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Rao" To: Daniel Borkmann , Alexei Starovoitov , Michael Ellerman , Steven Rostedt Subject: [RFC PATCH 3/3] powerpc64/bpf: Add support for bpf trampolines Date: Mon, 7 Feb 2022 12:37:22 +0530 Message-Id: X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: yqpcW8_Y4XCWOL2OIPsWd9CnBix4oMNs X-Proofpoint-GUID: 8PAdQbMmMQMP4CaSNFGp_B94GbHSCBpl X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-02-07_02,2022-02-03_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 mlxlogscore=999 impostorscore=0 phishscore=0 suspectscore=0 malwarescore=0 mlxscore=0 spamscore=0 priorityscore=1501 clxscore=1015 bulkscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2202070046 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Yauheni Kaliuta , Jordan Niethe , linuxppc-dev@lists.ozlabs.org, bpf@vger.kernel.org, Jiri Olsa , Hari Bathini Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Add support for bpf_arch_text_poke() and arch_prepare_bpf_trampoline() for powerpc64 -mprofile-kernel. We set aside space for two stubs at the beginning of each bpf program. These stubs are used if having to branch to locations outside the range of a branch instruction. BPF Trampolines adhere to the powerpc64 -mprofile-kernel ABI since these need to attach to ftrace locations using ftrace direct attach. Due to this, bpf_arch_text_poke() patches two instructions: 'mflr r0' and 'bl' for BPF_MOD_CALL. The trampoline code itself closely follows the x86 implementation. Signed-off-by: Naveen N. Rao --- arch/powerpc/net/bpf_jit.h | 8 + arch/powerpc/net/bpf_jit_comp.c | 5 +- arch/powerpc/net/bpf_jit_comp64.c | 619 +++++++++++++++++++++++++++++- 3 files changed, 630 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h index 0832235a274983..777b10650678af 100644 --- a/arch/powerpc/net/bpf_jit.h +++ b/arch/powerpc/net/bpf_jit.h @@ -19,6 +19,14 @@ #define FUNCTION_DESCR_SIZE 0 #endif +#ifdef PPC64_ELF_ABI_v2 +#define BPF_TRAMP_STUB_SIZE 32 +#else +#define BPF_TRAMP_STUB_SIZE 0 +#endif + +#define PPC_BPF_MAGIC() (0xeB9FC0DE) + #define PLANT_INSTR(d, idx, instr) \ do { if (d) { (d)[idx] = instr; } idx++; } while (0) #define EMIT(instr) PLANT_INSTR(image, ctx->idx, instr) diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c index 635f7448ff7952..5df2f15bfe4d75 100644 --- a/arch/powerpc/net/bpf_jit_comp.c +++ b/arch/powerpc/net/bpf_jit_comp.c @@ -220,7 +220,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) extable_len = fp->aux->num_exentries * sizeof(struct exception_table_entry); proglen = cgctx.idx * 4; - alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len; + alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len + BPF_TRAMP_STUB_SIZE * 2; bpf_hdr = bpf_jit_binary_alloc(alloclen, &image, 4, bpf_jit_fill_ill_insns); if (!bpf_hdr) { @@ -228,6 +228,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) goto out_addrs; } + image += BPF_TRAMP_STUB_SIZE * 2; + if (extable_len) fp->aux->extable = (void *)image + FUNCTION_DESCR_SIZE + proglen + fixup_len; @@ -251,6 +253,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) } /* Code generation passes 1-2 */ + *(code_base - 1) = PPC_BPF_MAGIC(); for (pass = 1; pass < 3; pass++) { /* Now build the prologue, body code & epilogue for real. */ cgctx.idx = 0; diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index c3cfe1f4338fca..20d8f6e3cc9bb0 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -73,6 +74,10 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx) { int i; + /* two nops for trampoline attach */ + EMIT(PPC_RAW_NOP()); + EMIT(PPC_RAW_NOP()); + #ifdef PPC64_ELF_ABI_v2 PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc)); #else @@ -93,7 +98,7 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx) EMIT(PPC_RAW_NOP()); } -#define BPF_TAILCALL_PROLOGUE_SIZE 12 +#define BPF_TAILCALL_PROLOGUE_SIZE 20 if (bpf_has_stack_frame(ctx)) { /* @@ -1133,3 +1138,615 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * return 0; } + +#ifdef PPC64_ELF_ABI_v2 + +static __always_inline int bpf_check_and_patch(u32 *ip, ppc_inst_t old_inst, ppc_inst_t new_inst) +{ + ppc_inst_t org_inst = ppc_inst_read(ip); + if (!ppc_inst_equal(org_inst, old_inst)) { + pr_info("bpf_check_and_patch: ip: 0x%lx, org_inst(0x%x) != old_inst (0x%x)\n", + (unsigned long)ip, ppc_inst_val(org_inst), ppc_inst_val(old_inst)); + return -EBUSY; + } + if (ppc_inst_equal(org_inst, new_inst)) + return 1; + return patch_instruction(ip, new_inst); +} + +static u32 *bpf_find_existing_stub(u32 *ip, enum bpf_text_poke_type t, void *old_addr) +{ + int branch_flags = t == BPF_MOD_JUMP ? 0 : BRANCH_SET_LINK; + u32 *stub_addr = 0, *stub1, *stub2; + ppc_inst_t org_inst, old_inst; + + if (!old_addr) + return 0; + + stub1 = ip - (BPF_TRAMP_STUB_SIZE / sizeof(u32)) - (t == BPF_MOD_CALL ? 1 : 0); + stub2 = stub1 - (BPF_TRAMP_STUB_SIZE / sizeof(u32)); + org_inst = ppc_inst_read(ip); + if (!create_branch(&old_inst, ip, (unsigned long)stub1, branch_flags) && + ppc_inst_equal(org_inst, old_inst)) + stub_addr = stub1; + if (!create_branch(&old_inst, ip, (unsigned long)stub2, branch_flags) && + ppc_inst_equal(org_inst, old_inst)) + stub_addr = stub2; + + return stub_addr; +} + +static u32 *bpf_setup_stub(u32 *ip, enum bpf_text_poke_type t, void *old_addr, void *new_addr) +{ + u32 *stub_addr, *stub1, *stub2; + ppc_inst_t org_inst, old_inst; + int i, ret; + u32 stub[] = { + PPC_RAW_LIS(12, 0), + PPC_RAW_ORI(12, 12, 0), + PPC_RAW_SLDI(12, 12, 32), + PPC_RAW_ORIS(12, 12, 0), + PPC_RAW_ORI(12, 12, 0), + PPC_RAW_MTCTR(12), + PPC_RAW_BCTR(), + }; + + /* verify we are patching the right location */ + if (t == BPF_MOD_JUMP) + org_inst = ppc_inst_read(ip - 1); + else + org_inst = ppc_inst_read(ip - 2); + old_inst = ppc_inst(PPC_BPF_MAGIC()); + if (!ppc_inst_equal(org_inst, old_inst)) + return 0; + + /* verify existing branch and note down the stub to use */ + stub1 = ip - (BPF_TRAMP_STUB_SIZE / sizeof(u32)) - (t == BPF_MOD_CALL ? 