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 <mark.rutland@arm.com>
Co-developed-by: Maxwell Bland <mbland@motorola.com>
Signed-off-by: Maxwell Bland <mbland@motorola.com>
Co-developed-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>
Tested-by: Dao Huang <huangdao1@oppo.com>
Acked-by: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20250801001004.1859976-6-samitolvanen@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/arch/riscv/kernel/cfi.c b/arch/riscv/kernel/cfi.c
index 64bdd3e1ab8ca48e57be56db9a153493af13316f..e7aec5f36dd50184191809d8aab5bb6bc13350ec 100644 (file)
--- 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 ea1d984166cdd404014a7896009eced253d47a14..a555665b4d9c4d9b9a7a3a5597594f5b437dd368 100644 (file)
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -2,6 +2,7 @@
 #define pr_fmt(fmt) "SMP alternatives: " fmt
 
 #include <linux/mmu_context.h>
+#include <linux/cfi_types.h>
 #include <linux/perf_event.h>
 #include <linux/vmalloc.h>
 #include <linux/memory.h>
@@ -1189,37 +1190,11 @@ 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 = __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);
-
-KCFI_REFERENCE(__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 6b87136757655c05d8254b76120f14d32a32f2ac..685f7181780f9233cc5fc06d1c5b2b3046d1cc07 100644 (file)
--- 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 __ro_after_init = __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 */