[RFC PATCH v7 24/37] perf tools: Call clang to compile C source to object code

Wang Nan
2015-06-12T05:40:38Z

This is the core patch for supporting eBPF on-the-fly compiling, does
the following work:

1. Search clang compiler using search_program().

2. Run command template defined in llvm-bpf-cmd-template option in
[llvm] config section using read_from_pipe(). Patch of clang and
source code path is injected into shell command using environment
variable using force_set_env().

Signed-off-by: Wang Nan <wangnan0@huawei.com>
---
tools/perf/util/llvm-utils.c | 222 +++++++++++++++++++++++++++++++++++++++++++
tools/perf/util/llvm-utils.h | 3 +
2 files changed, 225 insertions(+)

diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index 7dc1f1e..c01decd 100644
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -43,3 +43,225 @@ int perf_llvm_config(const char *var, const char *value)
return -1;
return 0;
}
+
+static int
+search_program(const char *def, const char *name,
+ char *output)
+{
+ char *env, *path, *tmp;
+ char buf[PATH_MAX];
+ int ret;
+
+ output[0] = '\0';
+ if (def && def[0] != '\0') {
+ if (def[0] == '/') {
+ if (access(def, F_OK) == 0) {
+ strlcpy(output, def, PATH_MAX);
+ return 0;
+ }
+ } else if (def[0] != '\0')
+ name = def;
+ }
+
+ env = getenv("PATH");
+ if (!env)
+ return -1;
+ env = strdup(env);
+ if (!env)
+ return -1;
+
+ ret = -ENOENT;
+ path = strtok_r(env, ":", &tmp);
+ while (path) {
+ scnprintf(buf, sizeof(buf), "%s/%s", path, name);
+ if (access(buf, F_OK) == 0) {
+ strlcpy(output, buf, PATH_MAX);
+ ret = 0;
+ break;
+ }
+ path = strtok_r(NULL, ":", &tmp);
+ }
+
+ free(env);
+ return ret;
+}
+
+#define READ_SIZE 4096
+static int
+read_from_pipe(const char *cmd, void **p_buf, size_t *p_read_sz)
+{
+ int err = 0;
+ void *buf = NULL;
+ FILE *file = NULL;
+ size_t read_sz = 0, buf_sz = 0;
+
+ file = popen(cmd, "r");
+ if (!file) {
+ pr_err("ERROR: unable to popen cmd: %s\n",
+ strerror(errno));
+ return -EINVAL;
+ }
+
+ while (!feof(file) && !ferror(file)) {
+ /*
+ * Make buf_sz always have obe byte extra space so we
+ * can put '\0' there.
+ */
+ if (buf_sz - read_sz < READ_SIZE + 1) {
+ void *new_buf;
+
+ buf_sz = read_sz + READ_SIZE + 1;
+ new_buf = realloc(buf, buf_sz);
+
+ if (!new_buf) {
+ pr_err("ERROR: failed to realloc memory\n");
+ err = -ENOMEM;
+ goto errout;
+ }
+
+ buf = new_buf;
+ }
+ read_sz += fread(buf + read_sz, 1, READ_SIZE, file);
+ }
+
+ if (buf_sz - read_sz < 1) {
+ pr_err("ERROR: internal error\n");
+ err = -EINVAL;
+ goto errout;
+ }
+
+ if (ferror(file)) {
+ pr_err("ERROR: error occured when reading from pipe: %s\n",
+ strerror(errno));
+ err = -EIO;
+ goto errout;
+ }
+
+ err = WEXITSTATUS(pclose(file));
+ file = NULL;
+ if (err) {
+ err = -EINVAL;
+ goto errout;
+ }
+
+ /*
+ * If buf is string, give it terminal '\0' to make our life
+ * easier. If buf is not string, that '\0' is out of space
+ * indicated by read_sz so caller won't even notice it.
+ */
+ ((char *)buf)[read_sz] = '\0';
+
+ if (!p_buf)
+ free(buf);
+ else
+ *p_buf = buf;
+
+ if (p_read_sz)
+ *p_read_sz = read_sz;
+ return 0;
+
+errout:
+ if (file)
