df24e1783e
Add minimal vDSO support, which provides the signal trampoline helpers, but none of the userspace syscall helpers like time wrappers. The big benefit of this vDSO implementation is, that we now don't need an executeable stack any longer. PA-RISC is one of the last architectures where an executeable stack was needed in oder to implement the signal trampolines by putting assembly instructions on the stack which then gets executed. Instead the kernel will provide the relevant code in the vDSO page and only put the pointers to the signal information on the stack. By dropping the need for executable stacks we avoid running into issues with applications which want non executable stacks for security reasons. Additionally, alternative stacks on memory areas without exec permissions are supported too. This code is based on an initial implementation by Randolph Chung from 2006: https://lore.kernel.org/linux-parisc/4544A34A.6080700@tausq.org/ I did the porting and lifted the code to current code base. Dave fixed the unwind code so that gdb and glibc are able to backtrace through the code. An additional patch to gdb will be pushed upstream by Dave. Signed-off-by: Helge Deller <deller@gmx.de> Signed-off-by: Dave Anglin <dave.anglin@bell.net> Cc: Randolph Chung <randolph@tausq.org> Signed-off-by: Helge Deller <deller@gmx.de>
33 lines
647 B
ArmAsm
33 lines
647 B
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Syscall restart trampoline for 32 and 64 bits processes.
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*
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* Copyright (C) 2018-2022 Helge Deller <deller@gmx.de>
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* Copyright (C) 2022 John David Anglin <dave.anglin@bell.net>
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*/
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#include <asm/unistd.h>
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#include <asm/vdso.h>
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#include <linux/linkage.h>
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.text
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ENTRY_CFI(__kernel_restart_syscall)
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/*
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* Setup a trampoline to restart the syscall
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* with __NR_restart_syscall
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*/
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/* load return pointer */
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#if defined(__VDSO64__)
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ldd 0(%sp), %r31
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#elif defined(__VDSO32__)
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ldw 0(%sp), %r31
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#endif
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be 0x100(%sr2, %r0)
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ldi __NR_restart_syscall, %r20
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ENDPROC_CFI(__kernel_restart_syscall)
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