llvm-utils.c

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// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2015, Wang Nan <wangnan0@huawei.com>
 * Copyright (C) 2015, Huawei Inc.
 */

#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <linux/err.h>
#include "debug.h"
#include "llvm-utils.h"
#include "config.h"
#include "util.h"
#include <sys/wait.h>
#include <subcmd/exec-cmd.h>

#define CLANG_BPF_CMD_DEFAULT_TEMPLATE              \
        "$CLANG_EXEC -D__KERNEL__ -D__NR_CPUS__=$NR_CPUS "\
        "-DLINUX_VERSION_CODE=$LINUX_VERSION_CODE " \
        "$CLANG_OPTIONS $KERNEL_INC_OPTIONS $PERF_BPF_INC_OPTIONS " \
        "-Wno-unused-value -Wno-pointer-sign "      \
        "-working-directory $WORKING_DIR "      \
        "-c \"$CLANG_SOURCE\" -target bpf -O2 -o -"

struct llvm_param llvm_param = {
    .clang_path = "clang",
    .clang_bpf_cmd_template = CLANG_BPF_CMD_DEFAULT_TEMPLATE,
    .clang_opt = NULL,
    .kbuild_dir = NULL,
    .kbuild_opts = NULL,
    .user_set_param = false,
};

int perf_llvm_config(const char *var, const char *value)
{
    if (!strstarts(var, "llvm."))
        return 0;
    var += sizeof("llvm.") - 1;

    if (!strcmp(var, "clang-path"))
        llvm_param.clang_path = strdup(value);
    else if (!strcmp(var, "clang-bpf-cmd-template"))
        llvm_param.clang_bpf_cmd_template = strdup(value);
    else if (!strcmp(var, "clang-opt"))
        llvm_param.clang_opt = strdup(value);
    else if (!strcmp(var, "kbuild-dir"))
        llvm_param.kbuild_dir = strdup(value);
    else if (!strcmp(var, "kbuild-opts"))
        llvm_param.kbuild_opts = strdup(value);
    else if (!strcmp(var, "dump-obj"))
        llvm_param.dump_obj = !!perf_config_bool(var, value);
    else {
        pr_debug("Invalid LLVM config option: %s\n", value);
        return -1;
    }
    llvm_param.user_set_param = true;
    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;
    char serr[STRERR_BUFSIZE];

    file = popen(cmd, "r");
    if (!file) {
        pr_err("ERROR: unable to popen cmd: %s\n",
               str_error_r(errno, serr, sizeof(serr)));
        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",
               str_error_r(errno, serr, sizeof(serr)));
        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 $PERF_BPF_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"
);
}

static int detect_kbuild_dir(char **kbuild_dir)
{
    const char *test_dir = llvm_param.kbuild_dir;
    const char *prefix_dir = "";
    const char *suffix_dir = "";

    char *autoconf_path;

    int err;

    if (!test_dir) {
        /* _UTSNAME_LENGTH is 65 */
        char release[128];

        err = fetch_kernel_version(NULL, release,
                       sizeof(release));
        if (err)
            return -EINVAL;

        test_dir = release;
        prefix_dir = "/lib/modules/";
        suffix_dir = "/build";
    }

    err = asprintf(&autoconf_path, "%s%s%s/include/generated/autoconf.h",
               prefix_dir, test_dir, suffix_dir);
    if (err < 0)
        return -ENOMEM;

    if (access(autoconf_path, R_OK) == 0) {
        free(autoconf_path);

        err = asprintf(kbuild_dir, "%s%s%s", prefix_dir, test_dir,
                   suffix_dir);
        if (err < 0)
            return -ENOMEM;
        return 0;
    }
    free(autoconf_path);
    return -ENOENT;
}

static const char *kinc_fetch_script =
"#!/usr/bin/env sh\n"
"if ! test -d \"$KBUILD_DIR\"\n"
"then\n"
"   exit -1\n"
"fi\n"
"if ! test -f \"$KBUILD_DIR/include/generated/autoconf.h\"\n"
"then\n"
"   exit -1\n"
"fi\n"
"TMPDIR=`mktemp -d`\n"
"if test -z \"$TMPDIR\"\n"
"then\n"
"    exit -1\n"
"fi\n"
"cat << EOF > $TMPDIR/Makefile\n"
"obj-y := dummy.o\n"
"\\$(obj)/%.o: \\$(src)/%.c\n"
"\t@echo -n \"\\$(NOSTDINC_FLAGS) \\$(LINUXINCLUDE) \\$(EXTRA_CFLAGS)\"\n"
"EOF\n"
"touch $TMPDIR/dummy.c\n"
"make -s -C $KBUILD_DIR M=$TMPDIR $KBUILD_OPTS dummy.o 2>/dev/null\n"
"RET=$?\n"
"rm -rf $TMPDIR\n"
"exit $RET\n";

