ARM32 doesn't have instructions to do 64-bit/64-bit divisions. So, to implement the following instructions: BPF_ALU64 | BPF_DIV BPF_ALU64 | BPF_MOD BPF_ALU64 | BPF_SDIV BPF_ALU64 | BPF_SMOD
We implement the above instructions by doing function calls to div64_u64() and div64_u64_rem() for unsigned division/mod and calls to div64_s64() for signed division/mod.
Signed-off-by: Puranjay Mohan puranjay12@gmail.com --- arch/arm/net/bpf_jit_32.c | 116 +++++++++++++++++++++++++++++++++++++- 1 file changed, 115 insertions(+), 1 deletion(-)
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index 6939546f4ddf..1d672457d02f 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -2,6 +2,7 @@ /* * Just-In-Time compiler for eBPF filters on 32bit ARM * + * Copyright (c) 2023 Puranjay Mohan puranjay12@gmail.com * Copyright (c) 2017 Shubham Bansal illusionist.neo@gmail.com * Copyright (c) 2011 Mircea Gherzan mgherzan@gmail.com */ @@ -15,6 +16,7 @@ #include <linux/string.h> #include <linux/slab.h> #include <linux/if_vlan.h> +#include <linux/math64.h>
#include <asm/cacheflush.h> #include <asm/hwcap.h> @@ -238,6 +240,34 @@ static s32 jit_smod32(s32 dividend, s32 divisor) return dividend % divisor; }
+/* Wrappers for 64-bit div/mod */ +static u64 jit_udiv64(u64 dividend, u64 divisor) +{ + return div64_u64(dividend, divisor); +} + +static u64 jit_mod64(u64 dividend, u64 divisor) +{ + u64 rem; + + div64_u64_rem(dividend, divisor, &rem); + return rem; +} + +static s64 jit_sdiv64(s64 dividend, s64 divisor) +{ + return div64_s64(dividend, divisor); +} + +static s64 jit_smod64(s64 dividend, s64 divisor) +{ + u64 q; + + q = div64_s64(dividend, divisor); + + return dividend - q * divisor; +} + static inline void _emit(int cond, u32 inst, struct jit_ctx *ctx) { inst |= (cond << 28); @@ -555,6 +585,78 @@ static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx, u8 op, emit(ARM_MOV_R(ARM_R0, tmp[1]), ctx); }
+static inline void emit_udivmod64(const s8 *rd, const s8 *rm, const s8 *rn, struct jit_ctx *ctx, + u8 op, u8 sign) +{ + u32 dst; + + /* Push caller-saved registers on stack */ + emit(ARM_PUSH(CALLER_MASK), ctx); + + /* + * As we are implementing 64-bit div/mod as function calls, We need to put the dividend in + * R0-R1 and the divisor in R2-R3. As we have already pushed these registers on the stack, + * we can recover them later after returning from the function call. + */ + if (rm[1] != ARM_R0 || rn[1] != ARM_R2) { + /* + * Move Rm to {R1, R0} if it is not already there. + */ + if (rm[1] != ARM_R0) { + if (rn[1] == ARM_R0) + emit(ARM_PUSH(BIT(ARM_R0) | BIT(ARM_R1)), ctx); + emit(ARM_MOV_R(ARM_R1, rm[0]), ctx); + emit(ARM_MOV_R(ARM_R0, rm[1]), ctx); + if (rn[1] == ARM_R0) { + emit(ARM_POP(BIT(ARM_R2) | BIT(ARM_R3)), ctx); + goto cont; + } + } + /* + * Move Rn to {R3, R2} if it is not already there. + */ + if (rn[1] != ARM_R2) { + emit(ARM_MOV_R(ARM_R3, rn[0]), ctx); + emit(ARM_MOV_R(ARM_R2, rn[1]), ctx); + } + } + +cont: + + /* Call appropriate function */ + if (sign) { + if (op == BPF_DIV) + dst = (u32)jit_sdiv64; + else + dst = (u32)jit_smod64; + } else { + if (op == BPF_DIV) + dst = (u32)jit_udiv64; + else + dst = (u32)jit_mod64; + } + + emit_mov_i(ARM_IP, dst, ctx); + emit_blx_r(ARM_IP, ctx); + + /* Save return value */ + if (rd[1] != ARM_R0) { + emit(ARM_MOV_R(rd[0], ARM_R1), ctx); + emit(ARM_MOV_R(rd[1], ARM_R0), ctx); + } + + /* Recover {R3, R2} and {R1, R0} from stack if they are not Rd */ + if (rd[1] != ARM_R0 && rd[1] != ARM_R2) { + emit(ARM_POP(CALLER_MASK), ctx); + } else if (rd[1] != ARM_R0) { + emit(ARM_POP(BIT(ARM_R0) | BIT(ARM_R1)), ctx); + emit(ARM_ADD_I(ARM_SP, ARM_SP, 8), ctx); + } else { + emit(ARM_ADD_I(ARM_SP, ARM_SP, 8), ctx); + emit(ARM_POP(BIT(ARM_R2) | BIT(ARM_R3)), ctx); + } +} + /* Is the translated BPF register on stack? */ static bool is_stacked(s8 reg) { @@ -1582,7 +1684,19 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) case BPF_ALU64 | BPF_DIV | BPF_X: case BPF_ALU64 | BPF_MOD | BPF_K: case BPF_ALU64 | BPF_MOD | BPF_X: - goto notyet; + rd = arm_bpf_get_reg64(dst, tmp2, ctx); + switch (BPF_SRC(code)) { + case BPF_X: + rs = arm_bpf_get_reg64(src, tmp, ctx); + break; + case BPF_K: + rs = tmp; + emit_a32_mov_se_i64(is64, rs, imm, ctx); + break; + } + emit_udivmod64(rd, rd, rs, ctx, BPF_OP(code), off); + arm_bpf_put_reg64(dst, rd, ctx); + break; /* dst = dst << imm */ /* dst = dst >> imm */ /* dst = dst >> imm (signed) */