[PATCH] perf build: Add LIBTRACEEVENT_DIR build option

[Yang Jihong]

Currently, when libtraceevent is not linked,
perf does not support tracepoint:

  # ./perf record -e sched:sched_switch -a sleep 10
  event syntax error: 'sched:sched_switch'
                       \___ unsupported tracepoint

  libtraceevent is necessary for tracepoint support
  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

For cross-compilation scenario, library may not be installed in the default
system path. Based on the above requirements, add LIBTRACEEVENT_DIR build
option to support specifying path of libtraceevent.

Example:

  1. Cross compile libtraceevent
  # cd /opt/libtraceevent
  # CROSS_COMPILE=aarch64-linux-gnu- make

  2. Cross compile perf
  # cd tool/perf
  # make VF=1 ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- NO_LIBELF=1 LDFLAGS=--static LIBTRACEEVENT_DIR=/opt/libtraceevent
  <SNIP>
  Auto-detecting system features:
  <SNIP>
  ...                       LIBTRACEEVENT_DIR: /opt/libtraceevent

Signed-off-by: Yang Jihong <yangjihong@xxxxxxxxxxxxx>
---
 tools/perf/Makefile.config | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 1fe8df97fe88..7783479de691 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -182,6 +182,16 @@ endif
 FEATURE_CHECK_CFLAGS-libzstd := $(LIBZSTD_CFLAGS)
 FEATURE_CHECK_LDFLAGS-libzstd := $(LIBZSTD_LDFLAGS)
 
+# for linking with debug library, run like:
+# make DEBUG=1 LIBTRACEEVENT_DIR=/opt/libtraceevent/
+TRACEEVENTLIBS := -ltraceevent
+ifdef LIBTRACEEVENT_DIR
+  LIBTRACEEVENT_CFLAGS  := -I$(LIBTRACEEVENT_DIR)/include
+  LIBTRACEEVENT_LDFLAGS := -L$(LIBTRACEEVENT_DIR)/lib
+endif
+FEATURE_CHECK_CFLAGS-libtraceevent := $(LIBTRACEEVENT_CFLAGS)
+FEATURE_CHECK_LDFLAGS-libtraceevent := $(LIBTRACEEVENT_LDFLAGS) $(TRACEEVENTLIBS)
+
 FEATURE_CHECK_CFLAGS-bpf = -I. -I$(srctree)/tools/include -I$(srctree)/tools/arch/$(SRCARCH)/include/uapi -I$(srctree)/tools/include/uapi
 # include ARCH specific config
 -include $(src-perf)/arch/$(SRCARCH)/Makefile
@@ -1165,9 +1175,10 @@ endif
 ifneq ($(NO_LIBTRACEEVENT),1)
   $(call feature_check,libtraceevent)
   ifeq ($(feature-libtraceevent), 1)
-    CFLAGS += -DHAVE_LIBTRACEEVENT
-    EXTLIBS += -ltraceevent
-    LIBTRACEEVENT_VERSION := $(shell $(PKG_CONFIG) --modversion libtraceevent)
+    CFLAGS += -DHAVE_LIBTRACEEVENT $(LIBTRACEEVENT_CFLAGS)
+    LDFLAGS += $(LIBTRACEEVENT_LDFLAGS)
+    EXTLIBS += ${TRACEEVENTLIBS}
+    LIBTRACEEVENT_VERSION := $(shell PKG_CONFIG_PATH=$(LIBTRACEEVENT_DIR) $(PKG_CONFIG) --modversion libtraceevent)
     LIBTRACEEVENT_VERSION_1 := $(word 1, $(subst ., ,$(LIBTRACEEVENT_VERSION)))
     LIBTRACEEVENT_VERSION_2 := $(word 2, $(subst ., ,$(LIBTRACEEVENT_VERSION)))
     LIBTRACEEVENT_VERSION_3 := $(word 3, $(subst ., ,$(LIBTRACEEVENT_VERSION)))
@@ -1175,7 +1186,7 @@ ifneq ($(NO_LIBTRACEEVENT),1)
     CFLAGS += -DLIBTRACEEVENT_VERSION=$(LIBTRACEEVENT_VERSION_CPP)
     $(call detected,CONFIG_LIBTRACEEVENT)
   else
-    $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel or build with NO_LIBTRACEEVENT=1)
+    $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel and/or set LIBTRACEEVENT_DIR or build with NO_LIBTRACEEVENT=1)
   endif
 
   $(call feature_check,libtracefs)
@@ -1301,6 +1312,7 @@ ifeq ($(VF),1)
   $(call print_var,LIBUNWIND_DIR)
   $(call print_var,LIBDW_DIR)
   $(call print_var,JDIR)
+  $(call print_var,LIBTRACEEVENT_DIR)
 
   ifeq ($(dwarf-post-unwind),1)
     $(call feature_print_text,"DWARF post unwind library", $(dwarf-post-unwind-text)) $(info $(MSG))
-- 
2.25.1