[PATCH v2 03/15] fuzz: Add PCI features to the general fuzzer

[Alexander Bulekov]

This patch compares TYPE_PCI_DEVICE objects against the user-provided
matching pattern. If there is a match, we use some hacks and leverage
QOS to map each possible BAR for that device. Now fuzzed inputs might be
converted to pci_read/write commands which target specific. This means
that we can fuzz a particular device's PCI configuration space,

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
---
 tests/qtest/fuzz/general_fuzz.c | 83 +++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)

diff --git a/tests/qtest/fuzz/general_fuzz.c b/tests/qtest/fuzz/general_fuzz.c
index 01bcb029b1..17b572a439 100644
--- a/tests/qtest/fuzz/general_fuzz.c
+++ b/tests/qtest/fuzz/general_fuzz.c
@@ -24,6 +24,7 @@
 #include "exec/ramblock.h"
 #include "exec/address-spaces.h"
 #include "hw/qdev-core.h"
+#include "hw/pci/pci.h"
 
 /*
  * SEPARATOR is used to separate "operations" in the fuzz input
@@ -35,12 +36,17 @@ enum cmds{
     OP_OUT,
     OP_READ,
     OP_WRITE,
+    OP_PCI_READ,
+    OP_PCI_WRITE,
     OP_CLOCK_STEP,
 };
 
 #define DEFAULT_TIMEOUT_US 100000
 #define USEC_IN_SEC 100000000
 
+#define PCI_HOST_BRIDGE_CFG 0xcf8
+#define PCI_HOST_BRIDGE_DATA 0xcfc
+
 typedef struct {
     size_t addr;
     size_t len; /* The number of bytes until the end of the I/O region */
@@ -52,6 +58,8 @@ static useconds_t timeout = 100000;
  * user for fuzzing.
  */
 static GPtrArray *fuzzable_memoryregions;
+static GPtrArray *fuzzable_pci_devices;
+
 /*
  * Here we want to convert a fuzzer-provided [io-region-index, offset] to
  * a physical address. To do this, we iterate over all of the matched
@@ -283,6 +291,65 @@ static void op_write(QTestState *s, const unsigned char * 
data, size_t len)
         break;
     }
 }
+static void op_pci_read(QTestState *s, const unsigned char * data, size_t len)
+{
+    enum Sizes {Byte, Word, Long, end_sizes};
+    struct {
+        uint8_t size;
+        uint8_t base;
+        uint8_t offset;
+    } a;
+    if (len < sizeof(a) || fuzzable_pci_devices->len == 0) {
+        return;
+    }
+    memcpy(&a, data, sizeof(a));
+    PCIDevice *dev = g_ptr_array_index(fuzzable_pci_devices,
+                                  a.base % fuzzable_pci_devices->len);
+    int devfn = dev->devfn;
+    qtest_outl(s, PCI_HOST_BRIDGE_CFG, (1U << 31) | (devfn << 8) | a.offset);
+    switch (a.size %= end_sizes) {
+    case Byte:
+        qtest_inb(s, PCI_HOST_BRIDGE_DATA);
+        break;
+    case Word:
+        qtest_inw(s, PCI_HOST_BRIDGE_DATA);
+        break;
+    case Long:
+        qtest_inl(s, PCI_HOST_BRIDGE_DATA);
+        break;
+    }
+}
+
+static void op_pci_write(QTestState *s, const unsigned char * data, size_t len)
+{
+    enum Sizes {Byte, Word, Long, end_sizes};
+    struct {
+        uint8_t size;
+        uint8_t base;
+        uint8_t offset;
+        uint32_t value;
+    } a;
+    if (len < sizeof(a) || fuzzable_pci_devices->len == 0) {
+        return;
+    }
+    memcpy(&a, data, sizeof(a));
+    PCIDevice *dev = g_ptr_array_index(fuzzable_pci_devices,
+                                  a.base % fuzzable_pci_devices->len);
+    int devfn = dev->devfn;
+    qtest_outl(s, PCI_HOST_BRIDGE_CFG, (1U << 31) | (devfn << 8) | a.offset);
+    switch (a.size %= end_sizes) {
+    case Byte:
+        qtest_outb(s, PCI_HOST_BRIDGE_DATA, a.value & 0xFF);
+        break;
+    case Word:
+        qtest_outw(s, PCI_HOST_BRIDGE_DATA, a.value & 0xFFFF);
+        break;
+    case Long:
+        qtest_outl(s, PCI_HOST_BRIDGE_DATA, a.value & 0xFFFFFFFF);
+        break;
+    }
+}
+
 static void op_clock_step(QTestState *s, const unsigned char *data, size_t len)
 {
     qtest_clock_step_next(s);
@@ -327,6 +394,8 @@ static void general_fuzz(QTestState *s, const unsigned char 
*Data, size_t Size)
         [OP_OUT]                = op_out,
         [OP_READ]               = op_read,
         [OP_WRITE]              = op_write,
+        [OP_PCI_READ]           = op_pci_read,
+        [OP_PCI_WRITE]          = op_pci_write,
         [OP_CLOCK_STEP]         = op_clock_step,
     };
     const unsigned char *cmd = Data;
@@ -418,6 +487,19 @@ static int locate_fuzz_objects(Object *child, void *opaque)
     if (g_pattern_match_simple(pattern, object_get_typename(child))) {
         /* Find and save ptrs to any child MemoryRegions */
         object_child_foreach_recursive(child, locate_fuzz_memory_regions, 
NULL);
+
+        /*
+         * We matched an object. If its a PCI device, store a pointer to it so
+         * we can map BARs and fuzz its config space.
+         */
+        if (object_dynamic_cast(OBJECT(child), TYPE_PCI_DEVICE)) {
+            /*
+             * Don't want duplicate pointers to the same PCIDevice, so remove
+             * copies of the pointer, before adding it.
+             */
+            g_ptr_array_remove_fast(fuzzable_pci_devices, PCI_DEVICE(child));
+            g_ptr_array_add(fuzzable_pci_devices, PCI_DEVICE(child));
+        }
     } else if (object_dynamic_cast(OBJECT(child), TYPE_MEMORY_REGION)) {
         if (g_pattern_match_simple(pattern,
             object_get_canonical_path_component(child))) {
@@ -445,6 +527,7 @@ static void general_pre_fuzz(QTestState *s)
     }
 
     fuzzable_memoryregions = g_ptr_array_new();
+    fuzzable_pci_devices   = g_ptr_array_new();
     char **result = g_strsplit (getenv("QEMU_FUZZ_OBJECTS"), " ", -1);
     for (int i = 0; result[i] != NULL; i++) {
         printf("Matching objects by name %s\n", result[i]);
-- 
2.27.0