[PATCHv2] btf_encoder: Add extra checks for symbol names

[Jiri Olsa <jolsa@xxxxxxxxxx>]

When processing kernel image build by clang we can
find some functions without the name, which causes
pahole to segfault.

Adding extra checks to make sure we always have
function's name defined before using it.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
  v2 changes:
    - reorg the code based on Andrii's suggestion

 btf_encoder.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/btf_encoder.c b/btf_encoder.c
index 333973054b61..5557c9efd365 100644
--- a/btf_encoder.c
+++ b/btf_encoder.c
@@ -68,10 +68,14 @@ static int collect_function(struct btf_elf *btfe, GElf_Sym *sym)
 	struct elf_function *new;
 	static GElf_Shdr sh;
 	static int last_idx;
+	const char *name;
 	int idx;
 
 	if (elf_sym__type(sym) != STT_FUNC)
 		return 0;
+	name = elf_sym__name(sym, btfe->symtab);
+	if (!name)
+		return 0;
 
 	if (functions_cnt == functions_alloc) {
 		functions_alloc = max(1000, functions_alloc * 3 / 2);
@@ -94,7 +98,7 @@ static int collect_function(struct btf_elf *btfe, GElf_Sym *sym)
 		last_idx = idx;
 	}
 
-	functions[functions_cnt].name = elf_sym__name(sym, btfe->symtab);
+	functions[functions_cnt].name = name;
 	functions[functions_cnt].addr = elf_sym__value(sym);
 	functions[functions_cnt].sh_addr = sh.sh_addr;
 	functions[functions_cnt].generated = false;
@@ -731,8 +735,13 @@ int cu__encode_btf(struct cu *cu, int verbose, bool force,
 			continue;
 		if (functions_cnt) {
 			struct elf_function *func;
+			const char *name;
+
+			name = function__name(fn, cu);
+			if (!name)
+				continue;
 
-			func = find_function(btfe, function__name(fn, cu));
+			func = find_function(btfe, name);
 			if (!func || func->generated)
 				continue;
 			func->generated = true;
-- 
2.26.2