* [PATCH bpf-next v7 1/2] cfi: add C CFI type macro
2024-06-17 16:27 [PATCH bpf-next v7 0/2] Support kCFI + BPF on arm64 Maxwell Bland
@ 2024-06-17 16:30 ` Maxwell Bland
2024-06-17 16:31 ` [PATCH bpf-next v7 2/2] arm64/cfi,bpf: Support kCFI + BPF on arm64 Maxwell Bland
1 sibling, 0 replies; 4+ messages in thread
From: Maxwell Bland @ 2024-06-17 16:30 UTC (permalink / raw)
To: open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)
Cc: Catalin Marinas, Will Deacon, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko, Martin KaFai Lau, Eduard Zingerman, Song Liu,
Yonghong Song, John Fastabend, KP Singh, Stanislav Fomichev,
Hao Luo, Jiri Olsa, Zi Shen Lim, Mark Rutland, Suzuki K Poulose,
Mark Brown, linux-arm-kernel, open list, Josh Poimboeuf,
Puranjay Mohan
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>
Signed-off-by: Maxwell Bland <mbland@motorola.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 89de61243272..933d0c13a0d8 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>
@@ -901,41 +902,11 @@ 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 */
--
2.43.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH bpf-next v7 2/2] arm64/cfi,bpf: Support kCFI + BPF on arm64
2024-06-17 16:27 [PATCH bpf-next v7 0/2] Support kCFI + BPF on arm64 Maxwell Bland
2024-06-17 16:30 ` [PATCH bpf-next v7 1/2] cfi: add C CFI type macro Maxwell Bland
@ 2024-06-17 16:31 ` Maxwell Bland
2024-06-18 13:30 ` Puranjay Mohan
1 sibling, 1 reply; 4+ messages in thread
From: Maxwell Bland @ 2024-06-17 16:31 UTC (permalink / raw)
To: open list:BPF [GENERAL] (Safe Dynamic Programs and Tools)
Cc: Catalin Marinas, Will Deacon, Alexei Starovoitov, Daniel Borkmann,
Andrii Nakryiko, Martin KaFai Lau, Eduard Zingerman, Song Liu,
Yonghong Song, John Fastabend, KP Singh, Stanislav Fomichev,
Hao Luo, Jiri Olsa, Zi Shen Lim, Mark Rutland, Suzuki K Poulose,
Mark Brown, linux-arm-kernel, open list, Josh Poimboeuf,
Puranjay Mohan
From: Puranjay Mohan <puranjay12@gmail.com>
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 <puranjay12@gmail.com>
Signed-off-by: Maxwell Bland <mbland@motorola.com>
---
arch/arm64/include/asm/cfi.h | 23 +++++++++++++++++++++++
arch/arm64/kernel/alternative.c | 18 ++++++++++++++++++
arch/arm64/net/bpf_jit_comp.c | 21 ++++++++++++++++++---
3 files changed, 59 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 000000000000..670e191f8628
--- /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 8ff6610af496..d7a58eca7665 100644
--- a/arch/arm64/kernel/alternative.c
+++ b/arch/arm64/kernel/alternative.c
@@ -8,11 +8,13 @@
#define pr_fmt(fmt) "alternatives: " fmt
+#include <linux/cfi_types.h>
#include <linux/init.h>
#include <linux/cpu.h>
#include <linux/elf.h>
#include <asm/cacheflush.h>
#include <asm/alternative.h>
+#include <asm/cfi.h>
#include <asm/cpufeature.h>
#include <asm/insn.h>
#include <asm/module.h>
@@ -298,3 +300,19 @@ 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 *hashp = func - cfi_get_offset();
+ return READ_ONCE(*hashp);
+}
+#endif
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c
index 720336d28856..211e1c29f004 100644
--- a/arch/arm64/net/bpf_jit_comp.c
+++ b/arch/arm64/net/bpf_jit_comp.c
@@ -17,6 +17,7 @@
#include <asm/asm-extable.h>
#include <asm/byteorder.h>
#include <asm/cacheflush.h>
+#include <asm/cfi.h>
#include <asm/debug-monitors.h>
#include <asm/insn.h>
#include <asm/patching.h>
@@ -162,6 +163,12 @@ 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
@@ -311,7 +318,6 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf,
const u8 tcc = bpf2a64[TCALL_CNT];
const u8 fpb = bpf2a64[FP_BOTTOM];
const u8 arena_vm_base = bpf2a64[ARENA_VM_START];
- const int idx0 = ctx->idx;
int cur_offset;
/*
@@ -337,6 +343,9 @@ 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
@@ -1849,9 +1858,9 @@ 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;
@@ -2104,6 +2113,12 @@ 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
--
2.43.0
^ permalink raw reply related [flat|nested] 4+ messages in thread