mirror of https://github.com/xemu-project/xemu.git
fuzz: Add generic virtual-device fuzzer
This is a generic fuzzer designed to fuzz a virtual device's MemoryRegions, as long as they exist within the Memory or Port IO (if it exists) AddressSpaces. The fuzzer's input is interpreted into a sequence of qtest commands (outb, readw, etc). The interpreted commands are separated by a magic seaparator, which should be easy for the fuzzer to guess. Without ASan, the separator can be specified as a "dictionary value" using the -dict argument (see libFuzzer documentation). Reviewed-by: Darren Kenny <darren.kenny@oracle.com> Signed-off-by: Alexander Bulekov <alxndr@bu.edu> Message-Id: <20201023150746.107063-3-alxndr@bu.edu> Signed-off-by: Thomas Huth <thuth@redhat.com>
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/*
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* Generic Virtual-Device Fuzzing Target
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*
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* Copyright Red Hat Inc., 2020
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*
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* Authors:
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* Alexander Bulekov <alxndr@bu.edu>
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*
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* This work is licensed under the terms of the GNU GPL, version 2 or later.
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* See the COPYING file in the top-level directory.
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*/
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#include "qemu/osdep.h"
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#include <wordexp.h>
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#include "hw/core/cpu.h"
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#include "tests/qtest/libqos/libqtest.h"
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#include "fuzz.h"
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#include "fork_fuzz.h"
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#include "exec/address-spaces.h"
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#include "string.h"
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#include "exec/memory.h"
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#include "exec/ramblock.h"
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#include "exec/address-spaces.h"
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#include "hw/qdev-core.h"
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/*
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* SEPARATOR is used to separate "operations" in the fuzz input
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*/
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#define SEPARATOR "FUZZ"
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enum cmds {
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OP_IN,
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OP_OUT,
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OP_READ,
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OP_WRITE,
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OP_CLOCK_STEP,
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};
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#define DEFAULT_TIMEOUT_US 100000
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#define USEC_IN_SEC 1000000000
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typedef struct {
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ram_addr_t addr;
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ram_addr_t size; /* The number of bytes until the end of the I/O region */
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} address_range;
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static useconds_t timeout = DEFAULT_TIMEOUT_US;
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static bool qtest_log_enabled;
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/*
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* List of memory regions that are children of QOM objects specified by the
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* user for fuzzing.
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*/
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static GHashTable *fuzzable_memoryregions;
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struct get_io_cb_info {
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int index;
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int found;
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address_range result;
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};
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static int get_io_address_cb(Int128 start, Int128 size,
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const MemoryRegion *mr, void *opaque) {
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struct get_io_cb_info *info = opaque;
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if (g_hash_table_lookup(fuzzable_memoryregions, mr)) {
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if (info->index == 0) {
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info->result.addr = (ram_addr_t)start;
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info->result.size = (ram_addr_t)size;
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info->found = 1;
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return 1;
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}
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info->index--;
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}
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return 0;
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}
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/*
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* Here we want to convert a fuzzer-provided [io-region-index, offset] to
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* a physical address. To do this, we iterate over all of the matched
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* MemoryRegions. Check whether each region exists within the particular io
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* space. Return the absolute address of the offset within the index'th region
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* that is a subregion of the io_space and the distance until the end of the
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* memory region.
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*/
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static bool get_io_address(address_range *result, AddressSpace *as,
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uint8_t index,
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uint32_t offset) {
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FlatView *view;
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view = as->current_map;
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g_assert(view);
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struct get_io_cb_info cb_info = {};
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cb_info.index = index;
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/*
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* Loop around the FlatView until we match "index" number of
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* fuzzable_memoryregions, or until we know that there are no matching
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* memory_regions.
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*/
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do {
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flatview_for_each_range(view, get_io_address_cb , &cb_info);
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} while (cb_info.index != index && !cb_info.found);
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*result = cb_info.result;
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return cb_info.found;
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}
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static bool get_pio_address(address_range *result,
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uint8_t index, uint16_t offset)
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{
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/*
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* PIO BARs can be set past the maximum port address (0xFFFF). Thus, result
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* can contain an addr that extends past the PIO space. When we pass this
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* address to qtest_in/qtest_out, it is cast to a uint16_t, so we might end
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* up fuzzing a completely different MemoryRegion/Device. Therefore, check
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* that the address here is within the PIO space limits.
