Linux-libre 4.2-gnu

1 files changed, 101 insertions, 3 deletions

diff --git a/arch/arm/kernel/tcm.c b/arch/arm/kernel/tcm.c
index 7a3be1d4d..b10e13607 100644
--- a/arch/arm/kernel/tcm.c
+++ b/arch/arm/kernel/tcm.c
@@ -17,6 +17,9 @@
 #include <asm/mach/map.h>
 #include <asm/memory.h>
 #include <asm/system_info.h>
+#include <asm/traps.h>
+
+#define TCMTR_FORMAT_MASK	0xe0000000U
 
 static struct gen_pool *tcm_pool;
 static bool dtcm_present;
@@ -176,6 +179,77 @@ static int __init setup_tcm_bank(u8 type, u8 bank, u8 banks,
 }
 
 /*
+ * When we are running in the non-secure world and the secure world
+ * has not explicitly given us access to the TCM we will get an
+ * undefined error when reading the TCM region register in the
+ * setup_tcm_bank function (above).
+ *
+ * There are two variants of this register read that we need to trap,
+ * the read for the data TCM and the read for the instruction TCM:
+ *  c0370628:       ee196f11        mrc     15, 0, r6, cr9, cr1, {0}
+ *  c0370674:       ee196f31        mrc     15, 0, r6, cr9, cr1, {1}
+ *
+ * Our undef hook mask explicitly matches all fields of the encoded
+ * instruction other than the destination register.  The mask also
+ * only allows operand 2 to have the values 0 or 1.
+ *
+ * The undefined hook is defined as __init and __initdata, and therefore
+ * must be removed before tcm_init returns.
+ *
+ * In this particular case (MRC with ARM condition code ALways) the
+ * Thumb-2 and ARM instruction encoding are identical, so this hook
+ * will work on a Thumb-2 kernel.
+ *
+ * See A8.8.107, DDI0406C_C ARM Architecture Reference Manual, Encoding
+ * T1/A1 for the bit-by-bit details.
+ *
+ *  mrc   p15, 0, XX, c9, c1, 0
+ *  mrc   p15, 0, XX, c9, c1, 1
+ *   |  |  |   |   |   |   |  +---- opc2           0|1 = 000|001
+ *   |  |  |   |   |   |   +------- CRm              0 = 0001
+ *   |  |  |   |   |   +----------- CRn              0 = 1001
+ *   |  |  |   |   +--------------- Rt               ? = ????
+ *   |  |  |   +------------------- opc1             0 =  000
+ *   |  |  +----------------------- coproc          15 = 1111
+ *   |  +-------------------------- condition   ALways = 1110
+ *   +----------------------------- instruction    MRC = 1110
+ *
+ * Encoding this as per A8.8.107 of DDI0406C, Encoding T1/A1, yields:
+ *  1111 1111 1111 1111 0000 1111 1101 1111 Required Mask
+ *  1110 1110 0001 1001 ???? 1111 0001 0001 mrc p15, 0, XX, c9, c1, 0
+ *  1110 1110 0001 1001 ???? 1111 0011 0001 mrc p15, 0, XX, c9, c1, 1
+ *  [  ] [  ] [ ]| [  ] [  ] [  ] [ ]| +--- CRm
+ *    |    |   | |   |    |    |   | +----- SBO
+ *    |    |   | |   |    |    |   +------- opc2
+ *    |    |   | |   |    |    +----------- coproc
+ *    |    |   | |   |    +---------------- Rt
+ *    |    |   | |   +--------------------- CRn
+ *    |    |   | +------------------------- SBO
+ *    |    |   +--------------------------- opc1
+ *    |    +------------------------------- instruction
+ *    +------------------------------------ condition
+ */
+#define TCM_REGION_READ_MASK		0xffff0fdf
+#define TCM_REGION_READ_INSTR		0xee190f11
+#define DEST_REG_SHIFT			12
+#define DEST_REG_MASK			0xf
+
+static int __init tcm_handler(struct pt_regs *regs, unsigned int instr)
+{
+	regs->uregs[(instr >> DEST_REG_SHIFT) & DEST_REG_MASK] = 0;
+	regs->ARM_pc += 4;
+	return 0;
+}
+
+static struct undef_hook tcm_hook __initdata = {
+	.instr_mask	= TCM_REGION_READ_MASK,
+	.instr_val	= TCM_REGION_READ_INSTR,
+	.cpsr_mask	= MODE_MASK,
+	.cpsr_val	= SVC_MODE,
+	.fn		= tcm_handler
+};
+
+/*
  * This initializes the TCM memory
  */
 void __init tcm_init(void)
@@ -204,9 +278,18 @@ void __init tcm_init(void)
 	}
 
