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[76.146.13.146]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2210001ea01sm110875785ad.176.2025.02.21.08.47.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Feb 2025 08:47:30 -0800 (PST) From: Amery Hung To: bpf@vger.kernel.org Cc: daniel@iogearbox.net, andrii@kernel.org, alexei.starovoitov@gmail.com, martin.lau@kernel.org, eddyz87@gmail.com, ameryhung@gmail.com, kernel-team@meta.com Subject: [PATCH bpf-next v3 1/2] bpf: Search and add kfuncs in struct_ops prologue and epilogue Date: Fri, 21 Feb 2025 08:47:20 -0800 Message-ID: <20250221164721.1794729-1-ameryhung@gmail.com> X-Mailer: git-send-email 2.47.1 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net From: Amery Hung Currently, add_kfunc_call() is only invoked once before the main verification loop. Therefore, the verifier could not find the bpf_kfunc_btf_tab of a new kfunc call which is not seen in user defined struct_ops operators but introduced in gen_prologue or gen_epilogue during do_misc_fixup(). Fix this by searching kfuncs in the patching instruction buffer and add them to prog->aux->kfunc_tab. Signed-off-by: Amery Hung Acked-by: Eduard Zingerman --- kernel/bpf/verifier.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8f1df279e432..212b487fd39d 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3215,6 +3215,21 @@ bpf_jit_find_kfunc_model(const struct bpf_prog *prog, return res ? &res->func_model : NULL; } +static int add_kfunc_in_insns(struct bpf_verifier_env *env, + struct bpf_insn *insn, int cnt) +{ + int i, ret; + + for (i = 0; i < cnt; i++, insn++) { + if (bpf_pseudo_kfunc_call(insn)) { + ret = add_kfunc_call(env, insn->imm, insn->off); + if (ret < 0) + return ret; + } + } + return 0; +} + static int add_subprog_and_kfunc(struct bpf_verifier_env *env) { struct bpf_subprog_info *subprog = env->subprog_info; @@ -20368,7 +20383,7 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) { struct bpf_subprog_info *subprogs = env->subprog_info; const struct bpf_verifier_ops *ops = env->ops; 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[76.146.13.146]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2210001ea01sm110875785ad.176.2025.02.21.08.47.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 21 Feb 2025 08:47:31 -0800 (PST) From: Amery Hung To: bpf@vger.kernel.org Cc: daniel@iogearbox.net, andrii@kernel.org, alexei.starovoitov@gmail.com, martin.lau@kernel.org, eddyz87@gmail.com, ameryhung@gmail.com, kernel-team@meta.com Subject: [PATCH bpf-next v3 2/2] selftests/bpf: Test gen_pro/epilogue that generate kfuncs Date: Fri, 21 Feb 2025 08:47:21 -0800 Message-ID: <20250221164721.1794729-2-ameryhung@gmail.com> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20250221164721.1794729-1-ameryhung@gmail.com> References: <20250221164721.1794729-1-ameryhung@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Patchwork-Delegate: bpf@iogearbox.net Test gen_prologue and gen_epilogue that generate kfuncs that have not been seen in the main program. The main bpf program and return value checks are identical to pro_epilogue.c introduced in commit 47e69431b57a ("selftests/bpf: Test gen_prologue and gen_epilogue"). However, now