[v2] fuzz: map all BARs and enable PCI devices

[PATCH v2] fuzz: map all BARs and enable PCI devices

Posted by Alexander Bulekov 4 years, 11 months ago

Prior to this patch, the fuzzer found inputs to map PCI device BARs and
enable the device. While it is nice that the fuzzer can do this, it
added significant overhead, since the fuzzer needs to map all the
BARs (regenerating the memory topology), at the start of each input.
With this patch, we do this once, before fuzzing, mitigating some of
this overhead.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
---

v2: do not mix statements and declarations

 tests/qtest/fuzz/generic_fuzz.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
index 07ad690683..92b598dea8 100644
--- a/tests/qtest/fuzz/generic_fuzz.c
+++ b/tests/qtest/fuzz/generic_fuzz.c
@@ -16,6 +16,7 @@
 
 #include "hw/core/cpu.h"
 #include "tests/qtest/libqos/libqtest.h"
+#include "tests/qtest/libqos/pci-pc.h"
 #include "fuzz.h"
 #include "fork_fuzz.h"
 #include "exec/address-spaces.h"
@@ -762,10 +763,28 @@ static int locate_fuzz_objects(Object *child, void *opaque)
     return 0;
 }
 
+
+static void pci_enum(gpointer pcidev, gpointer bus)
+{
+    PCIDevice *dev = pcidev;
+    QPCIDevice *qdev;
+    int i;
+
+    qdev = qpci_device_find(bus, dev->devfn);
+    g_assert(qdev != NULL);
+    for (i = 0; i < 6; i++) {
+        if (dev->io_regions[i].size) {
+            qpci_iomap(qdev, i, NULL);
+        }
+    }
+    qpci_device_enable(qdev);
+}
+
 static void generic_pre_fuzz(QTestState *s)
 {
     GHashTableIter iter;
     MemoryRegion *mr;
+    QPCIBus *pcibus;
     char **result;
 
     if (!getenv("QEMU_FUZZ_OBJECTS")) {
@@ -810,6 +829,10 @@ static void generic_pre_fuzz(QTestState *s)
         exit(1);
     }
 
+    pcibus = qpci_new_pc(s, NULL);
+    g_ptr_array_foreach(fuzzable_pci_devices, pci_enum, pcibus);
+    qpci_free_pc(pcibus);
+
     counter_shm_init();
 }
 
-- 
2.29.2

Re: [PATCH v2] fuzz: map all BARs and enable PCI devices

Posted by Thomas Huth 4 years, 11 months ago

On 15/12/2020 20.08, Alexander Bulekov wrote:
> Prior to this patch, the fuzzer found inputs to map PCI device BARs and
> enable the device. While it is nice that the fuzzer can do this, it
> added significant overhead, since the fuzzer needs to map all the
> BARs (regenerating the memory topology), at the start of each input.
> With this patch, we do this once, before fuzzing, mitigating some of
> this overhead.
> 
> Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
> Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
> ---
> 
> v2: do not mix statements and declarations
> 
>  tests/qtest/fuzz/generic_fuzz.c | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
> 
> diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
> index 07ad690683..92b598dea8 100644
> --- a/tests/qtest/fuzz/generic_fuzz.c
> +++ b/tests/qtest/fuzz/generic_fuzz.c
> @@ -16,6 +16,7 @@
>  
>  #include "hw/core/cpu.h"
>  #include "tests/qtest/libqos/libqtest.h"
> +#include "tests/qtest/libqos/pci-pc.h"
>  #include "fuzz.h"
>  #include "fork_fuzz.h"
>  #include "exec/address-spaces.h"
> @@ -762,10 +763,28 @@ static int locate_fuzz_objects(Object *child, void *opaque)
>      return 0;
>  }
>  
> +
> +static void pci_enum(gpointer pcidev, gpointer bus)
> +{
> +    PCIDevice *dev = pcidev;
> +    QPCIDevice *qdev;
> +    int i;
> +
> +    qdev = qpci_device_find(bus, dev->devfn);
> +    g_assert(qdev != NULL);
> +    for (i = 0; i < 6; i++) {
> +        if (dev->io_regions[i].size) {
> +            qpci_iomap(qdev, i, NULL);
> +        }
> +    }
> +    qpci_device_enable(qdev);
> +}

This new code just triggered a leak error in the gitlab-CI for me:

 https://gitlab.com/huth/qemu/-/jobs/920543745#L309

Could you please have a look?

 Thanks,
  Thomas