linux-kernel - [PATCH 22/31] perf tools: Add BPF_PROLOGUE config options for further patches

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Message-ID: <1441090789-108382-1-git-send-email-wangnan0@huawei.com>
Date:	Tue, 1 Sep 2015 06:59:48 +0000
From:	Wang Nan <wangnan0@...wei.com>
To:	<acme@...nel.org>
CC:	<linux-kernel@...r.kernel.org>, Wang Nan <wangnan0@...wei.com>,
	"Alexei Starovoitov" <ast@...mgrid.com>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	David Ahern <dsahern@...il.com>,
	"He Kuang" <hekuang@...wei.com>, Jiri Olsa <jolsa@...nel.org>,
	Kaixu Xia <xiakaixu@...wei.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Zefan Li <lizefan@...wei.com>, <pi3orama@....com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>
Subject: [PATCH 22/31] perf tools: Add BPF_PROLOGUE config options for further patches

If both LIBBPF and DWARF are detected, it is possible to create prologue
for eBPF programs to help them accessing kernel data. HAVE_BPF_PROLOGUE
and CONFIG_BPF_PROLOGUE is added as flags for this feature.

PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET indicates an architecture
supports converting name of a register to its offset in
'struct pt_regs'. Without this support, BPF_PROLOGUE should be turned off.

HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET is introduced as the corresponding
CFLAGS of PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET.

Signed-off-by: Wang Nan <wangnan0@...wei.com>
Cc: Alexei Starovoitov <ast@...mgrid.com>
Cc: Brendan Gregg <brendan.d.gregg@...il.com>
Cc: Daniel Borkmann <daniel@...earbox.net>
Cc: David Ahern <dsahern@...il.com>
Cc: He Kuang <hekuang@...wei.com>
Cc: Jiri Olsa <jolsa@...nel.org>
Cc: Kaixu Xia <xiakaixu@...wei.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Zefan Li <lizefan@...wei.com>
Cc: pi3orama@....com
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Link: http://lkml.kernel.org/n/1436445342-1402-33-git-send-email-wangnan0@huawei.com
[wawngnan:
 - Introduce new CFLAGS to control BPF prologue and arch_get_reg_info()
   separately.
 - Rename ARCH_GET_REG_INFO to ARCH_REGS_QUERY_REGISTER_OFFSET,
   arch_get_reg_info() to regs_query_register_offset(), change its API accordingly
   to make it similar to kernel's regs_query_register_offset().
]
---
 tools/perf/config/Makefile           | 17 +++++++++++++++++
 tools/perf/util/include/dwarf-regs.h |  8 ++++++++
 2 files changed, 25 insertions(+)

diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
index 38a4144..33785a1 100644
--- a/tools/perf/config/Makefile
+++ b/tools/perf/config/Makefile
@@ -110,6 +110,11 @@ FEATURE_CHECK_CFLAGS-bpf = -I. -I$(srctree)/tools/include -I$(srctree)/arch/$(AR
 # include ARCH specific config
 -include $(src-perf)/arch/$(ARCH)/Makefile
 
+ifneq ($(origin PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET), undefined)
+  CFLAGS += -DHAVE_ARCH_REGS_QUERY_REGISTER_OFFSET
+endif
+
+
 include $(src-perf)/config/utilities.mak
 
 ifeq ($(call get-executable,$(FLEX)),)
@@ -314,6 +319,18 @@ ifndef NO_LIBELF
       CFLAGS += -DHAVE_LIBBPF_SUPPORT
       $(call detected,CONFIG_LIBBPF)
     endif
+
+    ifndef NO_DWARF
+      ifneq ($(origin PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET), undefined)
+        CFLAGS += -DHAVE_BPF_PROLOGUE
+        $(call detected,CONFIG_BPF_PROLOGUE)
+      else
+        msg := $(warning BPF prologue is not supported by architecture $(ARCH), missing regs_query_register_offset());
+      endif
+    else
+      msg := $(warning DWARF support is off, BPF prologue is disabled);
+    endif
+
   endif # NO_LIBBPF
 endif # NO_LIBELF
 
diff --git a/tools/perf/util/include/dwarf-regs.h b/tools/perf/util/include/dwarf-regs.h
index 8f14965..07c644e 100644
--- a/tools/perf/util/include/dwarf-regs.h
+++ b/tools/perf/util/include/dwarf-regs.h
@@ -5,4 +5,12 @@
 const char *get_arch_regstr(unsigned int n);
 #endif
 
+#ifdef HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET
+/*
+ * Arch should support fetching the offset of a register in pt_regs
+ * by its name. See kernel's regs_query_register_offset in
+ * arch/xxx/kernel/ptrace.c.
+ */
+int regs_query_register_offset(const char *name);
+#endif
 #endif
-- 
1.8.3.4

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