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>
34 lines
654 B
ArmAsm
34 lines
654 B
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Userland implementation of getcpu() for 64 bits processes in a
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* s390 kernel for use in the vDSO
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*
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* Copyright IBM Corp. 2016
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* Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
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*/
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#include <asm/vdso.h>
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#include <asm/asm-offsets.h>
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#include <asm/dwarf.h>
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.text
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.align 4
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.globl __kernel_getcpu
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.type __kernel_getcpu,@function
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__kernel_getcpu:
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.cfi_startproc
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la %r4,0
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sacf 256
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l %r5,__VDSO_CPU_NR(%r4)
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l %r4,__VDSO_NODE_ID(%r4)
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sacf 0
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ltgr %r2,%r2
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jz 2f
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st %r5,0(%r2)
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2: ltgr %r3,%r3
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jz 3f
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st %r4,0(%r3)
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3: lghi %r2,0
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br %r14
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.cfi_endproc
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.size __kernel_getcpu,.-__kernel_getcpu
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