when bpf_testmod_st_ops detects a program name with prefix "test_kfunc_", it generates slightly different prologue and epilogue: They still add 1000 to args->a in prologue, add 10000 to args->a and set r0 to 2 * args->a in epilogue, but involve kfuncs. At high level, the alternative version of prologue and epilogue look like this: cgrp = bpf_cgroup_from_id(0); if (cgrp) bpf_cgroup_release(cgrp); else /* Perform what original bpf_testmod_st_ops prologue or * epilogue does */ Since 0 is never a valid cgroup id, the original prologue or epilogue logic will be performed. As a result, the __retval check should expect the exact same return value. Signed-off-by: Amery Hung --- include/linux/filter.h | 10 +++ kernel/bpf/btf.c | 1 + .../selftests/bpf/prog_tests/pro_epilogue.c | 2 + .../bpf/progs/pro_epilogue_with_kfunc.c | 87 ++++++++++++++++++ .../selftests/bpf/test_kmods/bpf_testmod.c | 90 +++++++++++++++++++ 5 files changed, 190 insertions(+) create mode 100644 tools/testing/selftests/bpf/progs/pro_epilogue_with_kfunc.c diff --git a/include/linux/filter.h b/include/linux/filter.h index a3ea46281595..3ed6eb9e7c73 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -469,6 +469,16 @@ static inline bool insn_is_cast_user(const struct bpf_insn *insn) .off = 0, \ .imm = BPF_CALL_IMM(FUNC) }) +/* Kfunc call */ + +#define BPF_CALL_KFUNC(OFF, IMM) \ + ((struct bpf_insn) { \ + .code = BPF_JMP | BPF_CALL, \ + .dst_reg = 0, \ + .src_reg = BPF_PSEUDO_KFUNC_CALL, \ + .off = OFF, \ + .imm = IMM }) + /* Raw code statement block */ #define BPF_RAW_INSN(CODE, DST, SRC, OFF, IMM) \ diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index 7a7e02dcde84..1927d7e53b5a 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -606,6 +606,7 @@ s32 bpf_find_btf_id(const char *name, u32 kind, struct btf **btf_p) spin_unlock_bh(&btf_idr_lock); return ret; } +EXPORT_SYMBOL_GPL(bpf_find_btf_id); const struct btf_type *btf_type_skip_modifiers(const struct btf *btf, u32 id, u32 *res_id) diff --git a/tools/testing/selftests/bpf/prog_tests/pro_epilogue.c b/tools/testing/selftests/bpf/prog_tests/pro_epilogue.c index 509883e6823a..5d3c00a08a88 100644 --- a/tools/testing/selftests/bpf/prog_tests/pro_epilogue.c +++ b/tools/testing/selftests/bpf/prog_tests/pro_epilogue.c @@ -6,6 +6,7 @@ #include "epilogue_tailcall.skel.h" #include "pro_epilogue_goto_start.skel.h" #include "epilogue_exit.skel.h" +#include "pro_epilogue_with_kfunc.skel.h" struct st_ops_args { __u64 a; @@ -55,6 +56,7 @@ void test_pro_epilogue(void) RUN_TESTS(pro_epilogue); RUN_TESTS(pro_epilogue_goto_start); RUN_TESTS(epilogue_exit); + RUN_TESTS(pro_epilogue_with_kfunc); if (test__start_subtest("tailcall")) test_tailcall(); } diff --git a/tools/testing/selftests/bpf/progs/pro_epilogue_with_kfunc.c b/tools/testing/selftests/bpf/progs/pro_epilogue_with_kfunc.c new file mode 100644 index 000000000000..52175716d5f9 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/pro_epilogue_with_kfunc.