1 : 0); + stub2 = stub1 - (BPF_TRAMP_STUB_SIZE / sizeof(u32)); + stub_addr = 0; + org_inst = ppc_inst_read(ip); + if (old_addr) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + /* existing instruction should branch to one of the two stubs */ + if (!stub_addr) + return 0; + } else { + old_inst = ppc_inst(PPC_RAW_NOP()); + if (!ppc_inst_equal(org_inst, old_inst)) + return 0; + } + if (stub_addr == stub1) + stub_addr = stub2; + else + stub_addr = stub1; + + /* setup stub */ + stub[0] |= IMM_L((unsigned long)new_addr >> 48); + stub[1] |= IMM_L((unsigned long)new_addr >> 32); + stub[3] |= IMM_L((unsigned long)new_addr >> 16); + stub[4] |= IMM_L((unsigned long)new_addr); + for (i = 0; i < sizeof(stub) / sizeof(u32); i++) { + ret = patch_instruction(stub_addr + i, ppc_inst(stub[i])); + if (ret) { + pr_err("bpf: patch_instruction() error while setting up stub: ret %d\n", ret); + return 0; + } + } + + return stub_addr; +} + +int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t, void *old_addr, void *new_addr) +{ + ppc_inst_t org_inst, old_inst, new_inst; + int ret = -EINVAL; + u32 *stub_addr; + + /* We currently only support poking bpf programs */ + if (!is_bpf_text_address((long)ip)) { + pr_info("bpf_arch_text_poke (0x%lx): kernel/modules are not supported\n", (unsigned long)ip); + return -EINVAL; + } + + mutex_lock(&text_mutex); + if (t == BPF_MOD_JUMP) { + /* + * This can point to the beginning of a bpf program, or to certain locations + * within a bpf program. We operate on a single instruction at ip here, + * converting among a nop and an unconditional branch. Depending on branch + * target, we may use the stub area at the beginning of the bpf program and + * we assume that BPF_MOD_JUMP and BPF_MOD_CALL are never used without + * transitioning to a nop. + */ + if (!old_addr && new_addr) { + /* nop -> b */ + old_inst = ppc_inst(PPC_RAW_NOP()); + if (create_branch(&new_inst, (u32 *)ip, (unsigned long)new_addr, 0)) { + stub_addr = bpf_setup_stub(ip, t, old_addr, new_addr); + if (!stub_addr || + create_branch(&new_inst, (u32 *)ip, (unsigned long)stub_addr, 0)) { + ret = -EINVAL; + goto out; + } + } + ret = bpf_check_and_patch(ip, old_inst, new_inst); + } else if (old_addr && !new_addr) { + /* b -> nop */ + new_inst = ppc_inst(PPC_RAW_NOP()); + if (create_branch(&old_inst, (u32 *)ip, (unsigned long)old_addr, 0)) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + if (!stub_addr || + create_branch(&old_inst, (u32 *)ip, (unsigned long)stub_addr, 0)) { + ret = -EINVAL; + goto out; + } + } + ret = bpf_check_and_patch(ip, old_inst, new_inst); + } else if (old_addr && new_addr) { + /* b -> b */ + stub_addr = 0; + if (create_branch(&old_inst, (u32 *)ip, (unsigned long)old_addr, 0)) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + if (!stub_addr || + create_branch(&old_inst, (u32 *)ip, (unsigned long)stub_addr, 0)) { + ret = -EINVAL; + goto out; + } + } + if (create_branch(&new_inst, (u32 *)ip, (unsigned long)new_addr, 0)) { + stub_addr = bpf_setup_stub(ip, t, old_addr, new_addr); + if (!stub_addr || + create_branch(&new_inst, (u32 *)ip, (unsigned long)stub_addr, 0)) { + ret = -EINVAL; + goto out; + } + } + ret = bpf_check_and_patch((u32 *)ip, old_inst, new_inst); + } + } else if (t == BPF_MOD_CALL) { + /* + * For a BPF_MOD_CALL, we expect ip to point at the start of a bpf program. + * We will have to patch two instructions to mimic -mprofile-kernel: a 'mflr r0' + * followed by a 'bl'. Instruction patching order matters: we always patch-in + * the 'mflr r0' first and patch it out the last. + */ + if (!old_addr && new_addr) { + /* nop -> bl */ + + /* confirm that we have two nops */ + old_inst = ppc_inst(PPC_RAW_NOP()); + org_inst = ppc_inst_read(ip); + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + org_inst = ppc_inst_read((u32 *)ip + 1); + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + + /* patch in the mflr */ + new_inst = ppc_inst(PPC_RAW_MFLR(_R0)); + ret = bpf_check_and_patch(ip, old_inst, new_inst); + if (ret) + goto out; + + /* prep the stub if needed */ + ip = (u32 *)ip + 1; + if (create_branch(&new_inst, (u32 *)ip, (unsigned long)new_addr, BRANCH_SET_LINK)) { + stub_addr = bpf_setup_stub(ip, t, old_addr, new_addr); + if (!stub_addr || + create_branch(&new_inst, (u32 *)ip, (unsigned long)stub_addr, BRANCH_SET_LINK)) { + ret = -EINVAL; + goto out; + } + } + + synchronize_rcu(); + + /* patch in the bl */ + ret = bpf_check_and_patch(ip, old_inst, new_inst); + } else if (old_addr && !new_addr) { + /* bl -> nop */ + + /* confirm the expected instruction sequence */ + old_inst = ppc_inst(PPC_RAW_MFLR(_R0)); + org_inst = ppc_inst_read(ip); + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + ip = (u32 *)ip + 1; + org_inst = ppc_inst_read(ip); + if (create_branch(&old_inst, (u32 *)ip, (unsigned long)old_addr, BRANCH_SET_LINK)) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + if (!stub_addr || + create_branch(&old_inst, (u32 *)ip, (unsigned long)stub_addr, BRANCH_SET_LINK)) { + ret = -EINVAL; + goto out; + } + } + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + + /* patch out the branch first */ + new_inst = ppc_inst(PPC_RAW_NOP()); + ret = bpf_check_and_patch(ip, old_inst, new_inst); + if (ret) + goto out; + + synchronize_rcu(); + + /* then, the mflr */ + old_inst = ppc_inst(PPC_RAW_MFLR(_R0)); + ret = bpf_check_and_patch((u32 *)ip - 1, old_inst, new_inst); + } else if (old_addr && new_addr) { + /* bl -> bl */ + + /* confirm the expected instruction sequence */ + old_inst = ppc_inst(PPC_RAW_MFLR(_R0)); + org_inst = ppc_inst_read(ip); + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + ip = (u32 *)ip + 1; + org_inst = ppc_inst_read(ip); + if (create_branch(&old_inst, (u32 *)ip, (unsigned long)old_addr, BRANCH_SET_LINK)) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + if (!stub_addr || + create_branch(&old_inst, (u32 *)ip, (unsigned long)stub_addr, BRANCH_SET_LINK)) { + ret = -EINVAL; + goto out; + } + } + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + + /* setup the new branch */ + if (create_branch(&new_inst, (u32 *)ip, (unsigned long)new_addr, BRANCH_SET_LINK)) { + stub_addr = bpf_setup_stub(ip, t, old_addr, new_addr); + if (!stub_addr || + create_branch(&new_inst, (u32 *)ip, (unsigned long)stub_addr, BRANCH_SET_LINK)) { + ret = -EINVAL; + goto out; + } + } + ret = bpf_check_and_patch(ip, old_inst, new_inst); + } + } + +out: + mutex_unlock(&text_mutex); + return ret; +} + +/* + * BPF Trampoline stack frame layout: + * + * [ prev sp ] <----- + * [ BPF_TRAMP_R26_SAVE ] 8 | + * [ BPF_TRAMP_R25_SAVE ] 8 | + * [ BPF_TRAMP_LR_SAVE ] 8 | + * [ ret val ] 8 | + * [ BPF_TRAMP_PROG_CTX ] 8 * 8 | + * [ BPF_TRAMP_FUNC_ARG_CNT] 8 | + * [ BPF_TRAMP_FUNC_IP ] 8 | + * sp (r1) ---> [ stack frame header ] ------ + */ + +/* stack frame header + data, quadword aligned */ +#define BPF_TRAMP_FRAME_SIZE (STACK_FRAME_MIN_SIZE + (14 * 8)) + +/* The below are offsets from r1 */ +/* upto 8 dword func parameters, as bpf prog ctx */ +#define BPF_TRAMP_PROG_CTX (STACK_FRAME_MIN_SIZE + 16) +/* bpf_get_func_arg_cnt() needs this before prog ctx */ +#define BPF_TRAMP_FUNC_ARG_CNT (BPF_TRAMP_PROG_CTX - 8) +/* bpf_get_func_ip() needs this here */ +#define BPF_TRAMP_FUNC_IP (BPF_TRAMP_PROG_CTX - 16) +/* lr save area, after space for upto 8 args followed by retval of orig_call/fentry progs */ +#define BPF_TRAMP_LR_SAVE (BPF_TRAMP_PROG_CTX + (8 * 8) + 8) +#define BPF_TRAMP_R25_SAVE (BPF_TRAMP_LR_SAVE + 8) +#define BPF_TRAMP_R26_SAVE (BPF_TRAMP_R25_SAVE + 8) + +#define BPF_INSN_SAFETY 64 + +static int invoke_bpf_prog(const struct btf_func_model *m, u32 *image, struct codegen_context *ctx, + struct bpf_prog *p, bool save_ret) +{ + ppc_inst_t branch_insn; + u32 jmp_idx; + int ret; + + /* __bpf_prog_enter(p) */ + PPC_LI64(_R3, (unsigned long)p); + EMIT(PPC_RAW_MR(_R25, _R3)); + ret = bpf_jit_emit_func_call_hlp(image, ctx, + p->aux->sleepable ? (u64)__bpf_prog_enter_sleepable : (u64)__bpf_prog_enter); + if (ret) + return ret; + + /* remember prog start time returned by __bpf_prog_enter */ + EMIT(PPC_RAW_MR(_R26, _R3)); + + /* + * if (__bpf_prog_enter(p) == 0) + * goto skip_exec_of_prog; + * + * emit a nop to be later patched with conditional branch, once offset is known + */ + EMIT(PPC_RAW_CMPDI(_R3, 0)); + jmp_idx = ctx->idx; + EMIT(PPC_RAW_NOP()); + + /* p->bpf_func() */ + EMIT(PPC_RAW_ADDI(_R3, _R1, BPF_TRAMP_PROG_CTX)); + if (!p->jited) + PPC_LI64(_R4, (unsigned long)p->insnsi); + if (is_offset_in_branch_range((unsigned long)p->bpf_func - (unsigned long)&image[ctx->idx])) { + PPC_BL((unsigned long)p->bpf_func); + } else { + PPC_BPF_LL(_R12, _R25, offsetof(struct bpf_prog, bpf_func)); + EMIT(PPC_RAW_MTCTR(_R12)); + EMIT(PPC_RAW_BCTRL()); + } + + if (save_ret) + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_PROG_CTX + (m->nr_args * 8)); + + /* fix up branch */ + if (create_cond_branch(&branch_insn, &image[jmp_idx], (unsigned long)&image[ctx->idx], COND_EQ << 16)) + return -EINVAL; + image[jmp_idx] = ppc_inst_val(branch_insn); + + /* __bpf_prog_exit(p, start_time) */ + EMIT(PPC_RAW_MR(_R3, _R25)); + EMIT(PPC_RAW_MR(_R4, _R26)); + ret = bpf_jit_emit_func_call_hlp(image, ctx, + p->aux->sleepable ? (u64)__bpf_prog_exit_sleepable : (u64)__bpf_prog_exit); + if (ret) + return ret; + + return 0; +} + +static int invoke_bpf(const struct btf_func_model *m, u32 *image, struct codegen_context *ctx, + struct bpf_tramp_progs *tp, bool save_ret) +{ + int i; + + for (i = 0; i < tp->nr_progs; i++) { + if (invoke_bpf_prog(m, image, ctx, tp->progs[i], save_ret)) + return -EINVAL; + } + + return 0; +} + +static int invoke_bpf_mod_ret(const struct btf_func_model *m, u32 *image, struct codegen_context *ctx, + struct bpf_tramp_progs *tp, u32 *branches) +{ + int i; + + /* + * The first fmod_ret program will receive a garbage return value. + * Set this to 0 to avoid confusing the program. + */ + EMIT(PPC_RAW_LI(_R3, 0)); + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_PROG_CTX + (m->nr_args * 8)); + for (i = 0; i < tp->nr_progs; i++) { + if (invoke_bpf_prog(m, image, ctx, tp->progs[i], true)) + return -EINVAL; + + /* + * mod_ret prog stored return value after prog ctx. Emit: + * if (*(u64 *)(ret_val) != 0) + * goto do_fexit; + */ + PPC_BPF_LL(_R3, _R1, BPF_TRAMP_PROG_CTX + (m->nr_args * 8)); + EMIT(PPC_RAW_CMPDI(_R3, 0)); + + /* + * Save the location of the branch and generate a nop, which is + * replaced with a conditional jump once do_fexit (i.e. the + * start of the fexit invocation) is finalized. + */ + branches[i] = ctx->idx; + EMIT(PPC_RAW_NOP()); + } + + return 0; +} + +static bool is_valid_bpf_tramp_flags(unsigned int flags) +{ + if ((flags & BPF_TRAMP_F_RESTORE_REGS) && (flags & BPF_TRAMP_F_SKIP_FRAME)) + return false; + + /* We only support attaching to function entry */ + if ((flags & BPF_TRAMP_F_CALL_ORIG) && !