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Date: Mon, 11 Jul 2022 12:57:52 +0100 From: Jean-Philippe Brucker <jean-philippe@...aro.org> To: Xu Kuohai <xukuohai@...wei.com> Cc: bpf@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, Will Deacon <will@...nel.org>, KP Singh <kpsingh@...nel.org>, Mark Rutland <mark.rutland@....com>, Catalin Marinas <catalin.marinas@....com>, Daniel Borkmann <daniel@...earbox.net>, Alexei Starovoitov <ast@...nel.org>, Andrii Nakryiko <andrii@...nel.org>, Zi Shen Lim <zlim.lnx@...il.com>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, "David S . Miller" <davem@...emloft.net>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, David Ahern <dsahern@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>, Jakub Kicinski <kuba@...nel.org>, Jesper Dangaard Brouer <hawk@...nel.org>, Russell King <rmk+kernel@...linux.org.uk>, James Morse <james.morse@....com>, Hou Tao <houtao1@...wei.com>, Jason Wang <wangborong@...rlc.com> Subject: Re: [PATCH bpf-next v7 4/4] bpf, arm64: bpf trampoline for arm64 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. Apart from that, for the series Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
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