void llvm__get_kbuild_opts(char **kbuild_dir, char **kbuild_include_opts)
{
    static char *saved_kbuild_dir;
    static char *saved_kbuild_include_opts;
    int err;

    if (!kbuild_dir || !kbuild_include_opts)
        return;

    *kbuild_dir = NULL;
    *kbuild_include_opts = NULL;

    if (saved_kbuild_dir && saved_kbuild_include_opts &&
        !IS_ERR(saved_kbuild_dir) && !IS_ERR(saved_kbuild_include_opts)) {
        *kbuild_dir = strdup(saved_kbuild_dir);
        *kbuild_include_opts = strdup(saved_kbuild_include_opts);

        if (*kbuild_dir && *kbuild_include_opts)
            return;

        zfree(kbuild_dir);
        zfree(kbuild_include_opts);
        /*
         * Don't fall through: it may breaks saved_kbuild_dir and
         * saved_kbuild_include_opts if detect them again when
         * memory is low.
         */
        return;
    }

    if (llvm_param.kbuild_dir && !llvm_param.kbuild_dir[0]) {
        pr_debug("[llvm.kbuild-dir] is set to \"\" deliberately.\n");
        pr_debug("Skip kbuild options detection.\n");
        goto errout;
    }

    err = detect_kbuild_dir(kbuild_dir);
    if (err) {
        pr_warning(
"WARNING:\tunable to get correct kernel building directory.\n"
"Hint:\tSet correct kbuild directory using 'kbuild-dir' option in [llvm]\n"
"     \tsection of ~/.perfconfig or set it to \"\" to suppress kbuild\n"
"     \tdetection.\n\n");
        goto errout;
    }

    pr_debug("Kernel build dir is set to %s\n", *kbuild_dir);
    force_set_env("KBUILD_DIR", *kbuild_dir);
    force_set_env("KBUILD_OPTS", llvm_param.kbuild_opts);
    err = read_from_pipe(kinc_fetch_script,
                 (void **)kbuild_include_opts,
                 NULL);
    if (err) {
        pr_warning(
"WARNING:\tunable to get kernel include directories from '%s'\n"
"Hint:\tTry set clang include options using 'clang-bpf-cmd-template'\n"
"     \toption in [llvm] section of ~/.perfconfig and set 'kbuild-dir'\n"
"     \toption in [llvm] to \"\" to suppress this detection.\n\n",
            *kbuild_dir);

        free(*kbuild_dir);
        *kbuild_dir = NULL;
        goto errout;
    }

    pr_debug("include option is set to %s\n", *kbuild_include_opts);

    saved_kbuild_dir = strdup(*kbuild_dir);
    saved_kbuild_include_opts = strdup(*kbuild_include_opts);

    if (!saved_kbuild_dir || !saved_kbuild_include_opts) {
        zfree(&saved_kbuild_dir);
        zfree(&saved_kbuild_include_opts);
    }
    return;
errout:
    saved_kbuild_dir = ERR_PTR(-EINVAL);
    saved_kbuild_include_opts = ERR_PTR(-EINVAL);
}

int llvm__get_nr_cpus(void)
{
    static int nr_cpus_avail = 0;
    char serr[STRERR_BUFSIZE];

    if (nr_cpus_avail > 0)
        return nr_cpus_avail;

    nr_cpus_avail = sysconf(_SC_NPROCESSORS_CONF);
    if (nr_cpus_avail <= 0) {
        pr_err(
"WARNING:\tunable to get available CPUs in this system: %s\n"
"        \tUse 128 instead.\n", str_error_r(errno, serr, sizeof(serr)));
        nr_cpus_avail = 128;
    }
    return nr_cpus_avail;
}

void llvm__dump_obj(const char *path, void *obj_buf, size_t size)
{
    char *obj_path = strdup(path);
    FILE *fp;
    char *p;

