microblaze: Unprivileged stream instruction awareness

Add cpuinfo support for the new MicroBlaze option permitting userspace
(unprivileged) access to the streaming instructions (FSL / AXI-stream).

Emit a noisy warning at bootup if this is enabled, because bad user code
can potentially lockup the CPU.

Signed-off-by: John A. Williams <john.williams@petalogix.com>
Signed-off-by: Michal Simek <monstr@monstr.eu>

4 files changed, 10 insertions, 0 deletions

diff --git a/arch/microblaze/kernel/cpu/cpuinfo-pvr-full.c b/arch/microblaze/kernel/cpu/cpuinfo-pvr-full.c
index f70a6047f08..916aaedf194 100644
--- a/arch/microblaze/kernel/cpu/cpuinfo-pvr-full.c
+++ b/arch/microblaze/kernel/cpu/cpuinfo-pvr-full.c
@@ -72,6 +72,7 @@ void set_cpuinfo_pvr_full(struct cpuinfo *ci, struct device_node *cpu)
         CI(pvr_user2, USER2);
 
         CI(mmu, USE_MMU);
+        CI(mmu_privins, MMU_PRIVINS);
         CI(endian, ENDIAN);
 
         CI(use_icache, USE_ICACHE);
diff --git a/arch/microblaze/kernel/cpu/cpuinfo-static.c b/arch/microblaze/kernel/cpu/cpuinfo-static.c
index b16b994ca3d..592bb2e838c 100644
--- a/arch/microblaze/kernel/cpu/cpuinfo-static.c
+++ b/arch/microblaze/kernel/cpu/cpuinfo-static.c
@@ -119,6 +119,7 @@ void __init set_cpuinfo_static(struct cpuinfo *ci, struct device_node *cpu)
         ci->pvr_user2 = fcpu(cpu, "xlnx,pvr-user2");
 
         ci->mmu = fcpu(cpu, "xlnx,use-mmu");
+        ci->mmu_privins = fcpu(cpu, "xlnx,mmu-privileged-instr");
         ci->endian = fcpu(cpu, "xlnx,endianness");
 
         ci->ver_code = 0;
diff --git a/arch/microblaze/kernel/cpu/cpuinfo.c b/arch/microblaze/kernel/cpu/cpuinfo.c
index c1640c52711..44394d80a68 100644
--- a/arch/microblaze/kernel/cpu/cpuinfo.c
+++ b/arch/microblaze/kernel/cpu/cpuinfo.c
@@ -88,4 +88,8 @@ void __init setup_cpuinfo(void)
                 printk(KERN_WARNING "%s: Unsupported PVR setting\n", __func__);
                 set_cpuinfo_static(&cpuinfo, cpu);
         }
+
+        if (cpuinfo.mmu_privins)
+                printk(KERN_WARNING "%s: Stream instructions enabled"
+                        " - USERSPACE CAN LOCK THIS KERNEL!\n", __func__);
 }
diff --git a/arch/microblaze/kernel/cpu/mb.c b/arch/microblaze/kernel/cpu/mb.c
index b4048af0261..0afebaebb5b 100644
--- a/arch/microblaze/kernel/cpu/mb.c
+++ b/arch/microblaze/kernel/cpu/mb.c
@@ -97,6 +97,10 @@ static int show_cpuinfo(struct seq_file *m, void *v)
                 (cpuinfo.use_exc & PVR2_FPU_EXC_MASK) ? "fpu " : "",
                 (cpuinfo.use_exc & PVR2_USE_FSL_EXC) ? "fsl " : "");
 
+        count += seq_printf(m,
+                        "Stream-insns:\t%sprivileged\n",
+                        cpuinfo.mmu_privins ? "un" : "");
+
         if (cpuinfo.use_icache)
                 count += seq_printf(m,
                                 "Icache:\t\t%ukB\tline length:\t%dB\n",