On Wed, Jun 07, 2023 at 08:59:09PM +0800, menglong8.dong@xxxxxxxxx wrote: > From: Menglong Dong <imagedong@xxxxxxxxxxx> > > For now, the BPF program of type BPF_PROG_TYPE_TRACING can only be used > on the kernel functions whose arguments count less than 6. This is not > friendly at all, as too many functions have arguments count more than 6. > > Therefore, let's enhance it by increasing the function arguments count > allowed in arch_prepare_bpf_trampoline(), for now, only x86_64. > > For the case that we don't need to call origin function, which means > without BPF_TRAMP_F_CALL_ORIG, we need only copy the function arguments > that stored in the frame of the caller to current frame. The arguments > of arg6-argN are stored in "$rbp + 0x18", we need copy them to > "$rbp - regs_off + (6 * 8)". > > For the case with BPF_TRAMP_F_CALL_ORIG, we need prepare the arguments > in stack before call origin function, which means we need alloc extra > "8 * (arg_count - 6)" memory in the top of the stack. Note, there should > not be any data be pushed to the stack before call the origin function. > Then, we have to store rbx with 'mov' instead of 'push'. x86-64 psABI requires stack to be 16-byte aligned when args are passed on the stack. I don't see this logic in the patch.
