Merge pull request #430 from iovisor/bblanco_dev

Add option to change kernel build search paths

CMakeLists.txt

@@ -39,6 +39,22 @@ FOREACH(DIR ${LLVM_INCLUDE_DIRS})
   include_directories("${DIR}/../tools/clang/include")
 ENDFOREACH()
 
+# Set to non-zero if system installs kernel headers with split source and build
+# directories in /lib/modules/`uname -r`/. This is the case for debian and
+# suse, to the best of my knowledge.
+if(BCC_KERNEL_HAS_SOURCE_DIR)
+  set(BCC_KERNEL_HAS_SOURCE_DIR 1)
+  set(BCC_KERNEL_MODULES_SUFFIX "source")
+else()
+  set(BCC_KERNEL_HAS_SOURCE_DIR 0)
+endif()
+
+# Similar to above, set to custom value if kernel headers in
+# /lib/modules/`uname -r` sit in a different location than build/.
+if(NOT DEFINED BCC_KERNEL_MODULES_SUFFIX)
+  set(BCC_KERNEL_MODULES_SUFFIX "build")
+endif()
+
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wall")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -Wall")
 endif()

src/cc/export/helpers.h

@@ -186,6 +186,10 @@ static int (*bpf_skb_load_bytes)(void *ctx, int offset, void *to, u32 len) =
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4,6,0)
 static int (*bpf_get_stackid_)(void *ctx, void *map, u64 flags) =
   (void *) BPF_FUNC_get_stackid;
+static inline __attribute__((always_inline))
+int bpf_get_stackid(uintptr_t map, void *ctx, u64 flags) {
+  return bpf_get_stackid_(ctx, (void *)map, flags);
+}
 static int (*bpf_csum_diff)(void *from, u64 from_size, void *to, u64 to_size, u64 seed) =
   (void *) BPF_FUNC_csum_diff;
 #endif
@@ -378,11 +382,6 @@ int bpf_map_delete_elem_(uintptr_t map, void *key) {
   return bpf_map_delete_elem((void *)map, key);
 }
 
-static inline __attribute__((always_inline))
-int bpf_get_stackid(uintptr_t map, void *ctx, u64 flags) {
-  return bpf_get_stackid_(ctx, (void *)map, flags);
-}
-
 static inline __attribute__((always_inline))
 SEC("helpers")
 int bpf_l3_csum_replace_(void *ctx, u64 off, u64 from, u64 to, u64 flags) {

src/cc/frontends/clang/CMakeLists.txt

 # Copyright (c) PLUMgrid, Inc.
 # Licensed under the Apache License, Version 2.0 (the "License")
 
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DKERNEL_MODULES_SUFFIX='\"${BCC_KERNEL_MODULES_SUFFIX}\"'")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DKERNEL_HAS_SOURCE_DIR=${BCC_KERNEL_HAS_SOURCE_DIR}")
 add_library(clang_frontend loader.cc b_frontend_action.cc kbuild_helper.cc)

src/cc/frontends/clang/kbuild_helper.cc

@@ -22,7 +22,7 @@ namespace ebpf {
 using std::string;
 using std::vector;
 
-KBuildHelper::KBuildHelper() {
+KBuildHelper::KBuildHelper(const std::string &kdir) : kdir_(kdir) {
 }
 
 // read the flags from cache or learn
@@ -58,6 +58,19 @@ int KBuildHelper::get_flags(const char *uname_machine, vector<string> *cflags) {
   cflags->push_back("-nostdinc");
   cflags->push_back("-isystem");
   cflags->push_back("/virtual/lib/clang/include");
+
+  // some module build directories split headers between source/ and build/
+  if (KERNEL_HAS_SOURCE_DIR) {
+    cflags->push_back("-I" + kdir_ + "/build/arch/"+arch+"/include");
+    cflags->push_back("-I" + kdir_ + "/build/arch/"+arch+"/include/generated/uapi");
+    cflags->push_back("-I" + kdir_ + "/build/arch/"+arch+"/include/generated");
+    cflags->push_back("-I" + kdir_ + "/build/include");
+    cflags->push_back("-I" + kdir_ + "/build/./arch/"+arch+"/include/uapi");
+    cflags->push_back("-I" + kdir_ + "/build/arch/"+arch+"/include/generated/uapi");
+    cflags->push_back("-I" + kdir_ + "/build/include/uapi");
+    cflags->push_back("-I" + kdir_ + "/build/include/generated/uapi");
+  }
+
   cflags->push_back("-I./arch/"+arch+"/include");
   cflags->push_back("-Iarch/"+arch+"/include/generated/uapi");
   cflags->push_back("-Iarch/"+arch+"/include/generated");
@@ -71,6 +84,7 @@ int KBuildHelper::get_flags(const char *uname_machine, vector<string> *cflags) {
   cflags->push_back("-D__KERNEL__");
   cflags->push_back("-Wno-unused-value");
   cflags->push_back("-Wno-pointer-sign");
+
   return 0;
 }
 

src/cc/frontends/clang/kbuild_helper.h

@@ -33,13 +33,13 @@ typedef std::unique_ptr<FILE, FileDeleter> FILEPtr;
 // Helper with pushd/popd semantics
 class DirStack {
  public:
-  explicit DirStack(const char *dst) : ok_(false) {
+  explicit DirStack(const std::string &dst) : ok_(false) {
     if (getcwd(cwd_, sizeof(cwd_)) == NULL) {
       ::perror("getcwd");
       return;
     }
-    if (::chdir(dst)) {
-      fprintf(stderr, "chdir(%s): %s\n", dst, strerror(errno));
+    if (::chdir(dst.c_str())) {
+      fprintf(stderr, "chdir(%s): %s\n", dst.c_str(), strerror(errno));
       return;
     }
     ok_ = true;
@@ -94,8 +94,10 @@ class TmpDir {
 //  case we eventually support non-root user programs, cache in $HOME.
 class KBuildHelper {
  public:
-  KBuildHelper();
+  explicit KBuildHelper(const std::string &kdir);
   int get_flags(const char *uname_machine, std::vector<std::string> *cflags);
+ private:
+  std::string kdir_;
 };
 
 }  // namespace ebpf

src/cc/frontends/clang/loader.cc

@@ -82,11 +82,10 @@ int ClangLoader::parse(unique_ptr<llvm::Module> *mod, unique_ptr<vector<TableDes
   unique_ptr<llvm::MemoryBuffer> main_buf;
   struct utsname un;
   uname(&un);
-  char kdir[256];
-  snprintf(kdir, sizeof(kdir), "%s/%s/build", KERNEL_MODULES_DIR, un.release);
+  string kdir = string(KERNEL_MODULES_DIR) + "/" + un.release;
 
   // clang needs to run inside the kernel dir
-  DirStack dstack(kdir);
+  DirStack dstack(kdir + "/" + KERNEL_MODULES_SUFFIX);
   if (!dstack.ok())
     return -1;
 
@@ -106,7 +105,7 @@ int ClangLoader::parse(unique_ptr<llvm::Module> *mod, unique_ptr<vector<TableDes
                                    "-Wno-gnu-variable-sized-type-not-at-end",
                                    "-x", "c", "-c", abs_file.c_str()});
 
-  KBuildHelper kbuild_helper;
+  KBuildHelper kbuild_helper(kdir);
   vector<string> kflags;
   if (kbuild_helper.get_flags(un.machine, &kflags))
     return -1;