[PATCH v4 04/18] perf clang: Pass full path to builtin clang

[Wang Nan]

If clang changes its working directory, relative path passed to
perf_clang__compile_bpf() becomes invalid. Before running clang,
convert it to absolute path so file can be found even working directory
is changed.

Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/util/c++/clang.cpp | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/c++/clang.cpp b/tools/perf/util/c++/clang.cpp
index 7fe0222c5..340c948 100644
--- a/tools/perf/util/c++/clang.cpp
+++ b/tools/perf/util/c++/clang.cpp
@@ -13,6 +13,7 @@
 #include "clang/Frontend/CompilerInstance.h"
 #include "clang/Frontend/TextDiagnosticPrinter.h"
 #include "clang/Tooling/Tooling.h"
+#include "llvm/ADT/SmallString.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Option/Option.h"
@@ -161,7 +162,7 @@ void perf_clang__cleanup(void)
 	llvm::llvm_shutdown();
 }
 
-int perf_clang__compile_bpf(const char *filename,
+int perf_clang__compile_bpf(const char *_filename,
 			    void **p_obj_buf,
 			    size_t *p_obj_buf_sz)
 {
@@ -170,8 +171,11 @@ int perf_clang__compile_bpf(const char *filename,
 	if (!p_obj_buf || !p_obj_buf_sz)
 		return -EINVAL;
 
+	llvm::SmallString<PATH_MAX> FileName(_filename);
+	llvm::sys::fs::make_absolute(FileName);
+
 	llvm::opt::ArgStringList CFlags;
-	auto M = getModuleFromSource(std::move(CFlags), filename);
+	auto M = getModuleFromSource(std::move(CFlags), FileName.data());
 	if (!M)
 		return  -EINVAL;
 	auto O = getBPFObjectFromModule(&*M);
-- 
2.10.1