[PATCH v2 for-7.2 2/2] pci: Sanity check mask argument to pci_set_*_by_mask()

[Peter Maydell]

Coverity complains that in functions like pci_set_word_by_mask()
we might end up shifting by more than 31 bits. This is true,
but only if the caller passes in a zero mask. Help Coverity out
by asserting that the mask argument is valid.

Fixes: CID 1487168

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
Note that only 1 of these 4 functions is used, and that only
in 2 places in the codebase. In both cases the mask argument
is a compile-time constant.
v1->v2 changes: remove unnecessary masking
---
 include/hw/pci/pci.h | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index c79144bc5ef..97937cc9221 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -688,7 +688,10 @@ static inline void
 pci_set_byte_by_mask(uint8_t *config, uint8_t mask, uint8_t reg)
 {
     uint8_t val = pci_get_byte(config);
-    uint8_t rval = reg << ctz32(mask);
+    uint8_t rval;
+
+    assert(mask);
+    rval = reg << ctz32(mask);
     pci_set_byte(config, (~mask & val) | (mask & rval));
 }
 
@@ -696,7 +699,10 @@ static inline void
 pci_set_word_by_mask(uint8_t *config, uint16_t mask, uint16_t reg)
 {
     uint16_t val = pci_get_word(config);
-    uint16_t rval = reg << ctz32(mask);
+    uint16_t rval;
+
+    assert(mask);
+    rval = reg << ctz32(mask);
     pci_set_word(config, (~mask & val) | (mask & rval));
 }
 
@@ -704,7 +710,10 @@ static inline void
 pci_set_long_by_mask(uint8_t *config, uint32_t mask, uint32_t reg)
 {
     uint32_t val = pci_get_long(config);
-    uint32_t rval = reg << ctz32(mask);
+    uint32_t rval;
+
+    assert(mask);
+    rval = reg << ctz32(mask);
     pci_set_long(config, (~mask & val) | (mask & rval));
 }
 
@@ -712,7 +721,10 @@ static inline void
 pci_set_quad_by_mask(uint8_t *config, uint64_t mask, uint64_t reg)
 {
     uint64_t val = pci_get_quad(config);
-    uint64_t rval = reg << ctz32(mask);
+    uint64_t rval;
+
+    assert(mask);
+    rval = reg << ctz32(mask);
     pci_set_quad(config, (~mask & val) | (mask & rval));
 }
 
-- 
2.25.1