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arm64/cfi,bpf: Support kCFI + BPF on arm64 

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>
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/20250801001004.1859976-8-samitolvanen@google.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
pull/1320/head
Puranjay Mohan 2025-08-01 00:10:08 +00:00 committed by Alexei Starovoitov
parent f1befc82ad
commit 710618c760
2 changed files with 34 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
arch/arm64/include/asm/cfi.h Normal file
View File

@ -0,0 +1,7 @@
/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_ARM64_CFI_H
#define _ASM_ARM64_CFI_H
#define __bpfcall
#endif /* _ASM_ARM64_CFI_H */

30
arch/arm64/net/bpf_jit_comp.c
View File

@ -10,6 +10,7 @@
#include <linux/arm-smccc.h>
#include <linux/bitfield.h>
#include <linux/bpf.h>
#include <linux/cfi.h>
#include <linux/filter.h>
#include <linux/memory.h>
#include <linux/printk.h>
@ -114,6 +115,14 @@ static inline void emit(const u32 insn, struct jit_ctx *ctx)
ctx->idx++;
}
static inline void emit_u32_data(const u32 data, struct jit_ctx *ctx)
{
if (ctx->image != NULL && ctx->write)
ctx->image[ctx->idx] = data;
ctx->idx++;
}
static inline void emit_a64_mov_i(const int is64, const int reg,
const s32 val, struct jit_ctx *ctx)
{
@ -174,6 +183,12 @@ 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_u32_data(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
@ -503,7 +518,6 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf)
const u8 arena_vm_base = bpf2a64[ARENA_VM_START];
const u8 priv_sp = bpf2a64[PRIVATE_SP];
void __percpu *priv_stack_ptr;
const int idx0 = ctx->idx;
int cur_offset;
/*
@ -529,6 +543,9 @@ 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
@ -2146,9 +2163,9 @@ skip_init_ctx:
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;
@ -2527,6 +2544,12 @@ 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
@ -3045,6 +3068,7 @@ void bpf_jit_free(struct bpf_prog *prog)
sizeof(jit_data->header->size));
kfree(jit_data);
}
prog->bpf_func -= cfi_get_offset();
hdr = bpf_jit_binary_pack_hdr(prog);
bpf_jit_binary_pack_free(hdr, NULL);
priv_stack_ptr = prog->aux->priv_stack_ptr;