Revision e35bdc123a4ace9f4d3fccaaf88907014e2438cd authored by Kevin Wolf on 05 October 2018, 16:57:40 UTC, committed by Kevin Wolf on 05 November 2018, 14:09:55 UTC
If a management application builds the block graph node by node, the protocol layer doesn't inherit its read-only option from the format layer any more, so it must be set explicitly. Backing files should work on read-only storage, but at the same time, a block job like commit should be able to reopen them read-write if they are on read-write storage. However, without option inheritance, reopen only changes the read-only option for the root node (typically the format layer), but not the protocol layer, so reopening fails (the format layer wants to get write permissions, but the protocol layer is still read-only). A simple workaround for the problem in the management tool would be to open the protocol layer always read-write and to make only the format layer read-only for backing files. However, sometimes the file is actually stored on read-only storage and we don't know whether the image can be opened read-write (for example, for NBD it depends on the server we're trying to connect to). This adds an option that makes QEMU try to open the image read-write, but allows it to degrade to a read-only mode without returning an error. The documentation for this option is consciously phrased in a way that allows QEMU to switch to a better model eventually: Instead of trying when the image is first opened, making the read-only flag dynamic and changing it automatically whenever the first BLK_PERM_WRITE user is attached or the last one is detached would be much more useful behaviour. Unfortunately, this more useful behaviour is also a lot harder to implement, and libvirt needs a solution now before it can switch to -blockdev, so let's start with this easier approach for now. Instead of adding a new auto-read-only option, turning the existing read-only into an enum (with a bool alternate for compatibility) was considered, but it complicated the implementation to the point that it didn't seem to be worth it. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
1 parent eeae6a5
win_dump.c
/*
* Windows crashdump
*
* Copyright (c) 2018 Virtuozzo International GmbH
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*
*/
#include "qemu/osdep.h"
#include "qemu/cutils.h"
#include "elf.h"
#include "cpu.h"
#include "exec/hwaddr.h"
#include "monitor/monitor.h"
#include "sysemu/kvm.h"
#include "sysemu/dump.h"
#include "sysemu/sysemu.h"
#include "sysemu/memory_mapping.h"
#include "sysemu/cpus.h"
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qemu/error-report.h"
#include "hw/misc/vmcoreinfo.h"
#include "win_dump.h"
static size_t write_run(WinDumpPhyMemRun64 *run, int fd, Error **errp)
{
void *buf;
uint64_t addr = run->BasePage << TARGET_PAGE_BITS;
uint64_t size = run->PageCount << TARGET_PAGE_BITS;
uint64_t len, l;
size_t total = 0;
while (size) {
len = size;
buf = cpu_physical_memory_map(addr, &len, false);
if (!buf) {
error_setg(errp, "win-dump: failed to map physical range"
" 0x%016" PRIx64 "-0x%016" PRIx64, addr, addr + size - 1);
return 0;
}
l = qemu_write_full(fd, buf, len);
cpu_physical_memory_unmap(buf, addr, false, len);
if (l != len) {
error_setg(errp, QERR_IO_ERROR);
return 0;
}
addr += l;
size -= l;
total += l;
}
return total;
}
static void write_runs(DumpState *s, WinDumpHeader64 *h, Error **errp)
{
WinDumpPhyMemDesc64 *desc = &h->PhysicalMemoryBlock;
WinDumpPhyMemRun64 *run = desc->Run;
Error *local_err = NULL;
int i;
for (i = 0; i < desc->NumberOfRuns; i++) {
s->written_size += write_run(run + i, s->fd, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
}
}
static void patch_mm_pfn_database(WinDumpHeader64 *h, Error **errp)
{
if (cpu_memory_rw_debug(first_cpu,
h->KdDebuggerDataBlock + KDBG_MM_PFN_DATABASE_OFFSET64,
(uint8_t *)&h->PfnDatabase, sizeof(h->PfnDatabase), 0)) {
error_setg(errp, "win-dump: failed to read MmPfnDatabase");
return;
}
}
static void patch_bugcheck_data(WinDumpHeader64 *h, Error **errp)
{
uint64_t KiBugcheckData;
if (cpu_memory_rw_debug(first_cpu,
h->KdDebuggerDataBlock + KDBG_KI_BUGCHECK_DATA_OFFSET64,
(uint8_t *)&KiBugcheckData, sizeof(KiBugcheckData), 0)) {
error_setg(errp, "win-dump: failed to read KiBugcheckData");
return;
}
if (cpu_memory_rw_debug(first_cpu,
KiBugcheckData,
h->BugcheckData, sizeof(h->BugcheckData), 0)) {
error_setg(errp, "win-dump: failed to read bugcheck data");
return;
}
/*
* If BugcheckCode wasn't saved, we consider guest OS as alive.
