[PATCH v3 05/16] fuzz: Declare DMA Read callback function

[Alexander Bulekov <alxndr@bu.edu>]

This patch declares the fuzz_dma_read_cb function and uses the
preprocessor and linker(weak symbols) to handle these cases:

When we build softmmu/all with --enable-fuzzing, there should be no
strong symbol defined for fuzz_dma_read_cb, and we link against a weak
stub function.

When we build softmmu/fuzz with --enable-fuzzing, we link against the
strong symbol in general_fuzz.c

When we build softmmu/all without --enable-fuzzing, fuzz_dma_read_cb is
an empty, inlined function. As long as we don't call any other functions
when building the arguments, there should be no overhead.

Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
---
 include/exec/memory.h | 15 +++++++++++++++
 softmmu/memory.c      | 13 +++++++++++++
 2 files changed, 28 insertions(+)

diff --git a/include/exec/memory.h b/include/exec/memory.h
index 975a90c871..d5511c7222 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -42,6 +42,21 @@ typedef struct IOMMUMemoryRegionClass IOMMUMemoryRegionClass;
 DECLARE_OBJ_CHECKERS(IOMMUMemoryRegion, IOMMUMemoryRegionClass,
                      IOMMU_MEMORY_REGION, TYPE_IOMMU_MEMORY_REGION)
 
+#ifdef CONFIG_FUZZ
+void fuzz_dma_read_cb(size_t addr,
+                      size_t len,
+                      MemoryRegion *mr,
+                      bool is_write);
+#else
+static inline void fuzz_dma_read_cb(size_t addr,
+                                    size_t len,
+                                    MemoryRegion *mr,
+                                    bool is_write)
+{
+    /* Do Nothing */
+}
+#endif
+
 extern bool global_dirty_log;
 
 typedef struct MemoryRegionOps MemoryRegionOps;
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 9db5fbe43a..24e59593ca 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -3232,6 +3232,19 @@ void memory_region_init_rom_device(MemoryRegion *mr,
     vmstate_register_ram(mr, owner_dev);
 }
 
+/*
+ * Support softmmu builds with CONFIG_FUZZ using a weak symbol and a stub for
+ * the fuzz_dma_read_cb callback
+ */
+#ifdef CONFIG_FUZZ
+void __attribute__((weak)) fuzz_dma_read_cb(size_t addr,
+                      size_t len,
+                      MemoryRegion *mr,
+                      bool is_write)
+{
+}
+#endif
+
 static const TypeInfo memory_region_info = {
     .parent             = TYPE_OBJECT,
     .name               = TYPE_MEMORY_REGION,
-- 
2.28.0