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structure. This field keeps track of how many levels deep we are nested into the kernel. The nesting level is bumped at the start of a trap, interrupt, syscall, or exception and is decremented on return. This is used to detect the case when the kernel is returning back to a kernel context in exception_return(). If we are returning to the kernel we need to update the globaldata pointer register saved in the stack frame in case we have switched CPU's between taking the initial interrupt that saved the frame and returning. If we don't do this fixup it is possible for a CPU to use the wrong per-cpu data. On UP systems this is not a problem, so the code is conditional on SMP. A count was used instead of simply checking the process status register in the frame during exception_return() since there are critical sections at the very start and end of a trap, exception, or interrupt from userland in which we could trash the t7 register being used in userland. The counter is incremented after adn before these critical sections respectively so that we will not overwrite the saved t7 register if we are interrupted during one of these critical sections.
67 lines
2.2 KiB
C
67 lines
2.2 KiB
C
/* $FreeBSD$ */
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/* From: NetBSD: proc.h,v 1.3 1997/04/06 08:47:36 cgd Exp */
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/*
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* Copyright (c) 1994, 1995 Carnegie-Mellon University.
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* All rights reserved.
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*
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* Author: Chris G. Demetriou
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*
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* Permission to use, copy, modify and distribute this software and
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* its documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND
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* FOR ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*/
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#ifndef _MACHINE_PROC_H_
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#define _MACHINE_PROC_H_
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#include <machine/globaldata.h>
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#include <machine/globals.h>
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/*
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* Machine-dependent part of the proc struct for the Alpha.
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*/
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struct mdbpt {
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vm_offset_t addr;
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u_int32_t contents;
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};
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struct mdproc {
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u_long md_flags;
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struct trapframe *md_tf; /* trap/syscall registers */
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struct pcb *md_pcbpaddr; /* phys addr of the pcb */
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struct mdbpt md_sstep[2]; /* two single step breakpoints */
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u_int64_t md_hae; /* user HAE register value */
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void *osf_sigtramp; /* user-level signal trampoline */
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u_int md_kernnest; /* nesting level in the kernel */
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};
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#define MDP_FPUSED 0x0001 /* Process used the FPU */
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#define MDP_STEP1 0x0002 /* Single step normal instruction */
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#define MDP_STEP2 0x0004 /* Single step branch instruction */
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#define MDP_HAEUSED 0x0008 /* Process used the HAE */
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#define MDP_UAC_NOPRINT 0x0010 /* Don't print unaligned traps */
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#define MDP_UAC_NOFIX 0x0020 /* Don't fixup unaligned traps */
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#define MDP_UAC_SIGBUS 0x0040 /* Deliver SIGBUS upon
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unaligned access */
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#define MDP_UAC_MASK (MDP_UAC_NOPRINT | MDP_UAC_NOFIX | MDP_UAC_SIGBUS)
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#endif /* !_MACHINE_PROC_H_ */
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