hw/misc/imx_rngc.c - qemu - Git at Google

 /*
  * Freescale i.MX RNGC emulation
  *
  * Copyright (C) 2020 Martin Kaiser <martin@kaiser.cx>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
  *
  * This driver provides the minimum functionality to initialize and seed
  * an rngc and to read random numbers. The rngb that is found in imx25
  * chipsets is also supported.
  */

 #include "qemu/osdep.h"
 #include "qemu/main-loop.h"
 #include "qemu/module.h"
 #include "qemu/guest-random.h"
 #include "hw/irq.h"
 #include "hw/misc/imx_rngc.h"
 #include "migration/vmstate.h"

 #define RNGC_NAME "i.MX RNGC"

 #define RNGC_VER_ID  0x00
 #define RNGC_COMMAND 0x04
 #define RNGC_CONTROL 0x08
 #define RNGC_STATUS  0x0C
 #define RNGC_FIFO    0x14

 /* These version info are reported by the rngb in an imx258 chip. */
 #define RNG_TYPE_RNGB 0x1
 #define V_MAJ 0x2
 #define V_MIN 0x40

 #define RNGC_CMD_BIT_SW_RST    0x40
 #define RNGC_CMD_BIT_CLR_ERR   0x20
 #define RNGC_CMD_BIT_CLR_INT   0x10
 #define RNGC_CMD_BIT_SEED      0x02
 #define RNGC_CMD_BIT_SELF_TEST 0x01

 #define RNGC_CTRL_BIT_MASK_ERR  0x40
 #define RNGC_CTRL_BIT_MASK_DONE 0x20
 #define RNGC_CTRL_BIT_AUTO_SEED 0x10

 /* the current status for self-test and seed operations */
 #define OP_IDLE 0
 #define OP_RUN  1
 #define OP_DONE 2

 static uint64_t imx_rngc_read(void *opaque, hwaddr offset, unsigned size)
 {
     IMXRNGCState *s = IMX_RNGC(opaque);
     uint64_t val = 0;

     switch (offset) {
     case RNGC_VER_ID:
         val |= RNG_TYPE_RNGB << 28 | V_MAJ << 8 | V_MIN;
         break;

     case RNGC_COMMAND:
         if (s->op_seed == OP_RUN) {
             val |= RNGC_CMD_BIT_SEED;
         }
         if (s->op_self_test == OP_RUN) {
             val |= RNGC_CMD_BIT_SELF_TEST;
         }
         break;

     case RNGC_CONTROL:
         /*
          * The CTL_ACC and VERIF_MODE bits are not supported yet.
          * They read as 0.
          */
         val |= s->mask;
         if (s->auto_seed) {
             val |= RNGC_CTRL_BIT_AUTO_SEED;
         }
         /*
          * We don't have an internal fifo like the real hardware.
          * There's no need for strategy to handle fifo underflows.
          * We return the FIFO_UFLOW_RESPONSE bits as 0.
          */
         break;

     case RNGC_STATUS:
         /*
          * We never report any statistics test or self-test errors or any
          * other errors. STAT_TEST_PF, ST_PF and ERROR are always 0.
          */

         /*
          * We don't have an internal fifo, see above. Therefore, we
          * report back the default fifo size (5 32-bit words) and
          * indicate that our fifo is always full.
          */
         val |= 5 << 12 | 5 << 8;

         /* We always have a new seed available. */
         val |= 1 << 6;

         if (s->op_seed == OP_DONE) {
             val |= 1 << 5;
         }
         if (s->op_self_test == OP_DONE) {
             val |= 1 << 4;
         }
         if (s->op_seed == OP_RUN || s->op_self_test == OP_RUN) {
             /*
              * We're busy if self-test is running or if we're
              * seeding the prng.
              */
             val |= 1 << 1;
         } else {
             /*
              * We're ready to provide secure random numbers whenever
              * we're not busy.
              */
             val |= 1;
         }
         break;

     case RNGC_FIFO:
         qemu_guest_getrandom_nofail(&val, sizeof(val));
         break;
     }

     return val;
 }

 static void imx_rngc_do_reset(IMXRNGCState *s)
 {
     s->op_self_test = OP_IDLE;
     s->op_seed = OP_IDLE;
     s->mask = 0;
     s->auto_seed = false;
 }

 static void imx_rngc_write(void *opaque, hwaddr offset, uint64_t value,
                            unsigned size)
 {
     IMXRNGCState *s = IMX_RNGC(opaque);

     switch (offset) {
     case RNGC_COMMAND:
         if (value & RNGC_CMD_BIT_SW_RST) {
             imx_rngc_do_reset(s);
         }

