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Thu, 21 Aug 2025 10:32:59 +0000 (GMT) From: Ilya Leoshkevich To: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko Cc: bpf@vger.kernel.org, Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Ilya Leoshkevich Subject: [PATCH bpf-next 1/5] s390/bpf: Add s390 JIT support for timed may_goto Date: Thu, 21 Aug 2025 12:23:37 +0200 Message-ID: <20250821103256.291412-2-iii@linux.ibm.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20250821103256.291412-1-iii@linux.ibm.com> References: <20250821103256.291412-1-iii@linux.ibm.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUwODE5MDIyMiBTYWx0ZWRfXwrACYDZgObmW dUZBLEkpfy6GajJ3mJCFZvO5CVRy19HYD3GVd22g9riEJuAdx/r9tQb+Q+Dx7zDFNNKsMc8cXvk Zl1zkZkjiWt15pOZcVcHZ5FEeW9U2ARyehpS3IHJXxgADg3MausA7w7W0p2IkKYNOXxVVmjL4LT Yncy0svgLbJTv1hHvyFbSL4oLhqR1KOY8/zDEoQOhxI4qBSt+jUrqw9V1ggQvOPQOJzpA+yTx+R pDoB0NdSWy/K0+aD7QqS5fIAkBYUhk5gGJq/8UiD1N8uZ3odTzfNVZ80egwCLVdYnb8QsaFMe2Y +JF/jHrFdws++OV2VYtmUzBPQIkBz7wLaTvr9/VmO9hJjEKpMabQ5CJ1gOOSRDlVuNU8lnd/WdH 6bwcOhwKsNX+05cyOXs8Ds0v4F+N+w== X-Authority-Analysis: v=2.4 cv=H62CA+Yi c=1 sm=1 tr=0 ts=68a6f5e0 cx=c_pps a=aDMHemPKRhS1OARIsFnwRA==:117 a=aDMHemPKRhS1OARIsFnwRA==:17 a=2OwXVqhp2XgA:10 a=VnNF1IyMAAAA:8 a=HY55ynAoVbFXyHn9r_EA:9 X-Proofpoint-ORIG-GUID: OLKs1-nH0GelGhnDqy35dhIiQDHeUeJO X-Proofpoint-GUID: OLKs1-nH0GelGhnDqy35dhIiQDHeUeJO X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1099,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-08-21_02,2025-08-20_03,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 suspectscore=0 bulkscore=0 adultscore=0 phishscore=0 priorityscore=1501 malwarescore=0 spamscore=0 impostorscore=0 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2508110000 definitions=main-2508190222 The verifier provides an architecture-independent implementation of the may_goto instruction, which is currently used on s390x, but it has a downside: there is no way to prevent progs using it from running for a very long time. The solution to this problem is an alternative timed implementation, which requires architecture-specific bits. Its availability is signaled to the verifier by bpf_jit_supports_timed_may_goto() returning true. The verifier then emits a call to arch_bpf_timed_may_goto() using a non-standard calling convention. This function must act as a trampoline for bpf_check_timed_may_goto(). Implement bpf_jit_supports_timed_may_goto(), account for the special calling convention in the BPF_CALL implementation, and implement arch_bpf_timed_may_goto(). Signed-off-by: Ilya Leoshkevich --- arch/s390/net/Makefile | 2 +- arch/s390/net/bpf_jit_comp.c | 25 ++++++++++++++--- arch/s390/net/bpf_timed_may_goto.S | 45 ++++++++++++++++++++++++++++++ 3 files changed, 67 insertions(+), 5 deletions(-) create mode 100644 arch/s390/net/bpf_timed_may_goto.S diff --git a/arch/s390/net/Makefile b/arch/s390/net/Makefile index 8cab6deb0403..9275cf63192a 