Commit a2546fae [ftrace: Add -mfentry to Makefile on function tracer]
adds support for using -mfentry when possible, whenever the ftrace
CONFIG_FUNCTION_TRACER option is enabled.
This unfortunately causes bogus dwarf debuginfo to be generated:
gcc Bug 54793 - the location of a formal_parameter is not started from a
function entry with -mfentry
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54793
This can be fixed by applying the gcc patch above, which will be
present in gcc-4.8, but in the meantime, the problem is currently
being worked around in different ways by various tools. One of those
tools that we support in Yocto, Systemtap, requires the DW_AT_producer
string contain -mfentry, which means that it's assuming
record-gcc-switches is also used:
SystemTap Bug 15123 - workaround for bad debuginfo for -mfentry
http://sourceware.org/bugzilla/show_bug.cgi?id=15123
The lack of -grecord-gcc-switches and therefore a missing -mfentry
string in Yocto leads to the following Yocto bug:
Bug 4099 - Crosstap script check fails
https://bugzilla.yoctoproject.org/show_bug.cgi?id=4099
Which is what this patch intends to fix.
It only affects architectures that HAVE_FENTRY when
CONFIG_FUNCTION_TRACER is turned on and in any case is just adding to
the debuginfo, so there doesn't seem to be much risk to adding it.
Signed-off-by: Tom Zanussi <tom.zanu...@linux.intel.com>
---
Makefile | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Makefile b/Makefile
index 61e2c24..c2988a6 100644
--- a/Makefile
+++ b/Makefile
@@ -624,7 +624,7 @@ endif
ifdef CONFIG_FUNCTION_TRACER
ifdef CONFIG_HAVE_FENTRY
-CC_USING_FENTRY := $(call cc-option, -mfentry -DCC_USING_FENTRY)
+CC_USING_FENTRY := $(call cc-option, -mfentry -DCC_USING_FENTRY
-grecord-gcc-switches)
endif
KBUILD_CFLAGS += -pg $(CC_USING_FENTRY)
KBUILD_AFLAGS += $(CC_USING_FENTRY)
--
1.7.11.4
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