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Mon, 13 May 2024 14:12:31 +0000 (UTC) Received: from ilclasset02 (ilclasset02.mot.com [100.64.49.13]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-256) server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: mbland) by va32lmmrp02.lenovo.com (Postfix) with ESMTPSA id 4VdLzM2HDhz2VZ3C; Mon, 13 May 2024 14:12:31 +0000 (UTC) Date: Mon, 13 May 2024 09:12:30 -0500 From: Maxwell Bland To: "open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)" Cc: Catalin Marinas , Will Deacon , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Zi Shen Lim , Mark Rutland , Suzuki K Poulose , Mark Brown , linux-arm-kernel@lists.infradead.org, open list , Josh Poimboeuf , Puranjay Mohan Subject: [PATCH bpf-next v4 2/3] arm64/cfi,bpf: Support kCFI + BPF on arm64 Message-ID: References: Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-Proofpoint-ORIG-GUID: PzYlCMG9O9xD3Nr_8BrOUIm-qRX8w2ji X-Proofpoint-GUID: PzYlCMG9O9xD3Nr_8BrOUIm-qRX8w2ji X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.650,FMLib:17.11.176.26 definitions=2024-05-13_10,2024-05-10_02,2023-05-22_02 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 adultscore=0 spamscore=0 malwarescore=0 phishscore=0 suspectscore=0 impostorscore=0 priorityscore=1501 mlxscore=0 clxscore=1015 mlxlogscore=999 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2405010000 definitions=main-2405130089 X-Patchwork-Delegate: bpf@iogearbox.net From: Puranjay Mohan Currently, bpf_dispatcher_*_func() is marked with `__nocfi` therefore calling BPF programs from this interface doesn't cause CFI warnings. When BPF programs are called directly from C: from BPF helpers or struct_ops, CFI warnings are generated. Implement proper CFI prologues for the BPF programs and callbacks and drop __nocfi for arm64. Fix the trampoline generation code to emit kCFI prologue when a struct_ops trampoline is being prepared. Signed-off-by: Puranjay Mohan --- Minor fix of authorship attribution by adding "From:" tag. arch/arm64/include/asm/cfi.h | 23 ++++++++++++++ arch/arm64/kernel/alternative.c | 54 +++++++++++++++++++++++++++++++++ arch/arm64/net/bpf_jit_comp.c | 18 +++++++++-- 3 files changed, 93 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/include/asm/cfi.h diff --git a/arch/arm64/include/asm/cfi.h b/arch/arm64/include/asm/cfi.h new file mode 100644 index 000000000000..670e191f8628 --- /dev/null +++ b/arch/arm64/include/asm/cfi.h @@ -0,0 +1,23 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_ARM64_CFI_H +#define _ASM_ARM64_CFI_H + +#ifdef CONFIG_CFI_CLANG +#define __bpfcall +static inline int cfi_get_offset(void) +{ + return 4; +} +#define cfi_get_offset cfi_get_offset +extern u32 cfi_bpf_hash; +extern u32 cfi_bpf_subprog_hash; +extern u32 cfi_get_func_hash(void *func); +#else +#define cfi_bpf_hash 0U +#define cfi_bpf_subprog_hash 0U +static inline u32 cfi_get_func_hash(void *func) +{ + return 0; +} +#endif /* CONFIG_CFI_CLANG */ +#endif /* _ASM_ARM64_CFI_H */ diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c index 8ff6610af496..1715da7df137 100644 --- a/arch/arm64/kernel/alternative.c +++ b/arch/arm64/kernel/alternative.c @@ -13,6 +13,7 @@ #include #include #include +#include #include #include #include @@ -298,3 +299,56 @@ noinstr void alt_cb_patch_nops(struct alt_instr *alt, __le32 *origptr, updptr[i] = cpu_to_le32(aarch64_insn_gen_nop()); } EXPORT_SYMBOL(alt_cb_patch_nops); + +#ifdef CONFIG_CFI_CLANG +struct bpf_insn; + +/* Must match bpf_func_t / DEFINE_BPF_PROG_RUN() */ +extern unsigned int __bpf_prog_runX(const void *ctx, + const struct bpf_insn *insn); + +/* + * Force a reference to the external symbol so the compiler generates + * __kcfi_typid. + */ +__ADDRESSABLE(__bpf_prog_runX); + +/* u32 __ro_after_init cfi_bpf_hash = __kcfi_typeid___bpf_prog_runX; */ +asm ( +" .pushsection .data..ro_after_init,\"aw\",@progbits \n" +" .type cfi_bpf_hash,@object \n" +" .globl cfi_bpf_hash \n" +" .p2align 2, 0x0 \n" +"cfi_bpf_hash: \n" +" .word __kcfi_typeid___bpf_prog_runX \n" +" .size cfi_bpf_hash, 4 \n" +" .popsection \n" +); + +/* Must match bpf_callback_t */ +extern u64 __bpf_callback_fn(u64, u64, u64, u64, u64); + +__ADDRESSABLE(__bpf_callback_fn); + +/* u32 __ro_after_init cfi_bpf_subprog_hash = __kcfi_typeid___bpf_callback_fn; */ +asm ( +" .pushsection .data..ro_after_init,\"aw\",@progbits \n" +" .type cfi_bpf_subprog_hash,@object \n" +" .globl cfi_bpf_subprog_hash \n" +" .p2align 2, 0x0 \n" +"cfi_bpf_subprog_hash: \n" +" .word __kcfi_typeid___bpf_callback_fn \n" +" .size cfi_bpf_subprog_hash, 4 \n" +" .popsection \n" +); + +u32 cfi_get_func_hash(void *func) +{ + u32 hash; + + if (get_kernel_nofault(hash, func - cfi_get_offset())) + return 0; + + return hash; +} +#endif diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 76b91f36c729..703247457409 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -17,6 +17,7 @@ #include #include #include +#include #include #include #include @@ -162,6 +163,12 @@ static inline void emit_bti(u32 insn, struct jit_ctx *ctx) emit(insn, ctx); } +static inline void emit_kcfi(u32 hash, struct jit_ctx *ctx) +{ + if (IS_ENABLED(CONFIG_CFI_CLANG)) + emit(hash, ctx); +} + /* * Kernel addresses in the vmalloc space use at most 48 bits, and the * remaining bits are guaranteed to be 0x1. So we can compose the address @@ -337,6 +344,7 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf, * */ + emit_kcfi(is_main_prog ? cfi_bpf_hash : cfi_bpf_subprog_hash, ctx); /* bpf function may be invoked by 3 instruction types: * 1. bl, attached via freplace to bpf prog via short jump * 2. br, attached via freplace to bpf prog via long jump @@ -1806,9 +1814,9 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) jit_data->ro_header = ro_header; } - prog->bpf_func = (void *)ctx.ro_image; + prog->bpf_func = (void *)ctx.ro_image + cfi_get_offset(); prog->jited = 1; - prog->jited_len = prog_size; + prog->jited_len = prog_size - cfi_get_offset(); if (!prog->is_func || extra_pass) { int i; @@ -2072,6 +2080,12 @@ static int prepare_trampoline(struct jit_ctx *ctx, struct bpf_tramp_image *im, /* return address locates above FP */ retaddr_off = stack_size + 8; + if (flags & BPF_TRAMP_F_INDIRECT) { + /* + * Indirect call for bpf_struct_ops + */ + emit_kcfi(cfi_get_func_hash(func_addr), ctx); + } /* bpf trampoline may be invoked by 3 instruction types: * 1. bl, attached to bpf prog or kernel function via short jump * 2. br, attached to bpf prog or kernel function via long jump