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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 b236512280:
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 <wangnan0@huawei.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kaixu Xia <xiakaixu@huawei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Zefan Li <lizefan@huawei.com>
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 <acme@redhat.com>
This commit is contained in:
Wang Nan
Arnaldo Carvalho de Melo
parent
aa61fd05ca
commit
4cea3a9cb3
@ -43,3 +43,229 @@ int perf_llvm_config(const char *var, const char *value)
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return -1;
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return 0;
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}
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static int
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search_program(const char *def, const char *name,
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char *output)
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{
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char *env, *path, *tmp = NULL;
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char buf[PATH_MAX];
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int ret;
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output[0] = '\0';
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if (def && def[0] != '\0') {
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if (def[0] == '/') {
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if (access(def, F_OK) == 0) {
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strlcpy(output, def, PATH_MAX);
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return 0;
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}
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} else if (def[0] != '\0')
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name = def;
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}
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env = getenv("PATH");
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if (!env)
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return -1;
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env = strdup(env);
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if (!env)
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return -1;
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ret = -ENOENT;
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path = strtok_r(env, ":", &tmp);
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while (path) {
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scnprintf(buf, sizeof(buf), "%s/%s", path, name);
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if (access(buf, F_OK) == 0) {
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strlcpy(output, buf, PATH_MAX);
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ret = 0;
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break;
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}
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path = strtok_r(NULL, ":", &tmp);
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}
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free(env);
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return ret;
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}
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#define READ_SIZE 4096
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static int
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read_from_pipe(const char *cmd, void **p_buf, size_t *p_read_sz)
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{
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int err = 0;
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void *buf = NULL;
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FILE *file = NULL;
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size_t read_sz = 0, buf_sz = 0;
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file = popen(cmd, "r");
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if (!file) {
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pr_err("ERROR: unable to popen cmd: %s\n",
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strerror(errno));
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return -EINVAL;
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}
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while (!feof(file) && !ferror(file)) {
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/*
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* Make buf_sz always have obe byte extra space so we
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* can put '\0' there.
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*/
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if (buf_sz - read_sz < READ_SIZE + 1) {
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void *new_buf;
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buf_sz = read_sz + READ_SIZE + 1;
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new_buf = realloc(buf, buf_sz);
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if (!new_buf) {
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pr_err("ERROR: failed to realloc memory\n");
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err = -ENOMEM;
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goto errout;
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}
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buf = new_buf;
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}
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read_sz += fread(buf + read_sz, 1, READ_SIZE, file);
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}
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if (buf_sz - read_sz < 1) {
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pr_err("ERROR: internal error\n");
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err = -EINVAL;
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goto errout;
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}
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if (ferror(file)) {
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pr_err("ERROR: error occurred when reading from pipe: %s\n",
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strerror(errno));
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err = -EIO;
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goto errout;
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}
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err = WEXITSTATUS(pclose(file));
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file = NULL;
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if (err) {
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err = -EINVAL;
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goto errout;
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}
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/*
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* If buf is string, give it terminal '\0' to make our life
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* easier. If buf is not string, that '\0' is out of space
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* indicated by read_sz so caller won't even notice it.
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*/
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((char *)buf)[read_sz] = '\0';
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if (!p_buf)
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free(buf);
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else
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*p_buf = buf;
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if (p_read_sz)
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*p_read_sz = read_sz;
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return 0;
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errout:
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if (file)
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pclose(file);
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free(buf);
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if (p_buf)
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*p_buf = NULL;
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if (p_read_sz)
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*p_read_sz = 0;
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return err;
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}
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static inline void
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force_set_env(const char *var, const char *value)
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{
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if (value) {
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setenv(var, value, 1);
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pr_debug("set env: %s=%s\n", var, value);
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} else {
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unsetenv(var);
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pr_debug("unset env: %s\n", var);
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}
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}
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static void
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version_notice(void)
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{
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pr_err(
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" \tLLVM 3.7 or newer is required. Which can be found from http://llvm.org\n"
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" \tYou may want to try git trunk:\n"
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" \t\tgit clone http://llvm.org/git/llvm.git\n"
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" \t\t and\n"
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" \t\tgit clone http://llvm.org/git/clang.git\n\n"
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" \tOr fetch the latest clang/llvm 3.7 from pre-built llvm packages for\n"
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" \tdebian/ubuntu:\n"
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" \t\thttp://llvm.org/apt\n\n"
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" \tIf you are using old version of clang, change 'clang-bpf-cmd-template'\n"
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" \toption in [llvm] section of ~/.perfconfig to:\n\n"
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" \t \"$CLANG_EXEC $CLANG_OPTIONS $KERNEL_INC_OPTIONS \\\n"
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" \t -working-directory $WORKING_DIR -c $CLANG_SOURCE \\\n"
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" \t -emit-llvm -o - | /path/to/llc -march=bpf -filetype=obj -o -\"\n"
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" \t(Replace /path/to/llc with path to your llc)\n\n"
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);
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}
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int llvm__compile_bpf(const char *path, void **p_obj_buf,
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size_t *p_obj_buf_sz)
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{
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int err;
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char clang_path[PATH_MAX];
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const char *clang_opt = llvm_param.clang_opt;
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const char *template = llvm_param.clang_bpf_cmd_template;
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void *obj_buf = NULL;
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size_t obj_buf_sz;
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if (!template)
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template = CLANG_BPF_CMD_DEFAULT_TEMPLATE;
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err = search_program(llvm_param.clang_path,
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"clang", clang_path);
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if (err) {
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pr_err(
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"ERROR:\tunable to find clang.\n"
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"Hint:\tTry to install latest clang/llvm to support BPF. Check your $PATH\n"
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" \tand 'clang-path' option in [llvm] section of ~/.perfconfig.\n");
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version_notice();
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return -ENOENT;
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}
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force_set_env("CLANG_EXEC", clang_path);
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force_set_env("CLANG_OPTIONS", clang_opt);
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force_set_env("KERNEL_INC_OPTIONS", NULL);
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force_set_env("WORKING_DIR", ".");
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/*
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* Since we may reset clang's working dir, path of source file
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* should be transferred into absolute path, except we want
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* stdin to be source file (testing).
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*/
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force_set_env("CLANG_SOURCE",
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(path[0] == '-') ? path :
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make_nonrelative_path(path));
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pr_debug("llvm compiling command template: %s\n", template);
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err = read_from_pipe(template, &obj_buf, &obj_buf_sz);
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if (err) {
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pr_err("ERROR:\tunable to compile %s\n", path);
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pr_err("Hint:\tCheck error message shown above.\n");
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pr_err("Hint:\tYou can also pre-compile it into .o using:\n");
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pr_err(" \t\tclang -target bpf -O2 -c %s\n", path);
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pr_err(" \twith proper -I and -D options.\n");
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goto errout;
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}
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if (!p_obj_buf)
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free(obj_buf);
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else
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*p_obj_buf = obj_buf;
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if (p_obj_buf_sz)
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*p_obj_buf_sz = obj_buf_sz;
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return 0;
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errout:
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free(obj_buf);
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if (p_obj_buf)
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*p_obj_buf = NULL;
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if (p_obj_buf_sz)
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*p_obj_buf_sz = 0;
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return err;
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}
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@ -33,4 +33,7 @@ struct llvm_param {
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extern struct llvm_param llvm_param;
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extern int perf_llvm_config(const char *var, const char *value);
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extern int llvm__compile_bpf(const char *path, void **p_obj_buf,
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size_t *p_obj_buf_sz);
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#endif
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