100644 --- a/arch/s390/net/Makefile +++ b/arch/s390/net/Makefile @@ -2,5 +2,5 @@ # # Arch-specific network modules # -obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o +obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o bpf_timed_may_goto.o obj-$(CONFIG_HAVE_PNETID) += pnet.o diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index fd45f03a213c..8b57d8532f36 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -1806,10 +1806,22 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, } } - /* brasl %r14,func */ - EMIT6_PCREL_RILB_PTR(0xc0050000, REG_14, (void *)func); - /* lgr %b0,%r2: load return value into %b0 */ - EMIT4(0xb9040000, BPF_REG_0, REG_2); + if ((void *)func == arch_bpf_timed_may_goto) { + /* + * arch_bpf_timed_may_goto() has a special ABI: the + * parameters are in BPF_REG_AX and BPF_REG_10; the + * return value is in BPF_REG_AX; and all GPRs except + * REG_W0, REG_W1, and BPF_REG_AX are callee-saved. + */ + + /* brasl %r0,func */ + EMIT6_PCREL_RILB_PTR(0xc0050000, REG_0, (void *)func); + } else { + /* brasl %r14,func */ + EMIT6_PCREL_RILB_PTR(0xc0050000, REG_14, (void *)func); + /* lgr %b0,%r2: load return value into %b0 */ + EMIT4(0xb9040000, BPF_REG_0, REG_2); + } /* * Copy the potentially updated tail call counter back. @@ -2993,3 +3005,8 @@ void arch_bpf_stack_walk(bool (*consume_fn)(void *, u64, u64, u64), prev_addr = addr; } } + +bool bpf_jit_supports_timed_may_goto(void) +{ + return true; +} diff --git a/arch/s390/net/bpf_timed_may_goto.S b/arch/s390/net/bpf_timed_may_goto.S new file mode 100644 index 000000000000..06f567a460d7 --- /dev/null +++ b/arch/s390/net/bpf_timed_may_goto.S @@ -0,0 +1,45 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#include +#include +#include +#include + +#define R2_OFF 0 +#define R5_OFF (R2_OFF + (5 - 2 + 1) * 8) +#define R14_OFF (R5_OFF + 8) +#define RETADDR_OFF (R14_OFF + 8) +#define R15_OFF (RETADDR_OFF + 8) +#define BACKCHAIN_OFF (R15_OFF + 8) +#define FRAME_SIZE (BACKCHAIN_OFF + 8) +#define FRAME_OFF (STACK_FRAME_OVERHEAD - FRAME_SIZE) +#if (FRAME_OFF + BACKCHAIN_OFF) != __SF_BACKCHAIN +#error Stack frame layout calculation is broken +#endif + + GEN_BR_THUNK %r1 + +SYM_FUNC_START(arch_bpf_timed_may_goto) + /* + * This function has a special ABI: the parameters are in %r12 and + * %r13; the return value is in %r12; all GPRs except %r0, %r1, and + * %r12 are callee-saved; and the return address is in %r0. + */ + stmg %r2,%r5,FRAME_OFF+R2_OFF(%r15) + stg %r14,FRAME_OFF+R14_OFF(%r15) + stg %r0,FRAME_OFF+RETADDR_OFF(%r15) + stg %r15,FRAME_OFF+R15_OFF(%r15) + lgr %r1,%r15 + lay %r15,-FRAME_SIZE(%r15) + stg %r1,__SF_BACKCHAIN(%r15) + + lay %r2,0(%r12,%r13) + brasl %r14,bpf_check_timed_may_goto + lgr %r12,%r2 + + lg %r15,FRAME_SIZE+FRAME_OFF+R15_OFF(%r15) + lmg %r2,%r5,FRAME_OFF+R2_OFF(%r15) + lg %r14,FRAME_OFF+R14_OFF(%r15) + lg %r1,FRAME_OFF+RETADDR_OFF(%r15) + BR_EX %r1 +SYM_FUNC_END(arch_bpf_timed_may_goto) -- 2.50.1