riscv, bpf: Optimize stack usage of trampoline

When BPF_TRAMP_F_CALL_ORIG is not set, stack space for passing arguments
on stack doesn't need to be reserved because the original function is
not called.

Only reserve space for stacked arguments when BPF_TRAMP_F_CALL_ORIG is
set.

Signed-off-by: Puranjay Mohan <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Acked-by: Pu Lehui <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

Author: puranjaymohan

arch/riscv/net/bpf_jit_comp64.c

@@ -892,7 +892,7 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im,
 	stack_size += 8;
 	sreg_off = stack_size;
 
-	if (nr_arg_slots - RV_MAX_REG_ARGS > 0)
+	if ((flags & BPF_TRAMP_F_CALL_ORIG) && (nr_arg_slots - RV_MAX_REG_ARGS > 0))
 		stack_size += (nr_arg_slots - RV_MAX_REG_ARGS) * 8;
 
 	stack_size = round_up(stack_size, STACK_ALIGN);