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arm32, bpf: add support for 32-bit signed division 

The cpuv4 added a new BPF_SDIV instruction that does signed division.
The encoding is similar to BPF_DIV but BPF_SDIV sets offset=1.

ARM32 already supports 32-bit BPF_DIV which can be easily extended to
support BPF_SDIV as ARM32 has the SDIV instruction. When the CPU is not
ARM-v7, we implement that SDIV/SMOD with the function call similar to
the implementation of DIV/MOD.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20230907230550.1417590-6-puranjay12@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Puranjay Mohan 2023-09-07 23:05:46 +00:00 committed by Alexei Starovoitov
parent 1cfb7eaebe
commit 5097faa559
2 changed files with 32 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
arch/arm/net/bpf_jit_32.c
View File

@ -228,6 +228,16 @@ static u32 jit_mod32(u32 dividend, u32 divisor)
return dividend % divisor;
}
static s32 jit_sdiv32(s32 dividend, s32 divisor)
{
return dividend / divisor;
}
static s32 jit_smod32(s32 dividend, s32 divisor)
{
return dividend % divisor;
}
static inline void _emit(int cond, u32 inst, struct jit_ctx *ctx)
{
inst |= (cond << 28);
@ -477,17 +487,18 @@ static inline int epilogue_offset(const struct jit_ctx *ctx)
return to - from - 2;
}
static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx, u8 op)
static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx, u8 op, u8 sign)
{
const int exclude_mask = BIT(ARM_R0) | BIT(ARM_R1);
const s8 *tmp = bpf2a32[TMP_REG_1];
u32 dst;
#if __LINUX_ARM_ARCH__ == 7
if (elf_hwcap & HWCAP_IDIVA) {
if (op == BPF_DIV)
emit(ARM_UDIV(rd, rm, rn), ctx);
else {
emit(ARM_UDIV(ARM_IP, rm, rn), ctx);
if (op == BPF_DIV) {
emit(sign ? ARM_SDIV(rd, rm, rn) : ARM_UDIV(rd, rm, rn), ctx);
} else {
emit(sign ? ARM_SDIV(ARM_IP, rm, rn) : ARM_UDIV(ARM_IP, rm, rn), ctx);
emit(ARM_MLS(rd, rn, ARM_IP, rm), ctx);
}
return;
@ -515,8 +526,19 @@ static inline void emit_udivmod(u8 rd, u8 rm, u8 rn, struct jit_ctx *ctx, u8 op)
emit(ARM_PUSH(CALLER_MASK & ~exclude_mask), ctx);
/* Call appropriate function */
emit_mov_i(ARM_IP, op == BPF_DIV ?
(u32)jit_udiv32 : (u32)jit_mod32, ctx);
if (sign) {
if (op == BPF_DIV)
dst = (u32)jit_sdiv32;
else
dst = (u32)jit_smod32;
} else {
if (op == BPF_DIV)
dst = (u32)jit_udiv32;
else
dst = (u32)jit_mod32;
}
emit_mov_i(ARM_IP, dst, ctx);
emit_blx_r(ARM_IP, ctx);
/* Restore caller-saved registers from stack */
@ -1551,7 +1573,7 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx)
rt = src_lo;
break;
}
emit_udivmod(rd_lo, rd_lo, rt, ctx, BPF_OP(code));
emit_udivmod(rd_lo, rd_lo, rt, ctx, BPF_OP(code), off);
arm_bpf_put_reg32(dst_lo, rd_lo, ctx);
if (!ctx->prog->aux->verifier_zext)
emit_a32_mov_i(dst_hi, 0, ctx);

2
arch/arm/net/bpf_jit_32.h
View File

@ -139,6 +139,7 @@
#define ARM_INST_TST_I 0x03100000
#define ARM_INST_UDIV 0x0730f010
#define ARM_INST_SDIV 0x0710f010
#define ARM_INST_UMULL 0x00800090
@ -267,6 +268,7 @@
#define ARM_TST_I(rn, imm) _AL3_I(ARM_INST_TST, 0, rn, imm)
#define ARM_UDIV(rd, rn, rm) (ARM_INST_UDIV | (rd) << 16 | (rn) | (rm) << 8)
#define ARM_SDIV(rd, rn, rm) (ARM_INST_SDIV | (rd) << 16 | (rn) | (rm) << 8)
#define ARM_UMULL(rd_lo, rd_hi, rn, rm) (ARM_INST_UMULL | (rd_hi) << 16 \
| (rd_lo) << 12 | (rm) << 8 | rn)