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*/
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bool found = get_io_address(result, &address_space_io, index, offset);
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return result->addr <= 0xFFFF ? found : false;
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}
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static bool get_mmio_address(address_range *result,
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uint8_t index, uint32_t offset)
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{
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return get_io_address(result, &address_space_memory, index, offset);
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}
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static void op_in(QTestState *s, const unsigned char * data, size_t len)
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{
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enum Sizes {Byte, Word, Long, end_sizes};
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struct {
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uint8_t size;
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uint8_t base;
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uint16_t offset;
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} a;
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address_range abs;
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if (len < sizeof(a)) {
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return;
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}
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memcpy(&a, data, sizeof(a));
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if (get_pio_address(&abs, a.base, a.offset) == 0) {
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return;
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}
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switch (a.size %= end_sizes) {
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case Byte:
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qtest_inb(s, abs.addr);
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break;
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case Word:
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if (abs.size >= 2) {
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qtest_inw(s, abs.addr);
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}
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break;
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case Long:
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if (abs.size >= 4) {
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qtest_inl(s, abs.addr);
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}
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break;
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}
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}
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static void op_out(QTestState *s, const unsigned char * data, size_t len)
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{
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enum Sizes {Byte, Word, Long, end_sizes};
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struct {
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uint8_t size;
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uint8_t base;
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uint16_t offset;
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uint32_t value;
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} a;
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address_range abs;
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if (len < sizeof(a)) {
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return;
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}
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memcpy(&a, data, sizeof(a));
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if (get_pio_address(&abs, a.base, a.offset) == 0) {
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return;
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}
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switch (a.size %= end_sizes) {
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case Byte:
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qtest_outb(s, abs.addr, a.value & 0xFF);
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break;
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case Word:
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if (abs.size >= 2) {
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qtest_outw(s, abs.addr, a.value & 0xFFFF);
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}
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break;
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case Long:
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if (abs.size >= 4) {
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qtest_outl(s, abs.addr, a.value);
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}
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break;
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}
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}
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static void op_read(QTestState *s, const unsigned char * data, size_t len)
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{
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enum Sizes {Byte, Word, Long, Quad, end_sizes};
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struct {
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uint8_t size;
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uint8_t base;
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uint32_t offset;
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} a;
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address_range abs;
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if (len < sizeof(a)) {
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return;
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}
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memcpy(&a, data, sizeof(a));
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if (get_mmio_address(&abs, a.base, a.offset) == 0) {
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return;
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}
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switch (a.size %= end_sizes) {
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case Byte:
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qtest_readb(s, abs.addr);
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break;
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case Word:
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if (abs.size >= 2) {
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qtest_readw(s, abs.addr);
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}
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break;
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case Long:
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if (abs.size >= 4) {
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qtest_readl(s, abs.addr);
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}
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break;
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case Quad:
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if (abs.size >= 8) {
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qtest_readq(s, abs.addr);
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}
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break;
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}
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}
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static void op_write(QTestState *s, const unsigned char * data, size_t len)
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{
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enum Sizes {Byte, Word, Long, Quad, end_sizes};
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struct {
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uint8_t size;
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uint8_t base;
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uint32_t offset;
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uint64_t value;
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} a;
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address_range abs;
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if (len < sizeof(a)) {
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return;
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}
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memcpy(&a, data, sizeof(a));
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if (get_mmio_address(&abs, a.base, a.offset) == 0) {
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return;
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}
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switch (a.size %= end_sizes) {
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case Byte:
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qtest_writeb(s, abs.addr, a.value & 0xFF);
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break;
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case Word:
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if (abs.size >= 2) {
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qtest_writew(s, abs.addr, a.value & 0xFFFF);
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}
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break;
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case Long:
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if (abs.size >= 4) {
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qtest_writel(s, abs.addr, a.value & 0xFFFFFFFF);
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}
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break;
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case Quad:
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if (abs.size >= 8) {
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qtest_writeq(s, abs.addr, a.value);
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}
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break;
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}
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}
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static void op_clock_step(QTestState *s, const unsigned char *data, size_t len)
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{
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qtest_clock_step_next(s);
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}
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static void handle_timeout(int sig)
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{
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if (qtest_log_enabled) {
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fprintf(stderr, "[Timeout]\n");
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fflush(stderr);
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}
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_Exit(0);
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}
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/*
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* Here, we interpret random bytes from the fuzzer, as a sequence of commands.
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* Some commands can be variable-width, so we use a separator, SEPARATOR, to
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* specify the boundaries between commands. SEPARATOR is used to separate
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* "operations" in the fuzz input. Why use a separator, instead of just using
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* the operations' length to identify operation boundaries?
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* 1. This is a simple way to support variable-length operations
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* 2. This adds "stability" to the input.
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* For example take the input "AbBcgDefg", where there is no separator and
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* Opcodes are capitalized.
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* Simply, by removing the first byte, we end up with a very different
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* sequence:
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* BbcGdefg...