    if (!obj_path) {
        pr_warning("WARNING: Not enough memory, skip object dumping\n");
        return;
    }

    p = strrchr(obj_path, '.');
    if (!p || (strcmp(p, ".c") != 0)) {
        pr_warning("WARNING: invalid llvm source path: '%s', skip object dumping\n",
               obj_path);
        goto out;
    }

    p[1] = 'o';
    fp = fopen(obj_path, "wb");
    if (!fp) {
        pr_warning("WARNING: failed to open '%s': %s, skip object dumping\n",
               obj_path, strerror(errno));
        goto out;
    }

    pr_info("LLVM: dumping %s\n", obj_path);
    if (fwrite(obj_buf, size, 1, fp) != 1)
        pr_warning("WARNING: failed to write to file '%s': %s, skip object dumping\n",
               obj_path, strerror(errno));
    fclose(fp);
out:
    free(obj_path);
}

int llvm__compile_bpf(const char *path, void **p_obj_buf,
              size_t *p_obj_buf_sz)
{
    size_t obj_buf_sz;
    void *obj_buf = NULL;
    int err, nr_cpus_avail;
    unsigned int kernel_version;
    char linux_version_code_str[64];
    const char *clang_opt = llvm_param.clang_opt;
    char clang_path[PATH_MAX], abspath[PATH_MAX], nr_cpus_avail_str[64];
    char serr[STRERR_BUFSIZE];
    char *kbuild_dir = NULL, *kbuild_include_opts = NULL,
         *perf_bpf_include_opts = NULL;
    const char *template = llvm_param.clang_bpf_cmd_template;
    char *command_echo = NULL, *command_out;
    char *perf_include_dir = system_path(PERF_INCLUDE_DIR);

    if (path[0] != '-' && realpath(path, abspath) == NULL) {
        err = errno;
        pr_err("ERROR: problems with path %s: %s\n",
               path, str_error_r(err, serr, sizeof(serr)));
        return -err;
    }

    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;
    }

    /*
     * This is an optional work. Even it fail we can continue our
     * work. Needn't to check error return.
     */
    llvm__get_kbuild_opts(&kbuild_dir, &kbuild_include_opts);

    nr_cpus_avail = llvm__get_nr_cpus();
    snprintf(nr_cpus_avail_str, sizeof(nr_cpus_avail_str), "%d",
         nr_cpus_avail);

    if (fetch_kernel_version(&kernel_version, NULL, 0))
        kernel_version = 0;

    snprintf(linux_version_code_str, sizeof(linux_version_code_str),
         "0x%x", kernel_version);
    if (asprintf(&perf_bpf_include_opts, "-I%s/bpf", perf_include_dir) < 0)
        goto errout;
    force_set_env("NR_CPUS", nr_cpus_avail_str);
    force_set_env("LINUX_VERSION_CODE", linux_version_code_str);
    force_set_env("CLANG_EXEC", clang_path);
    force_set_env("CLANG_OPTIONS", clang_opt);
    force_set_env("KERNEL_INC_OPTIONS", kbuild_include_opts);
    force_set_env("PERF_BPF_INC_OPTIONS", perf_bpf_include_opts);
    force_set_env("WORKING_DIR", kbuild_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 : abspath);

    pr_debug("llvm compiling command template: %s\n", template);

    if (asprintf(&command_echo, "echo -n \"%s\"", template) < 0)
        goto errout;

    err = read_from_pipe(command_echo, (void **) &command_out, NULL);
    if (err)
        goto errout;

    pr_debug("llvm compiling command : %s\n", command_out);

    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;
    }

    free(command_echo);
    free(command_out);
    free(kbuild_dir);
    free(kbuild_include_opts);
    free(perf_bpf_include_opts);
    free(perf_include_dir);

    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(command_echo);
    free(kbuild_dir);
    free(kbuild_include_opts);
    free(obj_buf);
    free(perf_bpf_include_opts);
    free(perf_include_dir);
    if (p_obj_buf)
        *p_obj_buf = NULL;
    if (p_obj_buf_sz)
        *p_obj_buf_sz = 0;
    return err;
}

int llvm__search_clang(void)
{
    char clang_path[PATH_MAX];

    return search_program(llvm_param.clang_path, "clang", clang_path);
}