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */ + +#include +#include +#include "bpf_misc.h" +#include "../test_kmods/bpf_testmod.h" +#include "../test_kmods/bpf_testmod_kfunc.h" + +char _license[] SEC("license") = "GPL"; + +void __kfunc_btf_root(void) +{ + bpf_kfunc_st_ops_inc10(NULL); +} + +static __noinline __used int subprog(struct st_ops_args *args) +{ + args->a += 1; + return args->a; +} + +__success +/* prologue */ +__xlated("0: r8 = r1") +__xlated("1: r1 = 0") +__xlated("2: call kernel-function") +__xlated("3: if r0 != 0x0 goto pc+5") +__xlated("4: r6 = *(u64 *)(r8 +0)") +__xlated("5: r7 = *(u64 *)(r6 +0)") +__xlated("6: r7 += 1000") +__xlated("7: *(u64 *)(r6 +0) = r7") +__xlated("8: goto pc+2") +__xlated("9: r1 = r0") +__xlated("10: call kernel-function") +__xlated("11: r1 = r8") +/* save __u64 *ctx to stack */ +__xlated("12: *(u64 *)(r10 -8) = r1") +/* main prog */ +__xlated("13: r1 = *(u64 *)(r1 +0)") +__xlated("14: r6 = r1") +__xlated("15: call kernel-function") +__xlated("16: r1 = r6") +__xlated("17: call pc+") +/* epilogue */ +__xlated("18: r1 = 0") +__xlated("19: call kernel-function") +__xlated("20: if r0 != 0x0 goto pc+6") +__xlated("21: r1 = *(u64 *)(r10 -8)") +__xlated("22: r1 = *(u64 *)(r1 +0)") +__xlated("23: r6 = *(u64 *)(r1 +0)") +__xlated("24: r6 += 10000") +__xlated("25: *(u64 *)(r1 +0) = r6") +__xlated("26: goto pc+2") +__xlated("27: r1 = r0") +__xlated("28: call kernel-function") +__xlated("29: r0 = r6") +__xlated("30: r0 *= 2") +__xlated("31: exit") +SEC("struct_ops/test_pro_epilogue") +__naked int test_kfunc_pro_epilogue(void) +{ + asm volatile ( + "r1 = *(u64 *)(r1 +0);" + "r6 = r1;" + "call %[bpf_kfunc_st_ops_inc10];" + "r1 = r6;" + "call subprog;" + "exit;" + : + : __imm(bpf_kfunc_st_ops_inc10) + : __clobber_all); +} + +SEC("syscall") +__retval(22022) /* (PROLOGUE_A [1000] + KFUNC_INC10 + SUBPROG_A [1] + EPILOGUE_A [10000]) * 2 */ +int syscall_pro_epilogue(void *ctx) +{ + struct st_ops_args args = {}; + + return bpf_kfunc_st_ops_test_pro_epilogue(&args); +} + +SEC(".struct_ops.link") +struct bpf_testmod_st_ops pro_epilogue_with_kfunc = { + .test_pro_epilogue = (void *)test_kfunc_pro_epilogue, +}; diff --git a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c index 578bfc40dd05..ba250e5d0b3e 100644 --- a/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c +++ b/tools/testing/selftests/bpf/test_kmods/bpf_testmod.c @@ -1309,6 +1309,83 @@ static int bpf_test_mod_st_ops__test_pro_epilogue(struct st_ops_args *args) return 0; } +static int bpf_cgroup_from_id_id; +static int bpf_cgroup_release_id; + +static int st_ops_gen_prologue_with_kfunc(struct bpf_insn *insn_buf, bool direct_write, + const struct bpf_prog *prog) +{ + struct bpf_insn *insn = insn_buf; + + /* r8 = r1; // r8 will be "u64 *ctx". + * r1 = 0; + * r0 = bpf_cgroup_from_id(r1); + * if r0 != 0 goto pc+5; + * r6 = r8[0]; // r6 will be "struct st_ops *args". + * r7 = r6->a; + * r7 += 1000; + * r6->a = r7; + * goto pc+2; + * r1 = r0; + * bpf_cgroup_release(r1); + * r1 = r8; + */ + *insn++ = BPF_MOV64_REG(BPF_REG_8, BPF_REG_1); + *insn++ = BPF_MOV64_IMM(BPF_REG_1, 0); + *insn++ = BPF_CALL_KFUNC(0, bpf_cgroup_from_id_id); + *insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 5); + *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_8, 0); + *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_7, BPF_REG_6, offsetof(struct st_ops_args, a)); + *insn++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_7, 