         /*
          * For now, both CLR_ERR and CLR_INT clear the interrupt. We
          * don't report any errors yet.
          */
         if (value & (RNGC_CMD_BIT_CLR_ERR | RNGC_CMD_BIT_CLR_INT)) {
             qemu_irq_lower(s->irq);
         }

         if (value & RNGC_CMD_BIT_SEED) {
             s->op_seed = OP_RUN;
             qemu_bh_schedule(s->seed_bh);
         }

         if (value & RNGC_CMD_BIT_SELF_TEST) {
             s->op_self_test = OP_RUN;
             qemu_bh_schedule(s->self_test_bh);
         }
         break;

     case RNGC_CONTROL:
         /*
          * The CTL_ACC and VERIF_MODE bits are not supported yet.
          * We ignore them if they're set by the caller.
          */

         if (value & RNGC_CTRL_BIT_MASK_ERR) {
             s->mask |= RNGC_CTRL_BIT_MASK_ERR;
         } else {
             s->mask &= ~RNGC_CTRL_BIT_MASK_ERR;
         }

         if (value & RNGC_CTRL_BIT_MASK_DONE) {
             s->mask |= RNGC_CTRL_BIT_MASK_DONE;
         } else {
             s->mask &= ~RNGC_CTRL_BIT_MASK_DONE;
         }

         if (value & RNGC_CTRL_BIT_AUTO_SEED) {
             s->auto_seed = true;
         } else {
             s->auto_seed = false;
         }
         break;
     }
 }

 static const MemoryRegionOps imx_rngc_ops = {
     .read  = imx_rngc_read,
     .write = imx_rngc_write,
     .endianness = DEVICE_NATIVE_ENDIAN,
 };

 static void imx_rngc_self_test(void *opaque)
 {
     IMXRNGCState *s = IMX_RNGC(opaque);

     s->op_self_test = OP_DONE;
     if (!(s->mask & RNGC_CTRL_BIT_MASK_DONE)) {
         qemu_irq_raise(s->irq);
     }
 }

 static void imx_rngc_seed(void *opaque)
 {
     IMXRNGCState *s = IMX_RNGC(opaque);

     s->op_seed = OP_DONE;
     if (!(s->mask & RNGC_CTRL_BIT_MASK_DONE)) {
         qemu_irq_raise(s->irq);
     }
 }

 static void imx_rngc_realize(DeviceState *dev, Error **errp)
 {
     IMXRNGCState *s = IMX_RNGC(dev);
     SysBusDevice *sbd = SYS_BUS_DEVICE(dev);

     memory_region_init_io(&s->iomem, OBJECT(s), &imx_rngc_ops, s,
                           TYPE_IMX_RNGC, 0x1000);
     sysbus_init_mmio(sbd, &s->iomem);

     sysbus_init_irq(sbd, &s->irq);
     s->self_test_bh = qemu_bh_new_guarded(imx_rngc_self_test, s,
                                           &dev->mem_reentrancy_guard);
     s->seed_bh = qemu_bh_new_guarded(imx_rngc_seed, s,
                                      &dev->mem_reentrancy_guard);
 }

 static void imx_rngc_reset(DeviceState *dev)
 {
     IMXRNGCState *s = IMX_RNGC(dev);

     imx_rngc_do_reset(s);
 }

 static const VMStateDescription vmstate_imx_rngc = {
     .name = RNGC_NAME,
     .version_id = 1,
     .minimum_version_id = 1,
     .fields = (const VMStateField[]) {
         VMSTATE_UINT8(op_self_test, IMXRNGCState),
         VMSTATE_UINT8(op_seed, IMXRNGCState),
         VMSTATE_UINT8(mask, IMXRNGCState),
         VMSTATE_BOOL(auto_seed, IMXRNGCState),
         VMSTATE_END_OF_LIST()
     }
 };

 static void imx_rngc_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);

     dc->realize = imx_rngc_realize;
     dc->reset = imx_rngc_reset;
     dc->desc = RNGC_NAME,
     dc->vmsd = &vmstate_imx_rngc;
 }

 static const TypeInfo imx_rngc_info = {
     .name          = TYPE_IMX_RNGC,
     .parent        = TYPE_SYS_BUS_DEVICE,
     .instance_size = sizeof(IMXRNGCState),
     .class_init    = imx_rngc_class_init,
 };

 static void imx_rngc_register_types(void)
 {
     type_register_static(&imx_rngc_info);
 }

 type_init(imx_rngc_register_types)
	/*
	* Freescale i.MX RNGC emulation
	*
	* Copyright (C) 2020 Martin Kaiser <martin@kaiser.cx>
	*
	* This work is licensed under the terms of the GNU GPL, version 2 or later.
	* See the COPYING file in the top-level directory.
	*
	* This driver provides the minimum functionality to initialize and seed
	* an rngc and to read random numbers. The rngb that is found in imx25
	* chipsets is also supported.
	*/

