riscv: bpf: Fix uninitialized symbol 'retval_off'

In the __arch_prepare_bpf_trampoline() function, retval_off is only
meaningful when save_ret is true, so the current logic is correct.
However, in the original logic, retval_off is only initialized under
certain conditions; for example, in the fmod_ret logic, the compiler is
not aware that the flags of the fmod_ret program (prog) have set
BPF_TRAMP_F_CALL_ORIG, which results in an uninitialized symbol
compilation warning.

So initialize retval_off unconditionally to fix it.

Signed-off-by: Chenghao Duan <[email protected]>
Reviewed-by: Pu Lehui <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: Chenghao Duan

arch/riscv/net/bpf_jit_comp64.c

@@ -1061,10 +1061,9 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 	stack_size += 16;
 
 	save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET);
-	if (save_ret) {
+	if (save_ret)
 		stack_size += 16; /* Save both A5 (BPF R0) and A0 */
-		retval_off = stack_size;
-	}
+	retval_off = stack_size;
 
 	stack_size += nr_arg_slots * 8;
 	args_off = stack_size;