(flags & BPF_TRAMP_F_SKIP_FRAME)) + return false; + + /* BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops, and it must be used alone */ + if ((flags & BPF_TRAMP_F_RET_FENTRY_RET) && (flags & ~BPF_TRAMP_F_RET_FENTRY_RET)) + return false; + + return true; +} + +/* + * We assume that orig_call is what this trampoline is being attached to and we use the link + * register for BPF_TRAMP_F_CALL_ORIG -- see is_valid_bpf_tramp_flags() for validating this. + */ +int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image_start, void *image_end, + const struct btf_func_model *m, u32 flags, + struct bpf_tramp_progs *tprogs, + void *orig_call __maybe_unused) +{ + bool save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET); + struct bpf_tramp_progs *fentry = &tprogs[BPF_TRAMP_FENTRY]; + struct bpf_tramp_progs *fexit = &tprogs[BPF_TRAMP_FEXIT]; + struct bpf_tramp_progs *fmod_ret = &tprogs[BPF_TRAMP_MODIFY_RETURN]; + struct codegen_context codegen_ctx, *ctx; + int i, ret, nr_args = m->nr_args; + u32 *image = (u32 *)image_start; + ppc_inst_t branch_insn; + u32 *branches = NULL; + + if (nr_args > 8 || !is_valid_bpf_tramp_flags(flags)) + return -EINVAL; + + ctx = &codegen_ctx; + memset(ctx, 0, sizeof(*ctx)); + + /* + * Prologue for the trampoline follows ftrace -mprofile-kernel ABI. + * On entry, LR has our return address while r0 has original return address. + * std r0, 16(r1) + * stdu r1, -144(r1) + * mflr r0 + * std r0, 112(r1) + * std r2, 24(r1) + * ld r2, PACATOC(r13) + * std r3, 40(r1) + * std r4, 48(r2) + * ... + * std r25, 120(r1) + * std r26, 128(r1) + */ + PPC_BPF_STL(_R0, _R1, PPC_LR_STKOFF); + PPC_BPF_STLU(_R1, _R1, -BPF_TRAMP_FRAME_SIZE); + EMIT(PPC_RAW_MFLR(_R0)); + PPC_BPF_STL(_R0, _R1, BPF_TRAMP_LR_SAVE); + PPC_BPF_STL(_R2, _R1, 24); + PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc)); + for (i = 0; i < nr_args; i++) + PPC_BPF_STL(_R3 + i, _R1, BPF_TRAMP_PROG_CTX + (i * 8)); + PPC_BPF_STL(_R25, _R1, BPF_TRAMP_R25_SAVE); + PPC_BPF_STL(_R26, _R1, BPF_TRAMP_R26_SAVE); + + /* save function arg count -- see bpf_get_func_arg_cnt() */ + EMIT(PPC_RAW_LI(_R3, nr_args)); + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_FUNC_ARG_CNT); + + /* save nip of the traced function before bpf prog ctx -- see bpf_get_func_ip() */ + if (flags & BPF_TRAMP_F_IP_ARG) { + /* TODO: should this be GEP? */ + EMIT(PPC_RAW_ADDI(_R3, _R0, -8)); + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_FUNC_IP); + } + + if (flags & BPF_TRAMP_F_CALL_ORIG) { + PPC_LI64(_R3, (unsigned long)im); + ret = bpf_jit_emit_func_call_hlp(image, ctx, (u64)__bpf_tramp_enter); + if (ret) + return ret; + } + + if (fentry->nr_progs) + if (invoke_bpf(m, image, ctx, fentry, flags & BPF_TRAMP_F_RET_FENTRY_RET)) + return -EINVAL; + + if (fmod_ret->nr_progs) { + branches = kcalloc(fmod_ret->nr_progs, sizeof(u32), GFP_KERNEL); + if (!branches) + return -ENOMEM; + + if (invoke_bpf_mod_ret(m, image, ctx, fmod_ret, branches)) { + ret = -EINVAL; + goto cleanup; + } + } + + /* call original function */ + if (flags & BPF_TRAMP_F_CALL_ORIG) { + PPC_BPF_LL(_R3, _R1, BPF_TRAMP_LR_SAVE); + EMIT(PPC_RAW_MTCTR(_R3)); + + /* restore args */ + for (i = 0; i < nr_args; i++) + PPC_BPF_LL(_R3 + i, _R1, BPF_TRAMP_PROG_CTX + (i * 8)); + + PPC_BPF_LL(_R2, _R1, 24); + EMIT(PPC_RAW_BCTRL()); + PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc)); + + /* remember return value in a stack for bpf prog to access */ + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_PROG_CTX + (nr_args * 8)); + + /* reserve space to patch branch instruction to skip fexit progs */ + im->ip_after_call = &image[ctx->idx]; + EMIT(PPC_RAW_NOP()); + } + + if (fmod_ret->nr_progs) { + /* update branches saved in invoke_bpf_mod_ret with aligned address of do_fexit */ + for (i = 0; i < fmod_ret->nr_progs; i++) { + if (create_cond_branch(&branch_insn, &image[branches[i]], + (unsigned long)&image[ctx->idx], COND_NE << 16)) { + ret = -EINVAL; + goto cleanup; + } + + image[branches[i]] = ppc_inst_val(branch_insn); + } + } + + if (fexit->nr_progs) + if (invoke_bpf(m, image, ctx, fexit, false)) { + ret = -EINVAL; + goto cleanup; + } + + if (flags & BPF_TRAMP_F_RESTORE_REGS) + for (i = 0; i < nr_args; i++) + PPC_BPF_LL(_R3 + i, _R1, BPF_TRAMP_PROG_CTX + (i * 8)); + + if (flags & BPF_TRAMP_F_CALL_ORIG) { + im->ip_epilogue = &image[ctx->idx]; + PPC_LI64(_R3, (unsigned long)im); + ret = bpf_jit_emit_func_call_hlp(image, ctx, (u64)__bpf_tramp_exit); + if (ret) + goto cleanup; + } + + /* restore return value of orig_call or fentry prog */ + if (save_ret) + PPC_BPF_LL(_R3, _R1, BPF_TRAMP_PROG_CTX + (nr_args * 8)); + + /* epilogue */ + PPC_BPF_LL(_R26, _R1, BPF_TRAMP_R26_SAVE); + PPC_BPF_LL(_R25, _R1, BPF_TRAMP_R25_SAVE); + PPC_BPF_LL(_R2, _R1, 24); + if (flags & BPF_TRAMP_F_SKIP_FRAME) { + /* skip our return address and return to parent */ + EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_TRAMP_FRAME_SIZE)); + PPC_BPF_LL(_R0, _R1, PPC_LR_STKOFF); + EMIT(PPC_RAW_MTCTR(_R0)); + } else { + PPC_BPF_LL(_R0, _R1, BPF_TRAMP_LR_SAVE); + EMIT(PPC_RAW_MTCTR(_R0)); + EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_TRAMP_FRAME_SIZE)); + PPC_BPF_LL(_R0, _R1, PPC_LR_STKOFF); + EMIT(PPC_RAW_MTLR(_R0)); + } + EMIT(PPC_RAW_BCTR()); + + /* make sure the trampoline generation logic doesn't overflow */ + if (WARN_ON_ONCE(&image[ctx->idx] > (u32 *)image_end - BPF_INSN_SAFETY)) { + ret = -EFAULT; + goto cleanup; + } + ret = (u8 *)&image[ctx->idx] - (u8 *)image; + +cleanup: + kfree(branches); + return ret; +} +#endif -- 2.34.1 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 271F0C433F5 for ; Mon, 7 Feb 2022 07:48:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233492AbiBGHre (ORCPT ); Mon, 7 Feb 2022 02:47:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37292 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236495AbiBGHlK (ORCPT ); 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Rao" To: Daniel Borkmann , Alexei Starovoitov , Michael Ellerman , Steven Rostedt Cc: , , Yauheni Kaliuta , Hari Bathini , Jordan Niethe , Jiri Olsa Subject: [RFC PATCH 3/3] powerpc64/bpf: Add support for bpf trampolines Date: Mon, 7 Feb 2022 12:37:22 +0530 Message-Id: X-Mailer: git-send-email 2.27.