1000); + *insn++ = BPF_STX_MEM(BPF_DW, BPF_REG_6, BPF_REG_7, offsetof(struct st_ops_args, a)); + *insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 2); + *insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_0); + *insn++ = BPF_CALL_KFUNC(0, bpf_cgroup_release_id), + *insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_8); + *insn++ = prog->insnsi[0]; + + return insn - insn_buf; +} + +static int st_ops_gen_epilogue_with_kfunc(struct bpf_insn *insn_buf, const struct bpf_prog *prog, + s16 ctx_stack_off) +{ + struct bpf_insn *insn = insn_buf; + + /* r1 = 0; + * r0 = bpf_cgroup_from_id(r1); + * if r0 != 0 goto pc+6; + * r1 = stack[ctx_stack_off]; // r1 will be "u64 *ctx" + * r1 = r1[0]; // r1 will be "struct st_ops *args" + * r6 = r1->a; + * r6 += 10000; + * r1->a = r6; + * goto pc+2 + * r1 = r0; + * bpf_cgroup_release(r1); + * r0 = r6; + * r0 *= 2; + * BPF_EXIT; + */ + *insn++ = BPF_MOV64_IMM(BPF_REG_1, 0); + *insn++ = BPF_CALL_KFUNC(0, bpf_cgroup_from_id_id); + *insn++ = BPF_JMP_IMM(BPF_JNE, BPF_REG_0, 0, 6); + *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_FP, ctx_stack_off); + *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_1, BPF_REG_1, 0); + *insn++ = BPF_LDX_MEM(BPF_DW, BPF_REG_6, BPF_REG_1, offsetof(struct st_ops_args, a)); + *insn++ = BPF_ALU64_IMM(BPF_ADD, BPF_REG_6, 10000); + *insn++ = BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_6, offsetof(struct st_ops_args, a)); + *insn++ = BPF_JMP_IMM(BPF_JA, 0, 0, 2); + *insn++ = BPF_MOV64_REG(BPF_REG_1, BPF_REG_0); + *insn++ = BPF_CALL_KFUNC(0, bpf_cgroup_release_id), + *insn++ = BPF_MOV64_REG(BPF_REG_0, BPF_REG_6); + *insn++ = BPF_ALU64_IMM(BPF_MUL, BPF_REG_0, 2); + *insn++ = BPF_EXIT_INSN(); + + return insn - insn_buf; +} + +#define KFUNC_PRO_EPI_PREFIX "test_kfunc_" static int st_ops_gen_prologue(struct bpf_insn *insn_buf, bool direct_write, const struct bpf_prog *prog) { @@ -1318,6 +1395,9 @@ static int st_ops_gen_prologue(struct bpf_insn *insn_buf, bool direct_write, strcmp(prog->aux->attach_func_name, "test_pro_epilogue")) return 0; + if (!strncmp(prog->aux->name, KFUNC_PRO_EPI_PREFIX, strlen(KFUNC_PRO_EPI_PREFIX))) + return st_ops_gen_prologue_with_kfunc(insn_buf, direct_write, prog); + /* r6 = r1[0]; // r6 will be "struct st_ops *args". r1 is "u64 *ctx". * r7 = r6->a; * r7 += 1000; @@ -1341,6 +1421,9 @@ static int st_ops_gen_epilogue(struct bpf_insn *insn_buf, const struct bpf_prog strcmp(prog->aux->attach_func_name, "test_pro_epilogue")) return 0; + if (!strncmp(prog->aux->name, KFUNC_PRO_EPI_PREFIX, strlen(KFUNC_PRO_EPI_PREFIX))) + return st_ops_gen_epilogue_with_kfunc(insn_buf, prog, ctx_stack_off); + /* r1 = stack[ctx_stack_off]; // r1 will be "u64 *ctx" * r1 = r1[0]; // r1 will be "struct st_ops *args" * r6 = r1->a; @@ -1411,6 +1494,13 @@ static void st_ops_unreg(void *kdata, struct bpf_link *link) static int st_ops_init(struct btf *btf) { + struct btf *kfunc_btf; + + bpf_cgroup_from_id_id = bpf_find_btf_id("bpf_cgroup_from_id", BTF_KIND_FUNC, &kfunc_btf); + bpf_cgroup_release_id = bpf_find_btf_id("bpf_cgroup_release", BTF_KIND_FUNC, &kfunc_btf); + if (!bpf_cgroup_from_id_id || !bpf_cgroup_release_id) + return -EINVAL; + return 0; }