+ pclose(file);
+ free(buf);
+ if (p_buf)
+ *p_buf = NULL;
+ if (p_read_sz)
+ *p_read_sz = 0;
+ return err;
+}
+
+static inline void
+force_set_env(const char *var, const char *value)
+{
+ if (value) {
+ setenv(var, value, 1);
+ pr_debug("set env: %s=%s\n", var, value);
+ } else {
+ unsetenv(var);
+ pr_debug("unset env: %s\n", var);
+ }
+}
+
+static void
+version_notice(void)
+{
+ pr_err(
+" \tLLVM 3.7 or newer is required. Which can be found from http://llvm.org\n"
+" \tYou may want to try git trunk:\n"
+" \t\tgit clone http://llvm.org/git/llvm.git\n"
+" \t\t and\n"
+" \t\tgit clone http://llvm.org/git/clang.git\n\n"
+" \tIf you are using old version of clang, change 'clang-bpf-cmd-template'\n"
+" \toption in [llvm] section of ~/.perfconfig to:\n\n"
+" \t \"$CLANG_EXEC $CLANG_OPTIONS $KERNEL_INC_OPTIONS \\\n"
+" \t -working-directory $WORKING_DIR -c $CLANG_SOURCE \\\n"
+" \t -emit-llvm -o - | /path/to/llc -march=bpf -filetype=obj -o -\"\n"
+" \t(Replace /path/to/llc with path to your llc)\n\n"
+);
+}
+
+int llvm__compile_bpf(const char *path, void **p_obj_buf,
+ size_t *p_obj_buf_sz)
+{
+ int err;
+ char clang_path[PATH_MAX];
+ const char *clang_opt = llvm_param.clang_opt;
+ const char *template = llvm_param.clang_bpf_cmd_template;
+ void *obj_buf = NULL;
+ size_t obj_buf_sz;
+
+ if (!template)
+ template = CLANG_BPF_CMD_DEFAULT_TEMPLATE;
+
+ err = search_program(llvm_param.clang_path,
+ "clang", clang_path);
+ if (err) {
+ pr_err(
+"ERROR:\tunable to find clang.\n"
+"Hint:\tTry to install latest clang/llvm to support BPF. Check your $PATH\n"
+" \tand 'clang-path' option in [llvm] section of ~/.perfconfig.\n");
+ version_notice();
+ return -ENOENT;
+ }
+
+ force_set_env("CLANG_EXEC", clang_path);
+ force_set_env("CLANG_OPTIONS", clang_opt);
+ force_set_env("KERNEL_INC_OPTIONS", NULL);
+ force_set_env("WORKING_DIR", ".");
+
+ /*
+ * Since we may reset clang's working dir, path of source file
+ * should be transfered into absolute path, except we want
+ * stdin to be source file (testing).
+ */
+ force_set_env("CLANG_SOURCE",
+ (path[0] == '-') ? path :
+ make_nonrelative_path(path));
+
+ pr_debug("llvm compiling command template: %s\n", template);
+ err = read_from_pipe(template, &obj_buf, &obj_buf_sz);
+ if (err) {
+ pr_err("ERROR:\tunable to compile %s\n", path);
+ pr_err("Hint:\tCheck error message shown above.\n");
+ version_notice();
+ pr_err("Hint:\tYou can also pre-compile it into .o\n");
+ goto errout;
+ }
+
+ if (!p_obj_buf)
+ free(obj_buf);
+ else
+ *p_obj_buf = obj_buf;
+
+ if (p_obj_buf_sz)
+ *p_obj_buf_sz = obj_buf_sz;
+ return 0;
+errout:
+ free(obj_buf);
+ if (p_obj_buf)
+ *p_obj_buf = NULL;
+ if (p_obj_buf_sz)
+ *p_obj_buf_sz = 0;
+ return err;
+}
diff --git a/tools/perf/util/llvm-utils.h b/tools/perf/util/llvm-utils.h
index 504b799..d23adbc 100644
--- a/tools/perf/util/llvm-utils.h
+++ b/tools/perf/util/llvm-utils.h
@@ -33,4 +33,7 @@ struct llvm_param {

extern struct llvm_param llvm_param;
extern int perf_llvm_config(const char *var, const char *value);
+
+extern int llvm__compile_bpf(const char *path, void **p_obj_buf,
+ size_t *p_obj_buf_sz);
#endif
--
1.8.3.4