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: yqpcW8_Y4XCWOL2OIPsWd9CnBix4oMNs X-Proofpoint-GUID: 8PAdQbMmMQMP4CaSNFGp_B94GbHSCBpl X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.816,Hydra:6.0.425,FMLib:17.11.62.513 definitions=2022-02-07_02,2022-02-03_01,2021-12-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 mlxlogscore=999 impostorscore=0 phishscore=0 suspectscore=0 malwarescore=0 mlxscore=0 spamscore=0 priorityscore=1501 clxscore=1015 bulkscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2201110000 definitions=main-2202070046 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Add support for bpf_arch_text_poke() and arch_prepare_bpf_trampoline() for powerpc64 -mprofile-kernel. We set aside space for two stubs at the beginning of each bpf program. These stubs are used if having to branch to locations outside the range of a branch instruction. BPF Trampolines adhere to the powerpc64 -mprofile-kernel ABI since these need to attach to ftrace locations using ftrace direct attach. Due to this, bpf_arch_text_poke() patches two instructions: 'mflr r0' and 'bl' for BPF_MOD_CALL. The trampoline code itself closely follows the x86 implementation. Signed-off-by: Naveen N. Rao --- arch/powerpc/net/bpf_jit.h | 8 + arch/powerpc/net/bpf_jit_comp.c | 5 +- arch/powerpc/net/bpf_jit_comp64.c | 619 +++++++++++++++++++++++++++++- 3 files changed, 630 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/net/bpf_jit.h b/arch/powerpc/net/bpf_jit.h index 0832235a274983..777b10650678af 100644 --- a/arch/powerpc/net/bpf_jit.h +++ b/arch/powerpc/net/bpf_jit.h @@ -19,6 +19,14 @@ #define FUNCTION_DESCR_SIZE 0 #endif +#ifdef PPC64_ELF_ABI_v2 +#define BPF_TRAMP_STUB_SIZE 32 +#else +#define BPF_TRAMP_STUB_SIZE 0 +#endif + +#define PPC_BPF_MAGIC() (0xeB9FC0DE) + #define PLANT_INSTR(d, idx, instr) \ do { if (d) { (d)[idx] = instr; } idx++; } while (0) #define EMIT(instr) PLANT_INSTR(image, ctx->idx, instr) diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c index 635f7448ff7952..5df2f15bfe4d75 100644 --- a/arch/powerpc/net/bpf_jit_comp.c +++ b/arch/powerpc/net/bpf_jit_comp.c @@ -220,7 +220,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) extable_len = fp->aux->num_exentries * sizeof(struct exception_table_entry); proglen = cgctx.idx * 4; - alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len; + alloclen = proglen + FUNCTION_DESCR_SIZE + fixup_len + extable_len + BPF_TRAMP_STUB_SIZE * 2; bpf_hdr = bpf_jit_binary_alloc(alloclen, &image, 4, bpf_jit_fill_ill_insns); if (!bpf_hdr) { @@ -228,6 +228,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) goto out_addrs; } + image += BPF_TRAMP_STUB_SIZE * 2; + if (extable_len) fp->aux->extable = (void *)image + FUNCTION_DESCR_SIZE + proglen + fixup_len; @@ -251,6 +253,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) } /* Code generation passes 1-2 */ + *(code_base - 1) = PPC_BPF_MAGIC(); for (pass = 1; pass < 3; pass++) { /* Now build the prologue, body code & epilogue for real. */ cgctx.idx = 0; diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index c3cfe1f4338fca..20d8f6e3cc9bb0 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -73,6 +74,10 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx) { int i; + /* two nops for trampoline attach */ + EMIT(PPC_RAW_NOP()); + EMIT(PPC_RAW_NOP()); + #ifdef PPC64_ELF_ABI_v2 PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc)); #else @@ -93,7 +98,7 @@ void bpf_jit_build_prologue(u32 *image, struct codegen_context *ctx) EMIT(PPC_RAW_NOP()); } -#define BPF_TAILCALL_PROLOGUE_SIZE 12 +#define BPF_TAILCALL_PROLOGUE_SIZE 20 if (bpf_has_stack_frame(ctx)) { /* @@ -1133,3 +1138,615 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * return 0; } + +#ifdef PPC64_ELF_ABI_v2 + +static __always_inline int bpf_check_and_patch(u32 *ip, ppc_inst_t old_inst, ppc_inst_t new_inst) +{ + ppc_inst_t org_inst = ppc_inst_read(ip); + if (!ppc_inst_equal(org_inst, old_inst)) { + pr_info("bpf_check_and_patch: ip: 0x%lx, org_inst(0x%x) != old_inst (0x%x)\n", + (unsigned long)ip, ppc_inst_val(org_inst), ppc_inst_val(old_inst)); + return -EBUSY; + } + if (ppc_inst_equal(org_inst, new_inst)) + return 1; + return patch_instruction(ip, new_inst); +} + +static u32 *bpf_find_existing_stub(u32 *ip, enum bpf_text_poke_type t, void *old_addr) +{ + int branch_flags = t == BPF_MOD_JUMP ? 0 : BRANCH_SET_LINK; + u32 *stub_addr = 0, *stub1, *stub2; + ppc_inst_t org_inst, old_inst; + + if (!old_addr) + return 0; + + stub1 = ip - (BPF_TRAMP_STUB_SIZE / sizeof(u32)) - (t == BPF_MOD_CALL ? 1 : 0); + stub2 = stub1 - (BPF_TRAMP_STUB_SIZE / sizeof(u32)); + org_inst = ppc_inst_read(ip); + if (!create_branch(&old_inst, ip, (unsigned long)stub1, branch_flags) && + ppc_inst_equal(org_inst, old_inst)) + stub_addr = stub1; + if (!create_branch(&old_inst, ip, (unsigned long)stub2, branch_flags) && + ppc_inst_equal(org_inst, old_inst)) + stub_addr = stub2; + + return stub_addr; +} + +static u32 *bpf_setup_stub(u32 *ip, enum bpf_text_poke_type t, void *old_addr, void *new_addr) +{ + u32 *stub_addr, *stub1, *stub2; + ppc_inst_t org_inst, old_inst; + int i, ret; + u32 stub[] = { + PPC_RAW_LIS(12, 0), + PPC_RAW_ORI(12, 12, 0), + PPC_RAW_SLDI(12, 12, 32), + PPC_RAW_ORIS(12, 12, 0), + PPC_RAW_ORI(12, 12, 0), + PPC_RAW_MTCTR(12), + PPC_RAW_BCTR(), + }; + + /* verify we are patching the right location */ + if (t == BPF_MOD_JUMP) + org_inst = ppc_inst_read(ip - 1); + else + org_inst = ppc_inst_read(ip - 2); + old_inst = ppc_inst(PPC_BPF_MAGIC()); + if (!ppc_inst_equal(org_inst, old_inst)) + return 0; + + /* verify existing branch and note down the stub to use */ + stub1 = ip - (BPF_TRAMP_STUB_SIZE / sizeof(u32)) - (t == BPF_MOD_CALL ? 