perf llvm: Pass LINUX_VERSION_CODE to BPF program when compiling

Arnaldo suggests to make LINUX_VERSION_CODE works like __func__ and
__FILE__ so user don't need to care setting right linux version too
much. In this patch, perf llvm transfers LINUX_VERSION_CODE macro
through clang cmdline.

[1] http://lkml.kernel.org/r/20151029223744.GK2923@kernel.org

Committer notes:

Before, forgetting to update the version:

  # uname -r
  4.3.0-rc1+
  # cat bpf.c
  __attribute__((section("fork=_do_fork"), used))
  int fork(void *ctx)
  {
          return 1;
  }

  char _license[] __attribute__((section("license"), used)) = "GPL";
  int _version __attribute__((section("version"), used)) = 0x40200;
  #
  # perf record -e bpf.c sleep 1
  event syntax error: 'bpf.c'
                       \___ Invalid argument: Are you root and runing a CONFIG_BPF_SYSCALL kernel?

  (add -v to see detail)
  Run 'perf list' for a list of valid events

   Usage: perf record [<options>] [<command>]
      or: perf record [<options>] -- <command> [<options>]

      -e, --event <event>   event selector. use 'perf list' to list available events
 #

After:

  # grep version bpf.c
  int _version __attribute__((section("version"), used)) = LINUX_VERSION_CODE;
  # perf record -e bpf.c sleep 1
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.017 MB perf.data ]
  # perf evlist -v
  perf_bpf_probe:fork: type: 2, size: 112, config: 0x5ee, { sample_period,
  sample_freq }: 1, sample_type: IP|TID|TIME|CPU|PERIOD|RAW, disabled: 1,
  inherit: 1, mmap: 1, comm: 1, enable_on_exec: 1, task: 1, sample_id_all:
  1, exclude_guest: 1, mmap2: 1, comm_exec: 1
  #

Suggested-and-Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1446636007-239722-3-git-send-email-wangnan0@huawei.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/util/llvm-utils.c b/tools/perf/util/llvm-utils.c
index 80eecefc604f29529f6228701f1979e6eaa19ea5..8ee25bea1b24a1be8730fec4b2146f6d0a008c21 100644 (file)
--- a/tools/perf/util/llvm-utils.c
+++ b/tools/perf/util/llvm-utils.c
@@ -12,6 +12,7 @@
 
 #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 "           \
                "-Wno-unused-value -Wno-pointer-sign "          \
                "-working-directory $WORKING_DIR "              \
@@ -324,11 +325,33 @@ get_kbuild_opts(char **kbuild_dir, char **kbuild_include_opts)
        pr_debug("include option is set to %s\n", *kbuild_include_opts);
 }
 
+static unsigned long
+fetch_kernel_version(void)
+{
+       struct utsname utsname;
+       int version, patchlevel, sublevel, err;
+
+       if (uname(&utsname))
+               return 0;
+
+       err = sscanf(utsname.release, "%d.%d.%d",
+                    &version, &patchlevel, &sublevel);
+
+       if (err != 3) {
+               pr_debug("Unablt to get kernel version from uname '%s'\n",
+                        utsname.release);
+               return 0;
+       }
+
+       return (version << 16) + (patchlevel << 8) + sublevel;
+}
+
 int llvm__compile_bpf(const char *path, void **p_obj_buf,
                      size_t *p_obj_buf_sz)
 {
        int err, nr_cpus_avail;
        char clang_path[PATH_MAX], nr_cpus_avail_str[64];
+       char linux_version_code_str[64];
        const char *clang_opt = llvm_param.clang_opt;
        const char *template = llvm_param.clang_bpf_cmd_template;
        char *kbuild_dir = NULL, *kbuild_include_opts = NULL;
@@ -365,7 +388,11 @@ int llvm__compile_bpf(const char *path, void **p_obj_buf,
        snprintf(nr_cpus_avail_str, sizeof(nr_cpus_avail_str), "%d",
                 nr_cpus_avail);
 
+       snprintf(linux_version_code_str, sizeof(linux_version_code_str),
+                "0x%lx", fetch_kernel_version());
+
        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);