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Message-ID: <CAAhV-H40rAPvVRMMQTkxmOsT3yu6V+CL3MC2gi3jvsXZtOzdkw@mail.gmail.com>
Date: Tue, 29 Jul 2025 10:32:13 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Chenghao Duan <duanchenghao@...inos.cn>
Cc: Hengqi Chen <hengqi.chen@...il.com>, ast@...nel.org, daniel@...earbox.net,
andrii@...nel.org, yangtiezhu@...ngson.cn, 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 Mon, Jul 28, 2025 at 9:34 PM Chenghao Duan <duanchenghao@...inos.cn> wrote:
>
> On Mon, Jul 28, 2025 at 06:55:52PM +0800, Hengqi Chen wrote:
> > 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.
>
> This patch was provided by Tiezhu Yang, and there was a discussion about
> it at the time.
> https://lore.kernel.org/all/cd190c8a-a7b9-53de-d363-c3d695fe3191@loongson.cn/
>From my opinion I also prefer to squash.
Huacai
>
> >
> > > /* 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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