On 7/11/2022 7:57 PM, Jean-Philippe Brucker wrote:
> On Fri, Jul 08, 2022 at 05:30:32AM -0400, Xu Kuohai wrote:
>> +static void invoke_bpf_prog(struct jit_ctx *ctx, struct bpf_tramp_link *l,
>> + int args_off, int retval_off, int run_ctx_off,
>> + bool save_ret)
>> +{
>> + u32 *branch;
>> + u64 enter_prog;
>> + u64 exit_prog;
>> + u8 r0 = bpf2a64[BPF_REG_0];
>> + struct bpf_prog *p = l->link.prog;
>> + int cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
>> +
>> + if (p->aux->sleepable) {
>> + enter_prog = (u64)__bpf_prog_enter_sleepable;
>> + exit_prog = (u64)__bpf_prog_exit_sleepable;
>> + } else {
>> + enter_prog = (u64)__bpf_prog_enter;
>> + exit_prog = (u64)__bpf_prog_exit;
>> + }
>> +
>> + if (l->cookie == 0) {
>> + /* if cookie is zero, one instruction is enough to store it */
>> + emit(A64_STR64I(A64_ZR, A64_SP, run_ctx_off + cookie_off), ctx);
>> + } else {
>> + emit_a64_mov_i64(A64_R(10), l->cookie, ctx);
>> + emit(A64_STR64I(A64_R(10), A64_SP, run_ctx_off + cookie_off),
>> + ctx);
>> + }
>> +
>> + /* save p to callee saved register x19 to avoid loading p with mov_i64
>> + * each time.
>> + */
>> + emit_addr_mov_i64(A64_R(19), (const u64)p, ctx);
>> +
>> + /* arg1: prog */
>> + emit(A64_MOV(1, A64_R(0), A64_R(19)), ctx);
>> + /* arg2: &run_ctx */
>> + emit(A64_ADD_I(1, A64_R(1), A64_SP, run_ctx_off), ctx);
>> +
>> + emit_call(enter_prog, ctx);
>> +
>> + /* if (__bpf_prog_enter(prog) == 0)
>> + * goto skip_exec_of_prog;
>> + */
>> + branch = ctx->image + ctx->idx;
>> + emit(A64_NOP, ctx);
>> +
>> + /* save return value to callee saved register x20 */
>> + emit(A64_MOV(1, A64_R(20), A64_R(0)), ctx);
>> +
>> + emit(A64_ADD_I(1, A64_R(0), A64_SP, args_off), ctx);
>> + if (!p->jited)
>> + emit_addr_mov_i64(A64_R(1), (const u64)p->insnsi, ctx);
>> +
>> + emit_call((const u64)p->bpf_func, ctx);
>> +
>> + /* store return value, which is held in r0 for JIT and in x0
>> + * for interpreter.
>> + */
>> + if (save_ret)
>> + emit(A64_STR64I(p->jited ? r0 : A64_R(0), A64_SP, retval_off),
>> + ctx);
>
> This should be only A64_R(0), not r0. r0 happens to equal A64_R(0) when
> jitted due to the way build_epilogue() builds the function at the moment,
> but we shouldn't rely on that.
>
looks like I misunderstood something, will change it to:
/* store return value, which is held in x0 for interpreter and in
* bpf register r0 for JIT, but r0 happens to equal x0 due to the
* way build_epilogue() builds the JIT image.
*/
if (save_ret)
emit(A64_STR64I(A64_R(0), A64_SP, retval_off), ctx);
> Apart from that, for the series
>
> Reviewed-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
>
> .
