libkvm - Add ability to access userspace from kgdb on cores

[dragonfly.git] / lib / libkvm / kvm_i386.c

/*-
 * Copyright (c) 1989, 1992, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software developed by the Computer Systems
 * Engineering group at Lawrence Berkeley Laboratory under DARPA contract
 * BG 91-66 and contributed to Berkeley.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * @(#)kvm_hp300.c	8.1 (Berkeley) 6/4/93
 * $FreeBSD: src/lib/libkvm/kvm_i386.c,v 1.11.2.1 2001/09/21 04:01:51 peter Exp $
 * $DragonFly: src/lib/libkvm/kvm_i386.c,v 1.3 2007/04/29 01:36:04 dillon Exp $
 */

/*
 * i386 machine dependent routines for kvm.  Hopefully, the forthcoming
 * vm code will one day obsolete this module.
 */

#include <sys/user.h>	/* MUST BE FIRST */
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/elf_common.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <nlist.h>
#include <kvm.h>

#include <vm/vm.h>
#include <vm/vm_param.h>

#include <machine/elf.h>

#include <limits.h>

#include "kvm_private.h"

#ifndef btop
#define	btop(x)		(i386_btop(x))
#define	ptob(x)		(i386_ptob(x))
#endif

/* minidump must be the first item! */
struct vmstate {
	int             minidump;       /* 1 = minidump mode */
	void		*mmapbase;
	size_t		mmapsize;
	void		*PTD;
};

/*
 * Map the ELF headers into the process' address space. We do this in two
 * steps: first the ELF header itself and using that information the whole
 * set of headers. (Taken from kvm_ia64.c)
 */
static int
_kvm_maphdrs(kvm_t *kd, size_t sz)
{
	struct vmstate *vm = kd->vmst;

	if (kd->vmst->minidump) {
		_kvm_minidump_freevtop(kd);
		return (0);
	}

	/* munmap() previous mmap(). */
	if (vm->mmapbase != NULL) {
		munmap(vm->mmapbase, vm->mmapsize);
		vm->mmapbase = NULL;
	}

	vm->mmapsize = sz;
	vm->mmapbase = mmap(NULL, sz, PROT_READ, MAP_PRIVATE, kd->pmfd, 0);
	if (vm->mmapbase == MAP_FAILED) {
		_kvm_err(kd, kd->program, "cannot mmap corefile");
		return (-1);
	}
	return (0);
}

/*
 * Translate a physical memory address to a file-offset in the crash-dump.
 * (Taken from kvm_ia64.c)
 */
static size_t
_kvm_pa2off(kvm_t *kd, uint64_t pa, off_t *ofs)
{
	Elf_Ehdr *e = kd->vmst->mmapbase;
	Elf_Phdr *p;
	int n;

	if (kd->rawdump) {
		*ofs = pa;
		return (PAGE_SIZE - ((size_t)pa & PAGE_MASK));
	}

	p = (Elf_Phdr*)((char*)e + e->e_phoff);
	n = e->e_phnum;

	while (n && (pa < p->p_paddr || pa >= p->p_paddr + p->p_memsz))
		p++, n--;
	if (n == 0)
		return (0);
	*ofs = (pa - p->p_paddr) + p->p_offset;
	return (PAGE_SIZE - ((size_t)pa & PAGE_MASK));
}

void
_kvm_freevtop(kvm_t *kd)
{
	struct vmstate	*vm = kd->vmst;

	if (kd->vmst->minidump) {
		_kvm_minidump_freevtop(kd);
		return;
	}

	if (vm->mmapbase != NULL)
		munmap(vm->mmapbase, vm->mmapsize);
	if (vm->PTD)
		free(vm->PTD);
	free(vm);
	kd->vmst = NULL;
}

int
_kvm_initvtop(kvm_t *kd)
{
	struct nlist nlist[2];
	u_long pa;
	u_long kernbase;
	char		*PTD;
	Elf_Ehdr	*ehdr;
	size_t		hdrsz;
	char		minihdr[8];
	struct pcb	dumppcb;

	if (pread(kd->pmfd, &minihdr, 8, 0) == 8)
		if (memcmp(&minihdr, "minidump", 8) == 0)
			return (_kvm_minidump_initvtop(kd));

	kd->vmst = (struct vmstate *)_kvm_malloc(kd, sizeof(*kd->vmst));
	if (kd->vmst == 0) {
		_kvm_err(kd, kd->program, "cannot allocate vm");
		return (-1);
	}
	kd->vmst->PTD = 0;

	if (_kvm_maphdrs(kd, sizeof(Elf_Ehdr)) == -1)
		return (-1);
	/*
	 * Check if this is indeed an ELF header. If not, assume old style dump or
	 * memory layout.
	 */
	ehdr = kd->vmst->mmapbase;
	if (!IS_ELF(*ehdr)) {
		kd->rawdump = 1;
		munmap(kd->vmst->mmapbase, kd->vmst->mmapsize);
		kd->vmst->mmapbase = NULL;
	} else {
		hdrsz = ehdr->e_phoff + ehdr->e_phentsize * ehdr->e_phnum;
		if (_kvm_maphdrs(kd, hdrsz) == -1)
			return (-1);
	}

