[PATCH v2] target/ppc/kvm: Fix const violation when trimming CPU alias suffix

[Vaibhav Jain <vaibhav@linux.ibm.com>]

GCC 16 tightens diagnostics around const correctness and now correctly
rejects attempts to modify strings referenced through const-qualified
pointers. In kvm_ppc_register_host_cpu_type(), ppc_cpu_aliases[i].model
is defined as const char *, but the code was using strstr() on it and
then modifying the returned pointer in-place to strip
POWERPC_CPU_TYPE_SUFFIX.

This results in a write through a pointer derived from const data,
triggering a build failure with GCC 16:

  error: assignment discards 'const' qualifier from pointer target type [-Werror=discarded-qualifiers]
        suffix = strstr(ppc_cpu_aliases[i].model, POWERPC_CPU_TYPE_SUFFIX);
               ^
Fix this by copying only the needed suffix from the object class-name to
'ppc_cpu_aliases.model' using g_strdup and g_strndup, which maintains the
constness of the allocated buffer assigned to 'ppc_cpu_aliases.model'
member of the 'ppc_cpu_aliases' struct array.

The patch also adds error handling for possible memory allocation failure
while calling g_str{n}dup functions so that the error is properly
propogated back from kvm_arch_init().

Signed-off-by: Amit Machhiwal <amachhiw@linux.ibm.com>
Signed-off-by: Vaibhav Jain (IBM) <vaibhav@linux.ibm.com>

---
Change-log:

v1->v2:
https://lore.kernel.org/all/20260504134344.38958-1-amachhiw@linux.ibm.com
* Avoid pointer aliasing
* Handle memory allocation failure error
---
 target/ppc/kvm.c | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
index 25c28ad089..42cd4f4fff 100644
--- a/target/ppc/kvm.c
+++ b/target/ppc/kvm.c
@@ -170,9 +170,8 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
 
     cap_rpt_invalidate = kvm_vm_check_extension(s, KVM_CAP_PPC_RPT_INVALIDATE);
     cap_ail_mode_3 = kvm_vm_check_extension(s, KVM_CAP_PPC_AIL_MODE_3);
-    kvm_ppc_register_host_cpu_type();
 
-    return 0;
+    return kvm_ppc_register_host_cpu_type();
 }
 
 int kvm_arch_irqchip_create(KVMState *s)
@@ -2654,14 +2653,17 @@ static int kvm_ppc_register_host_cpu_type(void)
     dc = DEVICE_CLASS(ppc_cpu_get_family_class(pvr_pcc));
     for (i = 0; ppc_cpu_aliases[i].alias != NULL; i++) {
         if (g_ascii_strcasecmp(ppc_cpu_aliases[i].alias, dc->desc) == 0) {
-            char *suffix;
+            const gchar *suffix, *cname = object_class_get_name(oc);
+
+            suffix = g_strstr_len(cname, -1, POWERPC_CPU_TYPE_SUFFIX);
+            ppc_cpu_aliases[i].model = unlikely(suffix) ?
+                g_strndup(cname, suffix - cname) : g_strdup(cname);
 
-            ppc_cpu_aliases[i].model = g_strdup(object_class_get_name(oc));
-            suffix = strstr(ppc_cpu_aliases[i].model, POWERPC_CPU_TYPE_SUFFIX);
-            if (suffix) {
-                *suffix = 0;
+            if (!ppc_cpu_aliases[i].model) {
+                return -ENOMEM;
+            } else {
+                return 0;
             }
-            break;
         }
     }
 
-- 
2.54.0