For R4000 erratas around multiplication and division instructions,
as our use of those instructions are always followed by mflo/mfhi
instructions, the only issue we need care is
"MIPS R4000PC/SC Errata, Processor Revision 2.2 and 3.0" Errata 28:
"A double-word or a variable shift may give an incorrect result if
executed while an integer multiplication is in progress."
We just emit a mfhi $0 to ensure the operation is completed after
every multiplication instruction according to workaround suggestion
in the document.
Signed-off-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
Reviewed-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
Acked-by: Johan Almbladh <johan.almbladh@xxxxxxxxxxxxxxxxx>
---
v2: Drop 32bit part
---
arch/mips/Kconfig | 4 +---
arch/mips/net/bpf_jit_comp64.c | 3 +++
2 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index df0910e3895c..5ea07c833c5b 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -63,9 +63,7 @@ config MIPS
select HAVE_DEBUG_STACKOVERFLOW
select HAVE_DMA_CONTIGUOUS
select HAVE_DYNAMIC_FTRACE
- select HAVE_EBPF_JIT if !CPU_MICROMIPS && \
- !CPU_R4000_WORKAROUNDS && \
- !CPU_R4400_WORKAROUNDS
+ select HAVE_EBPF_JIT if !CPU_MICROMIPS
select HAVE_EXIT_THREAD
select HAVE_FAST_GUP
select HAVE_FTRACE_MCOUNT_RECORD
diff --git a/arch/mips/net/bpf_jit_comp64.c b/arch/mips/net/bpf_jit_comp64.c
index 0e7c1bdcf914..fa7e9aa37f49 100644
--- a/arch/mips/net/bpf_jit_comp64.c
+++ b/arch/mips/net/bpf_jit_comp64.c
@@ -228,6 +228,9 @@ static void emit_alu_r64(struct jit_context *ctx, u8 dst, u8 src, u8 op)
} else {
emit(ctx, dmultu, dst, src);
emit(ctx, mflo, dst);
+ /* Ensure multiplication is completed */
+ if (IS_ENABLED(CONFIG_CPU_R4000_WORKAROUNDS))
+ emit(ctx, mfhi, MIPS_R_ZERO);
}
break;
/* dst = dst / src */
--
2.37.1 (Apple Git-137.1)
