examples/power: fix overflowed value

Fix the data type of last_branches, last_branch_misses
from uint32_t to uint64_t, and for hits_diff, miss_diff
from int to int64_t respectively to fix possible
overflow or truncation.

Coverity issue: 337677
Fixes: 4b1a631b8a ("examples/vm_power: add oob monitoring functions")
Cc: stable@dpdk.org
Signed-off-by: Reshma Pattan <reshma.pattan@intel.com>
Reviewed-by: Anatoly Burakov <anatoly.burakov@intel.com>

diff --git a/examples/vm_power_manager/oob_monitor_x86.c b/examples/vm_power_manager/oob_monitor_x86.c
index 589c604..ebd96b2 100644 (file)
--- a/examples/vm_power_manager/oob_monitor_x86.c
+++ b/examples/vm_power_manager/oob_monitor_x86.c
@@ -33,10 +33,10 @@ static float
 apply_policy(int core)
 {
        struct core_info *ci;
-       uint64_t counter;
+       uint64_t counter = 0;
        uint64_t branches, branch_misses;
-       uint32_t last_branches, last_branch_misses;
-       int hits_diff, miss_diff;
+       uint64_t last_branches, last_branch_misses;
+       int64_t hits_diff, miss_diff;
        float ratio;
        int ret;
 
@@ -54,6 +54,7 @@ apply_policy(int core)
                                core);
        branches = counter;
 
+       counter = 0;
        ret = pread(ci->cd[core].msr_fd, &counter,
                        sizeof(counter), IA32_PERFCTR1);
        if (ret < 0)
@@ -66,13 +67,25 @@ apply_policy(int core)
        ci->cd[core].last_branches = branches;
        ci->cd[core].last_branch_misses = branch_misses;
 
-       hits_diff = (int)branches - (int)last_branches;
+       /*
+        * Intentional right shift to make MSB 0 to avoid
+        * possible signed overflow or truncation.
+        */
+       branches >>= 1;
+       last_branches >>= 1;
+       hits_diff = (int64_t)branches - (int64_t)last_branches;
        if (hits_diff <= 0) {
                /* Likely a counter overflow condition, skip this round */
                return -1.0;
        }
 
-       miss_diff = (int)branch_misses - (int)last_branch_misses;
+       /*
+        * Intentional right shift to make MSB 0 to avoid
+        * possible signed overflow or truncation.
+        */
+       branch_misses >>= 1;
+       last_branch_misses >>= 1;
+       miss_diff = (int64_t)branch_misses - (int64_t)last_branch_misses;
        if (miss_diff <= 0) {
                /* Likely a counter overflow condition, skip this round */
                return -1.0;