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Message-ID: <CAEyhmHQKBQbidX_SpUF1ZPv7vkkhSR_UuRvxznyb6y5GYQS3qw@mail.gmail.com>
Date: Mon, 28 Jul 2025 18:55:52 +0800
From: Hengqi Chen <hengqi.chen@...il.com>
To: Chenghao Duan <duanchenghao@...inos.cn>
Cc: ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
yangtiezhu@...ngson.cn, chenhuacai@...nel.org, martin.lau@...ux.dev,
eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev,
john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me,
haoluo@...gle.com, jolsa@...nel.org, kernel@...0n.name,
linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev, bpf@...r.kernel.org,
guodongtai@...inos.cn, youling.tang@...ux.dev, jianghaoran@...inos.cn,
vincent.mc.li@...il.com
Subject: Re: [PATCH v4 5/5] LoongArch: BPF: Add struct ops support for trampoline
On Thu, Jul 24, 2025 at 10:22 PM Chenghao Duan <duanchenghao@...inos.cn> wrote:
>
> From: Tiezhu Yang <yangtiezhu@...ngson.cn>
>
> Use BPF_TRAMP_F_INDIRECT flag to detect struct ops and emit proper
> prologue and epilogue for this case.
>
> With this patch, all of the struct_ops related testcases (except
> struct_ops_multi_pages) passed on LoongArch.
>
> The testcase struct_ops_multi_pages failed is because the actual
> image_pages_cnt is 40 which is bigger than MAX_TRAMP_IMAGE_PAGES.
>
> Before:
>
> $ sudo ./test_progs -t struct_ops -d struct_ops_multi_pages
> ...
> WATCHDOG: test case struct_ops_module/struct_ops_load executes for 10 seconds...
>
> After:
>
> $ sudo ./test_progs -t struct_ops -d struct_ops_multi_pages
> ...
> #15 bad_struct_ops:OK
> ...
> #399 struct_ops_autocreate:OK
> ...
> #400 struct_ops_kptr_return:OK
> ...
> #401 struct_ops_maybe_null:OK
> ...
> #402 struct_ops_module:OK
> ...
> #404 struct_ops_no_cfi:OK
> ...
> #405 struct_ops_private_stack:SKIP
> ...
> #406 struct_ops_refcounted:OK
> Summary: 8/25 PASSED, 3 SKIPPED, 0 FAILED
>
> Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
> ---
> arch/loongarch/net/bpf_jit.c | 71 ++++++++++++++++++++++++------------
> 1 file changed, 47 insertions(+), 24 deletions(-)
>
> diff --git a/arch/loongarch/net/bpf_jit.c b/arch/loongarch/net/bpf_jit.c
> index ac5ce3a28..6a84fb104 100644
> --- a/arch/loongarch/net/bpf_jit.c
> +++ b/arch/loongarch/net/bpf_jit.c
> @@ -1603,6 +1603,7 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
> struct bpf_tramp_links *fentry = &tlinks[BPF_TRAMP_FENTRY];
> struct bpf_tramp_links *fexit = &tlinks[BPF_TRAMP_FEXIT];
> struct bpf_tramp_links *fmod_ret = &tlinks[BPF_TRAMP_MODIFY_RETURN];
> + bool is_struct_ops = flags & BPF_TRAMP_F_INDIRECT;
> int ret, save_ret;
> void *orig_call = func_addr;
> u32 **branches = NULL;
> @@ -1678,18 +1679,31 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
>
> stack_size = round_up(stack_size, 16);
>
> - /* For the trampoline called from function entry */
> - /* RA and FP for parent function*/
> - emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, -16);
> - emit_insn(ctx, std, LOONGARCH_GPR_RA, LOONGARCH_GPR_SP, 8);
> - emit_insn(ctx, std, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, 0);
> - emit_insn(ctx, addid, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, 16);
> -
> - /* RA and FP for traced function*/
> - emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, -stack_size);
> - emit_insn(ctx, std, LOONGARCH_GPR_T0, LOONGARCH_GPR_SP, stack_size - 8);
> - emit_insn(ctx, std, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_size - 16);
> - emit_insn(ctx, addid, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_size);
> + if (!is_struct_ops) {
> + /*
> + * For the trampoline called from function entry,
> + * the frame of traced function and the frame of
> + * trampoline need to be considered.
