Hi Athira,

+/* Function to return the extended register values */
+static u64 get_ext_regs_value(int idx)
+{
+       switch (idx) {
+       case PERF_REG_POWERPC_MMCR0:
+               return mfspr(SPRN_MMCR0);
+       case PERF_REG_POWERPC_MMCR1:
+               return mfspr(SPRN_MMCR1);
+       case PERF_REG_POWERPC_MMCR2:
+               return mfspr(SPRN_MMCR2);
+       default: return 0;
+       }
+}
+
  u64 perf_reg_value(struct pt_regs *regs, int idx)
  {
-       if (WARN_ON_ONCE(idx >= PERF_REG_POWERPC_MAX))
-               return 0;
+       u64 PERF_REG_EXTENDED_MAX;

PERF_REG_EXTENDED_MAX should be initialized. otherwise ...

+
+       if (cpu_has_feature(CPU_FTR_ARCH_300))
+               PERF_REG_EXTENDED_MAX = PERF_REG_MAX_ISA_300;
if (idx == PERF_REG_POWERPC_SIER &&
           (IS_ENABLED(CONFIG_FSL_EMB_PERF_EVENT) ||
@@ -85,6 +103,16 @@ u64 perf_reg_value(struct pt_regs *regs, int idx)
            IS_ENABLED(CONFIG_PPC32)))
                return 0;
+ if (idx >= PERF_REG_POWERPC_MAX && idx < PERF_REG_EXTENDED_MAX)
+               return get_ext_regs_value(idx);

On non p9/p10 machine, PERF_REG_EXTENDED_MAX may contain random value which will
allow user to pass this if condition unintentionally.

Neat: PERF_REG_EXTENDED_MAX is a local variable so it should be in lowercase.
Any specific reason to define it in capital?

Ravi

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