*/
if (!h->BugcheckCode) {
h->BugcheckCode = LIVE_SYSTEM_DUMP;
}
}
/*
* This routine tries to correct mistakes in crashdump header.
*/
static void patch_header(WinDumpHeader64 *h)
{
Error *local_err = NULL;
h->RequiredDumpSpace = sizeof(WinDumpHeader64) +
(h->PhysicalMemoryBlock.NumberOfPages << TARGET_PAGE_BITS);
h->PhysicalMemoryBlock.unused = 0;
h->unused1 = 0;
patch_mm_pfn_database(h, &local_err);
if (local_err) {
warn_report_err(local_err);
local_err = NULL;
}
patch_bugcheck_data(h, &local_err);
if (local_err) {
warn_report_err(local_err);
}
}
static void check_header(WinDumpHeader64 *h, Error **errp)
{
const char Signature[] = "PAGE";
const char ValidDump[] = "DU64";
if (memcmp(h->Signature, Signature, sizeof(h->Signature))) {
error_setg(errp, "win-dump: invalid header, expected '%.4s',"
" got '%.4s'", Signature, h->Signature);
return;
}
if (memcmp(h->ValidDump, ValidDump, sizeof(h->ValidDump))) {
error_setg(errp, "win-dump: invalid header, expected '%.4s',"
" got '%.4s'", ValidDump, h->ValidDump);
return;
}
}
static void check_kdbg(WinDumpHeader64 *h, Error **errp)
{
const char OwnerTag[] = "KDBG";
char read_OwnerTag[4];
uint64_t KdDebuggerDataBlock = h->KdDebuggerDataBlock;
bool try_fallback = true;
try_again:
if (cpu_memory_rw_debug(first_cpu,
KdDebuggerDataBlock + KDBG_OWNER_TAG_OFFSET64,
(uint8_t *)&read_OwnerTag, sizeof(read_OwnerTag), 0)) {
error_setg(errp, "win-dump: failed to read OwnerTag");
return;
}
if (memcmp(read_OwnerTag, OwnerTag, sizeof(read_OwnerTag))) {
if (try_fallback) {
/*
* If attempt to use original KDBG failed
* (most likely because of its encryption),
* we try to use KDBG obtained by guest driver.
*/
KdDebuggerDataBlock = h->BugcheckParameter1;
try_fallback = false;
goto try_again;
} else {
error_setg(errp, "win-dump: invalid KDBG OwnerTag,"
" expected '%.4s', got '%.4s'",
OwnerTag, read_OwnerTag);
return;
}
}
h->KdDebuggerDataBlock = KdDebuggerDataBlock;
}
struct saved_context {
WinContext ctx;
uint64_t addr;
};
static void patch_and_save_context(WinDumpHeader64 *h,
struct saved_context *saved_ctx,
Error **errp)
{
uint64_t KiProcessorBlock;
uint16_t OffsetPrcbContext;
CPUState *cpu;
int i = 0;
if (cpu_memory_rw_debug(first_cpu,
h->KdDebuggerDataBlock + KDBG_KI_PROCESSOR_BLOCK_OFFSET64,
(uint8_t *)&KiProcessorBlock, sizeof(KiProcessorBlock), 0)) {
error_setg(errp, "win-dump: failed to read KiProcessorBlock");
return;
}
if (cpu_memory_rw_debug(first_cpu,
h->KdDebuggerDataBlock + KDBG_OFFSET_PRCB_CONTEXT_OFFSET64,
(uint8_t *)&OffsetPrcbContext, sizeof(OffsetPrcbContext), 0)) {
error_setg(errp, "win-dump: failed to read OffsetPrcbContext");
return;
}
CPU_FOREACH(cpu) {
X86CPU *x86_cpu = X86_CPU(cpu);
CPUX86State *env = &x86_cpu->env;
uint64_t Prcb;
uint64_t Context;
WinContext ctx;
if (cpu_memory_rw_debug(first_cpu,
KiProcessorBlock + i * sizeof(uint64_t),
(uint8_t *)&Prcb, sizeof(Prcb), 0)) {
error_setg(errp, "win-dump: failed to read"
" CPU #%d PRCB location", i);
return;
}
if (cpu_memory_rw_debug(first_cpu,
Prcb + OffsetPrcbContext,
(uint8_t *)&Context, sizeof(Context), 0)) {
error_setg(errp, "win-dump: failed to read"
" CPU #%d ContextFrame location", i);
