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authorRussell King <rmk+kernel@armlinux.org.uk>2018-01-14 00:06:16 +0300
committerRussell King <rmk+kernel@armlinux.org.uk>2018-01-17 22:38:21 +0300
commitec19e02b343db991d2d1610c409efefebf4e2ca9 (patch)
treec631847a3e173367ef9ec46d38d1ebc4a4815278
parent02088d9b392f605c892894b46aa8c83e3abd0115 (diff)
downloadlinux-ec19e02b343db991d2d1610c409efefebf4e2ca9.tar.xz
ARM: net: bpf: fix LDX instructions
When the source and destination register are identical, our JIT does not generate correct code, which leads to kernel oopses. Fix this by (a) generating more efficient code, and (b) making use of the temporary earlier if we will overwrite the address register. Fixes: 39c13c204bb1 ("arm: eBPF JIT compiler") Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
-rw-r--r--arch/arm/net/bpf_jit_32.c61
1 files changed, 33 insertions, 28 deletions
diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index 95bb3f896c8f..715e7250de86 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c
@@ -913,33 +913,53 @@ static inline void emit_str_r(const u8 dst, const u8 src, bool dstk,
}
/* dst = *(size*)(src + off) */
-static inline void emit_ldx_r(const u8 dst, const u8 src, bool dstk,
- const s32 off, struct jit_ctx *ctx, const u8 sz){
+static inline void emit_ldx_r(const u8 dst[], const u8 src, bool dstk,
+ s32 off, struct jit_ctx *ctx, const u8 sz){
const u8 *tmp = bpf2a32[TMP_REG_1];
- u8 rd = dstk ? tmp[1] : dst;
+ const u8 *rd = dstk ? tmp : dst;
u8 rm = src;
+ s32 off_max;
- if (off) {
+ if (sz == BPF_H)
+ off_max = 0xff;
+ else
+ off_max = 0xfff;
+
+ if (off < 0 || off > off_max) {
emit_a32_mov_i(tmp[0], off, false, ctx);
emit(ARM_ADD_R(tmp[0], tmp[0], src), ctx);
rm = tmp[0];
+ off = 0;
+ } else if (rd[1] == rm) {
+ emit(ARM_MOV_R(tmp[0], rm), ctx);
+ rm = tmp[0];
}
switch (sz) {
- case BPF_W:
- /* Load a Word */
- emit(ARM_LDR_I(rd, rm, 0), ctx);
+ case BPF_B:
+ /* Load a Byte */
+ emit(ARM_LDRB_I(rd[1], rm, off), ctx);
+ emit_a32_mov_i(dst[0], 0, dstk, ctx);
break;
case BPF_H:
/* Load a HalfWord */
- emit(ARM_LDRH_I(rd, rm, 0), ctx);
+ emit(ARM_LDRH_I(rd[1], rm, off), ctx);
+ emit_a32_mov_i(dst[0], 0, dstk, ctx);
break;
- case BPF_B:
- /* Load a Byte */
- emit(ARM_LDRB_I(rd, rm, 0), ctx);
+ case BPF_W:
+ /* Load a Word */
+ emit(ARM_LDR_I(rd[1], rm, off), ctx);
+ emit_a32_mov_i(dst[0], 0, dstk, ctx);
+ break;
+ case BPF_DW:
+ /* Load a Double Word */
+ emit(ARM_LDR_I(rd[1], rm, off), ctx);
+ emit(ARM_LDR_I(rd[0], rm, off + 4), ctx);
break;
}
if (dstk)
- emit(ARM_STR_I(rd, ARM_SP, STACK_VAR(dst)), ctx);
+ emit(ARM_STR_I(rd[1], ARM_SP, STACK_VAR(dst[1])), ctx);
+ if (dstk && sz == BPF_DW)
+ emit(ARM_STR_I(rd[0], ARM_SP, STACK_VAR(dst[0])), ctx);
}
/* Arithmatic Operation */
@@ -1440,22 +1460,7 @@ exit:
rn = sstk ? tmp2[1] : src_lo;
if (sstk)
emit(ARM_LDR_I(rn, ARM_SP, STACK_VAR(src_lo)), ctx);
- switch (BPF_SIZE(code)) {
- case BPF_W:
- /* Load a Word */
- case BPF_H:
- /* Load a Half-Word */
- case BPF_B:
- /* Load a Byte */
- emit_ldx_r(dst_lo, rn, dstk, off, ctx, BPF_SIZE(code));
- emit_a32_mov_i(dst_hi, 0, dstk, ctx);
- break;
- case BPF_DW:
- /* Load a double word */
- emit_ldx_r(dst_lo, rn, dstk, off, ctx, BPF_W);
- emit_ldx_r(dst_hi, rn, dstk, off+4, ctx, BPF_W);
- break;
- }
+ emit_ldx_r(dst, rn, dstk, off, ctx, BPF_SIZE(code));
break;
/* R0 = ntohx(*(size *)(((struct sk_buff *)R6)->data + imm)) */
case BPF_LD | BPF_ABS | BPF_W: