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Date: Mon, 13 May 2024 09:10:36 -0500
From: Maxwell Bland <mbland@motorola.com>
To: "open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)" <bpf@vger.kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Andrii Nakryiko <andrii@kernel.org>,
        Martin KaFai Lau <martin.lau@linux.dev>,
        Eduard Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>,
        Yonghong Song <yonghong.song@linux.dev>,
        John Fastabend <john.fastabend@gmail.com>,
        KP Singh <kpsingh@kernel.org>, Stanislav Fomichev <sdf@google.com>,
        Hao Luo <haoluo@google.com>, Jiri Olsa <jolsa@kernel.org>,
        Zi Shen Lim <zlim.lnx@gmail.com>, Mark Rutland <mark.rutland@arm.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        Mark Brown <broonie@kernel.org>, linux-arm-kernel@lists.infradead.org,
        open list <linux-kernel@vger.kernel.org>,
        Josh Poimboeuf <jpoimboe@kernel.org>,
        Puranjay Mohan <puranjay12@gmail.com>
Subject: [PATCH bpf-next v4 1/3] cfi: add C CFI type macro
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From: Mark Rutland <mark.rutland@arm.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@arm.com>
---
Minor fix of authorship attribution by adding "From:" field!

 arch/riscv/kernel/cfi.c       | 34 ++--------------------------------
 arch/x86/kernel/alternative.c | 35 +++--------------------------------
 include/linux/cfi_types.h     | 23 +++++++++++++++++++++++
 3 files changed, 28 insertions(+), 64 deletions(-)

diff --git a/arch/riscv/kernel/cfi.c b/arch/riscv/kernel/cfi.c
index 64bdd3e1ab8c..b78a6f41df22 100644
--- a/arch/riscv/kernel/cfi.c
+++ b/arch/riscv/kernel/cfi.c
@@ -82,41 +82,11 @@ 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 45a280f2161c..a822699a40dd 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>
@@ -918,41 +919,11 @@ 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..f510e62ca8b1 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"	\
+	"	.long	__kcfi_typeid_" #func "				\n"	\
+	"	.size	" #name ", 4					\n"	\
+	"	.popsection						\n"	\
+	);
+#endif
+
 #endif /* __ASSEMBLY__ */
 #endif /* _LINUX_CFI_TYPES_H */
-- 
2.34.1