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mips, bpf: Add JIT workarounds for CPU errata

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This patch adds workarounds for the following CPU errata to the MIPS
eBPF JIT, if enabled in the kernel configuration.

  - R10000 ll/sc weak ordering
  - Loongson-3 ll/sc weak ordering
  - Loongson-2F jump hang

The Loongson-2F nop errata is implemented in uasm, which the JIT uses,
so no additional mitigations are needed for that.

Signed-off-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Link: https://lore.kernel.org/bpf/20211005165408.2305108-6-johan.almbladh@anyfinetworks.com
This commit is contained in:
Johan Almbladh 2021-10-05 18:54:06 +02:00 committed by Andrii Nakryiko
parent fbc802de6b
commit 72570224bb
3 changed files with 35 additions and 7 deletions
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6
arch/mips/net/bpf_jit_comp.c
View File

@ -404,6 +404,7 @@ void emit_alu_r(struct jit_context *ctx, u8 dst, u8 src, u8 op)
/* Atomic read-modify-write (32-bit) */
void emit_atomic_r(struct jit_context *ctx, u8 dst, u8 src, s16 off, u8 code)
{
LLSC_sync(ctx);
emit(ctx, ll, MIPS_R_T9, off, dst);
switch (code) {
case BPF_ADD:
@ -427,7 +428,7 @@ void emit_atomic_r(struct jit_context *ctx, u8 dst, u8 src, s16 off, u8 code)
break;
}
emit(ctx, sc, MIPS_R_T8, off, dst);
emit(ctx, beqz, MIPS_R_T8, -16);
emit(ctx, LLSC_beqz, MIPS_R_T8, -16 - LLSC_offset);
emit(ctx, nop); /* Delay slot */
if (code & BPF_FETCH) {
@ -439,11 +440,12 @@ void emit_atomic_r(struct jit_context *ctx, u8 dst, u8 src, s16 off, u8 code)
/* Atomic compare-and-exchange (32-bit) */
void emit_cmpxchg_r(struct jit_context *ctx, u8 dst, u8 src, u8 res, s16 off)
{
LLSC_sync(ctx);
emit(ctx, ll, MIPS_R_T9, off, dst);
emit(ctx, bne, MIPS_R_T9, res, 12);
emit(ctx, move, MIPS_R_T8, src); /* Delay slot */
emit(ctx, sc, MIPS_R_T8, off, dst);
emit(ctx, beqz, MIPS_R_T8, -20);
emit(ctx, LLSC_beqz, MIPS_R_T8, -20 - LLSC_offset);
emit(ctx, move, res, MIPS_R_T9); /* Delay slot */
clobber_reg(ctx, res);
}

26
arch/mips/net/bpf_jit_comp.h
View File

@ -87,7 +87,7 @@ struct jit_context {
};
/* Emit the instruction if the JIT memory space has been allocated */
#define emit(ctx, func, ...) \
#define __emit(ctx, func, ...) \
do { \
if ((ctx)->target != NULL) { \
u32 *p = &(ctx)->target[ctx->jit_index]; \
@ -95,6 +95,30 @@ do { \
} \
(ctx)->jit_index++; \
} while (0)
#define emit(...) __emit(__VA_ARGS__)
/* Workaround for R10000 ll/sc errata */
#ifdef CONFIG_WAR_R10000
#define LLSC_beqz beqzl
#else
#define LLSC_beqz beqz
#endif
/* Workaround for Loongson-3 ll/sc errata */
#ifdef CONFIG_CPU_LOONGSON3_WORKAROUNDS
#define LLSC_sync(ctx) emit(ctx, sync, 0)
#define LLSC_offset 4
#else
#define LLSC_sync(ctx)
#define LLSC_offset 0
#endif
/* Workaround for Loongson-2F jump errata */
#ifdef CONFIG_CPU_JUMP_WORKAROUNDS
#define JALR_MASK 0xffffffffcfffffffULL
#else
#define JALR_MASK (~0ULL)
#endif
/*
* Mark a BPF register as accessed, it needs to be

10
arch/mips/net/bpf_jit_comp64.c
View File

@ -375,6 +375,7 @@ static void emit_atomic_r64(struct jit_context *ctx,
u8 t1 = MIPS_R_T6;
u8 t2 = MIPS_R_T7;
LLSC_sync(ctx);
emit(ctx, lld, t1, off, dst);
switch (code) {
case BPF_ADD:
@ -398,7 +399,7 @@ static void emit_atomic_r64(struct jit_context *ctx,
break;
}
emit(ctx, scd, t2, off, dst);
emit(ctx, beqz, t2, -16);
emit(ctx, LLSC_beqz, t2, -16 - LLSC_offset);
emit(ctx, nop); /* Delay slot */
if (code & BPF_FETCH) {
@ -414,12 +415,13 @@ static void emit_cmpxchg_r64(struct jit_context *ctx, u8 dst, u8 src, s16 off)
u8 t1 = MIPS_R_T6;
u8 t2 = MIPS_R_T7;
LLSC_sync(ctx);
emit(ctx, lld, t1, off, dst);
emit(ctx, bne, t1, r0, 12);
emit(ctx, move, t2, src); /* Delay slot */
emit(ctx, scd, t2, off, dst);
emit(ctx, beqz, t2, -20);
emit(ctx, move, r0, t1); /* Delay slot */
emit(ctx, LLSC_beqz, t2, -20 - LLSC_offset);
emit(ctx, move, r0, t1); /* Delay slot */
clobber_reg(ctx, r0);
}
@ -443,7 +445,7 @@ static int emit_call(struct jit_context *ctx, const struct bpf_insn *insn)
push_regs(ctx, ctx->clobbered & JIT_CALLER_REGS, 0, 0);
/* Emit function call */
emit_mov_i64(ctx, tmp, addr);
emit_mov_i64(ctx, tmp, addr & JALR_MASK);
emit(ctx, jalr, MIPS_R_RA, tmp);
emit(ctx, nop); /* Delay slot */