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Message-ID: <20250728133418.GC1439240@chenghao-pc>
Date: Mon, 28 Jul 2025 21:34:18 +0800
From: Chenghao Duan <duanchenghao@...inos.cn>
To: Hengqi Chen <hengqi.chen@...il.com>
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 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/
>
> > /* 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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