Commit 4a4f66a1 authored Nov 04, 2015 by Wang Nan Committed by Arnaldo Carvalho de Melo Nov 05, 2015

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>

parent 59f41af9

tools/perf/util/llvm-utils.c

+27 −0

Original line number	Diff line number	Diff line
		@@ -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);