[PATCH v4 14/16] perf record: Support custom vmlinux path

[Wang Nan]

From: He Kuang <hekuang@xxxxxxxxxx>

Make perf-record command support --vmlinux option if BPF_PROLOGUE is on.

'perf record' needs vmlinux as the source of DWARF info to generate
prologue for BPF programs, so path of vmlinux should be specified.

Short name 'k' has been taken by 'clockid'. This patch skips the short
option name and use '--vmlinux' for vmlinux path.

Documentation is also updated.

Test result:

In a production (or broken) environment:
 (built by
  # rm -rf ~/.debug/
  # mv /lib/modules/`uname -r`/build/vmlinux /tmp/
 )

 # ./perf record -e ./test_bpf_base.c ls
 Failed to find the path for kernel: No such file or directory
 event syntax error: './test_bpf_base.c'
                      \___ You need to check probing points in BPF file
 ...

 # ./perf record --vmlinux /tmp/vmlinux -e ./test_bpf_base.c ls
 ...
 [ perf record: Woken up 1 times to write data ]
 [ perf record: Captured and wrote 0.011 MB perf.data ]

Help messages when build with NO_LIBBPF:

 # ./perf record -h
        --transaction     sample transaction flags (special events only)
        --vmlinux <file>  vmlinux pathname
                          (not build because NO_LIBBPF=1)
 # ./perf record --vmlinux /tmp/vmlinux ls /
  Warning: option `vmlinux' is not built because NO_LIBBPF=1
 ...
 [ perf record: Woken up 1 times to write data ]
 [ perf record: Captured and wrote 0.011 MB perf.data (11 samples) ]

Help messages when build with NO_DWARF:

 # ./perf record -h
        --transaction     sample transaction flags (special events only)
        --vmlinux <file>  vmlinux pathname
                          (not build because NO_DWARF=1)

Signed-off-by: He Kuang <hekuang@xxxxxxxxxx>
Signed-off-by: Wang Nan <wangnan0@xxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@xxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/Documentation/perf-record.txt | 10 ++++++++--
 tools/perf/builtin-record.c              | 16 ++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index e630a7d..8d032f4 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -314,11 +314,17 @@ This option sets the time out limit. The default value is 500 ms.
 Record context switch events i.e. events of type PERF_RECORD_SWITCH or
 PERF_RECORD_SWITCH_CPU_WIDE.
 
---clang-path::
+--clang-path=PATH::
 Path to clang binary to use for compiling BPF scriptlets.
+(enabled when BPF support is on)
 
---clang-opt::
+--clang-opt=OPTIONS::
 Options passed to clang when compiling BPF scriptlets.
+(enabled when BPF support is on)
+
+--vmlinux=PATH::
+Specify vmlinux path which has debuginfo.
+(enabled when BPF prologue is on)
 
 SEE ALSO
 --------
diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index 11bf32d..2230b85 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -1128,6 +1128,8 @@ struct option __record_options[] = {
 		   "clang binary to use for compiling BPF scriptlets"),
 	OPT_STRING(0, "clang-opt", &llvm_param.clang_opt, "clang options",
 		   "options passed to clang when compiling BPF scriptlets"),
+	OPT_STRING(0, "vmlinux", &symbol_conf.vmlinux_name,
+		   "file", "vmlinux pathname"),
 	OPT_END()
 };
 
@@ -1146,6 +1148,20 @@ int cmd_record(int argc, const char **argv, const char *prefix __maybe_unused)
 # undef set_nobuild
 #endif
 
+#ifndef HAVE_BPF_PROLOGUE
+# if !defined (HAVE_DWARF_SUPPORT)
+#  define REASON  "NO_DWARF=1"
+# elif !defined (HAVE_LIBBPF_SUPPORT)
+#  define REASON  "NO_LIBBPF=1"
+# else
+#  define REASON  "this architecture doesn't support BPF prologue"
+# endif
+# define set_nobuild(s, l, c) set_option_nobuild(record_options, s, l, REASON, c)
+	set_nobuild('\0', "vmlinux", true);
+# undef set_nobuild
+# undef REASON
+#endif
+
 	rec->evlist = perf_evlist__new();
 	if (rec->evlist == NULL)
 		return -ENOMEM;
-- 
1.8.3.4

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