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 2015-06-11 10:31:09 +00:00 committed by Arnaldo Carvalho de Melo
parent aa61fd05ca
commit 4cea3a9cb3
2 changed files with 229 additions and 0 deletions

View File

@ -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;
}

View File

@ -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