	#include "qemu/osdep.h"
	#include "qemu/main-loop.h"
	#include "qemu/module.h"
	#include "qemu/guest-random.h"
	#include "hw/irq.h"
	#include "hw/misc/imx_rngc.h"
	#include "migration/vmstate.h"

	#define RNGC_NAME "i.MX RNGC"

	#define RNGC_VER_ID 0x00
	#define RNGC_COMMAND 0x04
	#define RNGC_CONTROL 0x08
	#define RNGC_STATUS 0x0C
	#define RNGC_FIFO 0x14

	/* These version info are reported by the rngb in an imx258 chip. */
	#define RNG_TYPE_RNGB 0x1
	#define V_MAJ 0x2
	#define V_MIN 0x40

	#define RNGC_CMD_BIT_SW_RST 0x40
	#define RNGC_CMD_BIT_CLR_ERR 0x20
	#define RNGC_CMD_BIT_CLR_INT 0x10
	#define RNGC_CMD_BIT_SEED 0x02
	#define RNGC_CMD_BIT_SELF_TEST 0x01

	#define RNGC_CTRL_BIT_MASK_ERR 0x40
	#define RNGC_CTRL_BIT_MASK_DONE 0x20
	#define RNGC_CTRL_BIT_AUTO_SEED 0x10

	/* the current status for self-test and seed operations */
	#define OP_IDLE 0
	#define OP_RUN 1
	#define OP_DONE 2

	static uint64_t imx_rngc_read(void *opaque, hwaddr offset, unsigned size)
	{
	IMXRNGCState *s = IMX_RNGC(opaque);
	uint64_t val = 0;

	switch (offset) {
	case RNGC_VER_ID:
	val \|= RNG_TYPE_RNGB << 28 \| V_MAJ << 8 \| V_MIN;
	break;

	case RNGC_COMMAND:
	if (s->op_seed == OP_RUN) {
	val \|= RNGC_CMD_BIT_SEED;
	}
	if (s->op_self_test == OP_RUN) {
	val \|= RNGC_CMD_BIT_SELF_TEST;
	}
	break;

	case RNGC_CONTROL:
	/*
	* The CTL_ACC and VERIF_MODE bits are not supported yet.
	* They read as 0.
	*/
	val \|= s->mask;
	if (s->auto_seed) {
	val \|= RNGC_CTRL_BIT_AUTO_SEED;
	}
	/*
	* We don't have an internal fifo like the real hardware.
	* There's no need for strategy to handle fifo underflows.
	* We return the FIFO_UFLOW_RESPONSE bits as 0.
	*/
	break;

	case RNGC_STATUS:
	/*
	* We never report any statistics test or self-test errors or any
	* other errors. STAT_TEST_PF, ST_PF and ERROR are always 0.
	*/

	/*
	* We don't have an internal fifo, see above. Therefore, we
	* report back the default fifo size (5 32-bit words) and
	* indicate that our fifo is always full.
	*/
	val \|= 5 << 12 \| 5 << 8;

	/* We always have a new seed available. */
	val \|= 1 << 6;

	if (s->op_seed == OP_DONE) {
	val \|= 1 << 5;
	}
	if (s->op_self_test == OP_DONE) {
	val \|= 1 << 4;
	}
	if (s->op_seed == OP_RUN \|\| s->op_self_test == OP_RUN) {
	/*
	* We're busy if self-test is running or if we're
	* seeding the prng.
	*/
	val \|= 1 << 1;
	} else {
	/*
	* We're ready to provide secure random numbers whenever
	* we're not busy.
	*/
	val \|= 1;
	}
	break;

	case RNGC_FIFO:
	qemu_guest_getrandom_nofail(&val, sizeof(val));
	break;
	}

	return val;
	}

	static void imx_rngc_do_reset(IMXRNGCState *s)
	{
	s->op_self_test = OP_IDLE;
	s->op_seed = OP_IDLE;
	s->mask = 0;
	s->auto_seed = false;
	}

	static void imx_rngc_write(void *opaque, hwaddr offset, uint64_t value,
	unsigned size)
	{
	IMXRNGCState *s = IMX_RNGC(opaque);

	switch (offset) {
	case RNGC_COMMAND:
	if (value & RNGC_CMD_BIT_SW_RST) {
	imx_rngc_do_reset(s);
	}

	/*
	* For now, both CLR_ERR and CLR_INT clear the interrupt. We
	* don't report any errors yet.
	*/
	if (value & (RNGC_CMD_BIT_CLR_ERR \| RNGC_CMD_BIT_CLR_INT)) {
	qemu_irq_lower(s->irq);
	}

	if (value & RNGC_CMD_BIT_SEED) {
	s->op_seed = OP_RUN;
	qemu_bh_schedule(s->seed_bh);
	}

	if (value & RNGC_CMD_BIT_SELF_TEST) {
	s->op_self_test = OP_RUN;
	qemu_bh_schedule(s->self_test_bh);
	}
	break;

	case RNGC_CONTROL:
	/*
	* The CTL_ACC and VERIF_MODE bits are not supported yet.
	* We ignore them if they're set by the caller.
	*/

	if (value & RNGC_CTRL_BIT_MASK_ERR) {
	s->mask \|= RNGC_CTRL_BIT_MASK_ERR;
	} else {
	s->mask &= ~RNGC_CTRL_BIT_MASK_ERR;
	}

	if (value & RNGC_CTRL_BIT_MASK_DONE) {
	s->mask \|= RNGC_CTRL_BIT_MASK_DONE;
	} else {
	s->mask &= ~RNGC_CTRL_BIT_MASK_DONE;
	}

	if (value & RNGC_CTRL_BIT_AUTO_SEED) {
	s->auto_seed = true;
	} else {
	s->auto_seed = false;
	}
	break;
	}
	}

	static const MemoryRegionOps imx_rngc_ops = {
	.read = imx_rngc_read,
	.write = imx_rngc_write,
	.endianness = DEVICE_NATIVE_ENDIAN,
	};

	static void imx_rngc_self_test(void *opaque)
	{
	IMXRNGCState *s = IMX_RNGC(opaque);

	s->op_self_test = OP_DONE;
	if (!(s->mask & RNGC_CTRL_BIT_MASK_DONE)) {
	qemu_irq_raise(s->irq);
	}
	}

	static void imx_rngc_seed(void *opaque)
	{
	IMXRNGCState *s = IMX_RNGC(opaque);

	s->op_seed = OP_DONE;
	if (!(s->mask & RNGC_CTRL_BIT_MASK_DONE)) {
	qemu_irq_raise(s->irq);
	}
	}

	static void imx_rngc_realize(DeviceState dev, Error *errp)
	{
	IMXRNGCState *s = IMX_RNGC(dev);
	SysBusDevice *sbd = SYS_BUS_DEVICE(dev);

	memory_region_init_io(&s->iomem, OBJECT(s), &imx_rngc_ops, s,
	TYPE_IMX_RNGC, 0x1000);
	sysbus_init_mmio(sbd, &s->iomem);

	sysbus_init_irq(sbd, &s->irq);
	s->self_test_bh = qemu_bh_new_guarded(imx_rngc_self_test, s,
	&dev->mem_reentrancy_guard);
	s->seed_bh = qemu_bh_new_guarded(imx_rngc_seed, s,
	&dev->mem_reentrancy_guard);
	}

	static void imx_rngc_reset(DeviceState *dev)
	{
	IMXRNGCState *s = IMX_RNGC(dev);

	imx_rngc_do_reset(s);
	}

	static const VMStateDescription vmstate_imx_rngc = {
	.name = RNGC_NAME,
	.version_id = 1,
	.minimum_version_id = 1,
	.fields = (const VMStateField[]) {
	VMSTATE_UINT8(op_self_test, IMXRNGCState),
	VMSTATE_UINT8(op_seed, IMXRNGCState),
	VMSTATE_UINT8(mask, IMXRNGCState),
	VMSTATE_BOOL(auto_seed, IMXRNGCState),
	VMSTATE_END_OF_LIST()
	}
	};

	static void imx_rngc_class_init(ObjectClass klass, void data)
	{
	DeviceClass *dc = DEVICE_CLASS(klass);

	dc->realize = imx_rngc_realize;
	dc->reset = imx_rngc_reset;
	dc->desc = RNGC_NAME,
	dc->vmsd = &vmstate_imx_rngc;
	}

	static const TypeInfo imx_rngc_info = {
	.name = TYPE_IMX_RNGC,
	.parent = TYPE_SYS_BUS_DEVICE,
	.instance_size = sizeof(IMXRNGCState),
	.class_init = imx_rngc_class_init,
	};

	static void imx_rngc_register_types(void)
	{
	type_register_static(&imx_rngc_info);
	}

	type_init(imx_rngc_register_types)