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>
51 lines
1.2 KiB
ArmAsm
51 lines
1.2 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Userland implementation of clock_getres() 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. 2008
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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/unistd.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_clock_getres
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.type __kernel_clock_getres,@function
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__kernel_clock_getres:
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.cfi_startproc
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larl %r1,4f
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cghi %r2,__CLOCK_REALTIME_COARSE
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je 0f
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cghi %r2,__CLOCK_MONOTONIC_COARSE
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je 0f
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larl %r1,3f
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cghi %r2,__CLOCK_REALTIME
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je 0f
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cghi %r2,__CLOCK_MONOTONIC
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je 0f
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cghi %r2,__CLOCK_THREAD_CPUTIME_ID
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je 0f
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cghi %r2,-2 /* Per-thread CPUCLOCK with PID=0, VIRT=1 */
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jne 2f
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larl %r5,_vdso_data
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icm %r0,15,__LC_ECTG_OK(%r5)
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jz 2f
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0: ltgr %r3,%r3
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jz 1f /* res == NULL */
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lg %r0,0(%r1)
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xc 0(8,%r3),0(%r3) /* set tp->tv_sec to zero */
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stg %r0,8(%r3) /* store tp->tv_usec */
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1: lghi %r2,0
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br %r14
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2: lghi %r1,__NR_clock_getres /* fallback to svc */
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svc 0
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br %r14
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3: .quad __CLOCK_REALTIME_RES
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4: .quad __CLOCK_COARSE_RES
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.cfi_endproc
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.size __kernel_clock_getres,.-__kernel_clock_getres
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