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author | Puranjay Mohan <puranjay12@gmail.com> | 2023-09-08 02:05:43 +0300 |
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committer | Alexei Starovoitov <ast@kernel.org> | 2023-09-16 03:16:56 +0300 |
commit | f9e6981b1f1ce5e954e4e9b82e6d3e564d4a3254 (patch) | |
tree | 5e125b516330bfc497d3b6a44d2246dd507b32b6 /arch/arm/net/bpf_jit_32.c | |
parent | 471f3d4ee4a6db5c8621bb1c186a1d20a0639630 (diff) | |
download | linux-f9e6981b1f1ce5e954e4e9b82e6d3e564d4a3254.tar.xz |
arm32, bpf: add support for sign-extension load instruction
The cpuv4 added the support of an instruction that is similar to load
but also sign-extends the result after the load.
BPF_MEMSX | <size> | BPF_LDX means dst = *(signed size *) (src + offset)
here <size> can be one of BPF_B, BPF_H, BPF_W.
ARM32 has instructions to load a byte or a half word with sign
extension into a 32bit register. As the JIT uses two 32 bit registers
to simulate a 64-bit BPF register, an extra instruction is emitted to
sign-extent the result up to the second register.
Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/20230907230550.1417590-3-puranjay12@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'arch/arm/net/bpf_jit_32.c')
-rw-r--r-- | arch/arm/net/bpf_jit_32.c | 74 |
1 files changed, 73 insertions, 1 deletions
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index c03600fe86f6..1b3bd05878ab 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -333,6 +333,9 @@ static u32 arm_bpf_ldst_imm8(u32 op, u8 rt, u8 rn, s16 imm8) #define ARM_LDRD_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_LDRD_I, rt, rn, off) #define ARM_LDRH_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_LDRH_I, rt, rn, off) +#define ARM_LDRSH_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_LDRSH_I, rt, rn, off) +#define ARM_LDRSB_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_LDRSB_I, rt, rn, off) + #define ARM_STR_I(rt, rn, off) arm_bpf_ldst_imm12(ARM_INST_STR_I, rt, rn, off) #define ARM_STRB_I(rt, rn, off) arm_bpf_ldst_imm12(ARM_INST_STRB_I, rt, rn, off) #define ARM_STRD_I(rt, rn, off) arm_bpf_ldst_imm8(ARM_INST_STRD_I, rt, rn, off) @@ -1026,6 +1029,24 @@ static bool is_ldst_imm(s16 off, const u8 size) return -off_max <= off && off <= off_max; } +static bool is_ldst_imm8(s16 off, const u8 size) +{ + s16 off_max = 0; + + switch (size) { + case BPF_B: + off_max = 0xff; + break; + case BPF_W: + off_max = 0xfff; + break; + case BPF_H: + off_max = 0xff; + break; + } + return -off_max <= off && off <= off_max; +} + /* *(size *)(dst + off) = src */ static inline void emit_str_r(const s8 dst, const s8 src[], s16 off, struct jit_ctx *ctx, const u8 sz){ @@ -1105,6 +1126,50 @@ static inline void emit_ldx_r(const s8 dst[], const s8 src, arm_bpf_put_reg64(dst, rd, ctx); } +/* dst = *(signed size*)(src + off) */ +static inline void emit_ldsx_r(const s8 dst[], const s8 src, + s16 off, struct jit_ctx *ctx, const u8 sz){ + const s8 *tmp = bpf2a32[TMP_REG_1]; + const s8 *rd = is_stacked(dst_lo) ? tmp : dst; + s8 rm = src; + int add_off; + + if (!is_ldst_imm8(off, sz)) { + /* + * offset does not fit in the load/store immediate, + * construct an ADD instruction to apply the offset. + */ + add_off = imm8m(off); + if (add_off > 0) { + emit(ARM_ADD_I(tmp[0], src, add_off), ctx); + rm = tmp[0]; + } else { + emit_a32_mov_i(tmp[0], off, ctx); + emit(ARM_ADD_R(tmp[0], tmp[0], src), ctx); + rm = tmp[0]; + } + off = 0; + } + + switch (sz) { + case BPF_B: + /* Load a Byte with sign extension*/ + emit(ARM_LDRSB_I(rd[1], rm, off), ctx); + break; + case BPF_H: + /* Load a HalfWord with sign extension*/ + emit(ARM_LDRSH_I(rd[1], rm, off), ctx); + break; + case BPF_W: + /* Load a Word*/ + emit(ARM_LDR_I(rd[1], rm, off), ctx); + break; + } + /* Carry the sign extension to upper 32 bits */ + emit(ARM_ASR_I(rd[0], rd[1], 31), ctx); + arm_bpf_put_reg64(dst, rd, ctx); +} + /* Arithmatic Operation */ static inline void emit_ar_r(const u8 rd, const u8 rt, const u8 rm, const u8 rn, struct jit_ctx *ctx, u8 op, @@ -1603,8 +1668,15 @@ exit: case BPF_LDX | BPF_MEM | BPF_H: case BPF_LDX | BPF_MEM | BPF_B: case BPF_LDX | BPF_MEM | BPF_DW: + /* LDSX: dst = *(signed size *)(src + off) */ + case BPF_LDX | BPF_MEMSX | BPF_B: + case BPF_LDX | BPF_MEMSX | BPF_H: + case BPF_LDX | BPF_MEMSX | BPF_W: rn = arm_bpf_get_reg32(src_lo, tmp2[1], ctx); - emit_ldx_r(dst, rn, off, ctx, BPF_SIZE(code)); + if (BPF_MODE(insn->code) == BPF_MEMSX) + emit_ldsx_r(dst, rn, off, ctx, BPF_SIZE(code)); + else + emit_ldx_r(dst, rn, off, ctx, BPF_SIZE(code)); break; /* speculation barrier */ case BPF_ST | BPF_NOSPEC: |