Subject: x86: Add an option to compile with -ffunction-sections -fdata-sections Date: Wed, 4 Feb 2009 05:26:04 -0500 (EST) From: Anders Kaseorg On Wed, 4 Feb 2009, Rusty Russell wrote: > You need to make this depend on X86, otherwise allmodconfig will turn it on > and break other archs. Okay. > What's the conflict with FTRACE? This actually should have changed from FTRACE to FUNCTION_TRACER as of commit 606576ce816603d9fe1fb453a88bc6eea16ca709 in v2.6.28-rc3. The conflict is that FUNCTION_TRACER enables KBUILD_CFLAGS += -pg, and passing -pg to current gcc causes it to emit a warning and disable -ffunction-sections: (If this gcc problem is resolved in the future, the code should work fine with FUNCTION_TRACER. A small amount of extra matching code is needed to handle DYNAMIC_FTRACE.) Patch for these two issues: --- arch/x86/Kconfig | 1 + lib/Kconfig.debug | 6 +++++- 2 files changed, 6 insertions(+), 1 deletion(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -28,6 +28,7 @@ config X86 select HAVE_KPROBES select ARCH_WANT_OPTIONAL_GPIOLIB select ARCH_WANT_FRAME_POINTERS + select HAVE_FUNCTION_DATA_SECTIONS select HAVE_KRETPROBES select HAVE_FTRACE_MCOUNT_RECORD select HAVE_DYNAMIC_FTRACE diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -591,9 +591,13 @@ config FRAME_POINTER larger and slower, but it gives very useful debugging information in case of kernel bugs. (precise oopses/stacktraces/warnings) +config HAVE_FUNCTION_DATA_SECTIONS + bool + config FUNCTION_DATA_SECTIONS bool "Compile with -ffunction-sections -fdata-sections" - depends on !FTRACE + depends on HAVE_FUNCTION_DATA_SECTIONS + depends on !FUNCTION_TRACER help If you say Y here the compiler will give each function and data structure its own ELF section.