[PATCH v3] fuzz: map all BARs and enable PCI devices

[PATCH v3] fuzz: map all BARs and enable PCI devices

[Alexander Bulekov]

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>
---

v3: Plug the memory-leak pointed out by Thomas:
    https://gitlab.com/huth/qemu/-/jobs/920543745#L309

 tests/qtest/fuzz/generic_fuzz.c | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
index 07ad690683..be76d47d2d 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 +763,29 @@ 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);
+    g_free(qdev);
+}
+
 static void generic_pre_fuzz(QTestState *s)
 {
     GHashTableIter iter;
     MemoryRegion *mr;
+    QPCIBus *pcibus;
     char **result;
 
     if (!getenv("QEMU_FUZZ_OBJECTS")) {
@@ -810,6 +830,10 @@ 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 v3] fuzz: map all BARs and enable PCI devices

[Paolo Bonzini]

On 21/12/20 19:12, 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>
> ---
> 
> v3: Plug the memory-leak pointed out by Thomas:
>      https://gitlab.com/huth/qemu/-/jobs/920543745#L309
> 
>   tests/qtest/fuzz/generic_fuzz.c | 24 ++++++++++++++++++++++++
>   1 file changed, 24 insertions(+)
> 
> diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
> index 07ad690683..be76d47d2d 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 +763,29 @@ 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);
> +    g_free(qdev);
> +}
> +
>   static void generic_pre_fuzz(QTestState *s)
>   {
>       GHashTableIter iter;
>       MemoryRegion *mr;
> +    QPCIBus *pcibus;
>       char **result;
>   
>       if (!getenv("QEMU_FUZZ_OBJECTS")) {
> @@ -810,6 +830,10 @@ 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();
>   }
>   
> 

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Re: [PATCH v3] fuzz: map all BARs and enable PCI devices

[Philippe Mathieu-Daudé]

On 12/21/20 7:12 PM, 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>
> ---
> 
> v3: Plug the memory-leak pointed out by Thomas:
>     https://gitlab.com/huth/qemu/-/jobs/920543745#L309
> 
>  tests/qtest/fuzz/generic_fuzz.c | 24 ++++++++++++++++++++++++
>  1 file changed, 24 insertions(+)
> 
> diff --git a/tests/qtest/fuzz/generic_fuzz.c b/tests/qtest/fuzz/generic_fuzz.c
> index 07ad690683..be76d47d2d 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 +763,29 @@ 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);
> +    g_free(qdev);
> +}
> +
>  static void generic_pre_fuzz(QTestState *s)
>  {
>      GHashTableIter iter;
>      MemoryRegion *mr;
> +    QPCIBus *pcibus;
>      char **result;
>  
>      if (!getenv("QEMU_FUZZ_OBJECTS")) {
> @@ -810,6 +830,10 @@ static void generic_pre_fuzz(QTestState *s)
>          exit(1);
>      }
>  
> +    pcibus = qpci_new_pc(s, NULL);

FYI this patch restricted the "generic" fuzzer to the x86 arch.

> +    g_ptr_array_foreach(fuzzable_pci_devices, pci_enum, pcibus);
> +    qpci_free_pc(pcibus);
> +
>      counter_shm_init();
>  }
>  
>