linux-kernel - [PATCH bpf-next v3 3/3] arm64/cfi,bpf: Use DEFINE_CFI

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Date: Tue, 7 May 2024 18:47:46 -0500
From: Maxwell Bland <mbland@...orola.com>
To: "open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)" <bpf@...r.kernel.org>
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        Zi Shen Lim <zlim.lnx@...il.com>, Mark Rutland <mark.rutland@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Mark Brown <broonie@...nel.org>, linux-arm-kernel@...ts.infradead.org,
        open list <linux-kernel@...r.kernel.org>,
        Puranjay Mohan <puranjay12@...il.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>
Subject: [PATCH bpf-next v3 3/3] arm64/cfi,bpf: Use DEFINE_CFI_TYPE in arm64

Corrects Puranjay Mohan's commit to adopt Mark Rutland's
suggestion of using a C CFI type macro in kCFI+BPF.

Signed-off-by: Maxwell Bland <mbland@...orola.com>
---
 arch/arm64/kernel/alternative.c | 46 ++++-----------------------------
 1 file changed, 5 insertions(+), 41 deletions(-)

diff --git a/arch/arm64/kernel/alternative.c b/arch/arm64/kernel/alternative.c
index 1715da7df137..d7a58eca7665 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -8,6 +8,7 @@
 
 #define pr_fmt(fmt) "alternatives: " fmt
 
+#include <linux/cfi_types.h>
 #include <linux/init.h>
 #include <linux/cpu.h>
 #include <linux/elf.h>
@@ -302,53 +303,16 @@ 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);
-
-/*
- * 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)
 {
-	u32 hash;
-
-	if (get_kernel_nofault(hash, func - cfi_get_offset()))
-		return 0;
-
-	return hash;
+	u32 *hashp = func - cfi_get_offset();
+	return READ_ONCE(*hashp);
 }
 #endif
-- 
2.34.1