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a=openpgp; fpr=35CCFB63B283D6D3AEB783944CB5F6848BBC56EE X-Developer-Signature: v=1; a=openpgp-sha256; l=5250; i=samitolvanen@google.com; h=from:subject; bh=wKRcArm3I8YdLV7xUagIsjaFHkOg54K0GIqYgszVZFg=; b=owGbwMvMwCEWxa662nLh8irG02pJDBmSNv9K1st1fkzpOPgpqm9HvJ6izx0fP3eZM7ddDm3ff pbr0IuOjlIWBjEOBlkxRZaWr6u37v7ulPrqc5EEzBxWJpAhDFycAjCR9YoM/2u/Vn5ymMXkPVEj Y5nFhVMNq0JCk3uyGX6cbNw8aYnmg2hGhm0vH91YYKerum/zl3o2sWSho2YmT7/NTtTW4F61YrZ RHQMA X-Mailer: git-send-email 2.49.0.967.g6a0df3ecc3-goog Message-ID: <20250505223437.3722164-5-samitolvanen@google.com> Subject: [PATCH bpf-next v9 1/2] cfi: add C CFI type macro From: Sami Tolvanen To: bpf@vger.kernel.org, Puranjay Mohan , Alexei Starovoitov , Daniel Borkmann Cc: Catalin Marinas , Will Deacon , Andrii Nakryiko , Mark Rutland , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Maxwell Bland , Sami Tolvanen , Dao Huang Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Mark Rutland Currently x86 and riscv open-code 4 instances of the same logic to define a u32 variable with the KCFI typeid of a given function. Replace the duplicate logic with a common macro. Signed-off-by: Mark Rutland Co-developed-by: Maxwell Bland Signed-off-by: Maxwell Bland Co-developed-by: Sami Tolvanen Signed-off-by: Sami Tolvanen Tested-by: Dao Huang --- arch/riscv/kernel/cfi.c | 35 +++-------------------------------- arch/x86/kernel/alternative.c | 31 +++---------------------------- include/linux/cfi_types.h | 23 +++++++++++++++++++++++ 3 files changed, 29 insertions(+), 60 deletions(-) diff --git a/arch/riscv/kernel/cfi.c b/arch/riscv/kernel/cfi.c index 64bdd3e1ab8c..e7aec5f36dd5 100644 --- a/arch/riscv/kernel/cfi.c +++ b/arch/riscv/kernel/cfi.c @@ -4,6 +4,7 @@ * * Copyright (C) 2023 Google LLC */ +#include #include #include =20 @@ -82,41 +83,11 @@ 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 =3D __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" -); +DEFINE_CFI_TYPE(cfi_bpf_hash, __bpf_prog_runX); =20 /* 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 =3D __kcfi_typeid___bpf_callba= ck_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" -); +DEFINE_CFI_TYPE(cfi_bpf_subprog_hash, __bpf_callback_fn); =20 u32 cfi_get_func_hash(void *func) { diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index bf82c6f7d690..a5147fcd8397 100644 --- a/arch/x86/kernel/alternative.c +++ b/arch/x86/kernel/alternative.c @@ -1,6 +1,7 @@ // SPDX-License-Identifier: GPL-2.0-only #define pr_fmt(fmt) "SMP alternatives: " fmt =20 +#include #include #include #include @@ -947,37 +948,11 @@ 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); - -KCFI_REFERENCE(__bpf_prog_runX); - -/* u32 __ro_after_init cfi_bpf_hash =3D __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" -" .long __kcfi_typeid___bpf_prog_runX \n" -" .size cfi_bpf_hash, 4 \n" -" .popsection \n" -); +DEFINE_CFI_TYPE(cfi_bpf_hash, __bpf_prog_runX); =20 /* Must match bpf_callback_t */ extern u64 __bpf_callback_fn(u64, u64, u64, u64, u64); - -KCFI_REFERENCE(__bpf_callback_fn); - -/* u32 __ro_after_init cfi_bpf_subprog_hash =3D __kcfi_typeid___bpf_callba= ck_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" -" .long __kcfi_typeid___bpf_callback_fn \n" -" .size cfi_bpf_subprog_hash, 4 \n" -" .popsection \n" -); 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Mon, 05 May 2025 15:34:44 -0700 (PDT) Date: Mon, 5 May 2025 22:34:40 +0000 In-Reply-To: <20250505223437.3722164-4-samitolvanen@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250505223437.3722164-4-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=7DbjnHH5VAkImXf9y6kWO2Cpd7OKLAKDbR8A6OUcpSo=; b=owGbwMvMwCEWxa662nLh8irG02pJDBmSNv+n70wW3Td999qDnluU1h/qaZRrv6XgbvBB9fe9j n2HrxUxdJSyMIhxMMiKKbK0fF29dfd3p9RXn4skYOawMoEMYeDiFICJ3PVg+Kcseq1CSHzW1a6c rZ4n9e4dPmdvfbpob7XIB/7NkjLOEkcZGdbeDuLtcTvWJBP+IZHFKOjdccWdfaFpL+7dCbLplng aygEA X-Mailer: git-send-email 2.49.0.967.g6a0df3ecc3-goog Message-ID: <20250505223437.3722164-6-samitolvanen@google.com> Subject: [PATCH bpf-next v9 2/2] arm64/cfi,bpf: Support kCFI + BPF on arm64 From: Sami Tolvanen To: bpf@vger.kernel.org, Puranjay Mohan , Alexei Starovoitov , Daniel Borkmann Cc: Catalin Marinas , Will Deacon , Andrii Nakryiko , Mark Rutland , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Maxwell Bland , Puranjay Mohan , Sami Tolvanen , Dao Huang Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 Tested-by: Dao Huang --- 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/alternativ= e.c index 8ff6610af496..71c153488dad 100644 --- a/arch/arm64/kernel/alternative.c +++ b/arch/arm64/kernel/alternative.c @@ -8,11 +8,13 @@ =20 #define pr_fmt(fmt) "alternatives: " fmt =20 +#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] =3D 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..3b3691e88dd5 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -9,6 +9,7 @@ =20 #include #include +#include #include #include #include @@ -164,6 +165,12 @@ static inline void emit_bti(u32 insn, struct jit_ctx *= ctx) emit(insn, ctx); } =20 +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 ebp= f_from_cbpf) const bool is_main_prog =3D !bpf_is_subprog(prog); const u8 fp =3D bpf2a64[BPF_REG_FP]; const u8 arena_vm_base =3D bpf2a64[ARENA_VM_START]; - const int idx0 =3D ctx->idx; int cur_offset; =20 /* @@ -500,6 +506,9 @@ static int build_prologue(struct jit_ctx *ctx, bool ebp= f_from_cbpf) * */ =20 + emit_kcfi(is_main_prog ? cfi_bpf_hash : cfi_bpf_subprog_hash, ctx); + const int idx0 =3D 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 =3D ro_header; } =20 - prog->bpf_func =3D (void *)ctx.ro_image; + prog->bpf_func =3D (void *)ctx.ro_image + cfi_get_offset(); prog->jited =3D 1; - prog->jited_len =3D prog_size; + prog->jited_len =3D prog_size - cfi_get_offset(); =20 if (!prog->is_func || extra_pass) { int i; @@ -2271,6 +2280,12 @@ static int prepare_trampoline(struct jit_ctx *ctx, s= truct bpf_tramp_image *im, /* return address locates above FP */ retaddr_off =3D stack_size + 8; =20 + 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 -=3D cfi_get_offset(); hdr =3D bpf_jit_binary_pack_hdr(prog); bpf_jit_binary_pack_free(hdr, NULL); WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog)); --=20 2.49.0.967.g6a0df3ecc3-goog