> + */
> + emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, -16);
> + emit_insn(ctx, std, LOONGARCH_GPR_RA, LOONGARCH_GPR_SP, 8);
> + emit_insn(ctx, std, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, 0);
> + emit_insn(ctx, addid, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, 16);
> +
> + emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, -stack_size);
> + emit_insn(ctx, std, LOONGARCH_GPR_T0, LOONGARCH_GPR_SP, stack_size - 8);
> + emit_insn(ctx, std, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_size - 16);
> + emit_insn(ctx, addid, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_size);
> + } else {
> + /*
> + * For the trampoline called directly, just handle
> + * the frame of trampoline.
> + */
> + emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, -stack_size);
> + emit_insn(ctx, std, LOONGARCH_GPR_RA, LOONGARCH_GPR_SP, stack_size - 8);
> + emit_insn(ctx, std, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_size - 16);
> + emit_insn(ctx, addid, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_size);
> + }
>
The diff removes code added in patch 4/5, this should be squashed to
the trampoline patch if possible.
> /* callee saved register S1 to pass start time */
> emit_insn(ctx, std, LOONGARCH_GPR_S1, LOONGARCH_GPR_FP, -sreg_off);
> @@ -1779,21 +1793,30 @@ static int __arch_prepare_bpf_trampoline(struct jit_ctx *ctx, struct bpf_tramp_i
>
> emit_insn(ctx, ldd, LOONGARCH_GPR_S1, LOONGARCH_GPR_FP, -sreg_off);
>
> - /* trampoline called from function entry */
> - emit_insn(ctx, ldd, LOONGARCH_GPR_T0, LOONGARCH_GPR_SP, stack_size - 8);
> - emit_insn(ctx, ldd, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_size - 16);
> - emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, stack_size);
> + if (!is_struct_ops) {
> + /* trampoline called from function entry */
> + emit_insn(ctx, ldd, LOONGARCH_GPR_T0, LOONGARCH_GPR_SP, stack_size - 8);
> + emit_insn(ctx, ldd, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_size - 16);
> + emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, stack_size);
> +
> + emit_insn(ctx, ldd, LOONGARCH_GPR_RA, LOONGARCH_GPR_SP, 8);
> + emit_insn(ctx, ldd, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, 0);
> + emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, 16);
>
> - emit_insn(ctx, ldd, LOONGARCH_GPR_RA, LOONGARCH_GPR_SP, 8);
> - emit_insn(ctx, ldd, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, 0);
> - emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, 16);
> + if (flags & BPF_TRAMP_F_SKIP_FRAME)
> + /* return to parent function */
> + emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_RA, 0);
> + else
> + /* return to traced function */
> + emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_T0, 0);
> + } else {
> + /* trampoline called directly */
> + emit_insn(ctx, ldd, LOONGARCH_GPR_RA, LOONGARCH_GPR_SP, stack_size - 8);
> + emit_insn(ctx, ldd, LOONGARCH_GPR_FP, LOONGARCH_GPR_SP, stack_size - 16);
> + emit_insn(ctx, addid, LOONGARCH_GPR_SP, LOONGARCH_GPR_SP, stack_size);
>
> - if (flags & BPF_TRAMP_F_SKIP_FRAME)
> - /* return to parent function */
> emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_RA, 0);
> - else
> - /* return to traced function */
> - emit_insn(ctx, jirl, LOONGARCH_GPR_ZERO, LOONGARCH_GPR_T0, 0);
> + }
>
> ret = ctx->idx;
> out:
> --
> 2.25.1
>
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