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Mon, 10 Mar 2025 15:29:54 -0700 (PDT) Date: Mon, 10 Mar 2025 22:29:45 +0000 In-Reply-To: <20250310222942.1988975-4-samitolvanen@google.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250310222942.1988975-4-samitolvanen@google.com> X-Developer-Key: i=samitolvanen@google.com; a=openpgp; fpr=35CCFB63B283D6D3AEB783944CB5F6848BBC56EE X-Developer-Signature: v=1; a=openpgp-sha256; l=5846; i=samitolvanen@google.com; h=from:subject; bh=nnEDzY0cdXNg5DInXr2mCSLGjD0bJaDeFd9RiRfzo4M=; b=owGbwMvMwCEWxa662nLh8irG02pJDOnn02+zmk8qvM15+eOR4itv2iUe3WHXdDmQpuh0RL2HJ XRC9zWzjlIWBjEOBlkxRZaWr6u37v7ulPrqc5EEzBxWJpAhDFycAjCRlrOMDKcmnAxb6p/PI9cV fKYpXWXrHP6PV8RC60/NC0ueoXVa4ybDP/uXoo8XlLM7M3z/3v7y6PUg117paX8rA40TnV1qmSq mMwEA X-Mailer: git-send-email 2.49.0.rc0.332.g42c0ae87b1-goog Message-ID: <20250310222942.1988975-6-samitolvanen@google.com> Subject: [PATCH bpf-next v8 2/2] arm64/cfi,bpf: Support kCFI + BPF on arm64 From: Sami Tolvanen To: bpf@vger.kernel.org Cc: Catalin Marinas , Will Deacon , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Mark Rutland , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Puranjay Mohan , Maxwell Bland , Sami Tolvanen 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 Co-Developed-by: Maxwell Bland Signed-off-by: Maxwell Bland Co-Developed-by: Sami Tolvanen Signed-off-by: Sami Tolvanen --- arch/arm64/include/asm/cfi.h | 23 +++++++++++++++++++++++ arch/arm64/kernel/alternative.c | 25 +++++++++++++++++++++++++ arch/arm64/net/bpf_jit_comp.c | 22 +++++++++++++++++++--- 3 files changed, 67 insertions(+), 3 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..71c153488dad 100644 --- a/arch/arm64/kernel/alternative.c +++ b/arch/arm64/kernel/alternative.c @@ -8,11 +8,13 @@ #define pr_fmt(fmt) "alternatives: " fmt +#include #include #include #include #include #include +#include #include #include #include @@ -298,3 +300,26 @@ 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); +DEFINE_CFI_TYPE(cfi_bpf_hash, __bpf_prog_runX); + +/* Must match bpf_callback_t */ +extern u64 __bpf_callback_fn(u64, u64, u64, u64, u64); +DEFINE_CFI_TYPE(cfi_bpf_subprog_hash, __bpf_callback_fn); + +u32 cfi_get_func_hash(void *func) +{ + u32 hash; + + if (get_kernel_nofault(hash, func - cfi_get_offset())) + return 0; + + return hash; +} +#endif /* CONFIG_CFI_CLANG */ diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 70d7c89d3ac9..8870c205f934 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 @@ -164,6 +165,12 @@ 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 @@ -474,7 +481,6 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) const bool is_main_prog = !bpf_is_subprog(prog); const u8 fp = bpf2a64[BPF_REG_FP]; const u8 arena_vm_base = bpf2a64[ARENA_VM_START]; - const int idx0 = ctx->idx; int cur_offset; /* @@ -500,6 +506,9 @@ 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); + const int idx0 = ctx->idx; + /* 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 @@ -2009,9 +2018,9 @@ 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; @@ -2271,6 +2280,12 @@ 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 @@ -2790,6 +2805,7 @@ void bpf_jit_free(struct bpf_prog *prog) sizeof(jit_data->header->size)); kfree(jit_data); } + prog->bpf_func -= cfi_get_offset(); hdr = bpf_jit_binary_pack_hdr(prog); bpf_jit_binary_pack_free(hdr, NULL); WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog));