hw/m68k/mcf5208: Avoid shifting off end of integer

In m5208_sys_read(), we have a loop of n from 0 to 31, and we
calculate (2u << n).  For the n == 31 iteration this will shift off
the top of the unsigned 32 bit integer.

This is harmless, because we're going to stop the loop with n == 31
anyway, but we can avoid the error by using 64-bit arithmetic here.

(The SDCS0 register is documented at
https://www.nxp.com/docs/en/reference-manual/MCF5208RM.pdf
section 18.4.5; we want the lower 5 bits to indicate the
RAM size, where 31 == 4GB, 30 == 2GB, and so on down.
As it happens, the layout of the mcf5208evb board memory map
means it doesn't make sense to have more than 1GB of RAM
in any case.)

Resolves: Coverity CID 1547727
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Thomas Huth <huth@tuxfamily.org>
Message-ID: <20240830173452.2086140-2-peter.maydell@linaro.org>
Signed-off-by: Thomas Huth <huth@tuxfamily.org>

diff --git a/hw/m68k/mcf5208.c b/hw/m68k/mcf5208.c
index ec14096aa43b1b593b490285b6bdc5759790542f..0ad347dfa8198f6fddbc739c4fe665c899491920 100644 (file)
--- a/hw/m68k/mcf5208.c
+++ b/hw/m68k/mcf5208.c
@@ -158,7 +158,7 @@ static uint64_t m5208_sys_read(void *opaque, hwaddr addr,
         {
             int n;
             for (n = 0; n < 32; n++) {
-                if (current_machine->ram_size < (2u << n)) {
+                if (current_machine->ram_size < (2ULL << n)) {
                     break;
                 }
             }