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Message-ID: <CAAhV-H5yPPcU03MGenKDH=sUTkmMPnsGj13zkLA1h-uHVMcHOQ@mail.gmail.com>
Date: Wed, 16 Jul 2025 12:42:24 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Tiezhu Yang <yangtiezhu@...ngson.cn>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
Andrii Nakryiko <andrii@...nel.org>, Hengqi Chen <hengqi.chen@...il.com>, bpf@...r.kernel.org,
loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] LoongArch: BPF: Add struct ops support for trampoline
Hi, Tiezhu,
I hope this patch can be squashed to V4 of chenghao's patchset, as a
co-developer.
Huacai
On Wed, Jul 16, 2025 at 12:39 PM Tiezhu Yang <yangtiezhu@...ngson.cn> wrote:
>
> 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>
> ---
>
> This is a RFC patch, based on 6.16-rc6 and the following series:
>
> [PATCH v3 0/5] Support trampoline for LoongArch
> https://lore.kernel.org/loongarch/20250709055029.723243-1-duanchenghao@kylinos.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 6820558afce5..7663b84a4ff1 100644
> --- a/arch/loongarch/net/bpf_jit.c
> +++ b/arch/loongarch/net/bpf_jit.c
> @@ -1599,6 +1599,7 @@ 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;
> @@ -1674,18 +1675,31 @@ 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);
> + }
>
> /* callee saved register S1 to pass start time */
> emit_insn(ctx, std, LOONGARCH_GPR_S1, LOONGARCH_GPR_FP, -sreg_off);
> @@ -1772,21 +1786,30 @@ 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:
> --
> 2.42.0
>
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