From bc3703f21cec8a2ac6a64f6fb3686fbcb1ba1513 Mon Sep 17 00:00:00 2001 From: Hendrik Brueckner Date: Mon, 20 Nov 2017 11:41:07 +0100 Subject: s390/kernel: emit CFI data in .debug_frame and discard .eh_frame sections Using perf probe and libdw on kernel modules failed to find CFI data for symbols. The CFI data is stored in the .eh_frame section. The elfutils libdw is not able to extract the CFI data correctly, because the .eh_frame section requires "non-simple" relocations for kernel modules. The suggestion is to avoid these "non-simple" relocations by emitting the CFI data in the .debug_frame section. Let gcc emit respective directives by specifying the -fno-asynchronous-unwind-tables option. Using the .debug_frame section for CFI data, the .eh_frame section becomes unused and, thus, discard it for kernel and modules builds The vDSO requires the .eh_frame section and, hence, emit the CFI data in both, the .eh_frame and .debug_frame sections. See also discussion on elfutils/libdw bugzilla: https://sourceware.org/bugzilla/show_bug.cgi?id=22452 Suggested-by: Mark Wielaard Signed-off-by: Hendrik Brueckner Reviewed-by: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/Makefile | 1 + arch/s390/include/asm/dwarf.h | 25 +++++++++++++++++++++++++ arch/s390/kernel/vdso32/Makefile | 3 +++ arch/s390/kernel/vdso32/clock_getres.S | 1 + arch/s390/kernel/vdso32/clock_gettime.S | 1 + arch/s390/kernel/vdso32/getcpu.S | 1 + arch/s390/kernel/vdso32/gettimeofday.S | 1 + arch/s390/kernel/vdso64/Makefile | 3 +++ arch/s390/kernel/vdso64/clock_getres.S | 1 + arch/s390/kernel/vdso64/clock_gettime.S | 1 + arch/s390/kernel/vdso64/getcpu.S | 1 + arch/s390/kernel/vdso64/gettimeofday.S | 1 + arch/s390/kernel/vmlinux.lds.S | 3 +++ 13 files changed, 43 insertions(+) create mode 100644 arch/s390/include/asm/dwarf.h (limited to 'arch/s390') diff --git a/arch/s390/Makefile b/arch/s390/Makefile index de54cfc6109d..494bb9ad5edf 100644 --- a/arch/s390/Makefile +++ b/arch/s390/Makefile @@ -90,6 +90,7 @@ endif KBUILD_CFLAGS += -mbackchain -msoft-float $(cflags-y) KBUILD_CFLAGS += -pipe -fno-strength-reduce -Wno-sign-compare +KBUILD_CFLAGS += -fno-asynchronous-unwind-tables KBUILD_AFLAGS += $(aflags-y) OBJCOPYFLAGS := -O binary diff --git a/arch/s390/include/asm/dwarf.h b/arch/s390/include/asm/dwarf.h new file mode 100644 index 000000000000..dffdb81e534f --- /dev/null +++ b/arch/s390/include/asm/dwarf.h @@ -0,0 +1,25 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_S390_DWARF_H +#define _ASM_S390_DWARF_H + +#ifdef __ASSEMBLY__ + +#ifndef BUILD_VDSO + /* + * Emit CFI data in .debug_frame sections and not in .eh_frame + * sections. The .eh_frame CFI is used for runtime unwind + * information that is not being used. Hence, vmlinux.lds.S + * can discard the .eh_frame sections. + */ + .cfi_sections .debug_frame +#else + /* + * For vDSO, emit CFI data in both, .eh_frame and .debug_frame + * sections. + */ + .cfi_sections .eh_frame, .debug_frame +#endif + +#endif /* __ASSEMBLY__ */ + +#endif /* _ASM_S390_DWARF_H */ diff --git a/arch/s390/kernel/vdso32/Makefile b/arch/s390/kernel/vdso32/Makefile index 308564b9bf68..c5c856f320bc 100644 --- a/arch/s390/kernel/vdso32/Makefile +++ b/arch/s390/kernel/vdso32/Makefile @@ -10,6 +10,9 @@ obj-vdso32 = gettimeofday.o clock_getres.o clock_gettime.o note.o getcpu.o targets := $(obj-vdso32) vdso32.so