Re: [Qemu-devel] [PATCH v8 4/5] generic-loader: Add a generic loader

[Peter Maydell]

On 2 July 2016 at 02:07, Alistair Francis <address@hidden> wrote:
> Add a generic loader to QEMU which can be used to load images or set
> memory values.
>
> Signed-off-by: Alistair Francis <address@hidden>
> ---
> V8:
>  - Code corrections
>  - Rebase
> V7:
>  - Rebase
> V6:
>  - Add error checking
> V5:
>  - Rebase
> V4:
>  - Allow the loader to work with every architecture
>  - Move the file to hw/core
>  - Increase the maximum number of CPUs
>  - Make the CPU operations conditional
>  - Convert the cpu option to cpu-num
>  - Require the user to specify endianess
> V3:
>  - Pass the ram_size to load_image_targphys()
> V2:
>  - Add maintainers entry
>  - Perform bounds checking
>  - Register and unregister the reset in the realise/unrealise
> Changes since RFC:
>  - Add BE support
>
>  MAINTAINERS                      |   6 ++
>  hw/core/Makefile.objs            |   2 +
>  hw/core/generic-loader.c         | 177 
> +++++++++++++++++++++++++++++++++++++++
>  include/hw/core/generic-loader.h |  45 ++++++++++
>  4 files changed, 230 insertions(+)
>  create mode 100644 hw/core/generic-loader.c
>  create mode 100644 include/hw/core/generic-loader.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 2ab6e3b..0077e22 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -992,6 +992,12 @@ M: Dmitry Fleytman <address@hidden>
>  S: Maintained
>  F: hw/net/e1000e*
>
> +Generic Loader
> +M: Alistair Francis <address@hidden>
> +S: Maintained
> +F: hw/core/generic-loader.c
> +F: include/hw/core/generic-loader.h
> +
>  Subsystems
>  ----------
>  Audio
> diff --git a/hw/core/Makefile.objs b/hw/core/Makefile.objs
> index 82a9ef8..ab238fa 100644
> --- a/hw/core/Makefile.objs
> +++ b/hw/core/Makefile.objs
> @@ -16,3 +16,5 @@ common-obj-$(CONFIG_SOFTMMU) += null-machine.o
>  common-obj-$(CONFIG_SOFTMMU) += loader.o
>  common-obj-$(CONFIG_SOFTMMU) += qdev-properties-system.o
>  common-obj-$(CONFIG_PLATFORM_BUS) += platform-bus.o
> +
> +obj-$(CONFIG_SOFTMMU) += generic-loader.o
> diff --git a/hw/core/generic-loader.c b/hw/core/generic-loader.c
> new file mode 100644
> index 0000000..c9b0572
> --- /dev/null
> +++ b/hw/core/generic-loader.c
> @@ -0,0 +1,177 @@
> +/*
> + * Generic Loader
> + *
> + * Copyright (C) 2014 Li Guang
> + * Copyright (C) 2016 Xilinx Inc.
> + * Written by Li Guang <address@hidden>
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License as published by the
> + * Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful, but 
> WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
> + * for more details.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qom/cpu.h"
> +#include "hw/sysbus.h"
> +#include "sysemu/dma.h"
> +#include "hw/loader.h"
> +#include "qapi/error.h"
> +#include "hw/core/generic-loader.h"
> +
> +#define CPU_NONE 0xFFFF

This should be updated now we've widened the type from 16 bits.

> +
> +static void generic_loader_reset(void *opaque)
> +{
> +    GenericLoaderState *s = GENERIC_LOADER(opaque);
> +
> +    if (s->cpu) {
> +        CPUClass *cc = CPU_GET_CLASS(s->cpu);
> +        cpu_reset(s->cpu);
> +        if (cc) {
> +            cc->set_pc(s->cpu, s->addr);

If something else sets the PC later on this gets lost, which is
ugly and fragile. It's kinda-sorta OK that we bodge this for things
like the hw/arm/boot.c code because all the pieces are inside QEMU,
but when you start adding in command line devices I'm a bit
nervous. Maybe we should actually figure out our reset order
woes properly ?