return;
}
saved_ctx[i].addr = Context;
ctx = (WinContext){
.ContextFlags = WIN_CTX_ALL,
.MxCsr = env->mxcsr,
.SegEs = env->segs[0].selector,
.SegCs = env->segs[1].selector,
.SegSs = env->segs[2].selector,
.SegDs = env->segs[3].selector,
.SegFs = env->segs[4].selector,
.SegGs = env->segs[5].selector,
.EFlags = cpu_compute_eflags(env),
.Dr0 = env->dr[0],
.Dr1 = env->dr[1],
.Dr2 = env->dr[2],
.Dr3 = env->dr[3],
.Dr6 = env->dr[6],
.Dr7 = env->dr[7],
.Rax = env->regs[R_EAX],
.Rbx = env->regs[R_EBX],
.Rcx = env->regs[R_ECX],
.Rdx = env->regs[R_EDX],
.Rsp = env->regs[R_ESP],
.Rbp = env->regs[R_EBP],
.Rsi = env->regs[R_ESI],
.Rdi = env->regs[R_EDI],
.R8 = env->regs[8],
.R9 = env->regs[9],
.R10 = env->regs[10],
.R11 = env->regs[11],
.R12 = env->regs[12],
.R13 = env->regs[13],
.R14 = env->regs[14],
.R15 = env->regs[15],
.Rip = env->eip,
.FltSave = {
.MxCsr = env->mxcsr,
},
};
if (cpu_memory_rw_debug(first_cpu, Context,
(uint8_t *)&saved_ctx[i].ctx, sizeof(WinContext), 0)) {
error_setg(errp, "win-dump: failed to save CPU #%d context", i);
return;
}
if (cpu_memory_rw_debug(first_cpu, Context,
(uint8_t *)&ctx, sizeof(WinContext), 1)) {
error_setg(errp, "win-dump: failed to write CPU #%d context", i);
return;
}
i++;
}
}
static void restore_context(WinDumpHeader64 *h,
struct saved_context *saved_ctx)
{
int i;
Error *err = NULL;
for (i = 0; i < h->NumberProcessors; i++) {
if (cpu_memory_rw_debug(first_cpu, saved_ctx[i].addr,
(uint8_t *)&saved_ctx[i].ctx, sizeof(WinContext), 1)) {
error_setg(&err, "win-dump: failed to restore CPU #%d context", i);
warn_report_err(err);
}
}
}
void create_win_dump(DumpState *s, Error **errp)
{
WinDumpHeader64 *h = (WinDumpHeader64 *)(s->guest_note +
VMCOREINFO_ELF_NOTE_HDR_SIZE);
X86CPU *first_x86_cpu = X86_CPU(first_cpu);
uint64_t saved_cr3 = first_x86_cpu->env.cr[3];
struct saved_context *saved_ctx = NULL;
Error *local_err = NULL;
if (s->guest_note_size != sizeof(WinDumpHeader64) +
VMCOREINFO_ELF_NOTE_HDR_SIZE) {
error_setg(errp, "win-dump: invalid vmcoreinfo note size");
return;
}
check_header(h, &local_err);
if (local_err) {
error_propagate(errp, local_err);
return;
}
/*
* Further access to kernel structures by virtual addresses
* should be made from system context.
*/
first_x86_cpu->env.cr[3] = h->DirectoryTableBase;
check_kdbg(h, &local_err);
if (local_err) {
error_propagate(errp, local_err);
goto out_cr3;
}
patch_header(h);
saved_ctx = g_new(struct saved_context, h->NumberProcessors);
/*
* Always patch context because there is no way
* to determine if the system-saved context is valid
*/
patch_and_save_context(h, saved_ctx, &local_err);
if (local_err) {
error_propagate(errp, local_err);
goto out_free;
}
s->total_size = h->RequiredDumpSpace;
s->written_size = qemu_write_full(s->fd, h, sizeof(*h));
if (s->written_size != sizeof(*h)) {
error_setg(errp, QERR_IO_ERROR);
goto out_restore;
}
write_runs(s, h, &local_err);
if (local_err) {
error_propagate(errp, local_err);
goto out_restore;
}
out_restore:
restore_context(h, saved_ctx);
out_free:
g_free(saved_ctx);
out_cr3:
first_x86_cpu->env.cr[3] = saved_cr3;
return;
}
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