vdso32.so.dbg obj-vdso32 := $(addprefix $(obj)/, $(obj-vdso32)) +KBUILD_AFLAGS += -DBUILD_VDSO +KBUILD_CFLAGS += -DBUILD_VDSO + KBUILD_AFLAGS_31 := $(filter-out -m64,$(KBUILD_AFLAGS)) KBUILD_AFLAGS_31 += -m31 -s diff --git a/arch/s390/kernel/vdso32/clock_getres.S b/arch/s390/kernel/vdso32/clock_getres.S index f61df5253c23..6aeddf8e4bc7 100644 --- a/arch/s390/kernel/vdso32/clock_getres.S +++ b/arch/s390/kernel/vdso32/clock_getres.S @@ -9,6 +9,7 @@ #include #include #include +#include .text .align 4 diff --git a/arch/s390/kernel/vdso32/clock_gettime.S b/arch/s390/kernel/vdso32/clock_gettime.S index 2d6ec3abe095..d0ac32c413e2 100644 --- a/arch/s390/kernel/vdso32/clock_gettime.S +++ b/arch/s390/kernel/vdso32/clock_gettime.S @@ -9,6 +9,7 @@ #include #include #include +#include .text .align 4 diff --git a/arch/s390/kernel/vdso32/getcpu.S b/arch/s390/kernel/vdso32/getcpu.S index 5477a2c112fb..539d92a2c61b 100644 --- a/arch/s390/kernel/vdso32/getcpu.S +++ b/arch/s390/kernel/vdso32/getcpu.S @@ -8,6 +8,7 @@ */ #include #include +#include .text .align 4 diff --git a/arch/s390/kernel/vdso32/gettimeofday.S b/arch/s390/kernel/vdso32/gettimeofday.S index aa8bf13a2edb..435f819c3e65 100644 --- a/arch/s390/kernel/vdso32/gettimeofday.S +++ b/arch/s390/kernel/vdso32/gettimeofday.S @@ -9,6 +9,7 @@ #include #include #include +#include .text .align 4 diff --git a/arch/s390/kernel/vdso64/Makefile b/arch/s390/kernel/vdso64/Makefile index f81ae7998883..15b1ceafc4c1 100644 --- a/arch/s390/kernel/vdso64/Makefile +++ b/arch/s390/kernel/vdso64/Makefile @@ -10,6 +10,9 @@ obj-vdso64 = gettimeofday.o clock_getres.o clock_gettime.o note.o getcpu.o targets := $(obj-vdso64) vdso64.so vdso64.so.dbg obj-vdso64 := $(addprefix $(obj)/, $(obj-vdso64)) +KBUILD_AFLAGS += -DBUILD_VDSO +KBUILD_CFLAGS += -DBUILD_VDSO + KBUILD_AFLAGS_64 := $(filter-out -m64,$(KBUILD_AFLAGS)) KBUILD_AFLAGS_64 += -m64 -s diff --git a/arch/s390/kernel/vdso64/clock_getres.S b/arch/s390/kernel/vdso64/clock_getres.S index faf5213b15df..5b0d9c380de2 100644 --- a/arch/s390/kernel/vdso64/clock_getres.S +++ b/arch/s390/kernel/vdso64/clock_getres.S @@ -9,6 +9,7 @@ #include #include #include +#include .text .align 4 diff --git a/arch/s390/kernel/vdso64/clock_gettime.S b/arch/s390/kernel/vdso64/clock_gettime.S index 6046b3bfca46..deccd793b279 100644 --- a/arch/s390/kernel/vdso64/clock_gettime.S +++ b/arch/s390/kernel/vdso64/clock_gettime.S @@ -9,6 +9,7 @@ #include #include #include +#include .text .align 4 diff --git a/arch/s390/kernel/vdso64/getcpu.S b/arch/s390/kernel/vdso64/getcpu.S index e9c34364d97b..022acdecd5b9 100644 --- a/arch/s390/kernel/vdso64/getcpu.S +++ b/arch/s390/kernel/vdso64/getcpu.S @@ -8,6 +8,7 @@ */ #include #include +#include .text .align 4 diff --git a/arch/s390/kernel/vdso64/gettimeofday.S b/arch/s390/kernel/vdso64/gettimeofday.S index cc9dbc27da6f..964afb1de06d 100644 --- a/arch/s390/kernel/vdso64/gettimeofday.S +++ b/arch/s390/kernel/vdso64/gettimeofday.S @@ -9,6 +9,7 @@ #include #include #include +#include .text .align 4 diff --git a/arch/s390/kernel/vmlinux.lds.S b/arch/s390/kernel/vmlinux.lds.S index a049ff005f03..608cf2987d19 100644 --- a/arch/s390/kernel/vmlinux.lds.S +++ b/arch/s390/kernel/vmlinux.lds.S @@ -141,4 +141,7 @@ SECTIONS /* Sections to be discarded */ DISCARDS + /DISCARD/ : { + *(.eh_frame) + } } -- cgit v1.2.3