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>

arch/microblaze/include/asm/cpuinfo.h

@@ -38,6 +38,7 @@ struct cpuinfo {
 	u32 use_exc;
 	u32 ver_code;
 	u32 mmu;
+	u32 mmu_privins;
 	u32 endian;
 
 	/* CPU caches */

arch/microblaze/include/asm/pvr.h

@@ -117,10 +117,10 @@ struct pvr_s {
 #define PVR11_MMU_DTLB_SIZE		0x07000000
 #define PVR11_MMU_TLB_ACCESS		0x00C00000
 #define PVR11_MMU_ZONES			0x003C0000
+#define PVR11_MMU_PRIVINS		0x00010000
 /* MSR Reset value PVR mask */
 #define PVR11_MSR_RESET_VALUE_MASK	0x000007FF
 
-
 /* PVR access macros */
 #define PVR_IS_FULL(_pvr)	(_pvr.pvr[0] & PVR0_PVR_FULL_MASK)
 #define PVR_USE_BARREL(_pvr)	(_pvr.pvr[0] & PVR0_USE_BARREL_MASK)
@@ -216,6 +216,7 @@ struct pvr_s {
 #define PVR_MMU_DTLB_SIZE(_pvr)		(_pvr.pvr[11] & PVR11_MMU_DTLB_SIZE)
 #define PVR_MMU_TLB_ACCESS(_pvr)	(_pvr.pvr[11] & PVR11_MMU_TLB_ACCESS)
 #define PVR_MMU_ZONES(_pvr)		(_pvr.pvr[11] & PVR11_MMU_ZONES)
+#define PVR_MMU_PRIVINS(pvr)		(pvr.pvr[11] & PVR11_MMU_PRIVINS)
 
 /* endian */
 #define PVR_ENDIAN(_pvr)	(_pvr.pvr[0] & PVR0_ENDI)

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);

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;

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__);
 }

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",