From c0a80c0c27e5e65b180a25e6c4c2f7ef9e386cd3 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Fri, 9 Jan 2015 13:06:33 +0100 Subject: ftrace: allow architectures to specify ftrace compile options If the kernel is compiled with function tracer support the -pg compile option is passed to gcc to generate extra code into the prologue of each function. This patch replaces the "open-coded" -pg compile flag with a CC_FLAGS_FTRACE makefile variable which architectures can override if a different option should be used for code generation. Acked-by: Steven Rostedt Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- scripts/Makefile.build | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'scripts') diff --git a/scripts/Makefile.build b/scripts/Makefile.build index 649ce68..01df30a 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -234,8 +234,9 @@ sub_cmd_record_mcount = set -e ; perl $(srctree)/scripts/recordmcount.pl "$(ARCH "$(if $(part-of-module),1,0)" "$(@)"; recordmcount_source := $(srctree)/scripts/recordmcount.pl endif -cmd_record_mcount = \ - if [ "$(findstring -pg,$(_c_flags))" = "-pg" ]; then \ +cmd_record_mcount = \ + if [ "$(findstring $(CC_FLAGS_FTRACE),$(_c_flags))" = \ + "$(CC_FLAGS_FTRACE)" ]; then \ $(sub_cmd_record_mcount) \ fi; endif -- cgit v1.1 From e6d60b368b45b9be3aa068f8e5fa98c3487c9d4e Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Fri, 9 Jan 2015 13:08:28 +0100 Subject: s390/ftrace: hotpatch support for function tracing Make use of gcc's hotpatch support to generate better code for ftrace function tracing. The generated code now contains only a six byte nop in each function prologue instead of a 24 byte code block which will be runtime patched to support function tracing. With the new code generation the runtime overhead for supporting function tracing is close to zero, while the original code did show a significant performance impact. Acked-by: Steven Rostedt Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- scripts/recordmcount.pl | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) (limited to 'scripts') diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl index 56ea99a..be39be0 100755 --- a/scripts/recordmcount.pl +++ b/scripts/recordmcount.pl @@ -242,8 +242,13 @@ if ($arch eq "x86_64") { $cc .= " -m32"; } elsif ($arch eq "s390" && $bits == 64) { - $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$"; - $mcount_adjust = -14; + if ($cc =~ /-DCC_USING_HOTPATCH/) { + $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*c0 04 00 00 00 00\\s*brcl\\s*0,[0-9a-f]+ <([^\+]*)>\$"; + $mcount_adjust = 0; + } else { + $mcount_regex = "^\\s*([0-9a-fA-F]+):\\s*R_390_(PC|PLT)32DBL\\s+_mcount\\+0x2\$"; + $mcount_adjust = -14; + } $alignment = 8; $type = ".quad"; $ld .= " -m elf64_s390"; -- cgit v1.1