bc3703f21c
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 <mark@klomp.org> Signed-off-by: Hendrik Brueckner <brueckner@linux.vnet.ibm.com> Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
26 lines
593 B
C
26 lines
593 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_S390_DWARF_H
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#define _ASM_S390_DWARF_H
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#ifdef __ASSEMBLY__
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#ifndef BUILD_VDSO
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/*
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* Emit CFI data in .debug_frame sections and not in .eh_frame
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* sections. The .eh_frame CFI is used for runtime unwind
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* information that is not being used. Hence, vmlinux.lds.S
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* can discard the .eh_frame sections.
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*/
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.cfi_sections .debug_frame
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#else
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/*
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* For vDSO, emit CFI data in both, .eh_frame and .debug_frame
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* sections.
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*/
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.cfi_sections .eh_frame, .debug_frame
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#endif
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_S390_DWARF_H */
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