function is within ftrace addresses. */
-		if (bsearch(&addr, addrs, count, sizeof(addrs[0]), addrs_cmp)) {
+		if (is_ftrace_func(func, addrs, count)) {
 			/*
 			 * We iterate over sorted array, so we can easily skip
 			 * not valid item and move following valid field into