1 : 0); + stub2 = stub1 - (BPF_TRAMP_STUB_SIZE / sizeof(u32)); + stub_addr = 0; + org_inst = ppc_inst_read(ip); + if (old_addr) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + /* existing instruction should branch to one of the two stubs */ + if (!stub_addr) + return 0; + } else { + old_inst = ppc_inst(PPC_RAW_NOP()); + if (!ppc_inst_equal(org_inst, old_inst)) + return 0; + } + if (stub_addr == stub1) + stub_addr = stub2; + else + stub_addr = stub1; + + /* setup stub */ + stub[0] |= IMM_L((unsigned long)new_addr >> 48); + stub[1] |= IMM_L((unsigned long)new_addr >> 32); + stub[3] |= IMM_L((unsigned long)new_addr >> 16); + stub[4] |= IMM_L((unsigned long)new_addr); + for (i = 0; i < sizeof(stub) / sizeof(u32); i++) { + ret = patch_instruction(stub_addr + i, ppc_inst(stub[i])); + if (ret) { + pr_err("bpf: patch_instruction() error while setting up stub: ret %d\n", ret); + return 0; + } + } + + return stub_addr; +} + +int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t, void *old_addr, void *new_addr) +{ + ppc_inst_t org_inst, old_inst, new_inst; + int ret = -EINVAL; + u32 *stub_addr; + + /* We currently only support poking bpf programs */ + if (!is_bpf_text_address((long)ip)) { + pr_info("bpf_arch_text_poke (0x%lx): kernel/modules are not supported\n", (unsigned long)ip); + return -EINVAL; + } + + mutex_lock(&text_mutex); + if (t == BPF_MOD_JUMP) { + /* + * This can point to the beginning of a bpf program, or to certain locations + * within a bpf program. We operate on a single instruction at ip here, + * converting among a nop and an unconditional branch. Depending on branch + * target, we may use the stub area at the beginning of the bpf program and + * we assume that BPF_MOD_JUMP and BPF_MOD_CALL are never used without + * transitioning to a nop. + */ + if (!old_addr && new_addr) { + /* nop -> b */ + old_inst = ppc_inst(PPC_RAW_NOP()); + if (create_branch(&new_inst, (u32 *)ip, (unsigned long)new_addr, 0)) { + stub_addr = bpf_setup_stub(ip, t, old_addr, new_addr); + if (!stub_addr || + create_branch(&new_inst, (u32 *)ip, (unsigned long)stub_addr, 0)) { + ret = -EINVAL; + goto out; + } + } + ret = bpf_check_and_patch(ip, old_inst, new_inst); + } else if (old_addr && !new_addr) { + /* b -> nop */ + new_inst = ppc_inst(PPC_RAW_NOP()); + if (create_branch(&old_inst, (u32 *)ip, (unsigned long)old_addr, 0)) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + if (!stub_addr || + create_branch(&old_inst, (u32 *)ip, (unsigned long)stub_addr, 0)) { + ret = -EINVAL; + goto out; + } + } + ret = bpf_check_and_patch(ip, old_inst, new_inst); + } else if (old_addr && new_addr) { + /* b -> b */ + stub_addr = 0; + if (create_branch(&old_inst, (u32 *)ip, (unsigned long)old_addr, 0)) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + if (!stub_addr || + create_branch(&old_inst, (u32 *)ip, (unsigned long)stub_addr, 0)) { + ret = -EINVAL; + goto out; + } + } + if (create_branch(&new_inst, (u32 *)ip, (unsigned long)new_addr, 0)) { + stub_addr = bpf_setup_stub(ip, t, old_addr, new_addr); + if (!stub_addr || + create_branch(&new_inst, (u32 *)ip, (unsigned long)stub_addr, 0)) { + ret = -EINVAL; + goto out; + } + } + ret = bpf_check_and_patch((u32 *)ip, old_inst, new_inst); + } + } else if (t == BPF_MOD_CALL) { + /* + * For a BPF_MOD_CALL, we expect ip to point at the start of a bpf program. + * We will have to patch two instructions to mimic -mprofile-kernel: a 'mflr r0' + * followed by a 'bl'. Instruction patching order matters: we always patch-in + * the 'mflr r0' first and patch it out the last. + */ + if (!old_addr && new_addr) { + /* nop -> bl */ + + /* confirm that we have two nops */ + old_inst = ppc_inst(PPC_RAW_NOP()); + org_inst = ppc_inst_read(ip); + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + org_inst = ppc_inst_read((u32 *)ip + 1); + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + + /* patch in the mflr */ + new_inst = ppc_inst(PPC_RAW_MFLR(_R0)); + ret = bpf_check_and_patch(ip, old_inst, new_inst); + if (ret) + goto out; + + /* prep the stub if needed */ + ip = (u32 *)ip + 1; + if (create_branch(&new_inst, (u32 *)ip, (unsigned long)new_addr, BRANCH_SET_LINK)) { + stub_addr = bpf_setup_stub(ip, t, old_addr, new_addr); + if (!stub_addr || + create_branch(&new_inst, (u32 *)ip, (unsigned long)stub_addr, BRANCH_SET_LINK)) { + ret = -EINVAL; + goto out; + } + } + + synchronize_rcu(); + + /* patch in the bl */ + ret = bpf_check_and_patch(ip, old_inst, new_inst); + } else if (old_addr && !new_addr) { + /* bl -> nop */ + + /* confirm the expected instruction sequence */ + old_inst = ppc_inst(PPC_RAW_MFLR(_R0)); + org_inst = ppc_inst_read(ip); + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + ip = (u32 *)ip + 1; + org_inst = ppc_inst_read(ip); + if (create_branch(&old_inst, (u32 *)ip, (unsigned long)old_addr, BRANCH_SET_LINK)) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + if (!stub_addr || + create_branch(&old_inst, (u32 *)ip, (unsigned long)stub_addr, BRANCH_SET_LINK)) { + ret = -EINVAL; + goto out; + } + } + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + + /* patch out the branch