From 4cea3a9cb30a962fa759fcb081fb83351113d9c4 Mon Sep 17 00:00:00 2001 From: Wang Nan Date: Thu, 11 Jun 2015 10:31:09 +0000 Subject: [PATCH] perf tools: Call clang to compile C source to object code 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(). Commiter notice: When building with DEBUG=1 we get a compiler error that gets fixed with the same approach described in commit b236512280fb: perf kmem: Fix compiler warning about may be accessing uninitialized variable The last argument to strtok_r doesn't need to be initialized, its just a placeholder to make this routine reentrant, but gcc doesn't know about that and complains, breaking the build, fix it by setting it to NULL. Signed-off-by: Wang Nan Acked-by: Alexei Starovoitov Cc: Brendan Gregg Cc: Daniel Borkmann Cc: David Ahern Cc: He Kuang Cc: Jiri Olsa Cc: Kaixu Xia Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Zefan Li Cc: pi3orama@163.com Link: http://lkml.kernel.org/n/1436445342-1402-14-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/llvm-utils.c | 226 +++++++++++++++++++++++++++++++++++ tools/perf/util/llvm-utils.h | 3 + 2 files changed, 229 insertions(+) diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c index 472e8cd69361..5ae11249baad 100644 --- a/tools/perf/util/llvm-utils.c +++ b/tools/perf/util/llvm-utils.c @@ -43,3 +43,229 @@ 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 = NULL; + 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 occurred 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" +" \tOr fetch the latest clang/llvm 3.7 from pre-built llvm packages for\n" +" \tdebian/ubuntu:\n" +" \t\thttp://llvm.org/apt\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 transferred 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"); + pr_err("Hint:\tYou can also pre-compile it into .o using:\n"); + pr_err(" \t\tclang -target bpf -O2 -c %s\n", path); + pr_err(" \twith proper -I and -D options.\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 504b799687fb..d23adbca120b 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