linux-kernel - Re: [PATCH bpf-next v8 1/2] cfi: add C CFI type macro

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Message-ID: <1744624410-471661-1-git-send-email-huangdao1@oppo.com>
Date: Mon, 14 Apr 2025 17:53:30 +0800
From: Dao Huang <huangdao1@...o.com>
To: <samitolvanen@...gle.com>
CC: <andrii@...nel.org>, <ast@...nel.org>, <bpf@...r.kernel.org>,
	<catalin.marinas@....com>, <daniel@...earbox.net>,
	<linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
	<mark.rutland@....com>, <mbland@...orola.com>, <puranjay12@...il.com>,
	<will@...nel.org>
Subject: Re: [PATCH bpf-next v8 1/2] cfi: add C CFI type macro

> From: Mark Rutland <mark.rutland@....com>
> 
> 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 <mark.rutland@....com>
> Co-Developed-by: Maxwell Bland <mbland@...orola.com>
> Signed-off-by: Maxwell Bland <mbland@...orola.com>
> Co-Developed-by: Sami Tolvanen <samitolvanen@...gle.com>
> Signed-off-by: Sami Tolvanen <samitolvanen@...gle.com>
> ---
>  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 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 <linux/cfi_types.h>
>  #include <linux/cfi.h>
>  #include <asm/insn.h>
>  
> @@ -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 c71b575bf229..a9f415e873dd 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 <linux/cfi_types.h>
>  #include <linux/module.h>
>  #include <linux/sched.h>
>  #include <linux/perf_event.h>
> @@ -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 6b8713675765..209c8a16ac4e 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_<func>.						\
> +	 */									\
> +	__ADDRESSABLE(func);							\
> +	/* u32 name = __kcfi_typeid_<func> */					\
> +	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 */
> -- 
> 2.49.0.rc0.332.g42c0ae87b1-goog

we oppo team have tested this patch on Mediatek DX-5(arm64)
with a kernel based on android-16(kernel-6.12). It has been running
fine for a week on both machines.