bpf, mips: Implement DADDI workarounds for JIT

For DADDI errata we just workaround by disable immediate operation
for BPF_ADD / BPF_SUB to avoid generation of DADDIU.

All other use cases in JIT won't cause overflow thus they are all safe.

Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Acked-by: Johan Almbladh <johan.almbladh@anyfinetworks.com>
Link: https://lore.kernel.org/bpf/20230228113305.83751-2-jiaxun.yang@flygoat.com

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 15cb692..b89c4bf 100644 (file)
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -64,7 +64,6 @@ config MIPS
        select HAVE_DMA_CONTIGUOUS
        select HAVE_DYNAMIC_FTRACE
        select HAVE_EBPF_JIT if !CPU_MICROMIPS && \
-                               !CPU_DADDI_WORKAROUNDS && \
                                !CPU_R4000_WORKAROUNDS && \
                                !CPU_R4400_WORKAROUNDS
        select HAVE_EXIT_THREAD

diff --git a/arch/mips/net/bpf_jit_comp.c b/arch/mips/net/bpf_jit_comp.c
index b17130d..a40d926 100644 (file)
--- a/arch/mips/net/bpf_jit_comp.c
+++ b/arch/mips/net/bpf_jit_comp.c
@@ -218,9 +218,13 @@ bool valid_alu_i(u8 op, s32 imm)
                /* All legal eBPF values are valid */
                return true;
        case BPF_ADD:
+               if (IS_ENABLED(CONFIG_CPU_DADDI_WORKAROUNDS))
+                       return false;
                /* imm must be 16 bits */
                return imm >= -0x8000 && imm <= 0x7fff;
        case BPF_SUB:
+               if (IS_ENABLED(CONFIG_CPU_DADDI_WORKAROUNDS))
+                       return false;
                /* -imm must be 16 bits */
                return imm >= -0x7fff && imm <= 0x8000;
        case BPF_AND: