From: Puranjay Mohan 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 Co-developed-by: Maxwell Bland Signed-off-by: Maxwell Bland Co-developed-by: Sami Tolvanen Signed-off-by: Sami Tolvanen Tested-by: Dao Huang Acked-by: Will Deacon --- arch/arm64/include/asm/cfi.h | 7 +++++++ arch/arm64/net/bpf_jit_comp.c | 30 +++++++++++++++++++++++++++--- 2 files changed, 34 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..ab90f0351b7a --- /dev/null +++ b/arch/arm64/include/asm/cfi.h @@ -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 */ diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 89b1b8c248c6..993b5d6e1525 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -10,6 +10,7 @@ #include #include #include +#include #include #include #include @@ -106,6 +107,14 @@ 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) { @@ -166,6 +175,12 @@ 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 @@ -476,7 +491,6 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) const bool is_main_prog = !bpf_is_subprog(prog); const u8 fp = bpf2a64[BPF_REG_FP]; const u8 arena_vm_base = bpf2a64[ARENA_VM_START]; - const int idx0 = ctx->idx; int cur_offset; /* @@ -502,6 +516,9 @@ 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 @@ -2055,9 +2072,9 @@ 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; @@ -2426,6 +2443,12 @@ 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 @@ -2942,6 +2965,7 @@ 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); WARN_ON_ONCE(!bpf_prog_kallsyms_verify_off(prog)); -- 2.50.0.727.gbf7dc18ff4-goog