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Mon, 28 Jul 2025 21:34:37 +0800 Date: Mon, 28 Jul 2025 21:34:18 +0800 From: Chenghao Duan To: Hengqi Chen Cc: ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, yangtiezhu@loongson.cn, chenhuacai@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, kernel@xen0n.name, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, bpf@vger.kernel.org, guodongtai@kylinos.cn, youling.tang@linux.dev, jianghaoran@kylinos.cn, vincent.mc.li@gmail.com Subject: Re: [PATCH v4 5/5] LoongArch: BPF: Add struct ops support for trampoline Message-ID: <20250728133418.GC1439240@chenghao-pc> References: <20250724141929.691853-1-duanchenghao@kylinos.cn> <20250724141929.691853-6-duanchenghao@kylinos.cn> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Mon, Jul 28, 2025 at 06:55:52PM +0800, Hengqi Chen wrote: > On Thu, Jul 24, 2025 at 10:22 PM Chenghao Duan wrote: > > > > From: Tiezhu Yang > > > > 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 > > --- > > 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 > >