 	tcm_status = read_cpuid_tcmstatus();
+
+	/*
+	 * This code only supports v6-compatible TCMTR implementations.
+	 */
+	if (tcm_status & TCMTR_FORMAT_MASK)
+		return;
+
 	dtcm_banks = (tcm_status >> 16) & 0x03;
 	itcm_banks = (tcm_status & 0x03);
 
+	register_undef_hook(&tcm_hook);
+
 	/* Values greater than 2 for D/ITCM banks are "reserved" */
 	if (dtcm_banks > 2)
 		dtcm_banks = 0;
@@ -218,7 +301,7 @@ void __init tcm_init(void)
 		for (i = 0; i < dtcm_banks; i++) {
 			ret = setup_tcm_bank(0, i, dtcm_banks, &dtcm_end);
 			if (ret)
-				return;
+				goto unregister;
 		}
 		/* This means you compiled more code than fits into DTCM */
 		if (dtcm_code_sz > (dtcm_end - DTCM_OFFSET)) {
@@ -227,6 +310,12 @@ void __init tcm_init(void)
 				dtcm_code_sz, (dtcm_end - DTCM_OFFSET));
 			goto no_dtcm;
 		}
+		/*
+		 * This means that the DTCM sizes were 0 or the DTCM banks
+		 * were inaccessible due to TrustZone configuration.
+		 */
+		if (!(dtcm_end - DTCM_OFFSET))
+			goto no_dtcm;
 		dtcm_res.end = dtcm_end - 1;
 		request_resource(&iomem_resource, &dtcm_res);
 		dtcm_iomap[0].length = dtcm_end - DTCM_OFFSET;
@@ -250,15 +339,21 @@ no_dtcm:
 		for (i = 0; i < itcm_banks; i++) {
 			ret = setup_tcm_bank(1, i, itcm_banks, &itcm_end);
 			if (ret)
-				return;
+				goto unregister;
 		}
 		/* This means you compiled more code than fits into ITCM */
 		if (itcm_code_sz > (itcm_end - ITCM_OFFSET)) {
 			pr_info("CPU ITCM: %u bytes of code compiled to "
 				"ITCM but only %lu bytes of ITCM present\n",
 				itcm_code_sz, (itcm_end - ITCM_OFFSET));
-			return;
+			goto unregister;
 		}
+		/*
+		 * This means that the ITCM sizes were 0 or the ITCM banks
+		 * were inaccessible due to TrustZone configuration.
+		 */
+		if (!(itcm_end - ITCM_OFFSET))
+			goto unregister;
 		itcm_res.end = itcm_end - 1;
 		request_resource(&iomem_resource, &itcm_res);
 		itcm_iomap[0].length = itcm_end - ITCM_OFFSET;
@@ -275,6 +370,9 @@ no_dtcm:
 		pr_info("CPU ITCM: %u bytes of code compiled to ITCM but no "
 			"ITCM banks present in CPU\n", itcm_code_sz);
 	}
+
+unregister:
+	unregister_undef_hook(&tcm_hook);
 }
 
 /*