[lttng-dev] [PATCH lttng-modules 1/2] Fix: handle missing ftrace header on v4.12

[Mathieu Desnoyers]

Merged into master, 2.10, 2.9, 2.8, thanks!

Mathieu

----- On Jun 23, 2017, at 2:29 PM, Michael Jeanson mjeanson at efficios.com wrote:

> Properly handle the case where we build against the distro headers of a
> kernel >= 4.12 and ftrace is enabled but the private header is
> unavailable.
> 
> Signed-off-by: Michael Jeanson <mjeanson at efficios.com>
> ---
> Makefile.ABI.workarounds | 21 +++++++++++++++++++++
> lttng-events.h           |  2 +-
> probes/Kbuild            | 19 ++++---------------
> 3 files changed, 26 insertions(+), 16 deletions(-)
> 
> diff --git a/Makefile.ABI.workarounds b/Makefile.ABI.workarounds
> index c3717f8..2e6c4aa 100644
> --- a/Makefile.ABI.workarounds
> +++ b/Makefile.ABI.workarounds
> @@ -27,3 +27,24 @@ RT_PATCH_VERSION:=$(shell
> $(TOP_LTTNG_MODULES_DIR)/rt-patch-version.sh $(CURDIR)
> ifneq ($(RT_PATCH_VERSION), 0)
>   ccflags-y += -DRT_PATCH_VERSION=$(RT_PATCH_VERSION)
> endif
> +
> +# Starting with kernel 4.12, the ftrace header was moved to private headers
> +# and as such is not available when building against distro headers instead
> +# of the full kernel sources. In the situation, define
> LTTNG_FTRACE_MISSING_HEADER
> +# so we can enable the compat code even if CONFIG_DYNAMIC_FTRACE is enabled.
> +ifneq ($(CONFIG_DYNAMIC_FTRACE),)
> +  ftrace_dep = $(srctree)/kernel/trace/trace.h
> +  ftrace_dep_check = $(wildcard $(ftrace_dep))
> +  have_ftrace_header = $(shell \
> +    if [ $(VERSION) -ge 5 -o \( $(VERSION) -eq 4 -a $(PATCHLEVEL) -ge 12 \) ] ;
> then \
> +      if [ -z "$(ftrace_dep_check)" ] ; then \
> +        echo "no" ; \
> +        exit ; \
> +      fi; \
> +    fi; \
> +    echo "yes" ; \
> +    )
> +  ifeq ($(have_ftrace_header), no)
> +    ccflags-y += -DLTTNG_FTRACE_MISSING_HEADER
> +  endif
> +endif
> diff --git a/lttng-events.h b/lttng-events.h
> index f55bf66..17dd8d3 100644
> --- a/lttng-events.h
> +++ b/lttng-events.h
> @@ -810,7 +810,7 @@ int lttng_kretprobes_event_enable_state(struct lttng_event
> *event,
> }
> #endif
> 
> -#ifdef CONFIG_DYNAMIC_FTRACE
> +#if defined(CONFIG_DYNAMIC_FTRACE) && !defined(LTTNG_FTRACE_MISSING_HEADER)
> int lttng_ftrace_register(const char *name,
> 			  const char *symbol_name,
> 			  struct lttng_event *event);
> diff --git a/probes/Kbuild b/probes/Kbuild
> index 78bf3fb..cc1c065 100644
> --- a/probes/Kbuild
> +++ b/probes/Kbuild
> @@ -259,22 +259,11 @@ ifneq ($(CONFIG_KRETPROBES),)
> endif # CONFIG_KRETPROBES
> 
> ifneq ($(CONFIG_DYNAMIC_FTRACE),)
> -  ftrace_dep = $(srctree)/kernel/trace/trace.h
> -  ftrace_dep_check = $(wildcard $(ftrace_dep))
> -  ftrace = $(shell \
> -    if [ $(VERSION) -ge 5 -o \( $(VERSION) -eq 4 -a $(PATCHLEVEL) -ge 12 \) ] ;
> then \
> -      if [ -z "$(ftrace_dep_check)" ] ; then \
> -        echo "warn" ; \
> -        exit ; \
> -      fi; \
> -    fi; \
> -    echo "lttng-ftrace.o" ; \
> -    )
> -  ifeq ($(ftrace),warn)
> +  ifeq ($(have_ftrace_header),yes)
> +    obj-$(CONFIG_LTTNG) += lttng-ftrace.o
> +  else
>     $(warning Files $(ftrace_dep) not found. Probe "ftrace" is disabled. Use full
>     kernel source tree to enable it.)
> -    ftrace =
> -  endif # $(ftrace),warn
> -  obj-$(CONFIG_LTTNG) += $(ftrace)
> +  endif
> endif # CONFIG_DYNAMIC_FTRACE
> 
> # vim:syntax=make
> --
> 2.7.4

-- 
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com