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* By adding a separator, we avoid this problem:
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* Ab SEP Bcg SEP Defg -> B SEP Bcg SEP Defg
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* Since B uses two additional bytes as operands, the first "B" will be
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* ignored. The fuzzer actively tries to reduce inputs, so such unused
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* bytes are likely to be pruned, eventually.
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*
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* SEPARATOR is trivial for the fuzzer to discover when using ASan. Optionally,
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* SEPARATOR can be manually specified as a dictionary value (see libfuzzer's
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* -dict), though this should not be necessary.
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*
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* As a result, the stream of bytes is converted into a sequence of commands.
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* In a simplified example where SEPARATOR is 0xFF:
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* 00 01 02 FF 03 04 05 06 FF 01 FF ...
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* becomes this sequence of commands:
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* 00 01 02 -> op00 (0102) -> in (0102, 2)
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* 03 04 05 06 -> op03 (040506) -> write (040506, 3)
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* 01 -> op01 (-,0) -> out (-,0)
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* ...
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*
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* Note here that it is the job of the individual opcode functions to check
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* that enough data was provided. I.e. in the last command out (,0), out needs
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* to check that there is not enough data provided to select an address/value
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* for the operation.
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*/
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static void generic_fuzz(QTestState *s, const unsigned char *Data, size_t Size)
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{
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void (*ops[]) (QTestState *s, const unsigned char* , size_t) = {
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[OP_IN] = op_in,
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[OP_OUT] = op_out,
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[OP_READ] = op_read,
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[OP_WRITE] = op_write,
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[OP_CLOCK_STEP] = op_clock_step,
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};
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const unsigned char *cmd = Data;
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const unsigned char *nextcmd;
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size_t cmd_len;
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uint8_t op;
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if (fork() == 0) {
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/*
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* Sometimes the fuzzer will find inputs that take quite a long time to
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* process. Often times, these inputs do not result in new coverage.
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* Even if these inputs might be interesting, they can slow down the
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* fuzzer, overall. Set a timeout to avoid hurting performance, too much
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*/
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if (timeout) {
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struct sigaction sact;
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struct itimerval timer;
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sigemptyset(&sact.sa_mask);
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sact.sa_flags = SA_NODEFER;
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sact.sa_handler = handle_timeout;
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sigaction(SIGALRM, &sact, NULL);
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memset(&timer, 0, sizeof(timer));
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timer.it_value.tv_sec = timeout / USEC_IN_SEC;
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timer.it_value.tv_usec = timeout % USEC_IN_SEC;
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setitimer(ITIMER_VIRTUAL, &timer, NULL);
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}
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while (cmd && Size) {
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/* Get the length until the next command or end of input */
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nextcmd = memmem(cmd, Size, SEPARATOR, strlen(SEPARATOR));
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cmd_len = nextcmd ? nextcmd - cmd : Size;
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if (cmd_len > 0) {
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/* Interpret the first byte of the command as an opcode */
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op = *cmd % (sizeof(ops) / sizeof((ops)[0]));
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ops[op](s, cmd + 1, cmd_len - 1);
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/* Run the main loop */
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flush_events(s);
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}
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/* Advance to the next command */
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cmd = nextcmd ? nextcmd + sizeof(SEPARATOR) - 1 : nextcmd;
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Size = Size - (cmd_len + sizeof(SEPARATOR) - 1);
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}
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_Exit(0);
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} else {
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flush_events(s);
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wait(0);
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}
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}
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static void usage(void)
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{
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printf("Please specify the following environment variables:\n");
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printf("QEMU_FUZZ_ARGS= the command line arguments passed to qemu\n");
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printf("QEMU_FUZZ_OBJECTS= "
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"a space separated list of QOM type names for objects to fuzz\n");
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printf("Optionally: QEMU_FUZZ_TIMEOUT= Specify a custom timeout (us). "
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"0 to disable. %d by default\n", timeout);
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exit(0);
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}
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static int locate_fuzz_memory_regions(Object *child, void *opaque)
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{
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const char *name;
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MemoryRegion *mr;
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if (object_dynamic_cast(child, TYPE_MEMORY_REGION)) {
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mr = MEMORY_REGION(child);
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if ((memory_region_is_ram(mr) ||
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memory_region_is_ram_device(mr) ||
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memory_region_is_rom(mr)) == false) {
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name = object_get_canonical_path_component(child);
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/*
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* We don't want duplicate pointers to the same MemoryRegion, so
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* try to remove copies of the pointer, before adding it.
