[PATCH 08/13] perf tools: Add BPF_PROLOGUE config options for further patches

[Wang Nan]

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 is introduced in commit
63ab024a5b6f295ca17a293ad81b7c728f49a89a ("perf tools:
regs_query_register_offset() infrastructure"), which 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.

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: Zefan Li <lizefan@xxxxxxxxxx>
Cc: pi3orama@xxxxxxx
---
 tools/perf/config/Makefile | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
index de89ec5..6eb9a95 100644
--- a/tools/perf/config/Makefile
+++ b/tools/perf/config/Makefile
@@ -318,6 +318,18 @@ ifndef NO_LIBELF
       CFLAGS += -DHAVE_LIBBPF_SUPPORT
       $(call detected,CONFIG_LIBBPF)
     endif
+
+    ifndef NO_DWARF
+      ifdef PERF_HAVE_ARCH_REGS_QUERY_REGISTER_OFFSET
+        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
 
-- 
1.8.3.4

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