From: Alexander Bulekov <alxndr@bu.edu>
To: qemu-devel@nongnu.org
Cc: Laurent Vivier <lvivier@redhat.com>,
Thomas Huth <thuth@redhat.com>,
darren.kenny@oracle.com, f4bug@amsat.org,
Alexander Bulekov <alxndr@bu.edu>,
bsd@redhat.com, stefanha@redhat.com, pbonzini@redhat.com
Subject: [PATCH v2 2/3] fuzz: configure a sparse-mem device, by default
Date: Sat, 13 Mar 2021 18:18:58 -0500 [thread overview]
Message-ID: <20210313231859.941263-3-alxndr@bu.edu> (raw)
In-Reply-To: <20210313231859.941263-1-alxndr@bu.edu>
The generic-fuzzer often provides randomized DMA addresses to
virtual-devices. For a 64-bit address-space, the chance of these
randomized addresses coinciding with RAM regions, is fairly small. Even
though the fuzzer's instrumentation eventually finds valid addresses,
this can take some-time, and slows-down fuzzing progress (especially,
when multiple DMA buffers are involved). To work around this, create
"fake" sparse-memory that spans all of the 64-bit address-space. Adjust
the DMA call-back to populate this sparse memory, correspondingly
Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
---
tests/qtest/fuzz/generic_fuzz.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
index 387ae2020a..b5fe27aae1 100644
--- a/tests/qtest/fuzz/generic_fuzz.c
+++ b/tests/qtest/fuzz/generic_fuzz.c
@@ -28,6 +28,7 @@
#include "hw/pci/pci.h"
#include "hw/boards.h"
#include "generic_fuzz_configs.h"
+#include "hw/mem/sparse-mem.h"
/*
* SEPARATOR is used to separate "operations" in the fuzz input
@@ -64,6 +65,8 @@ static useconds_t timeout = DEFAULT_TIMEOUT_US;
static bool qtest_log_enabled;
+MemoryRegion *sparse_mem_mr;
+
/*
* A pattern used to populate a DMA region or perform a memwrite. This is
* useful for e.g. populating tables of unique addresses.
@@ -191,8 +194,7 @@ void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr)
*/
if (dma_patterns->len == 0
|| len == 0
- || mr != current_machine->ram
- || addr > current_machine->ram_size) {
+ || (mr != current_machine->ram && mr != sparse_mem_mr)) {
return;
}
@@ -238,7 +240,7 @@ void fuzz_dma_read_cb(size_t addr, size_t len, MemoryRegion *mr)
MEMTXATTRS_UNSPECIFIED);
if (!(memory_region_is_ram(mr1) ||
- memory_region_is_romd(mr1))) {
+ memory_region_is_romd(mr1)) && mr1 != sparse_mem_mr) {
l = memory_access_size(mr1, l, addr1);
} else {
/* ROM/RAM case */
@@ -814,6 +816,12 @@ static void generic_pre_fuzz(QTestState *s)
}
qts_global = s;
+ /*
+ * Create a special device that we can use to back DMA buffers at very
+ * high memory addresses
+ */
+ sparse_mem_mr = sparse_mem_init(0, UINT64_MAX);
+
dma_regions = g_array_new(false, false, sizeof(address_range));
dma_patterns = g_array_new(false, false, sizeof(pattern));
--
2.28.0
next prev parent reply other threads:[~2021-03-13 23:22 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-13 23:18 [PATCH v2 0/3] fuzz: Add a sparse-memory device to accelerate fuzzing Alexander Bulekov
2021-03-13 23:18 ` [PATCH v2 1/3] memory: add a sparse memory device for fuzzing Alexander Bulekov
2021-03-14 23:14 ` Alexander Bulekov
2021-03-15 12:09 ` Darren Kenny
2021-03-15 13:52 ` Alexander Bulekov
2021-03-13 23:18 ` Alexander Bulekov [this message]
2021-03-15 12:12 ` [PATCH v2 2/3] fuzz: configure a sparse-mem device, by default Darren Kenny
2021-03-13 23:18 ` [PATCH v2 3/3] fuzz: move some DMA hooks Alexander Bulekov
2021-03-15 12:12 ` Darren Kenny
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