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From: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Date: Tue, 5 Oct 2021 18:54:06 +0200
Subject: [PATCH] mips: bpf: Add JIT workarounds for CPU errata
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>
Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
---
--- a/arch/mips/net/bpf_jit_comp.c
+++ b/arch/mips/net/bpf_jit_comp.c
@@ -404,6 +404,7 @@ void emit_alu_r(struct jit_context *ctx,
/* 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:
@@ -420,18 +421,19 @@ void emit_atomic_r(struct jit_context *c
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 */
}
/* 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);
}
--- a/arch/mips/net/bpf_jit_comp.h
+++ b/arch/mips/net/bpf_jit_comp.h
@@ -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
--- a/arch/mips/net/bpf_jit_comp64.c
+++ b/arch/mips/net/bpf_jit_comp64.c
@@ -375,6 +375,7 @@ static void emit_atomic_r64(struct jit_c
u8 t1 = MIPS_R_T6;
u8 t2 = MIPS_R_T7;
+ LLSC_sync(ctx);
emit(ctx, lld, t1, off, dst);
switch (code) {
case BPF_ADD:
@@ -391,7 +392,7 @@ static void emit_atomic_r64(struct jit_c
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 */
}
@@ -414,7 +415,7 @@ static int emit_call(struct jit_context
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 */
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