Messages in this thread Patch in this message | | | From | Tim Abbott <> | Subject | [PATCH v2 2/4] x86: Add an option to compile with -ffunction-sections -fdata-sections | Date | Tue, 24 Feb 2009 19:21:53 -0500 |
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From: Waseem Daher <wdaher@mit.edu>
This patch makes it possible to link and boot an x86 kernel with -ffunction-sections and -fdata-sections enabled.
Modpost currently warns whenever it sees a section with a name matching [.][0-9]+$ because they are often caused by section flag mismatch errors. When compiling with -ffunction-sections -fdata-sections, gcc places various classes of local symbols in sections with names such as .rodata.__func__.12345, causing these warnings to be printed spuriously. The simplest fix is to disable the warning when CONFIG_FUNCTION_DATA_SECTIONS is enabled.
Signed-off-by: Waseem Daher <wdaher@mit.edu> [tabbott@mit.edu: modpost support] Signed-off-by: Tim Abbott <tabbott@mit.edu> [andersk@mit.edu: depend on x86, update CONFIG_FUNCTION_TRACER conflict] Signed-off-by: Anders Kaseorg <andersk@mit.edu> --- Makefile | 4 ++++ arch/x86/Kconfig | 1 + arch/x86/kernel/vmlinux_32.lds.S | 1 + arch/x86/kernel/vmlinux_64.lds.S | 1 + include/asm-generic/vmlinux.lds.h | 5 ++++- lib/Kconfig.debug | 18 ++++++++++++++++++ scripts/Makefile.modpost | 1 + scripts/mod/modpost.c | 10 ++++++++-- 8 files changed, 38 insertions(+), 3 deletions(-)
diff --git a/Makefile b/Makefile index 22d7584..b95cf67 100644 --- a/Makefile +++ b/Makefile @@ -550,6 +550,10 @@ ifdef CONFIG_FUNCTION_TRACER KBUILD_CFLAGS += -pg endif +ifdef CONFIG_FUNCTION_DATA_SECTIONS +KBUILD_CFLAGS += -ffunction-sections -fdata-sections +endif + # We trigger additional mismatches with less inlining ifdef CONFIG_DEBUG_SECTION_MISMATCH KBUILD_CFLAGS += $(call cc-option, -fno-inline-functions-called-once) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 9c39095..d3a991c 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -28,6 +28,7 @@ config X86 select HAVE_KPROBES select ARCH_WANT_OPTIONAL_GPIOLIB select ARCH_WANT_FRAME_POINTERS + select HAVE_FUNCTION_DATA_SECTIONS select HAVE_KRETPROBES select HAVE_FTRACE_MCOUNT_RECORD select HAVE_DYNAMIC_FTRACE diff --git a/arch/x86/kernel/vmlinux_32.lds.S b/arch/x86/kernel/vmlinux_32.lds.S index 31c131a..fbc5c3f 100644 --- a/arch/x86/kernel/vmlinux_32.lds.S +++ b/arch/x86/kernel/vmlinux_32.lds.S @@ -194,6 +194,7 @@ SECTIONS __bss_start = .; /* BSS */ *(.bss..page_aligned) *(.bss) + *(.bss.[A-Za-z$_]*) /* handle -fdata-sections */ . = ALIGN(4); __bss_stop = .; _end = . ; diff --git a/arch/x86/kernel/vmlinux_64.lds.S b/arch/x86/kernel/vmlinux_64.lds.S index 56ed592..6e03cb2 100644 --- a/arch/x86/kernel/vmlinux_64.lds.S +++ b/arch/x86/kernel/vmlinux_64.lds.S @@ -223,6 +223,7 @@ SECTIONS .bss : AT(ADDR(.bss) - LOAD_OFFSET) { *(.bss..page_aligned) *(.bss) + *(.bss.[A-Za-z$_]*) /* handle -fdata-sections */ } __bss_stop = .; diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index 0485f0b..2b31598 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -64,6 +64,7 @@ /* .data section */ #define DATA_DATA \ *(.data) \ + *(.data.