Messages in this thread | | | Subject | Re: [PATCH bpf-next v4] bpf: Add kernel function call support in 32-bit ARM for EABI | From | Daniel Borkmann <> | Date | Fri, 6 Jan 2023 15:46:07 +0100 |
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On 12/20/22 12:53 PM, Yang Jihong wrote: > This patch adds kernel function call support to 32-bit ARM bpf jit for > EABI. > > Signed-off-by: Yang Jihong <yangjihong1@huawei.com> > --- > > Changes since v3: > - Submit patches related to the ARM32 architecture separately. > > Changes since v2: > - Remove patches to adjust sk size check for CO_RE in 32-bit arch. > - Add check of kfunc's return value in insn_def_regno. > - Adjust is_reg64 for insn_def_regno. > - The check of CONFIG_AEABI is moved from emit_kfunc_call to > bpf_jit_supports_kfunc_call. > - Fix a comment error in fixup_kfunc_call. > > arch/arm/net/bpf_jit_32.c | 137 ++++++++++++++++++++++++++++++++++++++ > 1 file changed, 137 insertions(+) > > diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c > index 6a1c9fca5260..ae3a36d909f4 100644 > --- a/arch/arm/net/bpf_jit_32.c > +++ b/arch/arm/net/bpf_jit_32.c > @@ -1337,6 +1337,125 @@ static void build_epilogue(struct jit_ctx *ctx) > #endif > } > > +/* > + * Input parameters of function in 32-bit ARM architecture: > + * The first four word-sized parameters passed to a function will be > + * transferred in registers R0-R3. Sub-word sized arguments, for example, > + * char, will still use a whole register. > + * Arguments larger than a word will be passed in multiple registers. > + * If more arguments are passed, the fifth and subsequent words will be passed > + * on the stack. > + * > + * The first for args of a function will be considered for > + * putting into the 32bit register R1, R2, R3 and R4. > + * > + * Two 32bit registers are used to pass a 64bit arg. > + * > + * For example, > + * void foo(u32 a, u32 b, u32 c, u32 d, u32 e): > + * u32 a: R0 > + * u32 b: R1 > + * u32 c: R2 > + * u32 d: R3 > + * u32 e: stack > + * > + * void foo(u64 a, u32 b, u32 c, u32 d): > + * u64 a: R0 (lo32) R1 (hi32) > + * u32 b: R2 > + * u32 c: R3 > + * u32 d: stack > + * > + * void foo(u32 a, u64 b, u32 c, u32 d): > + * u32 a: R0 > + * u64 b: R2 (lo32) R3 (hi32) > + * u32 c: stack > + * u32 d: stack > + * > + * void foo(u32 a, u32 b, u64 c, u32 d): > + * u32 a: R0 > + * u32 b: R1 > + * u64 c: R2 (lo32) R3 (hi32) > + * u32 d: stack > + * > + * void foo(u64 a, u64 b): > + * u64 a: R0 (lo32) R1 (hi32) > + * u64 b: R2 (lo32) R3 (hi32) > + * > + * The return value will be stored in the R0 (and R1 for 64bit value). > + * > + * For example, > + * u32 foo(u32 a, u32 b, u32 c): > + * return value: R0 > + * > + * u64 foo(u32 a, u32 b, u32 c): > + * return value: R0 (lo32) R1 (hi32) > + * > + * The above is for AEABI only, OABI does not support this function. > + */ > +static int emit_kfunc_call(const struct bpf_insn *insn, struct jit_ctx *ctx, const u32 func) > +{ > + int i; > + const struct btf_func_model *fm; > + const s8 *tmp = bpf2a32[TMP_REG_1]; > + const u8 arg_regs[] = { ARM_R0, ARM_R1, ARM_R2, ARM_R3 }; > + int nr_arg_regs = ARRAY_SIZE(arg_regs); > + int arg_regs_idx = 0, stack_off = 0; > + const s8 *rd; > + s8 rt; > + > + fm = bpf_jit_find_kfunc_model(ctx->prog, insn); > + if (!fm) > + return -EINVAL; > + > + for (i = 0; i < fm->nr_args; i++) { > + if (fm->arg_size[i] > sizeof(u32)) { > + rd = arm_bpf_get_reg64(bpf2a32[BPF_REG_1 + i], tmp, ctx); > + > + if (arg_regs_idx + 1 < nr_arg_regs) { > + /* > + * AAPCS states: > + * A double-word sized type is passed in two > + * consecutive registers (e.g., r0 and r1, or > + * r2 and r3). The content of the registers is > + * as if the value had been loaded from memory > + * representation with a single LDM instruction. > + */ > + if (arg_regs_idx & 1) > + arg_regs_idx++; > + > + emit(ARM_MOV_R(arg_regs[arg_regs_idx++], rd[1]), ctx); > + emit(ARM_MOV_R(arg_regs[arg_regs_idx++], rd[0]), ctx); > + } else { > + stack_off = ALIGN(stack_off, STACK_ALIGNMENT); > + > + if (__LINUX_ARM_ARCH__ >= 6 || > + ctx->cpu_architecture >= CPU_ARCH_ARMv5TE) { > + emit(ARM_STRD_I(rd[1], ARM_SP, stack_off), ctx); > + } else { > + emit(ARM_STR_I(rd[1], ARM_SP, stack_off), ctx); > + emit(ARM_STR_I(rd[0], ARM_SP, stack_off), ctx); > + } > + > + stack_off += 8; > + } > + } else { > + rt = arm_bpf_get_reg32(bpf2a32[BPF_REG_1 + i][1], tmp[1], ctx); > + > + if (arg_regs_idx < nr_arg_regs) { > + emit(ARM_MOV_R(arg_regs[arg_regs_idx++], rt), ctx); > + } else { > + emit(ARM_STR_I(rt, ARM_SP, stack_off), ctx); > + stack_off += 4; > + } > + } > + } > + > + emit_a32_mov_i(tmp[1], func, ctx); > + emit_blx_r(tmp[1], ctx); > + > + return 0; > +} > + > /* > * Convert an eBPF instruction to native instruction, i.e > * JITs an eBPF instruction. > @@ -1603,6 +1722,10 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) > case BPF_LDX | BPF_MEM | BPF_H: > case BPF_LDX | BPF_MEM | BPF_B: > case BPF_LDX | BPF_MEM | BPF_DW: > + case BPF_LDX | BPF_PROBE_MEM | BPF_W: > + case BPF_LDX | BPF_PROBE_MEM | BPF_H: > + case BPF_LDX | BPF_PROBE_MEM | BPF_B: > + case BPF_LDX | BPF_PROBE_MEM | BPF_DW:
This doesn't look right, why is this part of the patch? It's not kfunc related and if you plan to add support for ldx_probe_mem then it should be separated from this set. Check out 800834285361 ("bpf, arm64: Add BPF exception tables"), why is this not needed for arm32?
> rn = arm_bpf_get_reg32(src_lo, tmp2[1], ctx); > emit_ldx_r(dst, rn, off, ctx, BPF_SIZE(code)); > break; > @@ -1785,6 +1908,16 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) > const s8 *r5 = bpf2a32[BPF_REG_5]; > const u32 func = (u32)__bpf_call_base + (u32)imm; > > + if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL) { > + int err; > + > + err = emit_kfunc_call(insn, ctx, func); > + > + if (err) > + return err; > + break; > + } > + > emit_a32_mov_r64(true, r0, r1, ctx); > emit_a32_mov_r64(true, r1, r2, ctx); > emit_push_r64(r5, ctx); > @@ -2022,3 +2155,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) > return prog; > } > > +bool bpf_jit_supports_kfunc_call(void) > +{ > + return IS_ENABLED(CONFIG_AEABI); > +} >
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