From: Puranjay Mohan Implement stack argument passing for BPF-to-BPF and kfunc calls with more than 5 parameters on arm64, following the AAPCS64 calling convention. BPF R1-R5 already map to x0-x4. With BPF_REG_0 moved to x8 by the previous commit, x5-x7 are free for arguments 6-8. Arguments 9-12 spill onto the stack at [SP+0], [SP+8], ... and the callee reads them from [FP+16], [FP+24], ... (above the saved FP/LR pair). BPF convention uses fixed offsets from BPF_REG_PARAMS (r11): off=-8 is always arg 6, off=-16 arg 7, etc. The verifier invalidates all outgoing stack arg slots after each call, so the compiler must re-store before every call. This means x5-x7 don't need to be saved on stack. Signed-off-by: Puranjay Mohan Signed-off-by: Yonghong Song --- arch/arm64/net/bpf_jit_comp.c | 88 ++++++++++++++++++++++++++++++++++- 1 file changed, 87 insertions(+), 1 deletion(-) diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index 085e650662e3..e3bbeaa94590 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -86,6 +86,7 @@ struct jit_ctx { __le32 *image; __le32 *ro_image; u32 stack_size; + u16 stack_arg_size; u64 user_vm_start; u64 arena_vm_start; bool fp_used; @@ -533,13 +534,19 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) * | | * +-----+ <= (BPF_FP - prog->aux->stack_depth) * |RSVD | padding - * current A64_SP => +-----+ <= (BPF_FP - ctx->stack_size) + * +-----+ <= (BPF_FP - ctx->stack_size) + * | | + * | ... | outgoing stack args (9+, if any) + * | | + * current A64_SP => +-----+ * | | * | ... | Function call stack * | | * +-----+ * low * + * Stack args 6-8 are passed in x5-x7, args 9+ at [SP]. + * Incoming args 9+ are at [FP + 16], [FP + 24], ... */ emit_kcfi(is_main_prog ? cfi_bpf_hash : cfi_bpf_subprog_hash, ctx); @@ -613,6 +620,9 @@ static int build_prologue(struct jit_ctx *ctx, bool ebpf_from_cbpf) if (ctx->stack_size && !ctx->priv_sp_used) emit(A64_SUB_I(1, A64_SP, A64_SP, ctx->stack_size), ctx); + if (ctx->stack_arg_size) + emit(A64_SUB_I(1, A64_SP, A64_SP, ctx->stack_arg_size), ctx); + if (ctx->arena_vm_start) emit_a64_mov_i64(arena_vm_base, ctx->arena_vm_start, ctx); @@ -673,6 +683,9 @@ static int emit_bpf_tail_call(struct jit_ctx *ctx) /* Update tail_call_cnt if the slot is populated. */ emit(A64_STR64I(tcc, ptr, 0), ctx); + if (ctx->stack_arg_size) + emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_arg_size), ctx); + /* restore SP */ if (ctx->stack_size && !ctx->priv_sp_used) emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_size), ctx); @@ -1034,6 +1047,9 @@ static void build_epilogue(struct jit_ctx *ctx, bool was_classic) const u8 r0 = bpf2a64[BPF_REG_0]; const u8 ptr = bpf2a64[TCCNT_PTR]; + if (ctx->stack_arg_size) + emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_arg_size), ctx); + /* We're done with BPF stack */ if (ctx->stack_size && !ctx->priv_sp_used) emit(A64_ADD_I(1, A64_SP, A64_SP, ctx->stack_size), ctx); @@ -1191,6 +1207,41 @@ static int add_exception_handler(const struct bpf_insn *insn, return 0; } +static const u8 stack_arg_reg[] = { A64_R(5), A64_R(6), A64_R(7) }; + +#define NR_STACK_ARG_REGS ARRAY_SIZE(stack_arg_reg) + +static void emit_stack_arg_load(u8 dst, s16 bpf_off, struct jit_ctx *ctx) +{ + int idx = bpf_off / sizeof(u64) - 1; + + if (idx < NR_STACK_ARG_REGS) + emit(A64_MOV(1, dst, stack_arg_reg[idx]), ctx); + else + emit(A64_LDR64I(dst, A64_FP, (idx - NR_STACK_ARG_REGS) * sizeof(u64) + 16), ctx); +} + +static void emit_stack_arg_store(u8 src_a64, s16 bpf_off, struct jit_ctx *ctx) +{ + int idx = -bpf_off / sizeof(u64) - 1; + + if (idx < NR_STACK_ARG_REGS) + emit(A64_MOV(1, stack_arg_reg[idx], src_a64), ctx); + else + emit(A64_STR64I(src_a64, A64_SP, (idx - NR_STACK_ARG_REGS) * sizeof(u64)), ctx); +} + +static void emit_stack_arg_store_imm(s32 imm, s16 bpf_off, const u8 tmp, struct jit_ctx *ctx) +{ + int idx = -bpf_off / sizeof(u64) - 1; + + emit_a64_mov_i(1, tmp, imm, ctx); + if (idx < NR_STACK_ARG_REGS) + emit(A64_MOV(1, stack_arg_reg[idx], tmp), ctx); + else + emit(A64_STR64I(tmp, A64_SP, (idx - NR_STACK_ARG_REGS) * sizeof(u64)), ctx); +} + /* JITs an eBPF instruction. * Returns: * 0 - successfully JITed an 8-byte eBPF instruction. @@ -1646,6 +1697,11 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn case BPF_LDX | BPF_MEM | BPF_H: case BPF_LDX | BPF_MEM | BPF_B: case BPF_LDX | BPF_MEM | BPF_DW: + if (insn->src_reg == BPF_REG_PARAMS) { + emit_stack_arg_load(dst, off, ctx); + break; + } + fallthrough; case BPF_LDX | BPF_PROBE_MEM | BPF_DW: case BPF_LDX | BPF_PROBE_MEM | BPF_W: case BPF_LDX | BPF_PROBE_MEM | BPF_H: @@ -1672,6 +1728,8 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn if (src == fp) { src_adj = ctx->priv_sp_used ? priv_sp : A64_SP; off_adj = off + ctx->stack_size; + if (!ctx->priv_sp_used) + off_adj += ctx->stack_arg_size; } else { src_adj = src; off_adj = off; @@ -1752,6 +1810,11 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn case BPF_ST | BPF_MEM | BPF_H: case BPF_ST | BPF_MEM | BPF_B: case BPF_ST | BPF_MEM | BPF_DW: + if (insn->dst_reg == BPF_REG_PARAMS) { + emit_stack_arg_store_imm(imm, off, tmp, ctx); + break; + } + fallthrough; case BPF_ST | BPF_PROBE_MEM32 | BPF_B: case BPF_ST | BPF_PROBE_MEM32 | BPF_H: case BPF_ST | BPF_PROBE_MEM32 | BPF_W: @@ -1763,6 +1826,8 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn if (dst == fp) { dst_adj = ctx->priv_sp_used ? priv_sp : A64_SP; off_adj = off + ctx->stack_size; + if (!ctx->priv_sp_used) + off_adj += ctx->stack_arg_size; } else { dst_adj = dst; off_adj = off; @@ -1814,6 +1879,11 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn case BPF_STX | BPF_MEM | BPF_H: case BPF_STX | BPF_MEM | BPF_B: case BPF_STX | BPF_MEM | BPF_DW: + if (insn->dst_reg == BPF_REG_PARAMS) { + emit_stack_arg_store(src, off, ctx); + break; + } + fallthrough; case BPF_STX | BPF_PROBE_MEM32 | BPF_B: case BPF_STX | BPF_PROBE_MEM32 | BPF_H: case BPF_STX | BPF_PROBE_MEM32 | BPF_W: @@ -1825,6 +1895,8 @@ static int build_insn(const struct bpf_verifier_env *env, const struct bpf_insn if (dst == fp) { dst_adj = ctx->priv_sp_used ? priv_sp : A64_SP; off_adj = off + ctx->stack_size; + if (!ctx->priv_sp_used) + off_adj += ctx->stack_arg_size; } else { dst_adj = dst; off_adj = off; @@ -2018,6 +2090,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr u8 *ro_image_ptr; int body_idx; int exentry_idx; + int out_cnt; if (!prog->jit_requested) return prog; @@ -2065,6 +2138,14 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_verifier_env *env, struct bpf_pr ctx.user_vm_start = bpf_arena_get_user_vm_start(prog->aux->arena); ctx.arena_vm_start = bpf_arena_get_kern_vm_start(prog->aux->arena); + out_cnt = bpf_out_stack_arg_cnt(env, prog); + if (out_cnt) { + int nr_on_stack = out_cnt - NR_STACK_ARG_REGS; + + if (nr_on_stack > 0) + ctx.stack_arg_size = round_up(nr_on_stack * sizeof(u64), 16); + } + if (priv_stack_ptr) ctx.priv_sp_used = true; @@ -2229,6 +2310,11 @@ bool bpf_jit_supports_kfunc_call(void) return true; } +bool bpf_jit_supports_stack_args(void) +{ + return true; +} + void *bpf_arch_text_copy(void *dst, void *src, size_t len) { if (!aarch64_insn_copy(dst, src, len)) -- 2.53.0-Meta