	nlist[0].n_name = "_kernbase";
	nlist[1].n_name = 0;

	if (kvm_nlist(kd, nlist) != 0)
		kernbase = KERNBASE;	/* for old kernels */
	else
		kernbase = nlist[0].n_value;

	nlist[0].n_name = "_dumppcb";
	nlist[1].n_name = 0;

	if (kvm_nlist(kd, nlist) != 0) {
		_kvm_err(kd, kd->program, "bad namelist");
		return (-1);
	}

	if (kvm_read(kd, (nlist[0].n_value - kernbase), &dumppcb,
		     sizeof(dumppcb)) != sizeof(dumppcb)) {
		_kvm_err(kd, kd->program, "cannot read dumppcb");
		return (-1);
	}
	pa = dumppcb.pcb_cr3 & PG_FRAME;

	PTD = _kvm_malloc(kd, PAGE_SIZE);
	if (kvm_read(kd, pa, PTD, PAGE_SIZE) != PAGE_SIZE) {
		_kvm_err(kd, kd->program, "cannot read PTD");
		return (-1);
	}
	kd->vmst->PTD = PTD;
	return (0);
}

static int
_kvm_vatop(kvm_t *kd, u_long va, off_t *pa)
{
	struct vmstate *vm;
	u_long offset;
	u_long pte_pa;
	u_long pde_pa;
	pd_entry_t pde;
	pt_entry_t pte;
	u_long pdeindex;
	u_long pteindex;
	size_t	s;
	u_long	a;
	off_t	ofs;
	uint32_t *PTD;


	vm = kd->vmst;
	PTD = (uint32_t *)vm->PTD;
	offset = va & (PAGE_SIZE - 1);

	/*
	 * If we are initializing (kernel page table descriptor pointer
	 * not yet set) then return pa == va to avoid infinite recursion.
	 */
	if (PTD == 0) {
		s = _kvm_pa2off(kd, va, pa);
		if (s == 0) {
			_kvm_err(kd, kd->program,
			    "_kvm_vatop: bootstrap data not in dump");
			goto invalid;
		} else {
			return (PAGE_SIZE - offset);
		}
	}

	pdeindex = va >> PDRSHIFT;
	pde = PTD[pdeindex];

	if (((u_long)pde & PG_V) == 0) {
		_kvm_err(kd, kd->program, "_kvm_vatop: pde not valid");
		goto invalid;
	}

	if ((u_long)pde & PG_PS) {
	      /*
	       * No second-level page table; ptd describes one 4MB page.
	       * (We assume that the kernel wouldn't set PG_PS without enabling
	       * it cr0, and that the kernel doesn't support 36-bit physical
	       * addresses).
	       */
#define	PAGE4M_MASK	(NBPDR - 1)
#define	PG_FRAME4M	(~PAGE4M_MASK)
#if 0
		*pa = ((u_long)pde & PG_FRAME4M) + (va & PAGE4M_MASK);
#endif
		pde_pa = ((u_long)pde & PG_FRAME4M) + (va & PAGE4M_MASK);
		s = _kvm_pa2off(kd, pde_pa, &ofs);
		if (s < sizeof pde) {
			_kvm_syserr(kd, kd->program,
			    "_kvm_vatop: pde_pa not found");
			goto invalid;
		}
		*pa = ofs;

		return (NBPDR - (va & PAGE4M_MASK));
	}

	pteindex = (va >> PAGE_SHIFT) & (NPTEPG-1);
	pte_pa = ((u_long)pde & PG_FRAME) + (pteindex * sizeof(pde));

	s = _kvm_pa2off(kd, pte_pa, &ofs);
	if (s < sizeof pte) {
		_kvm_err(kd, kd->program, "_kvm_vatop: pdpe_pa not found");
		goto invalid;
	}

	/* XXX This has to be a physical address read, kvm_read is virtual */
	if (lseek(kd->pmfd, ofs, 0) == -1) {
		_kvm_syserr(kd, kd->program, "_kvm_vatop: lseek");
		goto invalid;
	}
	if (read(kd->pmfd, &pte, sizeof pte) != sizeof pte) {
		_kvm_syserr(kd, kd->program, "_kvm_vatop: read");
		goto invalid;
	}
	if (((u_long)pte & PG_V) == 0) {
		_kvm_err(kd, kd->program, "_kvm_kvatop: pte not valid");
		goto invalid;
	}

	a = ((u_long)pte & PG_FRAME) + offset;
	s =_kvm_pa2off(kd, a, pa);
	if (s == 0) {
		_kvm_err(kd, kd->program, "_kvm_vatop: address not in dump");
		goto invalid;
	} else
		return (PAGE_SIZE - offset);

invalid:
	_kvm_err(kd, 0, "invalid address (0x%lx)", va);
	return (0);
}

int
_kvm_kvatop(kvm_t *kd, u_long va, off_t *pa)
{
	if (kd->vmst->minidump)
		return (_kvm_minidump_kvatop(kd, va, pa));

	if (kvm_ishost(kd)) {
		_kvm_err(kd, 0, "vatop called in live kernel!");
		return (0);
	}

	return (_kvm_vatop(kd, va, pa));
}