first */ + new_inst = ppc_inst(PPC_RAW_NOP()); + ret = bpf_check_and_patch(ip, old_inst, new_inst); + if (ret) + goto out; + + synchronize_rcu(); + + /* then, the mflr */ + old_inst = ppc_inst(PPC_RAW_MFLR(_R0)); + ret = bpf_check_and_patch((u32 *)ip - 1, old_inst, new_inst); + } else if (old_addr && new_addr) { + /* bl -> bl */ + + /* confirm the expected instruction sequence */ + old_inst = ppc_inst(PPC_RAW_MFLR(_R0)); + org_inst = ppc_inst_read(ip); + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + ip = (u32 *)ip + 1; + org_inst = ppc_inst_read(ip); + if (create_branch(&old_inst, (u32 *)ip, (unsigned long)old_addr, BRANCH_SET_LINK)) { + stub_addr = bpf_find_existing_stub(ip, t, old_addr); + if (!stub_addr || + create_branch(&old_inst, (u32 *)ip, (unsigned long)stub_addr, BRANCH_SET_LINK)) { + ret = -EINVAL; + goto out; + } + } + if (!ppc_inst_equal(org_inst, old_inst)) { + ret = -EINVAL; + goto out; + } + + /* setup the new branch */ + if (create_branch(&new_inst, (u32 *)ip, (unsigned long)new_addr, BRANCH_SET_LINK)) { + stub_addr = bpf_setup_stub(ip, t, old_addr, new_addr); + if (!stub_addr || + create_branch(&new_inst, (u32 *)ip, (unsigned long)stub_addr, BRANCH_SET_LINK)) { + ret = -EINVAL; + goto out; + } + } + ret = bpf_check_and_patch(ip, old_inst, new_inst); + } + } + +out: + mutex_unlock(&text_mutex); + return ret; +} + +/* + * BPF Trampoline stack frame layout: + * + * [ prev sp ] <----- + * [ BPF_TRAMP_R26_SAVE ] 8 | + * [ BPF_TRAMP_R25_SAVE ] 8 | + * [ BPF_TRAMP_LR_SAVE ] 8 | + * [ ret val ] 8 | + * [ BPF_TRAMP_PROG_CTX ] 8 * 8 | + * [ BPF_TRAMP_FUNC_ARG_CNT] 8 | + * [ BPF_TRAMP_FUNC_IP ] 8 | + * sp (r1) ---> [ stack frame header ] ------ + */ + +/* stack frame header + data, quadword aligned */ +#define BPF_TRAMP_FRAME_SIZE (STACK_FRAME_MIN_SIZE + (14 * 8)) + +/* The below are offsets from r1 */ +/* upto 8 dword func parameters, as bpf prog ctx */ +#define BPF_TRAMP_PROG_CTX (STACK_FRAME_MIN_SIZE + 16) +/* bpf_get_func_arg_cnt() needs this before prog ctx */ +#define BPF_TRAMP_FUNC_ARG_CNT (BPF_TRAMP_PROG_CTX - 8) +/* bpf_get_func_ip() needs this here */ +#define BPF_TRAMP_FUNC_IP (BPF_TRAMP_PROG_CTX - 16) +/* lr save area, after space for upto 8 args followed by retval of orig_call/fentry progs */ +#define BPF_TRAMP_LR_SAVE (BPF_TRAMP_PROG_CTX + (8 * 8) + 8) +#define BPF_TRAMP_R25_SAVE (BPF_TRAMP_LR_SAVE + 8) +#define BPF_TRAMP_R26_SAVE (BPF_TRAMP_R25_SAVE + 8) + +#define BPF_INSN_SAFETY 64 + +static int invoke_bpf_prog(const struct btf_func_model *m, u32 *image, struct codegen_context *ctx, + struct bpf_prog *p, bool save_ret) +{ + ppc_inst_t branch_insn; + u32 jmp_idx; + int ret; + + /* __bpf_prog_enter(p) */ + PPC_LI64(_R3, (unsigned long)p); + EMIT(PPC_RAW_MR(_R25, _R3)); + ret = bpf_jit_emit_func_call_hlp(image, ctx, + p->aux->sleepable ? (u64)__bpf_prog_enter_sleepable : (u64)__bpf_prog_enter); + if (ret) + return ret; + + /* remember prog start time returned by __bpf_prog_enter */ + EMIT(PPC_RAW_MR(_R26, _R3)); + + /* + * if (__bpf_prog_enter(p) == 0) + * goto skip_exec_of_prog; + * + * emit a nop to be later patched with conditional branch, once offset is known + */ + EMIT(PPC_RAW_CMPDI(_R3, 0)); + jmp_idx = ctx->idx; + EMIT(PPC_RAW_NOP()); + + /* p->bpf_func() */ + EMIT(PPC_RAW_ADDI(_R3, _R1, BPF_TRAMP_PROG_CTX)); + if (!p->jited) + PPC_LI64(_R4, (unsigned long)p->insnsi); + if (is_offset_in_branch_range((unsigned long)p->bpf_func - (unsigned long)&image[ctx->idx])) { + PPC_BL((unsigned long)p->bpf_func); + } else { + PPC_BPF_LL(_R12, _R25, offsetof(struct bpf_prog, bpf_func)); + EMIT(PPC_RAW_MTCTR(_R12)); + EMIT(PPC_RAW_BCTRL()); + } + + if (save_ret) + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_PROG_CTX + (m->nr_args * 8)); + + /* fix up branch */ + if (create_cond_branch(&branch_insn, &image[jmp_idx], (unsigned long)&image[ctx->idx], COND_EQ << 16)) + return -EINVAL; + image[jmp_idx] = ppc_inst_val(branch_insn); + + /* __bpf_prog_exit(p, start_time) */ + EMIT(PPC_RAW_MR(_R3, _R25)); + EMIT(PPC_RAW_MR(_R4, _R26)); + ret = bpf_jit_emit_func_call_hlp(image, ctx, + p->aux->sleepable ? (u64)__bpf_prog_exit_sleepable : (u64)__bpf_prog_exit); + if (ret) + return ret; + + return 0; +} + +static int invoke_bpf(const struct btf_func_model *m, u32 *image, struct codegen_context *ctx, + struct bpf_tramp_progs *tp, bool save_ret) +{ + int i; + + for (i = 0; i < tp->nr_progs; i++) { + if (invoke_bpf_prog(m, image, ctx, tp->progs[i], save_ret)) + return -EINVAL; + } + + return 0; +} + +static int invoke_bpf_mod_ret(const struct btf_func_model *m, u32 *image, struct codegen_context *ctx, + struct bpf_tramp_progs *tp, u32 *branches) +{ + int i; + + /* + * The first fmod_ret program will receive a garbage return value. + * Set this to 0 to avoid confusing the program. + */ + EMIT(PPC_RAW_LI(_R3, 0)); + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_PROG_CTX + (m->nr_args * 8)); + for (i = 0; i < tp->nr_progs; i++) { + if (invoke_bpf_prog(m, image, ctx, tp->progs[i], true)) + return -EINVAL; + + /* + * mod_ret prog stored return value after prog ctx. Emit: + * if (*(u64 *)(ret_val) != 0) + * goto do_fexit; + */ + PPC_BPF_LL(_R3, _R1, BPF_TRAMP_PROG_CTX + (m->nr_args * 8)); + EMIT(PPC_RAW_CMPDI(_R3, 0)); + + /* + * Save the location of the branch and generate a nop, which is + * replaced with a conditional jump once do_fexit (i.e. the + * start of the fexit invocation) is finalized. + */ + branches[i] = ctx->idx; + EMIT(PPC_RAW_NOP()); + } + + return 0; +} + +static bool is_valid_bpf_tramp_flags(unsigned int flags) +{ + if ((flags & BPF_TRAMP_F_RESTORE_REGS) && (flags & BPF_TRAMP_F_SKIP_FRAME)) + return false; + + /* We only support attaching to function entry */ + if ((flags & BPF_TRAMP_F_CALL_ORIG) && !