From a72a9be0fbde6e84bd493204bd1b75165980dd2c Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Mon, 10 Mar 2025 22:29:44 +0000 Subject: [PATCH 1/2] cfi: add C CFI type macro 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 --- arch/riscv/kernel/cfi.c | 35 +++-------------------------------- arch/x86/kernel/alternative.c | 35 +++-------------------------------- include/linux/cfi_types.h | 23 +++++++++++++++++++++++ 3 files changed, 29 insertions(+), 64 deletions(-) diff --git a/arch/riscv/kernel/cfi.c b/arch/riscv/kernel/cfi.c index 64bdd3e1ab8ca..e7aec5f36dd50 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 @@ -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 = __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); /* 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" -); +DEFINE_CFI_TYPE(cfi_bpf_subprog_hash, __bpf_callback_fn); u32 cfi_get_func_hash(void *func) { diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c index c71b575bf2292..a9f415e873dda 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 +#include #include #include #include @@ -934,41 +935,11 @@ 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 = __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); /* 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" -" .long __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); u32 cfi_get_func_hash(void *func) { diff --git a/include/linux/cfi_types.h b/include/linux/cfi_types.h index 6b87136757655..209c8a16ac4e6 100644 --- a/include/linux/cfi_types.h +++ b/include/linux/cfi_types.h @@ -41,5 +41,28 @@ SYM_TYPED_START(name, SYM_L_GLOBAL, SYM_A_ALIGN) #endif +#else /* __ASSEMBLY__ */ + +#ifdef CONFIG_CFI_CLANG +#define DEFINE_CFI_TYPE(name, func) \ + /* \ + * Force a reference to the function so the compiler generates \ + * __kcfi_typeid_. \ + */ \ + __ADDRESSABLE(func); \ + /* u32 name = __kcfi_typeid_ */ \ + extern u32 name; \ + asm ( \ + " .pushsection .data..ro_after_init,\"aw\",@progbits \n" \ + " .type " #name ",@object \n" \ + " .globl " #name " \n" \ + " .p2align 2, 0x0 \n" \ + #name ": \n" \ + " .4byte __kcfi_typeid_" #func " \n" \ + " .size " #name ", 4 \n" \ + " .popsection \n" \ + ); +#endif + #endif /* __ASSEMBLY__ */ #endif /* _LINUX_CFI_TYPES_H */ From 04fc3bb2f8cede96fa17bcd0d95e39fce5b562c0 Mon Sep 17 00:00:00 2001 From: Puranjay Mohan Date: Mon, 10 Mar 2025 22:29:45 +0000 Subject: [PATCH 2/2] arm64/cfi,bpf: Support kCFI + BPF on arm64 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 0000000000000..670e191f8628f --- /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 8ff6610af4966..71c153488dad6 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 70d7c89d3ac90..8870c205f934c 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));