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MIPS: bpf: Drop update_on_xread and always initialize the X register

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Previously, update_on_xread() only set the reset flag if SEEN_X hasn't
been set already. However, SEEN_X is used to indicate that X is used
as destination or source register so there are some cases where X
is only used as source register and we really need to make sure that it
has been initialized in time. As a result of which, drop this function and
always set X to zero if it's used in any of the opcodes.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: netdev@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7133/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Markos Chandras 2014-06-23 10:38:56 +01:00 committed by Ralf Baechle
parent 10c4d614d2
commit e5bb48b055
1 changed files with 1 additions and 21 deletions
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22
arch/mips/net/bpf_jit.c
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@ -119,8 +119,6 @@
/* Arguments used by JIT */
#define ARGS_USED_BY_JIT 2 /* only applicable to 64-bit */
#define FLAG_NEED_X_RESET (1 << 0)
#define SBIT(x) (1 << (x)) /* Signed version of BIT() */
/**
@ -549,14 +547,6 @@ static inline u16 align_sp(unsigned int num)
return num;
}
static inline void update_on_xread(struct jit_ctx *ctx)
{
if (!(ctx->flags & SEEN_X))
ctx->flags |= FLAG_NEED_X_RESET;
ctx->flags |= SEEN_X;
}
static bool is_load_to_a(u16 inst)
{
switch (inst) {
@ -701,7 +691,7 @@ static void build_prologue(struct jit_ctx *ctx)
if (ctx->flags & SEEN_SKB)
emit_reg_move(r_skb, MIPS_R_A0, ctx);
if (ctx->flags & FLAG_NEED_X_RESET)
if (ctx->flags & SEEN_X)
emit_jit_reg_move(r_X, r_zero, ctx);
/* Do not leak kernel data to userspace */
@ -876,7 +866,6 @@ load_common:
/* A <- P[X + k:1] */
load_order = 0;
load_ind:
update_on_xread(ctx);
ctx->flags |= SEEN_OFF | SEEN_X;
emit_addiu(r_off, r_X, k, ctx);
goto load_common;
@ -972,7 +961,6 @@ load_ind:
break;
case BPF_ALU | BPF_MUL | BPF_X:
/* A *= X */
update_on_xread(ctx);
ctx->flags |= SEEN_A | SEEN_X;
emit_mul(r_A, r_A, r_X, ctx);
break;
@ -1002,7 +990,6 @@ load_ind:
break;
case BPF_ALU | BPF_DIV | BPF_X:
/* A /= X */
update_on_xread(ctx);
ctx->flags |= SEEN_X | SEEN_A;
/* Check if r_X is zero */
emit_bcond(MIPS_COND_EQ, r_X, r_zero,
@ -1012,7 +999,6 @@ load_ind:
break;
case BPF_ALU | BPF_MOD | BPF_X:
/* A %= X */
update_on_xread(ctx);
ctx->flags |= SEEN_X | SEEN_A;
/* Check if r_X is zero */
emit_bcond(MIPS_COND_EQ, r_X, r_zero,
@ -1027,7 +1013,6 @@ load_ind:
break;
case BPF_ALU | BPF_OR | BPF_X:
/* A |= X */
update_on_xread(ctx);
ctx->flags |= SEEN_A;
emit_ori(r_A, r_A, r_X, ctx);
break;
@ -1039,7 +1024,6 @@ load_ind:
case BPF_ANC | SKF_AD_ALU_XOR_X:
case BPF_ALU | BPF_XOR | BPF_X:
/* A ^= X */
update_on_xread(ctx);
ctx->flags |= SEEN_A;
emit_xor(r_A, r_A, r_X, ctx);
break;
@ -1050,7 +1034,6 @@ load_ind:
break;
case BPF_ALU | BPF_AND | BPF_X:
/* A &= X */
update_on_xread(ctx);
ctx->flags |= SEEN_A | SEEN_X;
emit_and(r_A, r_A, r_X, ctx);
break;
@ -1062,7 +1045,6 @@ load_ind:
case BPF_ALU | BPF_LSH | BPF_X:
/* A <<= X */
ctx->flags |= SEEN_A | SEEN_X;
update_on_xread(ctx);
emit_sllv(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_RSH | BPF_K:
@ -1072,7 +1054,6 @@ load_ind:
break;
case BPF_ALU | BPF_RSH | BPF_X:
ctx->flags |= SEEN_A | SEEN_X;
update_on_xread(ctx);
emit_srlv(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_NEG:
@ -1243,7 +1224,6 @@ jmp_cmp:
case BPF_MISC | BPF_TXA:
/* A = X */
ctx->flags |= SEEN_A | SEEN_X;
update_on_xread(ctx);
emit_jit_reg_move(r_A, r_X, ctx);
break;
/* AUX */