From 7364d60c26618d7465602ac86717a5a325b342f3 Mon Sep 17 00:00:00 2001 From: Jiaxun Yang Date: Tue, 28 Feb 2023 11:33:05 +0000 Subject: [PATCH] bpf, mips: Implement R4000 workarounds for JIT MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Daniel Borkmann Reviewed-by: Philippe Mathieu-Daudé Acked-by: Johan Almbladh Link: https://lore.kernel.org/bpf/20230228113305.83751-3-jiaxun.yang@flygoat.com --- 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 b89c4bf2fa0a..363cd59a3bc0 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 */