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*/
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g_hash_table_insert(fuzzable_memoryregions, mr, (gpointer)true);
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}
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}
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return 0;
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}
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static int locate_fuzz_objects(Object *child, void *opaque)
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{
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char *pattern = opaque;
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if (g_pattern_match_simple(pattern, object_get_typename(child))) {
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/* Find and save ptrs to any child MemoryRegions */
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object_child_foreach_recursive(child, locate_fuzz_memory_regions, NULL);
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} else if (object_dynamic_cast(OBJECT(child), TYPE_MEMORY_REGION)) {
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if (g_pattern_match_simple(pattern,
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object_get_canonical_path_component(child))) {
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MemoryRegion *mr;
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mr = MEMORY_REGION(child);
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if ((memory_region_is_ram(mr) ||
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memory_region_is_ram_device(mr) ||
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memory_region_is_rom(mr)) == false) {
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g_hash_table_insert(fuzzable_memoryregions, mr, (gpointer)true);
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}
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}
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}
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return 0;
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}
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static void generic_pre_fuzz(QTestState *s)
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{
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GHashTableIter iter;
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MemoryRegion *mr;
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char **result;
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if (!getenv("QEMU_FUZZ_OBJECTS")) {
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usage();
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}
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if (getenv("QTEST_LOG")) {
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qtest_log_enabled = 1;
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}
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if (getenv("QEMU_FUZZ_TIMEOUT")) {
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timeout = g_ascii_strtoll(getenv("QEMU_FUZZ_TIMEOUT"), NULL, 0);
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}
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fuzzable_memoryregions = g_hash_table_new(NULL, NULL);
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result = g_strsplit(getenv("QEMU_FUZZ_OBJECTS"), " ", -1);
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for (int i = 0; result[i] != NULL; i++) {
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printf("Matching objects by name %s\n", result[i]);
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object_child_foreach_recursive(qdev_get_machine(),
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locate_fuzz_objects,
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result[i]);
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}
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g_strfreev(result);
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printf("This process will try to fuzz the following MemoryRegions:\n");
|
||||
|
||||
g_hash_table_iter_init(&iter, fuzzable_memoryregions);
|
||||
while (g_hash_table_iter_next(&iter, (gpointer)&mr, NULL)) {
|
||||
printf(" * %s (size %lx)\n",
|
||||
object_get_canonical_path_component(&(mr->parent_obj)),
|
||||
(uint64_t)mr->size);
|
||||
}
|
||||
|
||||
if (!g_hash_table_size(fuzzable_memoryregions)) {
|
||||
printf("No fuzzable memory regions found...\n");
|
||||
exit(1);
|
||||
}
|
||||
|
||||
counter_shm_init();
|
||||
}
|
||||
|
||||
static GString *generic_fuzz_cmdline(FuzzTarget *t)
|
||||
{
|
||||
GString *cmd_line = g_string_new(TARGET_NAME);
|
||||
if (!getenv("QEMU_FUZZ_ARGS")) {
|
||||
usage();
|
||||
}
|
||||
g_string_append_printf(cmd_line, " -display none \
|
||||
-machine accel=qtest, \
|
||||
-m 512M %s ", getenv("QEMU_FUZZ_ARGS"));
|
||||
return cmd_line;
|
||||
}
|
||||
|
||||
static void register_generic_fuzz_targets(void)
|
||||
{
|
||||
fuzz_add_target(&(FuzzTarget){
|
||||
.name = "generic-fuzz",
|
||||
.description = "Fuzz based on any qemu command-line args. ",
|
||||
.get_init_cmdline = generic_fuzz_cmdline,
|
||||
.pre_fuzz = generic_pre_fuzz,
|
||||
.fuzz = generic_fuzz,
|
||||
});
|
||||
}
|
||||
|
||||
fuzz_target_init(register_generic_fuzz_targets);
|
|
@ -5,6 +5,7 @@ specific_fuzz_ss.add(files('fuzz.c', 'fork_fuzz.c', 'qos_fuzz.c',
|
|||
specific_fuzz_ss.add(when: 'CONFIG_I440FX', if_true: files('i440fx_fuzz.c'))
|
||||
specific_fuzz_ss.add(when: 'CONFIG_VIRTIO_NET', if_true: files('virtio_net_fuzz.c'))
|
||||
specific_fuzz_ss.add(when: 'CONFIG_VIRTIO_SCSI', if_true: files('virtio_scsi_fuzz.c'))
|
||||
specific_fuzz_ss.add(files('generic_fuzz.c'))
|
||||
|
||||
fork_fuzz = declare_dependency(
|
||||
link_args: config_host['FUZZ_EXE_LDFLAGS'].split() +
|
||||
|
|
Loading…
Reference in New Issue