> +        }
> +    }
> +
> +    if (s->data_len) {
> +        assert(s->data_len < sizeof(s->data));
> +        dma_memory_write((s->cpu ? s->cpu : first_cpu)->as, s->addr, 
> &s->data,
> +                         s->data_len);

We rule out specifying cpu_num below, so when is s->cpu non-NULL?

> +    }
> +}
> +
> +static void generic_loader_realize(DeviceState *dev, Error **errp)
> +{
> +    GenericLoaderState *s = GENERIC_LOADER(dev);
> +    hwaddr entry;
> +    int big_endian;
> +    int size = 0;
> +
> +    /* Perform some error checking on the user's options */
> +    if (s->data || s->data_len  || s->data_be) {
> +        /* User is loading memory values */
> +        if (s->file) {
> +            error_setg(errp, "Specifying a file is not supported when 
> loading "
> +                       "memory values");
> +            return;
> +        } else if (s->force_raw) {
> +            error_setg(errp, "Specifying force raw is not supported when "

"force-raw", ie state the option name. Similarly in these other errors.

> +                       "loading memory values");
> +            return;
> +        } else if (!s->data || !s->data_len) {
> +            error_setg(errp, "Both data and data length must be specified");
> +            return;
> +        } else if (s->cpu_num) {
> +            error_setg(errp, "Setting data and a cpu number is not 
> supported");
> +            return;
> +        }
> +    } else if (s->file || s->force_raw)  {
> +        /* User is loading an image */
> +        if (s->data || s->data_len || s->data_be) {
> +            error_setg(errp, "Data can not be specified when loading an "
> +                       "image");
> +            return;
> +        }
> +    } else if (s->data_len) {
> +        if (s->data_len > 8) {
> +            error_setg(errp, "data-len cannot be greate then 8 bytes");

"greater"

> +            return;
> +        } else if (s->data_len > sizeof(s->data)) {
> +            error_setg(errp, "data-len cannot be more then the data size");
> +            return;
> +        }
> +    }
> +
> +    qemu_register_reset(generic_loader_reset, dev);

What's wrong with a device reset function set via dc->reset ?

> +
> +    if (s->cpu_num != CPU_NONE) {
> +        s->cpu = qemu_get_cpu(s->cpu_num);
> +        if (!s->cpu) {
> +            error_setg(errp, "Specified boot CPU#%d is nonexistent",
> +                       s->cpu_num);
> +            return;
> +        }
> +    }
> +
> +#ifdef TARGET_WORDS_BIGENDIAN
> +    big_endian = 1;
> +#else
> +    big_endian = 0;
> +#endif
> +
> +    if (s->file) {
> +        if (!s->force_raw) {
> +            size = load_elf_as(s->file, NULL, NULL, &entry, NULL, NULL,
> +                            big_endian, 0, 0, 0,
> +                            (s->cpu ? s->cpu : first_cpu)->as);
> +
> +            if (size < 0) {
> +                size = load_uimage(s->file, &entry, NULL, NULL, NULL, NULL);
> +            }
> +        }
> +
> +        if (size < 0 || s->force_raw) {
> +            /* Default to the maximum size being the machine's ram size */
> +            size = load_image_targphys(s->file, s->addr, ram_size);
> +        } else {
> +            s->addr = entry;
> +        }

We only use the CPU's address space for ELF loads, not for uimage or raw.
That's an annoying inconsistency. I think we need to use the CPU's
address space for everything or nothing, preferably for everything.

Changing that after this goes into the tree would be a command
line compatibility break, so this inclines me to saying that this
isn't baked enough for 2.7 and we should aim to put it into 2.8.

thanks
-- PMM