c0345a84aa
via the debug.minidump sysctl and tunable. Traditional dumps store all physical memory. This was once a good thing when machines had a maximum of 64M of ram and 1GB of kvm. These days, machines often have many gigabytes of ram and a smaller amount of kvm. libkvm+kgdb don't have a way to access physical ram that is not mapped into kvm at the time of the crash dump, so the extra ram being dumped is mostly wasted. Minidumps invert the process. Instead of dumping physical memory in in order to guarantee that all of kvm's backing is dumped, minidumps instead dump only memory that is actively mapped into kvm. amd64 has a direct map region that things like UMA use. Obviously we cannot dump all of the direct map region because that is effectively an old style all-physical-memory dump. Instead, introduce a bitmap and two helper routines (dump_add_page(pa) and dump_drop_page(pa)) that allow certain critical direct map pages to be included in the dump. uma_machdep.c's allocator is the intended consumer. Dumps are a custom format. At the very beginning of the file is a header, then a copy of the message buffer, then the bitmap of pages present in the dump, then the final level of the kvm page table trees (2MB mappings are expanded into a 4K page mappings), then the sparse physical pages according to the bitmap. libkvm can now conveniently access the kvm page table entries. Booting my test 8GB machine, forcing it into ddb and forcing a dump leads to a 48MB minidump. While this is a best case, I expect minidumps to be in the 100MB-500MB range. Obviously, never larger than physical memory of course. minidumps are on by default. It would want be necessary to turn them off if it was necessary to debug corrupt kernel page table management as that would mess up minidumps as well. Both minidumps and regular dumps are supported on the same machine.
86 lines
2.9 KiB
C
86 lines
2.9 KiB
C
/*-
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* Copyright (c) 1995 Bruce D. Evans.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the author nor the names of contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef _MACHINE_MD_VAR_H_
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#define _MACHINE_MD_VAR_H_
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/*
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* Miscellaneous machine-dependent declarations.
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*/
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extern long Maxmem;
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extern u_int basemem;
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extern int busdma_swi_pending;
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extern u_int cpu_exthigh;
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extern u_int cpu_feature;
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extern u_int cpu_feature2;
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extern u_int amd_feature;
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extern u_int amd_feature2;
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extern u_int cpu_fxsr;
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extern u_int cpu_high;
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extern u_int cpu_id;
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extern u_int cpu_procinfo;
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extern u_int cpu_procinfo2;
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extern char cpu_vendor[];
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extern char kstack[];
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extern char sigcode[];
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extern int szsigcode;
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extern uint64_t *vm_page_dump;
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extern int vm_page_dump_size;
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extern struct pcpu __pcpu[];
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typedef void alias_for_inthand_t(u_int cs, u_int ef, u_int esp, u_int ss);
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struct thread;
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struct reg;
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struct fpreg;
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struct dbreg;
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struct dumperinfo;
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void busdma_swi(void);
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void cpu_setregs(void);
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void doreti_iret(void) __asm(__STRING(doreti_iret));
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void doreti_iret_fault(void) __asm(__STRING(doreti_iret_fault));
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void dump_add_page(vm_paddr_t);
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void dump_drop_page(vm_paddr_t);
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void initializecpu(void);
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void fillw(int /*u_short*/ pat, void *base, size_t cnt);
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void fpstate_drop(struct thread *td);
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int is_physical_memory(vm_paddr_t addr);
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int isa_nmi(int cd);
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void pagecopy(void *from, void *to);
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void pagezero(void *addr);
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void setidt(int idx, alias_for_inthand_t *func, int typ, int dpl, int ist);
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int user_dbreg_trap(void);
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void minidumpsys(struct dumperinfo *);
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#endif /* !_MACHINE_MD_VAR_H_ */
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