[A-Za-z$_]*) /* handle -fdata-sections */ \ *(.data..init.refok) \ *(.ref.data) \ DEV_KEEP(init.data) \ @@ -87,7 +88,8 @@ . = ALIGN((align)); \ .rodata : AT(ADDR(.rodata) - LOAD_OFFSET) { \ VMLINUX_SYMBOL(__start_rodata) = .; \ - *(.rodata) *(.rodata.*) \ + *(.rodata) \ + *(.rodata.[A-Za-z$_]*) /* handle -fdata-sections */ \ *(__vermagic) /* Kernel version magic */ \ *(__markers_strings) /* Markers: strings */ \ *(__tracepoints_strings)/* Tracepoints: strings */ \ @@ -254,6 +256,7 @@ ALIGN_FUNCTION(); \ *(.text.hot) \ *(.text) \ + *(.text.[A-Za-z$_]*) /* handle -ffunction-sections */\ *(.ref.text) \ *(.text..init.refok) \ *(.text..exit.refok) \ diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 29044f5..3412706 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -591,6 +591,24 @@ 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 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. + + This option conflicts with CONFIG_FUNCTION_TRACER, which + enables profiling code generation, because current GCC does + not support compiling with -ffunction-sections -pg (see + <http://gcc.gnu.org/ml/gcc-help/2008-11/msg00128.html>). + + If unsure, say N. + config BOOT_PRINTK_DELAY bool "Delay each boot printk message by N milliseconds" depends on DEBUG_KERNEL && PRINTK && GENERIC_CALIBRATE_DELAY diff --git a/scripts/Makefile.modpost b/scripts/Makefile.modpost index f4053dc..a712bb2 100644 --- a/scripts/Makefile.modpost +++ b/scripts/Makefile.modpost @@ -87,6 +87,7 @@ modpost = scripts/mod/modpost \ $(if $(CONFIG_DEBUG_SECTION_MISMATCH),,-S) \ $(if $(CONFIG_MARKERS),-K $(kernelmarkersfile)) \ $(if $(CONFIG_MARKERS),-M $(markersfile)) \ + $(if $(filter -ffunction-sections -fdata-sections,$(KBUILD_CFLAGS) $(CFLAGS_KERNEL)),-F) \ $(if $(KBUILD_EXTMOD)$(KBUILD_MODPOST_WARN),-w) \ $(if $(cross_build),-c) diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index a7e282e..8a99299 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -32,6 +32,8 @@ static int warn_unresolved = 0; /* How a symbol is exported */ static int sec_mismatch_count = 0; static int sec_mismatch_verbose = 1; +/* Are we using -ffunction-sections or -fdata-sections? */ +static int function_data_sections = 0; enum export { export_plain, export_unused, export_gpl, @@ -736,7 +738,8 @@ static int check_section(const char *modname, const char *sec) /* consume all digits */ while (*e && e != sec && isdigit(*e)) e--; - if (*e == '.' && !strstr(sec, ".linkonce")) { + if (*e == '.' && !strstr(sec, ".linkonce") && + !function_data_sections) { warn("%s (%s): unexpected section name.\n" "The (.[number]+) following section name are " "ld generated and not expected.\n" @@ -2063,7 +2066,7 @@ int main(int argc, char **argv) struct ext_sym_list *extsym_iter; struct ext_sym_list *extsym_start = NULL; - while ((opt = getopt(argc, argv, "i:I:e:cmsSo:awM:K:")) != -1) { + while ((opt = getopt(argc, argv, "i:I:e:cFmsSo:awM:K:")) != -1) { switch (opt) { case 'i': kernel_read = optarg; @@ -2083,6 +2086,9 @@ int main(int argc, char **argv) extsym_iter->file = optarg; extsym_start = extsym_iter; break; + case 'F': + function_data_sections = 1; + break; case 'm': modversions = 1; break; -- 1.6.1.3
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