(flags & BPF_TRAMP_F_SKIP_FRAME)) + return false; + + /* BPF_TRAMP_F_RET_FENTRY_RET is only used by bpf_struct_ops, and it must be used alone */ + if ((flags & BPF_TRAMP_F_RET_FENTRY_RET) && (flags & ~BPF_TRAMP_F_RET_FENTRY_RET)) + return false; + + return true; +} + +/* + * We assume that orig_call is what this trampoline is being attached to and we use the link + * register for BPF_TRAMP_F_CALL_ORIG -- see is_valid_bpf_tramp_flags() for validating this. + */ +int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image_start, void *image_end, + const struct btf_func_model *m, u32 flags, + struct bpf_tramp_progs *tprogs, + void *orig_call __maybe_unused) +{ + bool save_ret = flags & (BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_RET_FENTRY_RET); + struct bpf_tramp_progs *fentry = &tprogs[BPF_TRAMP_FENTRY]; + struct bpf_tramp_progs *fexit = &tprogs[BPF_TRAMP_FEXIT]; + struct bpf_tramp_progs *fmod_ret = &tprogs[BPF_TRAMP_MODIFY_RETURN]; + struct codegen_context codegen_ctx, *ctx; + int i, ret, nr_args = m->nr_args; + u32 *image = (u32 *)image_start; + ppc_inst_t branch_insn; + u32 *branches = NULL; + + if (nr_args > 8 || !is_valid_bpf_tramp_flags(flags)) + return -EINVAL; + + ctx = &codegen_ctx; + memset(ctx, 0, sizeof(*ctx)); + + /* + * Prologue for the trampoline follows ftrace -mprofile-kernel ABI. + * On entry, LR has our return address while r0 has original return address. + * std r0, 16(r1) + * stdu r1, -144(r1) + * mflr r0 + * std r0, 112(r1) + * std r2, 24(r1) + * ld r2, PACATOC(r13) + * std r3, 40(r1) + * std r4, 48(r2) + * ... + * std r25, 120(r1) + * std r26, 128(r1) + */ + PPC_BPF_STL(_R0, _R1, PPC_LR_STKOFF); + PPC_BPF_STLU(_R1, _R1, -BPF_TRAMP_FRAME_SIZE); + EMIT(PPC_RAW_MFLR(_R0)); + PPC_BPF_STL(_R0, _R1, BPF_TRAMP_LR_SAVE); + PPC_BPF_STL(_R2, _R1, 24); + PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc)); + for (i = 0; i < nr_args; i++) + PPC_BPF_STL(_R3 + i, _R1, BPF_TRAMP_PROG_CTX + (i * 8)); + PPC_BPF_STL(_R25, _R1, BPF_TRAMP_R25_SAVE); + PPC_BPF_STL(_R26, _R1, BPF_TRAMP_R26_SAVE); + + /* save function arg count -- see bpf_get_func_arg_cnt() */ + EMIT(PPC_RAW_LI(_R3, nr_args)); + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_FUNC_ARG_CNT); + + /* save nip of the traced function before bpf prog ctx -- see bpf_get_func_ip() */ + if (flags & BPF_TRAMP_F_IP_ARG) { + /* TODO: should this be GEP? */ + EMIT(PPC_RAW_ADDI(_R3, _R0, -8)); + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_FUNC_IP); + } + + if (flags & BPF_TRAMP_F_CALL_ORIG) { + PPC_LI64(_R3, (unsigned long)im); + ret = bpf_jit_emit_func_call_hlp(image, ctx, (u64)__bpf_tramp_enter); + if (ret) + return ret; + } + + if (fentry->nr_progs) + if (invoke_bpf(m, image, ctx, fentry, flags & BPF_TRAMP_F_RET_FENTRY_RET)) + return -EINVAL; + + if (fmod_ret->nr_progs) { + branches = kcalloc(fmod_ret->nr_progs, sizeof(u32), GFP_KERNEL); + if (!branches) + return -ENOMEM; + + if (invoke_bpf_mod_ret(m, image, ctx, fmod_ret, branches)) { + ret = -EINVAL; + goto cleanup; + } + } + + /* call original function */ + if (flags & BPF_TRAMP_F_CALL_ORIG) { + PPC_BPF_LL(_R3, _R1, BPF_TRAMP_LR_SAVE); + EMIT(PPC_RAW_MTCTR(_R3)); + + /* restore args */ + for (i = 0; i < nr_args; i++) + PPC_BPF_LL(_R3 + i, _R1, BPF_TRAMP_PROG_CTX + (i * 8)); + + PPC_BPF_LL(_R2, _R1, 24); + EMIT(PPC_RAW_BCTRL()); + PPC_BPF_LL(_R2, _R13, offsetof(struct paca_struct, kernel_toc)); + + /* remember return value in a stack for bpf prog to access */ + PPC_BPF_STL(_R3, _R1, BPF_TRAMP_PROG_CTX + (nr_args * 8)); + + /* reserve space to patch branch instruction to skip fexit progs */ + im->ip_after_call = &image[ctx->idx]; + EMIT(PPC_RAW_NOP()); + } + + if (fmod_ret->nr_progs) { + /* update branches saved in invoke_bpf_mod_ret with aligned address of do_fexit */ + for (i = 0; i < fmod_ret->nr_progs; i++) { + if (create_cond_branch(&branch_insn, &image[branches[i]], + (unsigned long)&image[ctx->idx], COND_NE << 16)) { + ret = -EINVAL; + goto cleanup; + } + + image[branches[i]] = ppc_inst_val(branch_insn); + } + } + + if (fexit->nr_progs) + if (invoke_bpf(m, image, ctx, fexit, false)) { + ret = -EINVAL; + goto cleanup; + } + + if (flags & BPF_TRAMP_F_RESTORE_REGS) + for (i = 0; i < nr_args; i++) + PPC_BPF_LL(_R3 + i, _R1, BPF_TRAMP_PROG_CTX + (i * 8)); + + if (flags & BPF_TRAMP_F_CALL_ORIG) { + im->ip_epilogue = &image[ctx->idx]; + PPC_LI64(_R3, (unsigned long)im); + ret = bpf_jit_emit_func_call_hlp(image, ctx, (u64)__bpf_tramp_exit); + if (ret) + goto cleanup; + } + + /* restore return value of orig_call or fentry prog */ + if (save_ret) + PPC_BPF_LL(_R3, _R1, BPF_TRAMP_PROG_CTX + (nr_args * 8)); + + /* epilogue */ + PPC_BPF_LL(_R26, _R1, BPF_TRAMP_R26_SAVE); + PPC_BPF_LL(_R25, _R1, BPF_TRAMP_R25_SAVE); + PPC_BPF_LL(_R2, _R1, 24); + if (flags & BPF_TRAMP_F_SKIP_FRAME) { + /* skip our return address and return to parent */ + EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_TRAMP_FRAME_SIZE)); + PPC_BPF_LL(_R0, _R1, PPC_LR_STKOFF); + EMIT(PPC_RAW_MTCTR(_R0)); + } else { + PPC_BPF_LL(_R0, _R1, BPF_TRAMP_LR_SAVE); + EMIT(PPC_RAW_MTCTR(_R0)); + EMIT(PPC_RAW_ADDI(_R1, _R1, BPF_TRAMP_FRAME_SIZE)); + PPC_BPF_LL(_R0, _R1, PPC_LR_STKOFF); + EMIT(PPC_RAW_MTLR(_R0)); + } + EMIT(PPC_RAW_BCTR()); + + /* make sure the trampoline generation logic doesn't overflow */ + if (WARN_ON_ONCE(&image[ctx->idx] > (u32 *)image_end - BPF_INSN_SAFETY)) { + ret = -EFAULT; + goto cleanup; + } + ret = (u8 *)&image[ctx->idx] - (u8 *)image; + +cleanup: + kfree(branches); + return ret; +} +#endif -- 2.34.1